And it all checked out nicely — in an effort to rid himself of his nemesis once and for all, the Leader sent the Hulk back in time, 66 or so million years ago, to the Yucatán region, just in time for the Chicxulub (pronounced “chick-shaloob”) Impactor to hit. The dinosaurs the Hulk was fighting were appropriate for the time period, the location was right, and everything looked good.

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Actually, bad for the Hulk. The asteroid that wiped out the dinosaurs was coming, visible in the sky. The Cretaceous Period, the last act of the Mesozoic Era and the Age of Dinosaurs, was about to end in spectacular fashion.

So here’s how things start off…

Rock Smash Hulk

The Hulk (strongest one there is) is still fighting the dinosaurs he met at the end of the last issue (note: the Leader’s really flexing his intelligence here by pinpointing the time within an hour or two of the asteroid hitting Earth), and then, the impact.

Everything close to the impact site is instantly vaporized. Best research suggests that the rock that hit Earth was between 10 and 15 km across (6–9 miles), with a mass of roughly a trillion metric tons, traveling at about 20 kilometers per second, or roughly 45,000 miles per hour. It was most likely a clumpy mass of carbon-rich rock that originally called a region of our solar system beyond Jupiter home before it came in for a close-up look at Earth. Don’t ignore that speed — moving that fast, it could’ve crossed the United States in 4 minutes. Or, more importantly, when dinosaur eyes registered the flash of impact, the crater was already excavated.

I still love the fact that if you look up “Chixculub Impactor” on Google, the results pop up, an asteroid streaks across your screen, and the screen shakes with the impact.

The force of the asteroid’s impact cannot be overstated. It was so massive and moving so fast that when it struck the Yucatán Peninsula, it vaporized. Quick science lesson: think of it like an ice cube. You can heat an ice cube until it melts, and if you keep adding heat, you can boil the water, turning it into vapor. In a beaker or on your stove, it takes time for the energy to do its job. Now imagine skipping over the whole “solid turns to liquid, and then the liquid warms up” part and putting enough energy into the ice to turn it into a gas in less than a second.

That’s scary. And the asteroid had enough energy to do that and more.

Fun Fact: We know a lot about the impact. For instance, we know that the asteroid came in at a steep angle, probably around 60° relative to the impact surface. This was probably the worst possible angle it could have had. As a result, it blasted up more debris and vaporized more of the site than a shallower angle would have. We also know that the impactor hit during Northern Hemisphere spring, thanks to fossil evidence. This was a particularly bad time, as life was just starting up for the season—eggs were being laid, and trees and plants were flowering and kicking off their annual growth. And if the impact had happened just three hours later, the asteroid would not have struck the shallow sea covering the Yucatán region, but rather the deep Pacific Ocean, and things probably would have gone very differently. And finally, when the leading edge hit the ground, the trailing edge was still about 10 km above the surface - just about the altitude for airlines.

The crater from the impact is 180 kilometers in diameter (110 miles), but again, there’s nothing of the actual asteroid left down there. Just some broken and buckled bedrock that attests to the energy of the impact and its angle.

One of the reasons the impact was so devastating comes from the same adage used in real estate: location, location, location. The impact site was loaded with sulfur-rich bedrock, and much of it vaporized along with the asteroid. This resulted in sulfur compounds (sulfur dioxide, sulfur trioxide, and others), along with carbon compounds (lots of carbon dioxide) and soot, being blasted into the atmosphere.

After getting cooked and regrowing tissue a few times, the Hulk (who somehow survived being near ground zero) leaps himself out of there.

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After the Impact

While the Hulk was right to get as far away as he could from the impact site, in reality, it probably didn’t matter much. Earth was hell.

It’s not entirely clear how long the Hulk was jumping around post-impact (“After what feels like an eternity…”), but he wouldn’t have found safety anywhere. In the immediate hours to days after the impact, materials that had been blasted into the upper atmosphere—the ejecta—would be falling back to Earth. As the material fell, it compressed the air beneath it, heating both the air and the material itself (for more on this, check out the article about the Artemis II reentry and the Flash running really fast).

There’s still debate about exactly how hot it got and what that meant for life on Earth, but many dinosaurs were likely broiled to death, and much of Earth’s vegetation burned, releasing even more soot and carbon dioxide. During that time, it would have felt like you were inside a toaster oven, with the sky glowing red as millions of tons of material fell back toward the ground. And fires surrounded you. Extinction Wave #1.

Understandably, it would make the Hulk mad.

Then, things get really bad. After Earth’s temperature setting comes down from “broil,” all of the sulfur compounds and other particulate matter that remain airborne reduce the amount of sunlight reaching the surface, cooling the planet and wiping out even more plants (and, by extension, the herbivores and carnivores that depended on them). The oceans cooled as well, taking out many organisms that had been lucky enough to survive the immediate effects of the impact. All told: Extinction Wave #2.

But despite being dealt one of the worst hands imaginable, life somehow endures. Animals that could burrow, retreat deep enough into the water, or survive as scavengers—and those that were simply too mean to die (crocodiles, I’m looking at you)—eked out an existence and endured.

And for some of those poor creatures, the Hulk finds them.

Fun Fact: That stuff that fell from the sky after the impact—the soot from burning forests, particulates, and even the vapor that once made up the asteroid—settled all over Earth and is still around today. In some locations, if you know where to look, you can spot the line of dark material sandwiched between other layers of rock. This thin band of dark clay, often only a few centimeters thick, is called the K–Pg Boundary. In the rock layers below the K–Pg Boundary, you find fossils of the large non-avian dinosaurs. Above it, none. It’s a bookmark in Earth’s history, a physical reminder of one of the worst days our planet has ever experienced. It’s distinctive because of the combination of elements it contains—particularly iridium, which is rare in Earth’s crust but relatively common in asteroids.

The initial suggestion that the K–Pg Boundary represented an asteroid impact came from physicist Luis Alvarez and his son, geologist Walter Alvarez, in the late 1970s. Based on its composition, they proposed that a roughly 10-km-wide asteroid had struck Earth 66 million years ago. Remarkably, Alvarez and his colleagues advanced the hypothesis before the Chicxulub crater was identified, and later crater research largely confirmed their estimates of the impactor’s size. There is still debate about some of the details and methods because... science.

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Please Don’t Kill Our Ancestors

At some point after all his jumping, the Hulk lands near a dead dinosaur being nibbled on by a group of small mammals. Yes, mammals. They existed alongside dinosaurs right up until the end of the Cretaceous.

You may think the image is showing rats, and that’s what the Hulk calls them, but they are definitely not rats. Rats didn’t arrive on the scene until roughly 3 to 5 million years ago. More likely, what the Hulk sees is a representative visual of several types of mammals that were around at the time, such as:

Protungulatum - early placental mammal

Purgatorius – possibly one of the earliest primate relatives, and

Multituberculates — rodent-like mammals that survived the extinction remarkably well

They were all rodent-like in the sense that they could reproduce quickly, burrow, survive on small energy budgets, and eat almost anything.

Including a dead dinosaur.

In fact, if you let the evolutionary tree grow from small mammals like the ones the Hulk spots—mammals that are about to become very important to our story—it might look something like this:

66 million years ago
→ small mammal survivor

60 million years ago
→ early placental mammals

55–60 million years ago
→ primate lineage emerges

40 million years ago
→ early anthropoid primates

20–25 million years ago
→ apes

6–7 million years ago
→ last common ancestor of humans and chimpanzees

300,000 years ago
→ Homo sapiens. Yay!

The big idea here is that, with the non-avian dinosaurs out of the way (and the theropods doing their own thing, thanks guys), mammals were able to explode into thousands of different forms, each finding a niche in the biosphere left vacant by the impact.

It just so happens that the Hulk (still angry and looking to smash) showed up near a group that was incredibly important to the branch that would eventually lead to us.

Seeing our distant ancestors, the Hulk…

…smashes them. Great.

You kind of want to side with the Leader here, don’t you?

If Not Us, Then Who?

In the present, immediately after the smashing of our early ancestors by the Hulk, the Leader feels a temporal wave…one of a variety of hand-wavey time-travel conventions in science fiction that suggest changes in the deep past are only reflected in the present when they serve the plot. Quickly realizing that the Hulk somehow survived the asteroid impact, he jumps back 66 million years to make things right.

But wait— let’s just say, for a second, that he didn’t get to the time platform in…time, and the present reshaped itself around the past where the Hulk smashed the early placental mammals that were our ancient ancestors. Ignoring the idea that, if the Hulk stopped humans from existing, he would have stopped himself from existing and therefore wouldn’t have been around to smash the small ancestor mammals in the first place (I know, big ask)...what would the “present” be like?

So, take a peek outside the Leader’s base in the “present,” where the Hulk has destroyed all chance of primates evolving. What would you see?

Birds. Lots and lots of birds.

Smaller theropods, small feathered dinosaurs, were on the rise before the impact and survived after. Even the Leader pointed it out, saying later that the impact wiped out all “non-avian dinosaurs.” With mammals around as evolutionary competition, those surviving theropods evolved into the more than 10,000 species of birds known today. Without mammals competing for resources and ecological niches? Oh, they’d run the joint.

The extinction left behind a huge number of vacant ecological roles, and evolution hates empty real estate. Run down the list — the impactor took out:

• large herbivores

• small insectivores

• mid-sized predators

• scavengers

• seed eaters

• tree dwellers

• ocean hunters

In our timeline, mammals exploded into those niches. But if the Hulk somehow removes the mammalian lineage that eventually gives rise to primates, rodents, carnivores, whales, bats, and everything else, those niches don’t remain empty. They get filled by dinosaurs. Theropods.

Earth is Birdworld.

Research suggests that, by the end of the Cretaceous, some theropods were demonstrating at least modest intelligence, complex social behavior, and possibly even cooperative hunting. That requires information transfer, communication, and brains capable of handling both.

So yeah, after the impact’s aftermath, birds were ready to fly.

They were already:

• warm-blooded

• intelligent

• highly mobile

• diverse

• surviving the extinction successfully

Give them 66 million years, and the descendants of those ancient theropods would almost certainly diversify into forms we can barely imagine.

Think less “sparrows” and more:

• crow-equivalents filling primate niches

• giant flightless omnivores filling bear niches

• predatory terrestrial birds filling wolf niches

• highly manipulative beaks (maybe hand analogs) and feet evolving for tool use

After all that time to evolve, a corvid-like lineage becomes a very plausible candidate for producing human-level intelligence.

Okay—maybe the mammals Hulk killed weren’t our direct ancestors, but killing them caused a temporal storm anyway. Other contenders for winning the evolutionary lottery would include intelligent descendants of rodents, raccoon-like mammals, snakes and lizards, crocodilians, marsupials, or something we simply can’t imagine.

Evolution wasn’t and isn’t “pointed” towards humans as the end result. Large brains have evolved independently multiple times, so if you remove the branch that eventually sprouts humans, there are other contenders waiting for their shot.

But birds are probably the safest bet.

Which Marvel Earth is Bird-Earth again? I mean, if we go all TVA on this, that branch might still exist before it gets pruned back into the Sacred Timeline. I mean, Captain America is a bald eagle. Falcon is still a falcon (duh). Iron Man becomes a highly evolved crow in powered armor—Iron Corvid. Reed Richards is a parrot with frightening reserves of theoretical intelligence. Spider-Man is a starling.

Oh, it goes on and on.

Side Note: If going down these lines of thought makes your brain hungry for more, you’ve got to check out Adrian Tchikovsky’s Children of Time series (Children of Time, Children of Ruin, and Children of Memory), all of which explore civilizations where species other than primates took the lead.

The Leader and Family Trees

Arriving in the past (again, with uncanny precision), the Leader protects our early post-impact ancestors by tricking the Hulk and sending him into the next trap.

Yeah. “Hello, great-to-the-nth-degree grandmother.”

Strictly speaking, that’s not how evolution works. Sixty-six million years ago, individual family trees blur into populations. That little survivor isn’t a single grandmother waiting at the root of humanity’s family tree. She’s part of an entire population of survivors from which all later humans eventually emerge.

But for comic-book dialogue, it’s close enough.

And honestly, “Hello, member of my ancestral breeding population” doesn’t have quite the same ring to it.

As for the “nth” part, that can actually be estimated.

Sixty-six million years divided by roughly 25 years per generation means that, between that small mammal and the Leader, there would have been about 2.6 million generations. So, the technically ridiculous version would be:

“Hello, my 2,600,000th-great-grandmother.”

And even that probably understates the number, because early mammals reproduced much faster than humans do. If you account for shorter generation times throughout much of mammalian history, the true figure might be closer to five to ten million generations.

And if we want closer relatives for comparison:

Lucy-era hominins: ~150,000 generations ago
Human–chimp common ancestor: ~250,000–350,000 generations ago

So the Leader’s “great-to-the-nth-degree grandmother” is way, way deeper than Lucy. Lucy is ancient to us, but compared to those asteroid survivors, she’s practically family gossip.

Next Time…

We’ve wrung all the science out of this issue, so where are we heading next? In the final pages, the Leader uses the time platform as a space platform as well (no complaints here) and shoots Hulk to the black hole in the center of the Milky Way, Sagittarius-A*.

We’ll be back soon with a look inside, and trust us…

There will be spaghettification.

Curiosity is what brought me here.

Teaching is what I do with it.

If you’d like to read more about education, classrooms, students, and the craft of teaching, you’ll find those stories in Teacher, Teacher.

This piece was originally published on a previous version of The Science Of and has been recovered from the digital strata. Its lightly edited version is represented here because it’s useful, weird, fascinating, updated, or some combination of the four.

In the Wonder Woman film (2017), Dr. Poison has everything going for her as a classic villain. She’s broken. She’s creepy. She’s troubled. She’s brilliant. And she knows her science.

Apparently in the thrall of General Ludendorff, Dr. Poison – Isabel Maru, played by Elena Anaya - was responsible for developing, well…poison weapons for the German army in World War I, including a hydrogen-based gas (small molecular-sized particles could slip through filters) that could penetrate gas masks (and crack their glass too).

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As for where the character came from, Dr. Poison was Wonder Woman’s first “costumed” villain, appearing in 1942’s Sensation Comics #2. In that appearance, Dr. Poison (created by Marston and Harry Peter) was revealed to be Princess Maru, an Asian Princess tied to both the Yellow Peril and the rising anti-Japanese sentiment in the United States at the time. Since her first appearance, Dr. Poison has been rebooted three additional times in DC Comics, and is currently Marina Maru, leading an organization called…Poison (no, not the ‘80s hair band).

Dr. Poison in the film is frightening enough, but in this case, there’s a real-world analog, someone who has been celebrated and castigated through the years. Our world’s own complex character using science to help and hurt – Fritz Haber, the “Father of Chemical Weapons.”

And also, “the man who killed millions, but saved billions.”

Okay, but before we get into it, was Haber really the inspiration for the original Dr. Poison in 1942?

I mean…(waves hands).

Sensation Comics was originally written by William Moulton Marston, who created Wonder Woman and her initial cast, including Dr. Poison in issue #2. While there is no direct evidence connecting Dr. Poison with Haber, Marston was in college when chemical weapons made their debut.

The Wonder Woman creator was at Harvard from 1915 to 1921, earning a B.A., a law degree, and a PhD. in psychology. He was certainly no stranger to science and almost certainly would’ve heard of the use of chemical weapons by the Germans following their first use in the Second Battle of Ypres in the spring of 1915. The use of the gas was widely reported in papers throughout America, from The New York Times to The Chicago Tribune.

Firsthand accounts of the gas were stuff of nightmares – a sickly looking yellow-green gas rolling across the landscape, turning any vegetation brown and wilted, flowing down into depressions and pits in the ground, ultimately drifting down into the trenches where the Allied soldiers waited.

So does Haber equal Dr. Poison? The lines are conjecture, so… maybe not directly, but Haber and the memory of WWI gas warfare would have been part of the cultural atmosphere Marston inherited (and was probably goosed by the news of Haber’s death in January 1934).

Before we get into our suspected scientist-inspiration, we should note that Dr. Poison hasn’t been left behind in the ‘40s. Along with appearing in 2017’s Wonder Woman film, there have been other (five…six?) iterations of the character over the years thanks to continuity reboots and restarts.

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Most recently, Dr. Poison has returned in Absolute Wonder Woman, where she’s a member of Veronica Cale’s Suicide Squad. This time, the character gives more than a passing nod to poison gases - she is a sentient cloud of poison gas.

Her original version from Absolute Wonder Woman #8, designed by Kelly Thompson and Hayden Sherman

The image below is actually Poison’s second suit, after she…colorfully complained to Cale that the first one, which was bulkier, didn’t allow her to do delicate work.

So, back to Fritz Haber, our maybe kinda real-life inspiration for Doctor Poison.

If you can maybe remember him from a chemistry class or a YouTube video, you may already have a sense for who Haber is. But if we’re being honest, Haber, like Wonder Woman’s Dr. Poison, is a complex individual who resists the broad-brushing of turning him into a simple villain.

Fritz Haber is often cast as a lone German mad scientist in stories about chemical weapons used in World War I, but that’s not quite accurate. Chemistry was the hot science in the early 20^th century. In many ways, World War I was an opportunity for the leading industrial nations to showcase their technologies to the rest of the world. Despite the Hague Convention of 1899 and 1907, which prohibited the use of asphyxiating gas projectiles in war, France used tear gas/irritant agents on the Germans in 1914. Once the Germans introduced gases on the battlefield, the Allies answered with gases of their own. Lost to most history and chemistry texts, in fact, is Haber’s rivalry with the French chemist Victor Grignard, who also studied gas weapons. No, this wasn’t a case of Haber secretly toiling and developing chemical weapons for war. The whole world was headed in that direction. Haber just got there first.

But before we expose his dark side, let’s make one thing clear – Haber was a brilliant chemist. Before he became known for his work with chemical agents, Haber, in collaboration with Carl Bosch, invented the Haber-Bosch process, a means to literally pull nitrogen out of the air (with the use of a metal catalyst under high temperatures and pressures)

Chemistry students know the Haber-Bosch equation well – it’s usually the go-to equation to explain Le Chatelier’s Principle:

N₂ + H₂ -> 2NH₃

The ammonia (NH₃) is then used to produce fertilizer, which, in Haber’s time, was desperately needed to help feed the world’s rapidly growing population. The process is still used today and is often pointed to as one of the main factors that has allowed the Earth’s population to grow to over 7 billion. For their work on a process that benefits all humanity, Haber won the Nobel Prize in 1928 for ammonia synthesis, while Bosch won in 1931 for high-pressure chemical methods. Haber’s win in 1918 was…controversial to say the least, with the Nobel committee explaining that they only considered his work that benefited agriculture, rather than his wartime activities.

However, pulling all that nitrogen in the air and making it useful drew the attention of the German Army, which needed it for nitrogen-based explosives during the Great War.

When the Great War came, Haber saw himself as a German first and a chemist second (in opposition to his friend, Albert Einstein, who was critical of Germany), and told the German government he would do whatever his country needed to help in the war effort.

Like Dr. Poison, Haber was not regarded as a traditional war hero by the German military leadership. These were generals and soldiers of the Victorian Era – gentlemen first, soldiers second. Haber’s ideas of killing the enemy with gas were seen as “unchivalrous” and “repulsive.” But Haber was steadfast, insisting that the gas would be a means of reducing German casualties (while increasing those of the Allies) and of ending the war faster (with Germany on top). In the end, Haber’s plans for chlorine gas were a means to an end, and the generals finally took Haber’s advice of “using chemical warfare with conviction.”

With the military finally behind him, Haber threw himself and his lab at the Kaiser Wilhelm Institute for Physical Chemistry into the business of making a poison gas for the troops. By April of 1915, Haber had his perfect concoction and was on the front lines at Ypres, Belgium. There, he waited for weeks until the winds were just right, and on April 22nd, he released over 168 tons of the gas from canisters, which exploited the wording and was still plainly against the spirit of the Hague Convention, which outlawed gas projectiles whose sole purpose was spreading asphyxiating/deleterious gases.

Denser than air, the gas drifted like a low, yellow wall towards the French trenches. Hundreds to thousands (depending upon your source) of French and Algerian soldiers died from exposure. While the gas use did not lead to an immediate victory for the Germans, it emboldened Haber and the German High Command to view gas weapons in a favorable light.

Haber oversaw another attack at Ypres, this time on Canadian troops, and by May 2^nd, had been promoted to a uniform-wearing Captain and was headed home to Berlin for a party in his honor. He was living a celebrated existence at this point – a party on the 2^nd, and then on May 3^rd, he was headed to the Eastern front to oversee a gas attack on the Russians.

Haber’s wife, Clara Immerwahr (a brilliant chemist in her own right, and the first German woman to earn a PhD in chemistry), long disagreed with her husband’s militarization of science and development of chemical weapons, and on the night of the party, shot herself in the chest with his service revolver (she didn’t die immediately and was found by their 12-year-old son, Hermann, but Fritz reportedly slept through the shooting).

Haber was so not broken up by his wife’s death that he didn’t bother changing his plans and headed out to the Eastern Front the next day – though he later said Clara’s face and words still haunted him.

But whether or not his wife’s ghost haunted him, it didn’t slow down his work.

After the debut of Haber’s chlorine gas, the chemist went on to oversee the development of phosgene gas (COCl₂) and mustard gas ((ClCH₂CH₂)₂S). Each of the three gases used in World War I is horrible, and while both German and Allied armies rapidly developed gas mask technology to minimize the effects of the gases, there were approximately 1.3 million gas-related casualties and around 91,000 deaths from poison gases in World War I between their debut at Ypres in 1915 and the end of the war in November of 1918.

Strictly from the chlorine gas side of things, inhalation of the gas is a horrible way to go, thanks to the reaction that happens in the lungs that produces both hydrochloric acid and hypoclorous acid:

Cl₂ + H₂O <-> HCl + HOCl

The water on the reactant (left) side would be found in the lungs or on the surface of the eyes. The gas could blind those without protection, while in the lungs, the alveoli would be damaged or scarred, reducing the ability to absorb oxygen – if you were lucky. If you were unlucky, exposure to hydrochloric acid would cause lung cells to rupture (lyse), releasing their contents. Fluid-filled lungs would literally lead to drowning on dry land.

On April 26^th, 1915, The New York Times reported on the battle:

“Some (soldiers) got away in time, but many, alas, not understanding the new danger, were not so fortunate and were overcome by the fumes and died poisoned. Among those who escaped, nearly all cough up blood, the chlorine attacking the mucous membranes. The dead were turned black at once … (The Germans) made no prisoners. Whenever they saw a soldier whom the fumes had not quite killed they snatched away his rifle … and advised him to lie down to die better.”

Mustard gas and phosgene were, reportedly, even worse, sometimes delaying their deadly effects until after the battle was over. Haber also worked on a gas blend called maskenbrecher or “mask breaker” – an agent that would be small enough to get through the filters of a gas mask and cause a violent reaction from sneezing to vomiting, forcing soldiers to remove their gas masks, and then be exposed to the other, deadlier gases from which their masks were protecting them. Hey - what was that gas Dr. Poison was working on again?

Following World War I, Haber was designated a war criminal by the Allied Powers, but, like Dr. Poison in Wonder Woman, he escaped capture and prosecution, fleeing to Switzerland in 1919. His name was later removed from the list of wanted war criminals, and he returned to postwar Germany a hero.

During these postwar years, Haber continued his research into poisonous gases, in direct opposition to the Treaty of Versailles. Part of the research into poisonous gases led to the development of the pesticide Zyklon A in the 1920s. Another Haber project in the years of reparations being paid by Germany – he proposed that he could extract gold from seawater.

He wasn’t wrong about gold in seawater. There’s a little bit of everything in there. But Haber’s methods were not up to the challenge, and ultimately, his plans bore no fruit.

While he was initially seen as a favored son in his beloved Germany, the postwar years became difficult for Haber as the National Socialist Party rose to power. Haber’s Jewish ancestry, long known but previously overlooked because of his conversion to Christianity (1924) and patriotic service to Germany, suddenly became impossible to ignore under Nazi racial laws, effectively ending his scientific career.

Doors that were once thrown wide for him were firmly closed. Haber fled his beloved Germany for England in 1933, but his work with chemical weapons kept him from finding a home there. Haber wandered Europe for some time, ultimately dying of a heart attack in a Swiss hotel in January of 1934.

In a cruel twist of fate, or what some might see as karma, Haber had one final role to play in the story of poison gas.

Now, to be clear, Haber did not invent Zyklon B. That pesticide was developed by other German chemists in the 1920s. But it emerged from the same German chemical industry and scientific world that Haber had helped build and champion throughout his career.

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Years later, the Nazis would repurpose Zyklon B for something far darker than pest control. The gas became one of the primary tools of mass murder during the Holocaust, killing millions of people, including countless Jews.

And that’s where the story takes one final, bitter turn.

Haber had spent much of his life trying to prove he was German. He converted from Judaism to Christianity. He devoted his scientific genius to Germany’s war effort. He considered himself a patriot first and foremost.

It wasn’t enough.

The Nazis saw only his Jewish ancestry. He was forced from the country he loved, stripped of the place he had spent a lifetime earning. Worse still, likely, some of his own relatives would later become victims of the regime.

History rarely gives us neat endings. But it is difficult to imagine a more tragic irony than this: a man who helped pioneer chemical warfare, who dedicated his life to Germany, ultimately rejected by that same nation while a poison associated with the chemical establishment he helped create was turned against his own people.

A complex man during his lifetime, Haber’s legacy is equally complex. Some estimates suggest that half the world’s population would not be here if not for the Haber-Bosch process, which enabled the cheap, easy production of fertilizers in bulk. Conversely, the descendants of the victims of Haber’s gas attacks (including those killed by Zyklon B) are not here.

Real-life “villains” are indeed complex characters.

More:

A Brief Biography of Fritz Haber (1868 - 1934) (pdf)

Fritz Haber’s Experiments in Life and Death

Organisation for the Prohibition of Chemical Weapons

Chemical and Engineering News: 100 Years of Chemical Weapons

Curiosity is what brought me here.

Teaching is what I do with it.

If you’d like to read more about education, classrooms, students, and the craft of teaching, you’ll find those stories in Teacher, Teacher.

The Milky Way is enormous.

The neighborhood we’ll be visiting today? Not so much.

Well, relatively.

On the scale of the Solar System, the journey Ryland Grace undertook in Project Hail Mary was almost unimaginable. Sixteen light-years is such a ridiculous distance that our brains quietly file it under “basically infinite” and move on.

But that’s only if you’re thinking on Solar System scales.

Zoom out - way out.

Far enough that the entire Solar System disappears into a single pixel and the Sun becomes just another star among hundreds of billions.

From that perspective, Grace’s voyage wasn’t a trek across the galaxy.

It was a trip across the neighborhood.

In fact, the three systems we’ll be visiting today - the Sun, Tau Ceti, and Erid are so close together that, as far as the Milky Way is concerned, they’re on the same street. (If you zoom out to the scale of the observable universe, they really are in the same place. But that’s a different article.)

Today, we’ll travel from Earth to Tau Ceti and then onward to Erid, covering a total of about sixteen light-years without ever leaving the same galactic cul-de-sac.

Before we go, though, let’s make sure we’re all speaking the same language.

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Distance

On Earth, we measure distances in miles (if you’re in one of the few countries still clinging to Imperial units) or kilometers.

Just in case high school science was a long time ago, a kilometer is 1,000 meters, or about 0.62 miles.

That’s Earth-scale thinking. Astronomers gave up on that nonsense a long time ago.

The problem is that space is big. Really big. Distances that seem enormous on Earth become inconveniently small once you leave it.

For travel within a solar system, astronomers use the Astronomical Unit (AU): the average distance between Earth and the Sun.

One AU is about 93 million miles (150 million kilometers).

Using that scale:

• Earth orbits at 1 AU

• Jupiter orbits at 5.2 AU

• Neptune orbits at about 30 AU

For most of the Solar System, the AU is a perfectly useful yardstick. But once you start traveling between stars, even the AU starts feeling a little cramped.

That’s where the light-year comes in.

Despite the name, a light-year is a measure of distance, not time. It’s simply the distance light travels in one year.

One light-year equals:

• 63,241 AU

• 5.88 trillion miles

• 9.46 trillion kilometers

Which sounds enormous until you realize that the entire journey of Project Hail Mary takes place across only a handful of them.

Side Note: Parsecs

At some point, someone will ask why we’re using light-years instead of parsecs. Fair question.

A parsec is another unit of distance used by astronomers. One parsec is equal to about 3.26 light-years.

Unlike a light-year, which is based on how far light travels in a year, a parsec is a unit of distance derived from geometry. Specifically, it’s the distance at which 1 AU would appear to shift by one arcsecond against the background stars as Earth moves around the Sun.

If that sentence made your eyes glaze over, don’t worry. Mine too, and I teach this stuff. The important thing to know is that parsecs are incredibly useful for astronomers because they’re tied directly to how we measure distances to nearby stars.

The important thing to know for this article is that they’re annoying. Not because they’re bad. They’re perfectly good units.

But if I tell you that Tau Ceti is about 3.65 parsecs away and Erid is about 4.9 parsecs away, most people’s brains immediately respond with, “Cool. Is that close?”

If I tell you they’re about 12 and 16 light-years away, respectively, at least the unit itself provides a hint that we’re talking about really large distances.

Astronomers may grumble. They’ll survive.

As for the whole “parsecs in Star Wars” debate, we’re not opening that airlock today.

For the rest of this trip, we’ll mostly speak in AUs when we’re inside a solar system and light-years when we’re traveling between them.

The simplest version? Think of AUs as city blocks, and light-years as the distance between towns.

One final note before we leave Distance behind: If you draw lines between Earth, Tau Ceti, and Erid, you don’t get a straight line. You get a triangle.

Earth sits at one corner. Tau Ceti sits about 11.9 light-years away. Erid sits about 16.3 light-years away. The surprising part is the third side.

Tau Ceti and Erid are only about 10 light-years apart.

That’s still an absurd distance by human standards. But on a galactic scale, it’s another reminder that these systems are neighbors.

Again, if the Milky Way were a city, the Sun, Tau Ceti, and Erid wouldn’t be in different states.

They’d be on the same street.

Just for one final reference, and to drive home the point that Erid and Tau Ceti are our neighbors, the center of the galaxy is 26,000 light-years away, while one of our nearby galaxies, the Andromeda Galaxy, is 2.5 million light-years away. Yeah, given that, we can look at Tau Ceti or Erid and see if someone left a light on in the window.

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Types of Stars

Before we start hopping between solar systems, we need to talk about stars.

Not all stars are the same.

Some are larger, hotter, brighter, and burn through their fuel like a college freshman discovering energy drinks. Others are smaller, cooler, dimmer, and can keep shining for tens or even hundreds of billions of years. As a general rule, the cooler you burn, the longer you live.

Astronomers classify stars by their temperature and color using a system that ranges from hot blue stars to cool red stars. There are considerably more details than that, but for this trip, we only need to concern ourselves with three stars.

The Sun

Our Sun is a G-type main-sequence star.

It’s the standard unit for this part of the trip: 1 solar mass, 1 solar radius, 1 solar luminosity.

Convenient. Almost suspiciously convenient. Like we live next to the thing or something.

The Sun has been steadily converting hydrogen into helium for about 4.6 billion years. It is bright enough to keep Earth warm, quiet enough not to sterilize it, and massive enough to provide the gravity that holds the entire Solar System together.

When astronomers talk about another star’s mass, radius, or brightness, they often compare it to the Sun.

Think of the Sun as the Holiday Inn of stars. Not the biggest. Not the fanciest. But clean, reliable, and familiar enough that we use it as the baseline for comparison.

Tau Ceti

Tau Ceti is also a G-type main-sequence star, making it one of the Sun’s closest cousins in the neighborhood.

It is smaller and dimmer than our Sun:

• about 0.78 solar masses

• about 0.79 solar radii

• roughly 0.5 solar luminosities

In plain English: Tau Ceti has about 78% of the Sun’s mass, about 79% of its radius, and gives off about half as much energy (even before its Astrophage infection). So yes, it is Sun-like.

But “Sun-like” does not mean “basically the Sun with a different nametag.”

If you somehow swapped the Sun for Tau Ceti tomorrow, Earth would get colder. Not “instantly frozen death planet” colder, but colder enough that everyone would notice, especially the plants, the oceans, and everyone who already complains when the thermostat drops two degrees.

Tau Ceti is familiar enough to be useful and different enough to matter.

Which is exactly why astronomers care about it. It’s close enough to study, familiar enough to compare, and weird enough to keep things interesting, which we’ll talk about coming up.

Erid (40 Eridani A)

Erid is different.

The star Rocky calls home (which Grace eventually names “Erid”) is known to astronomers as 40 Eridani A. It is a K-type orange dwarf: cooler, dimmer, and longer-lived than the Sun. The “A” in its name is to keep track of it - 40 Eridani is a triple-star system, so there’s 40 Eridani A, B and C.

Side Note: No, we’re not going to lean into the 3-Body Problem here, either. This is Project Hail Mary. Focus.

Erid’s numbers are close to Tau Ceti’s in mass and size, but not in color or stellar personality:

• about 0.8–0.85 solar masses

• about 0.8 solar radii

• roughly 0.4–0.5 solar luminosities

That means any potentially habitable planet orbiting Erid needs to orbit closer to Erid than Earth does to the Sun to receive comparable energy if we’re talking about human life. Which we’re not.

The payoff for Erid’s lower energy output is longevity.

Stars like the Sun live for roughly ten billion years. K-type stars like Erid can remain stable for several times longer. That matters because life does not care whether a star impresses us.

Life cares about time.

A stable environment that lasts for tens of billions of years gives evolution an awful lot of opportunities to try new things.

And as we’ll soon discover, these three stars host very different neighborhoods.

Habitability and Amenities

Before we dig in, let’s recognize our bias.

When astronomers talk about a planet being “habitable,” they’re usually talking about conditions that could support life as we know it. That sounds narrow because it is.

The problem isn’t a lack of imagination. The problem is a lack of data. We currently have exactly one example of a life-bearing world. Earth. Every definition of habitability we use is built from that single sample.

Liquid water. Moderate temperatures. A stable energy source. An atmosphere thick enough to be useful and thin enough not to crush you. These aren’t necessarily the universal requirements for life.

They’re the requirements shared by every living thing we’ve ever met.

This distinction will become important later.

Our Solar System

If you’ve ever looked at an astronomy diagram and wondered why every solar system seems to be compared to ours, the answer is simple:

It’s the only one we’ve got.

The Sun is our home star, our calibration standard, and the source of nearly every assumption we make about how solar systems are supposed to work. This is both reasonable and dangerous.

Reasonable because Earth is the only life-bearing world we’ve ever found.

Dangerous because Earth is the only life-bearing world we’ve ever found.

Side Note: The Goldilocks Zone

The Sun’s habitable zone is the region where temperatures could allow liquid water to exist on a planet’s surface. Not too hot, not too cold, just right.

For our Sun, Earth sits comfortably inside this zone at 1 AU (our reference point for basically everything). Venus is a little too close and has paid the price by becoming a pressure cooker wrapped in sulfuric acid clouds. Mars sits near the outer edge and appears to have spent much of its history arguing with itself about whether it wanted to remain habitable.

Being in the Goldilocks Zone does not guarantee habitability.

It simply means the thermostat is set correctly.

The rest of the house still has to be worked on.

Local Attractions

Our Solar System offers a surprisingly diverse set of destinations: inner, rocky planets that include Earth (the only place known to support life), and then the gas giants, each with enough moons to qualify as miniature solar systems in their own right.

Debris and Other Hazards

The Solar System is remarkably tidy. That’s not because there isn’t debris.

There is.

The Asteroid Belt between Mars and Jupiter contains millions of rocky bodies. Beyond Neptune lies the Kuiper Belt, home to Pluto and countless icy objects. Far beyond that lurks the Oort Cloud, a vast spherical reservoir of comets that extends almost halfway to the nearest stars.

But compared to what we’re about to see, our Solar System looks positively well-maintained.

The neighborhood association has clearly been doing its job.

The Tau Ceti System

If the Solar System is the neighborhood’s well-maintained reference property, Tau Ceti is the house down the street where the yard has gotten a little out of hand.

At first glance, Tau Ceti looks reassuringly familiar. The star itself is one of the Sun’s closest cousins: slightly smaller, slightly dimmer, and a bit older. If you were somehow able to stand on a planet orbiting Tau Ceti and look up, the star in the sky would not strike you as wildly alien. You’d recognize it as a star much like our own.

The similarities are one reason astronomers have spent so much time studying it. If the Sun and Tau Ceti started with broadly similar ingredients, comparing the two systems gives us a chance to understand how solar systems can evolve in different directions.

Local Attractions

Current evidence suggests that Tau Ceti hosts between 3 and 5 planets, including several super-Earth candidates. As with many exoplanet discoveries, we don’t see these planets directly. Instead, we watch Tau Ceti wobble slightly as unseen worlds tug on it with their gravity.

This means the exact planetary census around Tau Ceti remains a work in progress. As instruments improve and additional observations accumulate, the details continue to be refined. That’s not astronomers being indecisive. It’s astronomers doing exactly what they’re supposed to do when new evidence arrives.

Some of the planets may lie within or near the system’s habitable zone. Whether any of them are actually habitable is a different question entirely.

Debris and Other Hazards

The biggest difference between the Solar System and Tau Ceti isn’t the planets.

It’s the leftovers.

Surrounding Tau Ceti is a massive debris disk containing far more material than we find in our own Solar System. Depending on which estimates you use, the system may contain roughly ten times as much cometary and asteroidal material as ours.

That’s a lot of leftover construction debris.

The implication is fairly straightforward. If planets are orbiting Tau Ceti, they are likely sharing the neighborhood with considerably more asteroids and comets than Earth does. Over long periods, that could mean more impacts, more disruption, and fewer opportunities for a planet’s surface environment to remain stable for billions of years.

That doesn’t make life impossible. Life has proven remarkably stubborn here on Earth. It does suggest, however, that a habitable-zone planet around Tau Ceti may have a more eventful history than our own.

Tau Ceti feels familiar enough to be recognizable, but different enough to remind us that solar systems are not manufactured from a standard template.

The 40 Eridani System

While Tau Ceti is one of the Sun’s closest cousins, 40 Eridani A belongs to a somewhat more complicated family.

As mentioned earlier, 40 Eridani is not a solitary star. It is part of a triple-star system. The primary star, 40 Eridani A, is an orange dwarf. Orbiting far away are two stellar companions: 40 Eridani B, a white dwarf, and 40 Eridani C, a red dwarf.

That’s already enough to make the system interesting.

One member of the family is still in the prime of its life (A). Another has reached stellar retirement and shed its outer layers (B). The third is a small, efficient star that may continue shining long after the others are gone (C).

Local Attractions

The main attraction here is the star itself.

As an orange dwarf, 40 Eridani A occupies a sweet spot that has attracted increasing attention from astronomers over the last few decades. It is smaller and dimmer than the Sun, but not dramatically so. A planet receiving Earth-like levels of energy would need to orbit somewhat closer to the star than Earth does to the Sun, but not so close that it would face some of the challenges associated with smaller red dwarf stars.

Stars like 40 Eridani A burn their fuel slowly.

Very slowly.

Current models suggest that orange dwarfs can remain stable for tens of billions of years—long enough that the Sun will be a memory before they’re done. And potentially long enough for biological and geological processes to play out over extraordinary stretches of time.

When astronomers talk about promising stars for long-term habitability, orange dwarfs frequently find themselves near the top of the list.

Exoplanet searches around 40 Eridani A have produced intriguing but inconclusive results, with some research suggesting a single planet closer to the star than Mercury is to our Sun, far inside the Sun’s habitable zone.

Side Note: Erid and Science Fiction

Writers seem to look at 40 Eridani A and have the same reaction astronomers do: ‘There’s probably something interesting there.’

Andy Weir wasn’t the first to place a planet that supports life around the star. In Star Trek, the star is home to the planet Vulcan, while in the Dune universe, the fourth planet in the star’s system is Richese, home to a technologically advanced culture.

Debris and Other Hazards

While exoplanets have not yet been confirmed for 40 Eridani A, neither has a massive debris disk surrounding the star. If such a structure exists, it appears to be far less prominent than the one that dominates Tau Ceti’s outer regions.

For anyone hoping for long-term planetary stability, that’s good news.

Large debris disks can act as reservoirs of comets and asteroids, increasing the likelihood of impacts over long periods. Without evidence for a substantial disk, 40 Eridani A appears, at least from our current vantage point, to be a comparatively orderly environment.

Of course, astronomy has a habit of humbling anyone who becomes too confident. Future observations may reveal additional surprises.

For now, however, 40 Eridani stands out not because of what surrounds it, but because of what the star itself offers: stability, longevity, and time.

Lots and lots of time.

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Getting There

Project Hail Mary needed, essentially, magic to get Ryland Grace to Tau Ceti, and used the astonishingly convenient properties of Astrophage to do it.

The problem with traveling to nearby stars isn’t speed. The problem is enough speed.

The stars in our little neighborhood are between 12 and 16 light-years away. At the speeds achieved by current spacecraft, the trip would take tens of thousands of years. That’s less “vacation” and more “geological process.”

Astrophage made the problem workable, powering the spacecraft to achieve a speed that is a significant fraction of the speed of light.

And that’s where things get weird. Keeping track of deadlines in Project Hail Mary got a little weird. Earth had only a limited amount of time before environmental catastrophe, the trip to Tau Ceti would take years, and any solution would then need years more to make its way back home.

Huh?

It’s workable, but you have to invite Einstein to your party.

Okay - light touch.

Travel Time and Time Zone Considerations

Keeping things as simple as possible, one of the stranger consequences of Einstein’s theory of relativity is that time itself doesn’t pass at the same rate for everyone.

The faster you move, the more slowly time passes for you compared to people who stay behind. It’s not by much at everyday speeds, but at a substantial fraction of the speed of light, the effect becomes impossible to ignore.

Ryland Grace and the Hail Mary crew don’t just travel a great distance. They travel in a way that causes their clocks to run more slowly than clocks back on Earth. The trip still takes years, just not the same number of years for everyone involved.

If the Hail Mary reached roughly 92% of the speed of light, then, thanks to time dilation, the crew only experienced around 5 years of travel time. Still long enough to require the coma technology, of which Grace turned out to be the only beneficiary. Back on Earth, 13 years would pass.

If you want math, I’ve got math — but be warned: for pretty high-concept physics, the time dilation formula and Lorentz factors are really easy to calculate.

And to travel from Tau Ceti’s region ot space to Erid (picking up Rocky along the way), that’s 10ish light-years, which, at 92% the speed of light, would have taken them around 4.3 years, with another 10-11 years passing on Earth.

Time Zone Information

From Earth’s point of view, the mission takes about 13 years to reach Tau Ceti. Add in the return trip for the Beetles, and you’re looking at roughly a quarter-century between launch and solution.

As for Grace and Rocky, time is different. Everyone on earth is a quarter century older by the end of the story; Grace has aged more slowly. As he explains near the end of the novel, he’s given up trying to figure out how old he is; his best guess is that he’s biologically in his mid-50s, but chronologically, by an earth-based measure, he’s in his early 70s.

Time is not the same at any two points in the universe. It’s not a bug; it’s a feature.

The Neighborhood

At the beginning of this article, I described the Sun, Tau Ceti, and Erid as a galactic cul-de-sac.

That wasn’t entirely a joke.

On human scales, these systems are impossibly far apart. The nearest is nearly twelve light-years away. The farthest is more than sixteen. Even with Astrophage, the trip takes years. Without it, the journey becomes the sort of thing that civilizations attempt rather than that people do.

And yet, on the scale of the Milky Way, these three stars are practically neighbors.

One hosts the only known life-bearing world in the universe, one appears to be surrounded by far more planetary debris than our own Solar System, and one may remain stable for tens of billions of years after the Sun has finished its work.

Three nearby stars.

Three very different stories.

That’s one of the lessons hidden inside Project Hail Mary. The universe doesn’t need to be exotic to be interesting. Sometimes all you have to do is look closely at the neighborhood.

The next time you see Tau Ceti or 40 Eridani A mentioned in a science article, a science fiction novel, or a planetarium show, remember that they aren’t abstract dots on a star chart.

They’re places.

Real stars.

Real systems.

Real neighborhoods orbiting quietly around the same galaxy as our own.

And they’re close enough that, for a brief moment in one very good novel, a science teacher managed to visit them.

Your homework: using your favorite astronomy app, go out and spot Tau Ceti and 40 Eridani A. Both are visible to the naked eye.

Curiosity is what brought me here.

Teaching is what I do with it.

If you’d like to read more about education, classrooms, students, and the craft of teaching, you’ll find those stories in Teacher, Teacher.

This piece was originally published on a previous version of The Science Of and has been recovered from the digital strata. Its lightly edited version is represented here because it’s useful, weird, fascinating, updated, or some combination of the four.

DC Comics’ Fury of Firestorm #2 had a cover with a familiar look to it.

The issue continues the tradition of Leonardo da Vinci’s famous Vitruvian Man sketch appearing on comic book covers.

Vitru-whovian Man?

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While Leonardo put the sketch to paper, he named it after the observations of Marcus Vitruvius Pollio, a Roman architect from the time of Caesar Augustus (ca. 80 - 70 BCE - 15 BCE). Vitrivius’ observations about the proportions of a human being were among the first ever recorded and included many different ratios:

• From the chin to the top of the forehead is 1/10 of the person’s height.

• From the wrist to the tip of the middle finger is also 1/10 of the height

• From the chin to the crown of the head is ⅛ height

• From the bottom of the neck (in line with the tops of the shoulders) is ⅙ height

• Mid-chest to the top of the head is ¼ height

• The length of the foot is ⅙ of the height

• The length of the forearm is ¼ of the height

• The breadth of the chest is ¼ of the height

And, of course, the circle thing. As Vitruvius wrote in Book III of his Ten Books on Architecture,

“For if a man be placed flat on his back, with his hands and feet extended, and a pair of compasses centered at his navel, the fingers and toes of his two hands and feet will touch the circumference of a circle described therefrom. And just as the human body yields a circular outline, so too a square figure may be found from it. For if we measure the distance from the soles of the feet to the top of the head and then apply that measure to the outstretched arms, the breadth will be found to be the same as the height, as in the case of plane surfaces which are perfectly square.”

As a result, Vitruvius’ version looks like this:

Vitruvius himself pointed out that these measurements didn’t originate with him. They came largely from his observations of sculptors and artists of antiquity.

Over the centuries since he put the ideas to paper, Vitruvius’ man was illustrated by countless artists, but da Vinci’s is the one that stands out. No shade-throwing at modern comic book cover artists intended.

LEONARDO’S OG VITRUVIAN MAN

First sketched around 1490 by da Vinci, the work is still debated by scholars over whether it’s worth the title the artist used. Leonardo pointed out (and his illustration reflects this) that Vitruvius’ square and circle cannot share the same center.

At least with humans as we know them.

As a result, Leonardo’s figure is centered at the groin rather than the navel, pulling the square down so it doesn’t rest inside the circle. Along with centering the figure differently, Leonardo showed the figure with hands raised to the top of its head, then superimposed the image on top of the other. The result is a figure with 16 different poses that owes as much, if not more, to Leonardo as to Vitruvius.

Also a scientist (and honestly one of history’s most aggressively curious people), Leonardo based his Vitruvian Man on data. He took meticulous measurements of Italian models and let that inform his final result. One cool note on Leonardo’s version is that the text at the top and bottom is in his iconic “mirror writing.” It’s written backward on the page but can be read normally by viewing the text’s reflection in a mirror.

While based on the work of the ancient architect, Leonardo’s Vitruvian Man was a radical statement for his time, one of the countless thought-bombs of the Renaissance. The image put humanity at the center of two perfect shapes: the circle and the square. Instead of being passive observers of the universe, people could understand it, measure it, and perhaps even shape it. In line with Humanist ideals of the age, Leonardo’s work shows that man — in body, mind, and soul — is the center of the universe.

On that last one, perhaps HBO’s Westworld employs the Vitruvian Man motif the best. In the series, the robotic hosts produced by Delos, first to populate the park and then in later seasons to take over the earth, are meant to be perfected versions of their human “ancestors.” What better way to show them as perfect than to put them in a pose tied to the ideal human proportions?

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WHY DOES THIS KEEP SHOWING UP?

Art is hard, and established proportions are a quick cheat for drawing people?

Okay - that’s oversimplifying, but the core is there.

Lessons on drawing the human body (and many other animals) rest on proportions. Vitruvius’ list of proportions in Ten Books on Architecture documents only some of the proportions that artists and other observers have realized over the centuries. For example, the pelvis’s width is the head’s height plus one-third of the face. The width of the foot is one-half the height of the head. The list goes on and on, most often expressing the human form in terms of the head as a unit of measurement.

It’s also eye-catching on the stands, amid a sea of other covers, blending into a wall of color. It pops, even with the familiarity that it carries. It’s also a way to produce a character reference pose and can suggest meaning for the story inside. In Flashpoint Beyond #4, for instance, Thomas Wayne is hunting the Clockwork Killer, so a clockwork theme informs the interior. While there is no iconic square with Batman in the image, the character is a natural for a Vitruvian homage, given Wayne’s obsession with physical and mental perfection.

As for other comics, how about a quick gallery...

Galactus? we’ve got Gatlactus.

Big coffee table books about DC superhero anatomy? Sure

Wonder Woman? Of course (issue #604, by the way)…

And that’s just getting started…

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Doctor Doom? If anyone would voluntarily pose as the ideal human form, it would be Doctor Doom.

Flash has two and counting…

Love it when science-based characters get a shot at homaging da Vinci…

And then of course, Goofy…

And that’s just a start. If you’re looking for a theme to your comics collection, there are worse.

Make Vitruvian Man a character and put him inside a comic? Sure...been there. And the results were...troubling. The character “Vitruvian Man” (Piero Rosci) showed up in DC Comics’ relaunched Stormwatch series in issue #9 by Peter Milligan and Miguel Sepulveda. Rosci had been changed by a former incarnation of Stormwatch, based on da Vinci’s drawing. Yeah.

For equally horrifying measure, a giant “Vitruvian Man” showed up in Boom Studios’ Mighty Morphin’ Power Rangers #5, with predictably horrifying results.

Probably should point out here that using Vitruvian Man for a body horror character is about as 180 degrees as you can go from the original intent of both Vitruvius, Leonardo, and every artist who’s tried to make their own representation. Vitruvian Man does not have four arms. A human with four arms is not ideal.

And if you’re really keeping track, Leonardo himself is a major figure in the history of the Marvel Universe...first appearing in 1956’s Mystery Tales #41, and then pulled into the history of SHIELD by Jonathan Hickman and a variety of other creators in SHIELD series in 2010.

And you can’t have da Vinci show up in a comic without something going all Vitruvian Man. In this case, it was Leonid, a Deviant-human hybrid named Leonid.

While the above is just scratching the surface of offical, published comics, there are thousands of fan-produced homages and pastiches out there. While we couldn’t find anything that was official in this vein, the one that makes the most sense is:

STEM LEARNING APPLICATIONS

Vitruvian Man is at the heart of the often-used wingspan-to-height measurement/graphing exercise.

Using the classic Vitruvian Man as an example (warning: it shows his junk, out there for everyone to see), have students measure their wingspan (from middle fingertip to middle fingertip) and their shoeless height. While individual measurements will vary from student to student, the class data, when graphed, will show a clear trend. A quick calculation shows that the slope of the data is close to 1.

Some studies report that, on average, the male wingspan-to-height ratio is greater than 1, while that of women tends to be closer to Leonardo’s expected value. In males, sometimes this difference is extreme - in the 2019 NBA Draft Combine, Tacko Fall’s measurements came in with an 8-foot, 2.25-inch wingspan compared to a height of 7 feet, 5.25 inches. That’s circle-busting as far as Vitruvian Man is concerned, but not close to the record holders.

According to Rookie Wire, seven players have wingspans that are ten inches (or more) larger than their heights, with the record held by Doug Wren, whose wingspan was 13.75 inches greater than his height of 6 feet, 5.75 inches.

A wingspan-to-height ratio of greater than one doesn’t land you a starting position, though. Wren went undrafted by the NBA in 2003 but did play basketball for teams in Iceland, Montenegro, and Korea.

In many sports, the difference between wingspan and ratio is referred to as the “ape index,” and high values are seen in MMA fighters, boxers, and mountain climbers, to name a few.

Scientific American has an excellent outline for activities (along with images of a clothed Virtruvian figure) here. Still, you’ll need to adjust and adapt for whole-class activities that tie in a slope calculation. Better yet - build your own, integrating data collection, graphing, finding reliable online resources, and a template for students to draw themselves, a character, or a data outlier as Vitruvian Man.

Final note - of course, there’s an action figure.

But move his arms and legs around and boom…right back into body horror.

Thanks for accompanying us on this trip down The Science Of’s memory lane! Keep an eye out for more articles from years past coming your way.

Curiosity is what brought me here.

Teaching is what I do with it.

If you’d like to read more about education, classrooms, students, and the craft of teaching, you’ll find those stories in Teacher, Teacher.

When the Artemis II came home, it didn’t look like engineering— it looked like the sky was trying to burn the spacecraft right out of existence.

The Orion capsule hit the upper atmosphere and was quickly wrapped in a glowing sheath — the video from inside, looking out, was terrifying. It was orange and white, and flickering like it was alive. When my physics students see that kind of thing, they go right to friction. Friction opposes forward motion and produces heat. What we saw must have been due to friction.

That’s a good “gut” answer, but it’s not a good “head” answer. It feels right, but it doesn’t quite feel right when physics enters the chat.

The capsule wasn’t burning — the air was breaking.

The Orion was moving through the upper atmosphere at about 11 km per second (close to 25,000 mph). That’s so fast that air can’t act like a fluid and flow around it. The capsule was smashing through the air, colliding hard with air molecules (nitrogen, oxygen, a few trace gases). They don’t have time to get out of the way.

The air couldn’t flow, so it compressed. It got squeezed so that the same amount of air occupied less volume.

Air molecules typically move at a few hundred meters per second (around 340 m/s at room temperature). Take them, and push them into a smaller space; they’ll move faster and hit each other more often. At the atomic level, the speed of a particle is directly related to how much heat energy it has, so squeeze a gas, you get a hot gas. That’s partly why a hand pump heats up when you’re pumping up a bike tire — you’re compressing gas over and over again.

But the air in front of the Orion capsule was way hotter than a bike pump. It was heading toward 5000 degrees C, about half the surface temperature of the sun. At that temperature, particles stop being nice and start getting real. The temperature is so high that oxygen and nitrogen, normally in the air as molecules (O₂ and N₂), break apart into individual atoms.

And things keep heating up. Particles keep hitting each other. The hits get so powerful that they knock electrons off their atoms. Now, instead of a mix of atomic gases, you’ve got electrons along with positive ions (charged particles that have lost electrons). Get enough ions into the mix, and you no longer have gas — you’ve got plasma. That’s a cool name for a soup of electrons and charged particles. And it’s really, really hot.

It’s also what was glowing. Electrons will grab onto positive ions, get excited, then fall back down to their normal energy levels, and everyone will be smacking into each other. All of that creates visible light. The light of atoms being torn apart and partially rebuilding themselves, and getting torn apart again.

Quick sidebar: The communication blackout during reentry? Thank the plasma. Radio waves are blocked because the free electrons in the plasma can move fast enough to absorb and re-radiate them, preventing them from traveling through. The plasma around Orion doesn’t block all radiation—it blocks the kind we use to communicate. The capsule doesn’t disappear. It just becomes unreachable.

Everything you just read is real — we just watched it happen. The atmosphere turned into plasma because something moved fast enough that the air couldn’t behave like air anymore.

Now imagine realizing that applies to you.

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The Fastest Man Alive

That’s exactly what Ryan North does in his take on The Flash.

He lets the Flash (Wally West) reflect on his own powers—not like a superhero, but like a smart guy who’s studied up and gleefully points out where things don’t add up. And how that requires a hall pass from the laws of physics.

Let’s see how Wally explains it. The following sequence is from The Flash #31, written by North, with art by Gavin Guidry and Adriano Lucas.

Reaction time? He’s 100% right. Human reaction time is about 0.2-0.25 seconds. That’s the time it takes the brain to register sensory input (sight, hearing, touch, and taste) and trigger a motor response. Hearing and touch are a little quicker, but at the speed Wally’s running at, it doesn’t matter. By the time his brain registered that something was in his way, he would already have crashed into it. So there’s that.

Wally’s call on friction? Perfectly understandable. My students would’ve said that—but think back to the Orion capsule. Wally’s moving faster. Maybe not light speed, but a percentage of it, which is still stupid fast. Like the capsule, Wally’s not rubbing his way through the air (which is what would cause friction), rather he’s slamming into the air—the individual molecules and atoms. The air in front of Wally? Just like the air in front of the Orion, gets compressed and the temperature spikes, molecules fall apart, electrons are knocked free from atoms, and you get plasma.

Friction occurs at normal speeds and under normal conditions. The Orion capsule? The Flash? Not normal. But I love what Wally is thinking — he’s like a student who’s just realized something is wrong… but hasn’t yet followed the physics all the way down.

Short sidebar: There might be some friction as Wally initially accelerates from a standstill, but given the final speed he reaches, the time when friction is the major issue is vanishingly small.

Let’s continue on:

Alright — here we go. Now Wally brings the physics in and separates himself from the Orion. We (normies) can move fast enough that air acts like a fluid and flows around us. The Orion on reentry was moving so fast that it was compressing the air in front of it, causing it to heat up. The Flash? He’s moving so fast that the air can’t get out of the way, and before it can compress, he’s hitting it. Physically smacking into the molecules. That’s not good, as Wally explains above.

The plasma from Orion? That’s at lower speeds, not Flash speeds.

Now, the air particles cannot get out of the way, and compression occurs even more violently. We’re now in conditions where collisions become extreme enough to even consider fusion. In the Flash’s case, it’s atomic nuclei—positively charged because of the protons in the nucleus—getting close enough to stick together. And they really don’t want to do that. You need absurd energy for that to happen. It happens in the Sun. That level of absurd.

At Flash speeds? Maybe. In the most extreme collisions, some tiny fraction of nuclei might actually fuse. And if they do, you’d get exactly what he describes—high-energy particles, gamma rays, radiation you definitely don’t want to be anywhere near.

But again, let’s back away from the scary fusion for a moment. In our world, at Flash speeds, there would already be radiation present.

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Radiation isn’t some special nuclear thing. It’s just energy moving as waves. Light is radiation. X-rays are radiation. Gamma rays are radiation. Same family, different energy levels.

So the real question isn’t “is there fusion?” It’s: are there charged particles getting thrown around? The moment the answer is yes, you’re going to get radiation. And the second the air turns into plasma—which we already walked through—you’ve got exactly that situation.

You’ve got free electrons, positive ions, and everything colliding, changing direction, speeding up, and slowing down. It’s chaos at the particle level. And charged particles that accelerate give off radiation.

Not “sometimes.” Not “if conditions are right” — always.

Electrons get knocked loose → radiation.
Electrons slam into ions → radiation.
Electrons get captured again and drop to a lower energy state → radiation.

And to answer your radiation question, yes—in our world, this is dangerous. Not in a vague way, but in a very specific, physics-has-names-for-this way. You’d be producing X-rays from electrons slamming to a stop (bremsstrahlung), visible and ultraviolet light from electrons dropping back into atoms, and at higher energies, even gamma rays. In other words: not just heat, but radiation that can ionize, damage, and destroy matter—including you. Bad bad bad.

So by the time the Flash is even thinking about fusion—nuclei sticking together, which is actually very hard to do—the situation is already out of control. The air is plasma, the particles are colliding, and radiation is already pouring out of the system.

Fusion isn’t step one.

Fusion is what you get if you somehow make an already catastrophic situation even worse, which is kind of the running theme here. You don’t need nuclear reactions to make this deadly.

You just need to take ordinary matter, hit it hard enough, and let physics take over. Things get bad very quickly.

Mr. Fusion

So let’s go with Flash’s claim that fusion is—or should be—starting to happen. Thankfully, it’s not in the DC Universe (because the DC Universe has magic. More on that in a second). That’s very cool from the physics side of things, but very, very bad from the “continuing to live” side of things.

Fusion is what happens when atomic nuclei—the dense, positively charged centers of atoms—are forced close enough together that they stick and form a new nucleus. The problem is that those nuclei repel each other. Strongly. So getting fusion requires collisions energetic enough to overcome that repulsion and push them into contact long enough for the strong nuclear force to take over. That’s why fusion is hard in stars and even harder in labs. You don’t get it just because things are hot—you get it because things are absurdly energetic.

If we’re willing to say the Flash is moving fast enough to reach that regime, then what’s happening at the leading edge of his motion isn’t just plasma anymore. It’s a region where bare nuclei—nitrogen and oxygen nuclei from the air—are colliding at energies high enough that, occasionally, a pair doesn’t bounce apart. They fuse.

And when they do, something important happens.

The new nucleus that forms has slightly less mass than the two nuclei you started with. That “missing” mass hasn’t vanished—it’s been converted into energy. This is the part you’ve heard before, but it matters here in a very literal way:

E=mc²

Yep = the energy contained in matter is equal to the matter’s mass multiplied by the speed of light (3.0 x 10⁸ meters per second), squared.

Because the speed of light (“c”) squared is such a huge number, even a tiny loss of mass turns into a large release of energy. Not in a vague, hand-wavy sense—very specifically, and very violently. Collision by collision. And there can be many collisions.

That energy doesn’t come out as a gentle warming of the air. It comes out as high-energy radiation and fast-moving particles. Gamma rays. Subatomic fragments. Nuclei and protons kicked away at high speed. In other words, every fusion event is a tiny burst of energy that doesn’t stay put—it punches outward into whatever is nearby.

And that’s where this stops being a single reaction and becomes a problem.

Because those particles and that radiation don’t just leave the system. They interact with it. They slam into the surrounding plasma, dumping more energy into it, driving more collisions, raising temperatures, and increasing the likelihood that more nuclei will collide with enough energy to fuse. You don’t get one neat fusion event at the front of the Flash. You get a cascade—small, sporadic nuclear reactions feeding energy back into an already violent environment.

So if you take the comic seriously on this point, what the Flash should be carrying with him isn’t just heat, or even just plasma. It’s a moving region where nuclear reactions occasionally occur, where energy is released as radiation and particle showers, and where that energy continuously feeds back into the system.

At that point, the situation isn’t about “running fast” anymore. It’s about driving the atmosphere into a regime where the nuclei themselves start to stick, and every time they do, they release energy in the worst possible way—outward, into everything around them, including him.

Fusion doesn’t replace the plasma problem.

It sits on top of it—and makes it violently worse.

And the Flash actually explains that pretty well, too.

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The End of the Flash?

The Flash finishes his reflection on his powers in the worst possible way.

If all of that is happening—if the air has gone from gas to plasma, if collisions are dumping energy into the system faster than it can dissipate, and if even a fraction of those collisions are crossing into fusion—then there isn’t really a “runner” anymore.

There’s just energy being released along a path.

Wally’s line about nanoseconds matters. At these speeds, everything we’ve been talking about—compression, ionization, radiation, even the possibility of fusion—is happening incredibly fast. Not over seconds. Not even over milliseconds. Over billionths of a second. There’s no time for the system to stabilize. No time for heat to spread out. No time for anything to behave gently.

Energy gets dumped into the air all at once. When you release a large amount of energy into a small region in a very short time, physics has a name for that.

Explosion.

Not metaphorically. Not “like an explosion.”

An explosion.

The “mushroom cloud” line isn’t comic book exaggeration—it’s a rough description of what happens when hot, energized material expands outward rapidly and drives a shockwave through the air. That’s exactly what you’d expect if you took everything we’ve just walked through and let it run to completion.

So the panel lands the conclusion, even if it takes a slightly messy path to get there:

At those speeds, you don’t stay a person moving through the atmosphere. You become a moving release of energy.

That’s the point where the character stops being about speed and starts being about survival. Because if this is the physics—and it is, just pushed to an extreme—then there are only two options: either the Flash doesn’t exist,

or the rules do not apply to him.

In the comics, that answer has a name: the Speed Force. It’s not a boost or an upgrade. It’s a workaround.

Created by Mark Waid in The Flash (vol 2) #91 in 1994, the Speed Force is just that—a little wink, a nod, and an awe-inspiring sense of the DC Universe’s unknown, and possibly unknowable cosmos. Waid — no physics slouch—knew what he was doing when he created it. It’s not just a “magic” get-out-of-jail-free card—it was created as something more, and became even more than that.

The Speed Force is a way to run without turning the air into plasma, without dumping his kinetic energy into the world, without becoming the explosion that physics insists he should be. Without it, the Flash doesn’t outrun anything.

Given the quasi-spiritual nature of the Speed Force, a member of the “Flash Family” in the DC Universe that somehow rejects the protection it grants and can still run at “Flash” speeds has just signed their death warrant—and that for thousands of people around them when they take their final run.

Thankfully, Wally isn’t down with that.

Of Spacecraft and Superheroes

We just watched a spacecraft survive this.

That’s the part that’s easy to miss.

When Artemis II’s Orion capsule came back to Earth, it didn’t glide through the atmosphere. It didn’t slip past the air. It slammed into it, turned it into plasma, and then survived by managing the energy involved as carefully as humanly possible. Heat shields. Ablation. Angles of entry are calculated to within a degree or less. Everything about that moment was engineered around one idea:

Don’t let the physics win all at once.

And even then, it’s not comfortable. It’s not gentle. It’s a controlled argument with the atmosphere that the spacecraft only barely wins. Now take that same process and scale it up.

Faster speeds. More energy. Less time for anything to spread out or dissipate. Strip away the heat shield. Strip away the careful entry profile. Replace it with a person taking a step.

That’s the Flash.

Not the lightning. Not the blur. Not the cool pose mid-stride.

The physics. The part where the air stops behaving like air, where matter starts coming apart, where energy stops being something you carry and starts being something you release. The realization—quietly sitting inside those panels—is that this isn’t a problem you solve by trying harder.

You don’t train your way past it. You don’t build better muscles or faster reflexes.

You don’t win.

Unless you change the rules.

So the story does exactly that. It gives him something the Orion capsule doesn’t have and never could: not better engineering, but an escape hatch. A way to run without triggering everything we just walked through.

A way to move without turning the atmosphere into plasma, without dumping his kinetic energy into the world, without becoming the explosion physics insists he should be.

It gives him the Speed Force.

Not a cheat, a requirement. Because the universe already lets things move that fast. We see it in particle accelerators, in cosmic rays, in the jets of distant black holes.

It just never lets anything survive it.

Orion survives by respecting that boundary.

The Flash survives by stepping outside it.

And if you watch that reentry footage again—the glow, the plasma, the silence—you can almost see the moment where the real world stops…

…and the Speed Force would have to take over.

Final sidenote: for another version of this, that both The Flash and this article give a relativistic hat tip to, check out the GOAT, Randal Munro’s explanation of what would happen if a baseball were pitched at near light speed. Spoilers - same as here. Nothing good.

In Project Hail Mary, Astrophage is both the miracle and the problem.

It eats starlight—that’s the name: astro, “star,” and phage, “eater”—stores absurd amounts of energy, and somehow turns that energy into propulsion and survival. It’s the central problem in the story—and at the same time, the only reason any of it works.

Science tends to do that. The same idea can be both the problem and the solution, depending on where you’re standing. So let’s get into the science of Astrophage.

The quick version is simple: if Astrophage were real, it would change everything. It does inside the world of Project Hail Mary. So instead of treating it like fiction we hand-wave past, we’re going to take it seriously—real physics seriously—and see how far that gets us.

Out of the gate, it’s tempting to compare Astrophage to a plant. It eats sunlight. It reproduces. Is the Sun just being overgrown by space kudzu?

Not quite.

A better starting point is this: Astrophage behaves more like a microscopic space whale.

Whales don’t stay in one place. They feed in one part of the ocean, migrate across vast distances, and reproduce somewhere else entirely. Their lives are defined by moving between environments that provide different resources.

Astrophage is doing the same thing. Just replace oceans with space, plankton with starlight, and breeding grounds with Venus. That analogy gets us in the door—but it doesn’t go far enough.

Astrophage isn’t just biology. It’s a system that sits at the boundary of biology, chemistry, and physics—one that has access to energy on a scale that looks less like life on Earth and more like a particle accelerator.

More CERN than a cell.

Let’s build it up.

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Astrophage: Physical Characteristics

Astrophage is a life form that exists in the extreme environment of stellar surfaces, making it hyperthermophilic, capable of thriving at temperatures that would destroy most life on Earth. Astrophage cells are on the order of 10 micrometers (microns), which places them in the same range as Earth-bound eukaryotic cells, and roughly the same size as human cells. As Grace finds out in Project Hail Mary, Astrophage is extremely similar to Earth-based eukaryotic cells (cells with a nucleus surrounded by a nuclear membrane and specialized organelles), strong enough that panspermia is proposed as an explanation for the origin of life on Earth.

A Life on Earth Aside: Panspermia is the idea that life didn’t start on Earth; it arrived here. Not fully formed organisms, but the raw ingredients or early microbial life, hitching rides on comets, asteroids, or interstellar dust. Space, in this view, isn’t empty. It’s a delivery system. Rocks get blasted off one world by impacts, drift for millions of years, and—if the physics lines up—land somewhere else with their biological cargo still intact. Panspermia doesn’t explain how life begins. It just punts the question elsewhere.

What it does say is that life might spread. It might be resilient enough to survive vacuum, radiation, and time—and if that’s true, then biology isn’t a local accident. It’s something that can leak from world to world.

Like life on Earth, Astrophage appears to be carbon-based, contains water, and has very similar organelles.

While alive, Astrophage cells are effectively opaque across the electromagnetic spectrum and have a super-strong outer coating capable of withstanding the vacuum of space and the stellar corona. Despite its strength, the Astrophage coating can be pierced by something very sharp, such as the nanoneedle Grace used, which unexpectedly killed the cell. When Astrophage dies, they become translucent or clear, revealing their internal structure.

For Astrophage, that line between life and death comes down to one thing: energy.

Astrophage: Diet

Astrophage derives its energy from starlight. Rather than just the visible light that Earth’s plants absorb, Astrophage absorb across the entire electromagnetic spectrum. The preferred habitat of Astrophage is a star’s corona, giving it direct access to the energy being released. It’s the “infection” of the opaque Astrophage in the outer layers of the star, which blocks energy from the sun, causing it to dim. It’s like a mold growing across a clean window - as it grows, more and more light is blocked, and less light can enter.

The “how” of Astrophage eating all the energy produced by a star is the result of a property referred to as “super cross-sectionality.” And it’s poorly understood— that is, it shouldn’t work, but it does. Thanks to this property, nothing — nothing — can pass through Astrophage, not even neutrinos (which normally pass through matter almost without interacting) or subatomic particles that should be able to quantum tunnel through it. Weirdly, Astrophage also blocks wavelengths of light longer than its own size.

Light Interaction Aside: This is the diffraction limit, the reason why light microscopes only work up to a point. If an object is smaller than the wavelength of light, the light diffracts around it, instead of reflecting off of it, making it functionally invisible to that light. At 10 microns, Astrophage are larger than visible wavelengths (Grace can see them with a standard light microscope). Longer-wavelength radiation, such as infrared and radio waves, is also stopped by Astrophage, which is impossible according to physics as we know it. How? Super cross-sectionality. In short, nothing gets through, which is why Astrophage makes excellent heat and radiation shielding, and kind of a problem when they’re dimming your star.

And to make one thing clear: if Astrophage follows biological rules, we can ratchet back some of the hyperbole about what it does. Astrophage isn’t a “star-killer.” It doesn’t extinguish a star; it just turns it down. The Astrophage population in a system will stabilize at whatever level the star can support, given incoming energy, reproduction rate, and losses to predation and other unknowns.

So, like so many biological systems, Astrophage won’t destroy the system. It finds a balance point and holds.

Astrophage: Diet, part 2

What does Astrophage do with the energy it absorbs? Here’s where things get really cool.

Astrophage converts energy into mass. No other form of life we know does this. Not plants, not us, not chemotrophs living near deep-sea vents. This makes them unique. The core idea is simple. Start with the equation that everyone knows from Einstein: E = mc². That’s what underlies atomic energy, nuclear weapons, and a lot of subatomic physics. But that’s not what Astrophage does. They reverse it.

Just solve that equation for mass. That is, m = E/c². That’s it.

In theory.

Prior to their discovery in Project Hail Mary, the idea of energy-to-mass conversion was full-on bonkers, both that it could happen at all and that it could happen in something alive.

The “how” of it all going on inside Astrophage goes pretty deep into particle physics. We’ll try to stay shallow…

Astrophage are basically tiny biological batteries—but they don’t store energy the way anything on Earth does. They have a “sweet spot” temperature: about 96.4°C. That’s their critical temperature. At that exact temperature, something wild happens—when two protons (just hydrogen nuclei) slam into each other, their motion can turn into neutrinos, in a way that shouldn’t be possible under known physics. Neutrinos are tiny, almost massless particles that barely interact with anything.

Now here’s the trick: if the Astrophage gets hotter than that, instead of heating up more like normal matter would, it just keeps converting that extra heat into more neutrinos. So the temperature stays locked right around that same point. It’s like a built-in thermostat—but instead of turning off a heater, it converts heat directly into mass.

So even sitting near a star, where temperatures should keep rising, Astrophage just… doesn’t get hotter. It absorbs the energy and packs it away. And it packs a lot.

A single Astrophage cell can store about 1.5 megajoules of energy—an enormous amount of energy for something microscopic. Then, when it needs that energy back, two of those neutrinos collide and turn into light—specifically a very precise kind of infrared light called the Petrova wavelength.

That light does three jobs: it can power the Astrophage’s internal processes, warm it back up if it cools down, and, most importantly, be fired out the back of the cell like exhaust, propelling it forward.

Astrophage’s diet is directly connected to its motion. There are no flagella, cilia, or pseudopods to move them — they’d be useless in space anyway — there’s nothing to push back against. They use rockets. “Toot to scoot,” as Grace put it. Astrophage converts stored energy into light and blasts it out, which pushes them forward. And because the energy density is so high, they can accelerate to ridiculous speeds—up to about 92% the speed of light (2.76 x 10⁸ m/s, or about 617,000,000 miles per hour).

Light Propulsion Aside: Astrophage is essentially a biological version of laser propulsion. Photons don’t have mass, but they carry energy—and that energy carries momentum. Laser propulsion leans on that. Shine a powerful laser at a spacecraft, and the light hitting it delivers a tiny push. It’s small, but continuous, so over time it adds up and accelerates the craft. The problem is that the energy required is enormous and expensive. Astrophage is doing the same thing, with no external fuel cost, just converting its own stored mass into energy. Instead of an external laser, it generates its own light and fires it out in a tight beam. That beam carries momentum away, and the Astrophage gets pushed in the opposite direction. It’s basically a self-contained laser drive: no traditional propellant mass. Just light doing the pushing.

Astrophage is wild because it’s not running on the kind of chemistry life on Earth depends on. No sugars, no ATP, no familiar metabolic pathways. Instead, it’s tapping directly into mass–energy conversion—the kind of physics we usually only see in stars and nuclear reactions.

Life on Earth lives in the shallow end of the energy pool, moving electrons around. Astrophage is down in the deep end, where energy and mass are interchangeable.

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Astrophage: Migration

Astrophage has effectively unlimited food coming from a star, a mechanism that allows it to convert all of that energy into mass, as well as a mechanism for keeping its body temperature at a comfortable (for it) 96.415^oC. Why would it ever want to go anywhere else?

Two reasons: reproduction and colonization.

The first — that’s the easiest one to understand. Once Astrophage is full of energy (there is an upper limit - about 1.5 megajoules of energy, about 17 nanograms of neutrinos), it’s stuffed, and time to reproduce.

Energy Aside: “mega” = millions, so a single Astrophage cell can hold 1.5 million joules. “Joules” is the unit of energy (it underlies all energy measurements, even the kilowatt hours of electricity that electric companies bill us for), and 1.5 million joules is considerable. For instance, at 1.5 megajoules, a single Astrophage cell is carrying about 360 food calories of energy. That’s a full meal. Not a snack—an actual, sit-down, plate-of-food meal. Or, if you want to talk water, a single Astrophage cell can store enough energy to raise roughly a gallon of water from room temperature to boiling.

That is an absolutely stupid amount of energy for something microscopic to be carrying around.

Okay - so it’s full of energy, and it’s time to reproduce. There’s a catch: while an Astrophage converts energy into mass, it still requires specific elements to replicate through mitosis. Over millions of years, Astrophage has evolved to seek out planets with abundant carbon. Again, an Astrophage may be a space-bound organism, but it’s similar to us and, like us, it’s carbon-based.

Using our solar system as an example, Astrophage migrates to Venus, which has an atmosphere made of 96.5% carbon dioxide and 3.5% nitrogen. Getting there, no problem. But “seeing” Venus? That’s a trick.

Astrophage doesn’t “see” as we do. No eyes, no images. What they can detect is the spectrum of light, which wavelengths are present and which are missing. When light passes through a planet’s atmosphere, certain gases absorb very specific wavelengths. Carbon dioxide, for example, absorbs particular parts of the infrared spectrum. So what’s left in the light carries a fingerprint.

A CO₂-rich world leaves behind a very distinct pattern—a set of “missing” wavelengths in the light coming off that planet or its star. Astrophage can detect that pattern. It’s like they’re reading the barcode of the atmosphere.

Once spotted, it’s time to go, and boy, do they go. Millions, billions follow the same path to get to the planet, all jetting along at near-light speed, so it’s a short trip. At full burn, Astrophage could cross the distance from the Sun to Venus in about six to seven minutes.

As they propel themselves through space, the Astrophage’s “jets” (toot to scoot) release infrared radiation at a wavelength of exactly 25.984 microns. That’s what was discovered by Dr. Irina Petrova, the Russian scientist who first spotted the infrared “line” connecting the sun and Venus. The Petrova line is the signal of Astrophage infection in a star system.

The quick travel time between the Sun and Venus assumes Astrophage is at top speed the whole way. Realistically, you’d have a short acceleration phase—but given how absurd their acceleration is, it barely changes the answer. And they don’t slow down when they get to their target. They air-brake. Astrophage rely on the planet’s atmosphere to slow them down— they hit the atmosphere. Hard.

Traveling at such high speed and hitting the atmosphere would destroy any human-sized ship, but for the microscopic Astrophage, it’s no big thing. Compressing air in front of them heats it to ridiculous levels, and they just gobble that energy, turning it into mass, replacing the mass converted to energy for their flight to the planet. With atmospheric deceleration, Astrophage stops when the air pressure is 0.02 atmospheres. Once there, it takes in carbon dioxide to produce biomass for the daughter cells and undergoes mitosis, splitting into two cells.

Astrophage: Migration, 2

Astrophage’s other large-scale movement comes from cells presumably forming spores and traveling to other, uninfected stars. The limit of this travel seems to be about eight light-years, the distance between nearby stars. The reason for this behavior is unknown, but, like Astrophage itself, most likely just biology doing biology.

When conditions are good, life grows. When things get crowded or uncertain, it spreads. On Earth, that looks like spores, seeds, bacteria drifting on air currents—millions launched, most failing, a few landing somewhere that works. That’s bet-hedging. You don’t need all of them to survive. You just need enough.

Astrophage follows the same strategy, just scaled up. A star is a finite resource. Upon finding a star, the population of Astrophage grows exponentially and reaches some carrying capacity. This would— if biology is universal— trigger some fraction of the population to break off, launch itself into space, looking for the next star. Not randomly—they follow light signatures, the spectral “fingerprints” that tell them where conditions might work. It’s not an invasion or even action undertaken with an intention. It’s reproduction, dispersal, and gradient-following, the same playbook life uses here, just written across stars instead of soil.

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Astrophage: Ecology

That spread we just talked about? Astrophage isn’t evil. It just is biology doing biology. Life being all life-y. Its home system, the place where it evolved, is Tau Ceti, where Grace and Rocky discover each other. In that system, Astrophage feeds off of energy from Tau Ceti and reproduces on Tau Ceti E (“Adrian”). But what Grace and Rocky discover is that Adrian is home to a rich biosphere, including Astrophage’s natural predator — the Taumoeba.

Star Course Aside: If Astrophage is the problem, then Tau Ceti looked like the place where Astrophage was either behaving differently or being actively reduced. The Petrova line is the fingerprint of Astrophage metabolism, and Tau Ceti’s strong signal meant that its metabolism is being pushed hard or disrupted. That’s exactly where you look for a solution. The Hail Mary wasn’t sent to Tau Ceti because it was close, interesting, or habitable. It was sent there because, in a sky full of stars being drained, Tau Ceti looked like it might be fighting back.

On Adrian, the Taumoeba keeps the Astrophage population in check by eating it. The presence of a predator is the strongest signal that the system is Astrophage’s home - predators don’t show up before prey. Taumoeba don’t show up unless there’s a long-standing, stable food source to evolve with. Predators are a response to the presence of prey.

Find a creature that specifically hunts Astrophage? Two things are almost certainly true:

First, Astrophage have been present there for a long time—long enough for natural selection to shape something that can find them, catch them, and survive off them. Second, the environment consistently supports that interaction. Not a one-off arrival. A system.

Mirror it to Earth.

Specialized predators don’t show up for something that washed up on the island last week. They show up where the prey has been long enough and abundant enough to matter. That kind of specialization takes time. Taumoeba tells you Astrophage weren’t just passing through the Tau Ceti system. They were native, persistent, and abundant enough for evolution to build around them.

And that’s the real point: Taumoeba isn’t the headline, Astrophage is. From an evolutionary perspective, Astrophage isn’t just an organism. It’s a massive, reliable energy source. And life does not ignore energy like that.

So in the Tau Ceti system, Astrophage is pretty benign. The system, including Astrophage on the star, is stable. Astrophage doesn’t grow unchecked, dimming the star and upsetting the energy balance on Adrian and other planets of the system where life probably exists.

Seen through this lens, Astrophage is an invasive species. A really good one at that. And in Earth’s system as well as Erid’s, Astrophage found an environment with no natural predator, and its population increased at a predictable exponential rate.

Earth version? Think wolves and deer. When deer have plenty of food and no predators, their population explodes. They overgraze, strip the environment, and start to crash under their own success. Introduce wolves, and everything changes.

The wolves don’t wipe out the deer. They keep them in check. The deer population drops to a sustainable level, vegetation recovers, and the whole system stabilizes. Predator and prey rise and fall together, but neither takes over completely. That’s the Astrophage–Taumoeba relationship.

Without the predator, the system gets overwhelmed. With it, the system finds a steady state.

Same biology. Just scaled from forests… to stars.

First — I teach physics.

Ask me what I love most about Andy Weir’s Project Hail Mary? The moment I realized I was never going to be without a copy of it?

It happens in the first chapter, and most readers probably glide right past it, because…math.

It starts with a problem I’ve used on physics tests for years — one that always makes my students look at me and ask, “When would this ever happen?” I feel so very validated. Thanks, Andy. Because suddenly that ridiculous physics-test question had a real-world use.

In the opening pages of the novel, Ryland Grace wakes up unsure of where he is — or even who he is — but aware enough to notice that something feels off. Following up on those instincts, he does a physics experiment.

In chapter freakin’ 1.

AMAZE!

Let me just grab a quick (non-copyright violation) taste of that sweet, nerdy angle, Ryland Grace:

In quick order, Grace drops a test tube off a table that’s 91 centimeters off the floor.

But he doesn’t trust a single measurement. Grace repeats the drop twenty times and averages the results. That’s not just good science fiction — it’s good science. When your stopwatch reaction time might be two-tenths of a second, and the fall only lasts three-tenths of a second, repeating the experiment is the only way to get a reliable number.

Grace writes all the times on his arm (he hasn’t found paper yet), and finds that, when the measurements are averaged, it takes 0.348 seconds for the test tube to hit the floor. He’s got data, and the data supports the “off” feeling he has.

Now he can get to work.

But before that, just a quick shout-out for this entire scene. Grace’s memory is gone, but his scientific habits survived. And that’s actually one of the smartest character signals in the entire opening scene, and one that many of us with decades of science training and teaching know too well. It tells us something important before the plot even starts moving: the man may not remember who he is, but he’s still a scientist.

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How Grace’s Body “Knew”

Before the math shows up, Grace’s body already knew something was wrong. To understand that, we have to sidestep physics for just a second.

Humans evolved inside a very particular environment: one planet, one atmosphere, and one gravitational field pulling downward at about 9.8 meters per second squared (32.15 feet/second²). Every movement you make—standing up, catching a ball, dropping a set of keys—happens inside that invisible constant. Everything speeds up downward at that rate — about 9.8 meters per second faster every second.

Over a lifetime of countless observations, your nervous system builds a model of it.

Your inner ear, deep inside the skull, is constantly measuring acceleration. Tiny fluid-filled canals shift when your head moves, letting your brain know when you start, stop, or change direction. Your muscles and tendons are doing their own measurements at the same time, sensing force and balance. And your brain is always predicting what should happen next—how fast something should fall, how hard you should land, how much force it takes to lift something.

Most of the time, you never notice this system running — it’s automatic.

But it means that when gravity changes—even a little—your body notices immediately.

• Drop something, and it hangs in the air a fraction longer than it should.

• Jump, and you rise just a little too easily.

• Your sense of weight shifts.

You don’t reach for a calculator. You just feel that something is off.

The universe is no longer behaving the way it always has.

It’s why the footage of astronauts on the moon looks weird (not faked, it just looks weird). The moon’s gravity is 1.6 m/s². Literally, things fall more slowly on the moon. There’s less “pull” downward on them than there is on Earth. Watching astronauts move across the lunar surface can feel eerie — something in our brains tells us that’s not how things should be.

That’s the moment Ryland Grace hits in the opening pages of Project Hail Mary. Before he remembers who he is, before he understands where he is, his brain notices the mismatch. The falling object takes too long, and that tiny delay is enough to trigger the most basic scientific response there is: that’s weird.

In a minute, we’re going to run the exact same experiment Grace does, but to get back to the story — Grace hasn’t recovered his memory yet, but the part of him that understands gravity is already awake.

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Back to the Math

Once Grace notices the fall feels wrong, the next step is the same one scientists have been doing for centuries: estimate first, calculate second. The physics of falling objects is about as simple as it gets. If something drops under gravity alone, the distance it falls is given by the formula:

d = ½gt²

Every intro physics class on Earth eventually meets this equation.

That is, the distance (d) something falls is equal to one-half multiplied by the gravitational acceleration ( g = 9.8 m/s² on Earth) multiplied by the time it takes the object to fall, squared. In other words, the distance an object falls depends on how strong gravity is, and how long the object has been falling.

In most physics classes, we solve this equation for the distance, not for g. But Grace isn’t in a physics class. If you want to solve for gravity instead, you just rearrange the equation:

That’s the version Grace is working with.

Now plug in what he observes. The object falls about 3 feet, which is roughly 0.91 meters. And the fall takes about 0.348 seconds.

Put those numbers into the equation and you get a gravitational acceleration of about 15 m/s².

Again, on Earth, gravity is about 9.8 meters per second squared.

So wherever Grace has woken up, the gravity is only about one and a half times that of Earth.

That’s a huge difference. In a place like that, everything would feel heavier. Grace couldn’t jump as high, and objects would fall faster (and hit harder, as Grace learned). Movements would feel heavier and more deliberate. Anything that depends on gravity would happen faster.

Grace takes this result and reaches one of two possibilities: he’s either somewhere with stronger gravity than Earth, or — thanks to Einstein’s equivalence principle — he’s inside a sealed chamber accelerating at 15 m/s².

Don’t worry — I didn’t ruin either the book or the upcoming movie for you. There’s a lot more for Grace to figure out before he fully realizes where he is. This happens in the first few pages.

Try It Yourself

You can do the same experiment Grace did here on Earth — just duplicate his method. Drop something a bunch of times. Aim for at least a meter of drop height, because your reaction time (how quickly you can start and stop a stopwatch) is locked in at about 0.250 seconds. Grace’s 91 centimeters? Right at the edge of the sweet spot.

Take lots of measurements — 20 repetitions wasn’t overkill, it was a best practice, given that human reaction time was involved. Drop something that’s streamlined — a test tube was perfect. You can use a pen or something similar. Do the same math as above, and see what you get.

And Just In Case…

If you’re feeling like my old students and thinking this is all very contrived…shhh. Just read the book (you have a little bit before the movie comes out). It all makes perfect sense.

Drop something and see what gravity says.

One Final Note

Just in case you’re a STEM Teacher, I did run this question by my physics class, and they loved the heck out of it, particularly the question of “logically, what can Ryland Grace conclude from his finding?”

They all answered it pretty quickly, and pretty well. I’ve got a room full of would-be saviors of the earth in first period.

In Hulk Smash Everything #1, the Leader comes up with a simple solution to his Hulk problem: remove him from the present entirely. Instead of fighting Hulk directly, he throws him backward through time—far enough that the Hulk simply can’t get back.

Where does he land?

About 66 million years ago, at the very end of the Cretaceous Period.

The Hulk has always had strong ties to science—and because of that, he’s long had an outsized pull on scientists and (ahem) science teachers. This series, Hulk Smash Science, takes a closer look at the real science behind those stories.

Let’s go!

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The Worst Place the Leader Could Send the Hulk(*)

In Hulk Smash Everything #1, the Leader comes up with a simple solution to his Hulk problem: remove him from the present entirely. Instead of fighting Hulk directly, he throws him backward through time—far enough that the Hulk simply can’t get back.

Where does he land?

About 66 million years ago, at the very end of the Cretaceous Period.

Geologists call this moment the Maastrichtian, the final stage of a world dominated by dinosaurs for more than 160 million years.

It’s a good choice on the surface. The Leader didn’t just send Hulk somewhere vaguely in the distant past, like a villain with access to a time machine but no clear grasp of history. Nope—the Leader dropped Hulk into one of the most dangerous moments in Earth’s history: the last quiet minutes before the asteroid arrives.

Before we get to that asteroid, though, we need to understand just how much history has already happened before Hulk arrives.

To do that, we need to talk about deep time.

The History Beneath Hulk’s Feet

Scientists use the phrase deep time to describe the enormous span of Earth’s history. Human history covers thousands of years. Recorded civilization spans perhaps ten thousand.

Earth’s story unfolds across billions. The planet formed about 4.54 billion years ago, when dust and rock in the early solar system collided and merged to form the young Earth.

Not long after the planet cooled enough for oceans to exist, life appeared. The earliest evidence dates to roughly 4.28 billion years ago, when microscopic organisms were already thriving in ancient seas. It took about 628 million years for life to appear on the newly formed Earth. Through the lens of deep time, that’s practically an eyeblink.

For most of Earth’s history, life was microscopic. Tiny organisms dominated the planet for billions of years, gradually reshaping the chemistry of the oceans and atmosphere.

One of the most important transformations happened around 2.4 billion years ago, when photosynthetic microbes began releasing large amounts of oxygen into the atmosphere. This event—known as the Great Oxidation Event—fundamentally changed Earth’s environment and helped make more complex life possible.

Much later, around 540 million years ago, animals with shells, skeletons, and complex body plans began appearing in the fossil record during the Cambrian Explosion. From that point forward, ecosystems became increasingly complex.

Over the hundreds of millions of years that followed, continents drifted, oceans opened and closed, and ecosystems rose and vanished again and again.

By the time the Hulk arrives 66 million years ago, Earth has already hosted life for more than 4 billion years.

The ground beneath his feet contains the remains of countless earlier worlds. Layer upon layer of ancient rock preserves organisms that lived hundreds of millions of years ago. Fossils from long-vanished oceans, forests, and coastlines lie buried deep beneath the surface.

Even the oil and natural gas deposits we rely on today began forming long before Hulk arrived. Petroleum originates when enormous quantities of microscopic marine organisms sink to the seafloor and become buried under sediments. Over tens of millions of years, heat and pressure transform that buried organic material into hydrocarbons (which will return for a cameo next time).

Beneath Hulk’s feet lies a stack of ancient worlds—oceans, forests, and reefs that lived and died hundreds of millions of years before dinosaurs ever appeared. So when Hulk lands in the Late Cretaceous, he isn’t stepping into the beginning of Earth’s story.

He’s arriving very late in it.

And the world he sees is only one more chapter in a very long history.

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North America, 66 Million Years Ago

The next surprise Hulk would notice is that the continent doesn’t look the way it does today.

The asteroid that will soon strike Earth will hit near the modern Yucatán Peninsula, at the location now known as the Chicxulub crater. Today, that region is covered by dry tropical forest.

But 66 million years ago, it looked more like coastal Florida or the Bahamas.

Sea levels were much higher than today, and the Yucatán region sat on a warm, shallow marine platform filled with lagoons, reefs, and low limestone islands.

Most evidence suggests the asteroid struck shallow ocean water, roughly 100–300 meters deep. So Hulk probably wouldn’t be standing in dense inland jungle near the impact site. Instead, he’d likely be somewhere along a tropical shoreline, surrounded by coastal wetlands and warm, shallow seas.

In fact, issue #1 seems to place Hulk in almost exactly the right environment. The panels show him fighting small raptor-like dinosaurs along a tropical coastline dotted with palm-like trees and low rocky outcrops. That setting lines up well with what scientists think the Yucatán region looked like at the end of the Cretaceous—a warm coastal landscape along the edge of a shallow sea.

Zoom out further, and we see Hulk fighting on a peninsula-like stretch of land jutting into the ocean—something that closely resembles reconstructions of the ancient carbonate platforms that once formed much of the Yucatán region.

If that interpretation is right, Hulk wasn’t placed randomly in the dinosaur world.

He’s standing very close to one of the worst possible places on Earth to be 66 million years ago.

But the continent’s most important geographic feature at this time lay farther north. Instead of a single continent, Hulk would be looking at a North America split nearly in half by a warm inland ocean.

For tens of millions of years, a vast inland sea called the Western Interior Seaway stretched from the Gulf of Mexico to the Arctic Ocean, covering areas that are now Kansas, Nebraska, South Dakota, and eastern Colorado.

By the time Hulk arrives, the sea is retreating—but its influence (and its salt, which we still mine today) is everywhere. The continent remains divided into two regions:

To the west lies Laramidia, a narrow strip of land squeezed between the rising Rocky Mountains and the inland sea.

To the east lies Appalachia, a much older landscape built around the worn-down Appalachian Mountains.

Laramidia is where most of the famous dinosaur fossils are found today.

The environment there would feel surprisingly familiar to modern Americans. Imagine a prehistoric version of the Mississippi River basin or the Gulf Coast wetlands—broad river valleys, seasonal flooding, dense vegetation, and enormous floodplains stretching for hundreds of miles.

These landscapes supported vast herds of plant-eating animals.

And where there are herds of herbivores, there are predators.

The Dinosaurs of This Ecosystem

By the end of the Cretaceous, dinosaur ecosystems were highly developed and diverse.

Large herbivores dominated the floodplains. Among the most common were duck-billed dinosaurs like Edmontosaurus, animals up to 12 meters long that grazed on vegetation using hundreds of tightly packed grinding teeth known as dental batteries.

Nearby moved horned dinosaurs like Triceratops, massive animals roughly the size of elephants but equipped with three horns and enormous bony frills protecting their necks.

At the top of this ecosystem stood Tyrannosaurus rex.

At roughly 12 meters long and weighing several tons, T. rex was one of the largest land predators that ever lived. Biomechanical studies suggest its bite force exceeded 30,000 newtons (about 3-4 times the weight of a typical car), powerful enough not only to slice flesh but also to crush bone.

Sharing the environment were smaller, feathered predators such as Dakotaraptor, agile hunters armed with curved sickle claws on their feet. Overhead flew birds—small feathered descendants of earlier dinosaur groups, because birds didn’t replace dinosaurs.

Birds are dinosaurs.

By the time Hulk arrives, these ecosystems have been stable for millions of years.

Nothing about the world suggests it’s about to change.

The Hulk’s Sparring Partners

One of the fun surprises in Hulk Smash Everything #1 is that the dinosaurs Hulk encounters are actually pretty grounded in real Late Cretaceous biology. Ryan North and artist Vincenzo Carratu clearly did their homework.

Let’s play who’s who.

For help, we brought in a specialist: paleontologist Jimmy Waldron from Dinosaurs Will Always Be Awesome.

So let’s ID some dinos.

Hulk completes his time jump next to the carcass of a much larger dinosaur that’s already had its tastier bits eaten by smaller predators. From the image, it looks like a classic long-necked sauropod—the kind of enormous plant-eating dinosaur made famous by Apatosaurus and Brontosaurus. But there’s a catch.

“There was a period of time in the early days of the Late Cretaceous that we call the Sauropod Hiatus,” Waldron explains. “It was a time when we simply don’t find very many sauropod bones in North American rocks. We don’t really know why yet, and it’s very strange.”

Brontosaurus and Apatosaurus lived earlier in the Jurassic, but sauropods as a group persisted into the Late Cretaceous as titanosaurs. The panel leans into the visual shorthand of a gigantic long-necked herbivore to show just how immense the animals of this world could be.

“The only real sauropod known from Late Cretaceous North America is Alamosaurus,” Waldron says. “An absolute unit of a titanosaur, living between Utah, New Mexico, Texas, and northern Mexico.”

Given that the range of Alamosaurus may have been larger than what we’ve discovered so far—and considering its size—the half-eaten dinosaur Hulk encounters could plausibly be an Alamosaurus.

But before Hulk can get his bearings—or get us a positive ID—he’s surrounded by a group of small, fast-moving predators.

These are the raptors we were all expecting: versions of the creatures that have been haunting people’s nightmares ever since Jurassic Park arrived in 1993.

They look very much like dromaeosaurs, the same general family as Velociraptor. The long tails, narrow snouts, and raised sickle claws on their feet match what paleontologists recognize as classic raptor anatomy.

And then there are the feathers—a detail that reflects what paleontology has learned since Jurassic Park. For decades, dinosaurs were depicted as scaly reptiles, but fossil discoveries now show that many theropods—including raptor-like predators—were feathered.

In other words, the “giant murder turkey” aesthetic scientists sometimes joke about is actually pretty close to reality.

“Our raptor friends here are very Jurassified,” Waldron says, “based largely on the Velociraptors of Jurassic Park in their design and determination to rattle Hulk like a spoonful of green Jell-O.”

However, the real Velociraptor lived in Mongolia and was long extinct by this time.

“With their size and habitat range, these are likely Utahraptor,” Waldron continues. “And yes, spielbergensis was almost the species name—it ended up being Utahraptor ostrommaysi, named after two prominent raptor researchers.”

Fun fact #1: spielbergensis literally means “of Spielberg,” a nod to the director of Jurassic Park—and a shorthand scientists sometimes use for slightly fictionalized movie raptors.

Fun Fact #2: The sauropod skeleton in the Jurassic Park visitor’s center in the first film? That’s our buddy, Alamosaurus!

Fun fact #2: Dromaeosaurs and their close relatives, the troodontids, were a Late Cretaceous success story. These dinosaurs filled ecological niches across the planet, and many paleontologists think they may already have been developing flocking or pack-like behavior.

Some evolutionary biologists, including Jonathan Losos, have even speculated that if the asteroid had missed Earth—or struck harmlessly in the Pacific—raptor-like dinosaurs might have continued evolving into the planet’s dominant intelligent life.

Also notice the body plan: long balancing tails and grasping arms, exactly what you’d expect for agile predators in Late Cretaceous ecosystems.

None of the animals are drawn perfectly to scale or with museum-level anatomical precision—this is still a Hulk comic, after all. But the overall choices are impressively close to what paleontologists think actually lived in North America at the end of the Cretaceous.

So if you dropped a very large green superhero onto Earth 66 million years ago and waited for the Chicxulub asteroid to finish the job…

“Well,” Waldron concludes, “considering the geography near the impact, the giant sauropod, and the large North American dromaeosaurs, my estimation is that Dr. Banner is somewhere in central Texas—66 million years ago—smashing Utahraptors and avenging Alamosaurus.”

The Light in the Sky

And as that final panel shows, far out in space, a mountain-sized rock is already on its way.

The asteroid that will strike Earth is roughly 10 kilometers wide—about the size of Mount Everest laid on its side. It’s traveling at roughly 20 kilometers per second, or about 45,000 miles per hour.

When it strikes near the Yucatán coast, the energy released will equal billions of nuclear bombs detonating at once.

The impact will blast out a crater nearly 200 kilometers wide, launch molten rock high into the atmosphere, and trigger massive earthquakes and tsunamis.

Debris blasted into space will rain back through the atmosphere, turning the sky itself into an oven and igniting wildfires across entire continents.

Dust and aerosols will block sunlight for months to years, collapsing ecosystems worldwide.

And the world Hulk has just stepped into—this stable, thriving planet—will begin to unravel.

Not instantly.

But permanently.

Next time: the impact itself—and what happened after—in Hulk Smash Science #2.

Hulk Smash Science is a four-part series exploring the real science behind Marvel’s Hulk Smash Everything.

(*) - or so we thought! Just wait until issue #2!

All comic images © Marvel Comics, used for commentary and review.

Superman (2025) trailer © DC Studios / Warner Bros. Used under fair use.

So cool. Superman fighting a giant monster.

But a stupid voice in my head reminded me — we don’t have giant monsters in our world.

Sometimes the little kid in me shakes his fist at the universe.

The reasons why are locked in stone, as far as life as we know it on earth, and it all boils down to something called the cube-square law.

Friggin’ Laws.

As far as physics and biology go, the cube-square law is pretty straightforward: if you make an animal larger, the surface area increases by the square of the growth factor, while the volume (and mass) increases by the cube of that factor.

For instance, say you want to double (2x) the size of your pet dog. Your dog weighs 10 kg.

Your new, larger pet’s surface area would be about 4 times (2² = 4) its original size, while its mass (volume) would be 8 times (2³ = 8) more.

So far, so good. That’s just the physics – a square vs. a cube.

Now, let’s bring in some more physics and some biology.

You’re Gonna Need Thicc Legs

As everything has been getting bigger on your dog, we start to run into real problems with their legs.

Bigger muscles (to move the bigger animal) have more strength, sure, but that strength is related to the cross-sectional area (think the area of a circle, A = πr²) of the muscles and bones. Again, the mass increases by the cube, but the strength of the muscle and the bones (together = “leg strength”) increases by the square of the cross-sectional area.

It’s why elephants have uniform, thick legs.

But we’re not talking about elephants, we’re talking about your 10 kg dog. Let’s give them legs that are 2 cm in diameter (so a radius of 1 cm). Ready for some math? So am I!

Cross-sectional area of the leg:

A = πr²
A = π(1)²
A = 3.14 cm²

Your dog has a mass of 10 kg, so each leg is supporting one-quarter of that mass, in other words, 2.5 kg per leg. Per square cm, then —

2.5 kg/3.13 cm² = 0.79 kg/cm².

That’s the ratio that works for this dog, given its normal, doggy dimensions. Goof that ratio up, and things won’t work. It must be 0.79 kg/cm². That’s the stress it can handle, per leg. Yeah, dogs walking on two legs might be cool to see on TikTok, but they can’t do it for long, given this and other structural reasons (they’re not built that way).

Okay, so let’s double that dog’s size (and cube its mass).

New mass = 80 kg (10 kg x 8)

Now, each leg has to support 80/4 = 20 kg. Will that work?

Spoilers – no.

Scale up the leg size, doubling all its dimensions, making it twice as tall and twice as thick, with legs that are twice the diameter of the original. They were 2 cm, so now they’re 4 cm; therefore, our new radius is 2 cm. Running that through the same calculation as above:

A = πr²
A = 12.57 cm²
Each leg now supports 80/4 = 20 kg.

Our original ratio (for our normal-sized pup) was 0.79 kg/cm2. That’s what works for the proportions of the animal, large or small. When we run through the mass/area ratio after doubling…

20 kg/12.57 cm² = 1.59 kg/cm².

No bueno. Given the dog’s proportions, it can only handle 0.79 kg/cm². We need to pull that ratio down by making those legs thicc. How much thicker?

Well, algebra:

We divided the mass by the cross-sectional area to get the stress load. Let’s just rearrange:

mass/area = stress load.

How about —

mass/stress load = area

20 kg/0.79 kg/cm² = 25.32 cm².

That’s the area, so pull that back to get our radius from:

A = πr²
25.32 cm² = πr²
25.32/π = r²

r = 2.84 cm

diameter = 2 x radius = 5.7 cm.

Compare that to our original leg diameter (2 cm) at our original mass (10 kg). To stand up, our double dog’s legs must be 43% thicker than their original diameter. That’s just the legs – the rest of the double-sized doggo will be in proportion (which brings more problems), but those legs would be noticeably thicker. Your dog won’t look like a normal, proportionate dog anymore. It will look like there was a rhinoceros somewhere in its family tree.

The Kaiju in Superman has pretty thick legs (and big feets that need a pedi ASAP). Superman (2025) trailer © DC Studios / Warner Bros. Used under fair use

And remember, that’s the thickness of the legs for standing on all four. If our double doggo wants to stand on two legs, now that’s 80 kg of mass spread over two legs, so 40 kg per leg. A quick check of the math, and we’re now looking at legs that have to be 8.03 cm in diameter, or otherwise, they’d break from the stress load on them.

Oh, and all of this also applies to other structural elements of bodies, including those that are external. Spiders, scorpions and all insects have to obey the cube-square law. Body mass and structure limits will always be partners in a well-choreographed dance.

No dog-sized spiders are allowed on Earth.

Thicc Legs Were Just the Start

A few more issues to quickly consider that are all related to the bigger picture:

• Energy: As that volume increases by the cube, its energy demands are also going to increase…by the cube. Big, big animals need to eat a lot to keep their fires burning. There are all kinds of environmental implications with this. An enormous Kaiju has the potential to decimate populations of prey and find itself really hungry.
  
  Food is eaten, chemical bonds broken, and energy released that the animal can use. On our scale, with our metabolism, it’s what gives us our 98-ish oF body temperature.

• Heat: Animals get rid of heat through their skin, or whatever surface is in contact with the air or water around them. The surface area of the skin increases by the square, but the stuff inside — the stuff making the heat — that increases by the cube. An animal’s metabolism is responsible for the heat on the inside, and the inside increases by the cube. So, apply that to animals big and small.
  
  The smaller the animal, the faster it will lose heat, therefore the faster its “engine” is running. Mice have seriously fast heart rates. Additionally, mice must eat constantly to maintain their metabolism. On the other hand, an elephant has a slower metabolism, loses its heat slowly; therefore, it doesn’t have to eat as often, and moves on the whole, slower than smaller animals (though they can move fast when needed).
  
  Following our rules (as we understand life), Kaiju, given their huge size, would rarely eat, move very slowly, and have a serious problem with heat, due to their large volume. They’d need some mechanism for getting rid of that excess heat, whether it’s radiators (fins, fans) or, now and again, blowing off jets of plasma.

It may not be mean, it may just need to get rid of heat… Superman (2025) trailer © DC Studios / Warner Bros. Used under fair use

• Movement: Mentioned above, the larger the animal, the slower the movement. Movement takes muscles, and remember, muscles scale up by the square, not the cube. Physically, a larger animal has less muscular force per mass than a smaller animal does.
  
  Thanks to that, it’s more difficult for a large animal to start, stop, or redirect any motion. The force provided by muscles in smaller animals just isn’t there for larger ones. Throw in things like momentum and inertia, and Kaiju on the whole would have a much harder time throwing (and stopping that swinging arm) a punch than a smaller animal. Again — force to start the motion and to stop the motion.

• Cells: That volume of the larger animal that increases by the cube? That volume is made up of cells, fluids, and living creature stuff, but let’s focus on cells. Cells are where the metabolism happens — that’s the unit that creates the heat, needs the food, and all the rest of the living stuff. Cells need oxygen — it’s why we breathe, and other organisms have figured out their own methods of getting the gas into their inner workings.
  
  Oxygen diffuses into cells from the blood (or whatever is carrying it through the body) – the bigger the cell, the longer it takes for the oxygen to get to the good stuff — cellular respiration. For small animals, this pathway is short, and the delivery can be quick. The larger the animal, the longer the path, and the more complex the circulatory system. Paths have limits on their lengths — too long, and the oxygen can’t reach the parts of the cell efficiently. And also, the larger you are, the bigger and stronger the pump you need to move that blood through the body without it stalling out.
  
  Kaiju — without invoking magic, this is another dealbreaker. There are ways around this that can be imagined, such as smaller cells, a more complex circulatory system, multiple hearts, or membranes to extract oxygen from the atmosphere… All plausible in their own way, but each adaptation to provide for the Kaiju’s system takes energy to build and maintain. More energy to maintain, higher metabolism.

Just hangry for a Big Belly Burger? Superman (2025) trailer © DC Studios / Warner Bros. Used under fair use

• Food: Been talking about metabolism and energy — larger animals need more energy, and we all get energy from food. Small animals with fast metabolisms eat constantly to replace the energy as its used up (and have relatively small poops per capita). Larger animals flip that – they eat less (but a lot of them’re vegetarians — grasses and feed vegetables have less energy than meat) because their slower metabolism allows for it. They also have relatively larger poops per capita. And given the size of stocks of what Kaiju would consider food, they would decimate entire regions of large animals, leaving only the small ones that could easily hide and quickly run away.
  
  Kaiju — as shown historically (and in the trailer), tend to move quickly given their size. That would be supported by a faster metabolism (gas exchange, and heat considerations too) that would require a lot of energy to support it. A lot. And Kaiju would have, per monster, epic poops.

Our “Kaiju”

Yes, we do have some big animals on Earth, but nothing approaching Superman’s Kaiju, Godzilla, Kong, or any of the others that hit screens. Unfortunately (shakes fist at universe), our earthly kaiju have to follow the cube-square law.

Our own “kaiju” are worth a look, largely because we have three distinctive environments: air, land, and water. The main player in how big our kaiju in these environments can grow is an oldie but a goodie — gravity.

Gravity determines weight. So while mass (the “stuff” inside a thing, molecules and atoms) doesn’t change, weight does. Less gravity, less weight. More gravity, more weight.

“Living” in the air gives a little help against gravity — wings can help provide lift, and lighter structures than land animals (birds’ hollow bones, for example) can assist with a size boost, but when birds land, they’ve got the same problems with mass that land animals do. So let’s just consider two environments: land and water.

On land, the current champion is the African bush elephant, weighing approximately 6,000 kg. It matches everything you’d think — slow, thick legs, low metabolism, eating infrequently (but as a vegetarian, eating a lot). We’ve had bigger, like the Argentinosaurus, which probably topped off at 100 metric tons (100,000 kg), but we’re unlikely to see anything that big again.

African bush elephant size comparison. By Stevoc86, Wikimedia Commons, used under CC BY 4.0

Our Kaiju can manage the sufficient skeletal structure and metabolism that Argentinosaurus must have had, but the giant dinosaur had a couple of other factors going for it — a stable food supply (lush forests and grasses), and a stable environment (both in terms of climate and predators). Given Earth’s gravity and environmental/climatic conditions, most researchers feel that the 100 metric tons of Argentinosaurus is at the practical limit for land creatures on Earth.

Argentinosaurus was big. Not just big. But BIG big. by Slate_Weasel Wikimedia Commons, used under CC BY 4.0

Jump into the ocean and float. A body’s buoyancy reduces the effects of gravity, so the water can allow larger animals to develop. The current champion is the Blue Whale, weighing approximately 200,000 kg. Water does help. As far as we know, there’s never been a challenger to the blue whale’s title as the biggest, although, to be fair, monstrous marine dinosaurs could have existed, but they tend to sink when they die.

It’s hard to grasp the size of blue whales — even with comparisons. Image (c)Orca Ireland

But the blue whale is strictly limited to the water. If one wanted to come up against the African bush elephant on land, it would immediately realize its mistake. Without the structural support of a skeleton made for living on land, the whale’s mass would crush it.

But…But…But

I get you — the “what about if…”s. Yeah — what if it was nuclear powered (looking at you, Godzilla), uses stronger stuff in its skeleton, has radiant fins on its back to get rid of heat, or has some other exotic biology that allowed it to grow to a massive size that we just don’t know about. All fine options…

in fiction. In our world, we’re stuck — the cube-square law wins the day.

But we can keep hope alive. Real Kaiju would be cool. Terrifying, but cool.

Or maybe you got here because of a link and now can’t find the article?

We’ve been at this since…I want to say 2014, so there’s a bit.

We’ll be bringing the good stuff over as we go. It’s going to take a minute, but it will be coming. Keep an eye out, and you’ll be back in touch with some old nerd science soon!

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