Could a giant monster even stand up?

The full story

The episode's narration, word for word. Numbers link to the sources below; timestamps play that moment.

Out of the sea 0:00

In the 1954 film Godzilla, a monster rises out of the sea and walks into Tokyo ^1,2. The original was about fifty metres tall ³. By 2019, it had more than doubled ³. So here's the puzzle. If you took something built like you and simply made it that big, could it even stand up? Not fight, not roar, just stand. The answer was worked out almost four hundred years ago, by a man whose books had been banned ⁴.

Twice as big 0:33

Start with a block. Make it twice as long, twice as wide and twice as tall ⁵. Each face gets four times the area, but the block holds eight times the stuff, so it weighs eight times as much ^4,6,5. Stand it on its base, and every square centimetre of that base now carries twice the load ⁶. Double the size, and you double the strain on whatever holds it up ⁶.

A banned book 0:59

After his trial, an order banned the printing of any work by Galileo Galilei ⁴. So the manuscript of Two New Sciences left Italy with a Dutch publisher, and was printed in Leiden in 1638 ⁴. And in the middle of a discussion about beams, Galileo turns to giants ⁴.

Galileo's bone 1:20

His character Salviati argues that you can't make a man or a horse enormously taller and keep it working ⁴. You'd need bone made of something stronger, or bones so thickened that the animal looks like a monstrosity ⁴. Galileo even drew one, a bone three times longer and thickened to do the same job, and pointed out how out of proportion it looked ⁴. A giant built like us, he wrote, would fall and be crushed under his own weight ⁴.

The square-cube law 1:50

A bone's strength depends on its cross-section, the area of the slice you'd see if you cut it through ^4,6. That grows with the square of the size, but the weight it carries grows with the cube ⁶. So the force on every square centimetre of bone, which engineers call stress, rises in step with height ⁶. Make an animal ten times taller, and its same-shaped bones work ten times as hard ⁶. This is called the square-cube law ⁵.

Pope and Pagan 2:20

In 1926, the biologist J B S Haldane put numbers on it, in an essay called On Being the Right Size ⁶. He remembered two giants from a picture book, sixty feet tall, ten times the height of the hero ⁶. That made them a thousand times heavier, on bones with only a hundred times the cross-section ⁶. A human thigh bone breaks under about ten times your body weight, he wrote, so those giants would have broken their thighs with every step ⁶. That, he suggested, was why they were sitting down in the picture ⁶.

Godzilla's numbers 2:57

So let's try it on Godzilla. Take a person, one point seven five metres tall and seventy kilograms, and scale them up to fifty metres ¹. That's about twenty-nine times taller ¹. Their weight goes up more than twenty-three thousand times, to about one thousand six hundred tonnes ^6,1. Every bone now works about twenty-nine times as hard, and Haldane's margin was about ten ⁶. So our giant would snap its thigh bones just standing there ⁶.

How much margin do bones have? 3:28

And standing is the easy part. In 1990, Andrew Biewener showed that when mammals run, peak stresses in their bones reach a quarter to a half of what breaks them ⁷. That's a safety factor of two to four, about the same in small mammals as in big ones ^8,7. So, on this simple scaling, a runner built exactly like us would start breaking bones at around two to four times our height: about three and a half to seven metres ^8,7. By Haldane's figure, standing still, you'd top out near seventeen ⁶.

The leg it would need 4:05

Galileo's way out was thicker bones, so how thick ⁴? To keep the stress the same, a bone's cross-section must grow as fast as the weight ^4,6. Our fifty-metre giant's thigh bone would be eleven metres long ⁹. Built in proportion, it's just over a metre across ⁹. To carry the load, it would need to be about six metres across, more than half as wide as it is long ^6,9.

Real giants 4:31

Real giants do roughly what Galileo said ^4,7. Large mammals stand on straight, column-like legs lined up with the force from the ground, and their bones get relatively thicker ^8,7. One of the heaviest land animals we know of, the long-necked dinosaur Patagotitan, has been estimated at about sixty-nine tonnes ¹⁰. A person-shaped Godzilla would weigh more than twenty of them ^1,10.

Could it run? 4:59

In Jurassic Park, a Tyrannosaurus chases a Jeep, which was Spielberg's own idea ^11,12. In 2002, John Hutchinson and Mariano Garcia worked out how much leg muscle a six-tonne Tyrannosaurus would need to run fast ¹³. The answer was an unreasonably large amount, so they concluded it's doubtful the biggest dinosaurs were capable runners ¹³. The very biggest animals trade speed for safety: they stride rather than sprint ^7,13.

Why whales can be huge 5:30

Galileo had one more escape hatch, and it's the sea ⁴. Salviati explains that in water, the flesh supports the bones instead of the bones carrying the flesh ⁴. That's how the largest animal ever, the blue whale, reaches about a hundred and fifty tonnes ¹⁴. But another character adds that a giant fish pulled ashore would be crushed under its own mass ⁴. So Godzilla's trouble starts the moment it walks out of the bay ^4,1.

Too hot 6:01

Size brings a second problem, which is heat ⁶. Your body makes heat in every kilogram but loses it through your skin ⁶. Scale up twenty-nine times, and if every kilogram burned like ours, each square metre of skin would have to shed twenty-nine times as much heat ⁶. Real big animals avoid this by running each kilogram slower ^15,16. Exactly how much slower is still argued over, but either measured rule makes most of the heat problem disappear ^15,16.

Out of breath 6:32

Oxygen has the same problem ⁶. You need it in proportion to your volume, but it gets in through a surface, which is why lungs are a surface folded up inside you ⁶. If every kilogram burned like ours, a giant built like us would need twenty-nine times more lung surface than a scaled-up copy of our chest holds ⁶. Insects have it worse: Haldane reckoned oxygen seeps only a short way along their tiny air tubes, so hardly any are much more than a centimetre thick ⁶. The giant ants of the 1954 film Them would have been starved of oxygen deep inside ^6,17.

King Kong's lucky number 7:11

In 1933, King Kong's models were scaled to eighteen feet tall on his island and twenty-four feet on stage in New York ^18,19. His creator, Merian Cooper, deliberately changed his size from shot to shot, because the drama mattered more ¹⁸. The biggest real ape, Gigantopithecus, known only from jaws and teeth, is estimated to have stood about three metres ²⁰. Kong on stage is about two and a half times taller, so his bones work about two and a half times as hard ^18,20. That's fine for standing, and right at the edge for running ^8,7. So the stage-sized Kong might just have managed ^8,18. On top of the Empire State Building, where Cooper made him far bigger, he wouldn't ^8,7,18,19.

Honey, I shrunk the physics 7:59

Now run it the other way. In Honey, I Shrunk the Kids, children are shrunk to a quarter of an inch ^21,22. For a grown-up, that's about two hundred and seventy-six times smaller, so each kilogram has two hundred and seventy-six times as much skin to lose heat through ^6,21. Haldane noted that a mouse eats about a quarter of its own weight in food every day, mostly to keep warm ⁶. By his rule, a quarter-inch person would need about four times their own weight in food every day; even the gentler rule from earlier says about their own weight ^6,16.

The perks of being small 8:36

Being tiny does have perks ⁶. Air resistance grows with your surface and weight with your volume, so small things fall gently ⁶. Haldane said a mouse dropped down a mine shaft onto soft ground walks away ⁶. And jumping height hardly depends on size: a flea jumps about two feet, Haldane wrote, and a man about five ⁶.

The crew that got it right 9:00

And the people who got it right were Godzilla's own effects crew ²³. Toho's effects director, Makoto Kamiya, walked a Japanese government site, Kids Web Japan, through it ²³. In the films of the early 2000s, the page explains, the monster was sixty metres tall on screen, but two point two metres in real life: an actor in a heavy suit ²³. When they blow up a miniature city, they run the camera about ten times faster than normal ²³. Played back, a blast that lasted a moment unfolds slowly, and looks enormous ²³.

Why slow means big 9:39

That trick is real physics ²⁴. Gravity sets the clock: the time to fall grows with the square root of the height ²⁴. A fifty-metre fall takes over three seconds, but on a set built to the same scale as the suit, twenty-seven times smaller, it's over in just over half a second ^23,24. Slow the film by the square root of the scale, about five times here, and falling rubble looks the right size ²⁴. Toho's ten times suits a model a hundred times smaller ^23,24. For Godzilla himself, they did the opposite, slowing the camera so the heavy suit would look fast ²³. Physics says a real giant would move slowly; the films chose a monster quick enough to catch you ^8,7,23.

So, could it stand? 10:25

So could a giant monster stand up? Built like us, no: by Haldane's figure, past about seventeen metres its bones fail under its own weight ⁶. Bigger means thicker legs, slower steps, slower-burning bodies, or a life at sea ^4,7,15. Galileo saw the first and last of those in 1638 ⁴. The films bend that on purpose, because a monster has to move like a threat ²³. Next time, another favourite movie moment: could you outrun a fireball, or walk away from an explosion?

Sources

Every factual claim in the episode is tied to one of these. Spotted an error? Tell us.

1. Wikipedia, "Godzilla (1954 film)", Plot section (plot summary only) — en.wikipedia.org
2. Kids Web Japan (Web Japan, Ministry of Foreign Affairs of Japan), "The Birth of… — web.archive.org
3. Andrew Whalen, "'Godzilla' Size Chart Shows How Much the 'King of Monsters' Has Grown… — newsweek.com
4. Galileo Galilei, Dialogues Concerning Two New Sciences, translated by Henry Crew and… — archive.org
5. Wikipedia, "Square–cube law" (name and attribution to Two New Sciences only) — en.wikipedia.org
6. J. B. S. Haldane, "On Being the Right Size", Harper's Magazine, March 1926; text read… — web.archive.org
7. Andrew A. Biewener, "Biomechanics of mammalian terrestrial locomotion", Science… — pubmed.ncbi.nlm.nih.gov
8. Andrew A. Biewener, "Scaling body support in mammals: limb posture and muscle… — pubmed.ncbi.nlm.nih.gov
9. OpenStax, College Physics 2e, section 5.3 "Elasticity: Stress and Strain", Example 5.4… — openstax.org
10. José L. Carballido et al., "A new giant titanosaur sheds light on body mass evolution… — pmc.ncbi.nlm.nih.gov
11. Wikipedia, "Jurassic Park" (film), production sections "New writers" and "California"… — en.wikipedia.org
12. The A.V. Club, "David Koepp: Writer's block", interview (no byline on the page;… — web.archive.org
13. John R. Hutchinson and Mariano Garcia, "Tyrannosaurus was not a fast runner", Nature… — pubmed.ncbi.nlm.nih.gov
14. NOAA Fisheries, "Blue Whale" species page — fisheries.noaa.gov
15. Craig R. White and Roger S. Seymour, "Mammalian basal metabolic rate is proportional… — pubmed.ncbi.nlm.nih.gov
16. Geoffrey B. West, James H. Brown and Brian J. Enquist, "A general model for the origin… — pubmed.ncbi.nlm.nih.gov
17. Wikipedia, "Them!", Plot section (plot summary only) — en.wikipedia.org
18. Wikipedia, "King Kong", section "Appearances and abilities" (Kong's scale in the 1933… — en.wikipedia.org
19. Roger Ebert, "King Kong" (1933), Great Movies review, RogerEbert.com, 3 February 2002… — web.archive.org
20. Yingqi Zhang, Kira E. Westaway et al., "The demise of the giant ape Gigantopithecus… — pmc.ncbi.nlm.nih.gov
21. Wikipedia, "Honey, I Shrunk the Kids" (lead and Plot; shrunk to a quarter of an inch) — en.wikipedia.org
22. Disney D23, "Honey, I Shrunk the Kids (film)", A to Z entry (the studio's own… — d23.com
23. Kids Web Japan (Web Japan, Ministry of Foreign Affairs of Japan), "Amazing and… — web.archive.org
24. OpenStax, University Physics Volume 1, section 3.5 "Free Fall" (equations 3.15–3.17, g… — openstax.org

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