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One thing Cannon didn’t understand—no one did yet—was what a staggering amount of energy the body requires at the cellular level in order to maintain itself. It took a very long time to figure that out, and when the answer came, it was provided not by some mighty research institute but by an eccentric Englishman working pretty much on his own in a pleasant country house in the west of England.
We now know that inside and outside the cell are charged particles called ions. Between them in the cell membrane is a kind of tiny air lock known as an ion channel. When the air lock is opened, the ions flow through, and that generates a little buzz of electricity—though “little” here is entirely a matter of perspective. Although each electrical twitch at the cellular level produces just one hundred millivolts of energy, that translates as thirty million volts per meter—about the same as in a bolt of lightning. Put another way, the amount of electricity going on within your cells is a thousand times greater than the electricity within your house. You are, in a very small way, exceedingly energetic.
It’s all a matter of scale. Imagine, for purposes of demonstration, firing a bullet into my abdomen. It really hurts and it does a lot of damage. Now imagine firing the same bullet into a giant fifty miles tall. It doesn’t even penetrate his skin. It’s the same bullet and gun, just a different scale. That’s more or less the situation with the electricity in your cells.
The stuff responsible for the energy in our cells is a chemical called adenosine triphosphate, or ATP, which may be the most important thing in your body you have never heard of. Every molecule of ATP is like a tiny battery in that it stores up energy and then releases it to power all the activities required by your cells—and indeed by all cells, in plants as well as animals. The chemistry involved is magnificently complex. Here is one sentence from a chemistry textbook explaining a little of what it does: “Being polyanionic and featuring a potentially chelatable polyphosphate group, ATP binds metal cations with high affinity.” For our purposes here it is enough to know that we are powerfully dependent on ATP to keep our cells humming. Every day you produce and consume your own body weight in ATP—some 200 trillion trillion molecules of it. From ATP’s point of view, you are really just a machine for producing ATP. Everything else about you is by-product. Because ATP is consumed more or less instantaneously, you have only sixty grams—that is a little over two ounces—of it within you at any given moment.
It took a long time to figure any of this out, and when it came, almost no one at first believed it. The person who discovered the answer was a retiring, self-funded scientist named Peter Mitchell who in the early 1960s inherited a fortune from the Wimpey house-building company and used it to set up a research center in a stately home in Cornwall. Mitchell was something of an eccentric. He wore shoulder-length hair and an earring at a time when that was especially unusual among serious scientists. He was also famously forgetful. At his daughter’s wedding, he approached another guest and confessed that she looked familiar, though he couldn’t quite place her.
“I was your first wife,” she answered.
Mitchell’s ideas were universally dismissed, not altogether surprisingly. As one chronicler has noted, “At the time that Mitchell proposed his hypothesis there was not a shred of evidence in support of it.” But he was eventually vindicated and in 1978 was awarded the Nobel Prize in Chemistry—an extraordinary accomplishment for someone who worked from a home lab. The eminent British biochemist Nick Lane has suggested that Mitchell should be as famous as Watson and Crick.
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The surface law also dictates how big we can get. As the British scientist and writer J. B. S. Haldane observed almost a century ago in a famous essay, “On Being the Right Size,” a human scaled up to the hundred-foot height of the giants of Brobdingnag in Gulliver’s Travels would weigh 280 tons. That would make him forty-six hundred times heavier than a normal-sized human, but his bones would be just three hundred times thicker, not nearly robust enough to support such a load. In a word, we are the size we are because that is about the only size we can be.
Body size has a great deal to do with how we are affected by gravity. It will not have escaped your notice that a small bug that falls off a tabletop will land unharmed and continue on its way unperturbed. That is because its small size (strictly, its surface area-to-volume ratio) means that it is scarcely affected by gravity. What is less well known is that the same thing applies, albeit on a different scale, to small humans. A child half your height who falls and strikes her head will experience only one thirty-second the force of impact that a grown person would feel, which is part of the reason that children so often seem to be mercifully indestructible.
Adults are not nearly so fortunate. Few grown humans can normally survive a fall of much more than twenty-five or thirty feet, though there have been some notable exceptions—none more memorable perhaps than that of a British airman in World War II named Nicholas Alkemade.
In the late winter of 1944, while on a bombing run over Germany, Flight Sergeant Alkemade, the tail gunner on a British Lancaster bomber, found himself in a literally tight spot when his plane was hit by enemy flak and quickly filled with smoke and flames. Tail gunners on Lancasters couldn’t wear parachutes because the space in which they operated was too confined, and by the time Alkemade managed to haul himself out of his turret and reach for his parachute, he found it was on fire and beyond salvation. He decided to leap from the plane anyway rather than perish horribly in flames, so he hauled open a hatch and tumbled out into the night.
He was three miles above the ground and falling at 120 miles per hour. “It was very quiet,” Alkemade recalled years later, “the only sound being the drumming of aircraft engines in the distance, and no sensation of falling at all. I felt suspended in space.” Rather to his surprise, he found himself to be strangely composed and at peace. He was sorry to die, of course, but accepted it philosophically, as something that happened to airmen sometimes. The experience was so surreal and dreamy that Alkemade was never certain afterward whether he lost consciousness, but he was certainly jerked back to reality when he crashed through the branches of some lofty pine trees and landed with a resounding thud in a snowbank, in a sitting position. He had somehow lost both his boots, and had a sore knee and some minor abrasions, but otherwise was quite unharmed.
Alkemade’s survival adventures did not quite end there. After the war, he took a job in a chemical plant in Loughborough, in the English Midlands. While he was working with chlorine gas, his gas mask came loose, and he was instantly exposed to dangerously high levels of the gas. He lay unconscious for fifteen minutes before co-workers noticed his unconscious form and dragged him to safety. Miraculously, he survived. Some time after that, he was adjusting a pipe when it ruptured and sprayed him from head to foot with sulfuric acid. He suffered extensive burns but again survived. Shortly after he returned to work from that setback, a nine-foot-long metal pole fell on him from a height and very nearly killed him, but once again he recovered. This time, however, he decided to tempt fate no longer. He took a safer job as a furniture salesman and lived out the rest of his life without incident. He died peacefully, in bed, aged sixty-four in 1987.