The Godzilla of recent movies is huge — about 350 feet tall — which about half the height of the Gateway Arch in St. Louis. Such a big animal is physically impossible. Here’s why:

• Increasing size in one dimension scales linearly. For example, as you spool out a garden hose foot by foot, the length increases by the amount you pull out the hose. This concept is so simple that it’s hard to explain.

• Increasing size in two dimensions scales as a square of the lengths. For example, a 10 x 10 room is 100 square feet while a 20 x 20 room is 400 square feet — so doubling the lengths quadruples the area.

• Volume scales cubically. For example, a room 10 x 10 with 10 foot high ceilings has a total volume of air of 1,000 cubic feet. A 20 x 20 room with a 20 foot ceiling has 8,000 cubic feet of air volume.

What these three simple rules reveal is that when an object is scaled up in size, volume scales much faster than area. This concept — that volume increases faster than area — creates issues for animals as they grow in size. One issue is the ability to dissipate heat generated by an animal’s metabolism becomes more difficult as it increases in size because the surface area through which heat is dissipated is proportionally smaller as compared to the animal’s volume. This is why elephants have evolved to have such large ears — they have large amounts of surface area for heat dissipation.

Another issue created by volume increasing faster than the area rule is that as an animal increases in size it puts greater stress on the body structure because an animal’s weight is proportional to its volume. At a certain size, the skeleton and connective tissue can no longer support the animal’s weight. That’s why the largest land mammal was about 20 tons and the largest dinosaur was about 50 tons.

How about Godzilla? How big is he? So big that an animal the size of Godzilla would collapse under his own weight (unless his skeleton was made of steel). Geoffrey West, a physicist, calculated the stats on Godzilla’s size and other attributes. It’s pretty interesting:

In his latest incarnation, Godzilla is 350 feet long, which translates into a weight of about 20,000 tons, about 100 times heavier than the biggest blue whales. To support this gargantuan amount of tissue Godzilla would have to eat about 25 tons of food a day, corresponding to a metabolic rate of about 20 million food calories a day, the food requirements of a small town of 10,000 people. His heart, which would weigh about 100 tons and have a diameter of about 50 feet, would have to pump almost 2 million liters of blood around his body. However, to counterbalance that, it would have to beat only just over a couple of times a minute and sustain a blood pressure similar to ours. Note, by the way, that his heart alone is comparable in size to an entire blue whale. His aorta through which this enormous amount of blood flows would be about 10 feet across, easily big enough for us to walk through quite comfortably. Godzilla might live for up to two thousand years and would need to sleep less than an hour a day. Relatively speaking, he would have a tiny brain representing less than 0.01 percent of his body weight, compared with the approximately 2 percent of ours. This doesn’t mean that he would be stupid, but that’s all he would need to carry out all of his neurological and physiological functions. As to the possibly less savory parts of his life, he would need to pee about 20,000 liters of urine a day, comparable to the size of a small swimming pool, and poop about 3 tons of feces, a good-size truckload. I shall leave speculations about his sex life to your imagination.

Estimating his walking and running speeds is even more speculative because of the biomechanical inconsistency inherent in such an animal. However, blindly extrapolating from other animals leads to an estimate of a modest 15 miles per hour for his walking speed, so the average person would have some difficulty escaping his clutches should he be aggressive. But this brings up the catch in all of this: the diameter of each of his legs would have to be about 60 feet and his thighs probably much bigger, possibly close to 100 feet. In other words, he would have to be almost all leg in order to avoid collapse and be mobile, so the design is no longer feasible. As stressed earlier, to evolve something this big requires new materials and probably new design principles.

Source: Scale by Geoffrey West