Our eyes can keep up with our walking pace, but if you need to examine something close to you while you’re walking or running, you usually feel an overwhelming urge to stop for a bit to have a good look. Your eyes can’t collect information fast enough to get all the detail while you’re moving. Humans actually play exactly the same game as the pigeon (without the head-bobbing), and our brain stitches things together so that we’d never know. Our eyes dart rapidly from place to place, adding information to our mental image on each stop. If you look at yourself in a mirror and look directly at the reflection of one of your eyes and then the other, you will notice that you never see your eyes move, even though someone standing next to you will see them flick from one side to the other. Your brain has stitched your perception of the scene together in such a way that you’d never know there was a jump; but those jumps are happening all the time.
The point is that we’re only a tiny bit faster than the pigeon, and this highlights how much there must be that’s faster than us. We are used to life at a limited range of timescales—we can follow things that last from about a second to a few years—but that’s not all there is. Without science to help us, we are blind to anything happening over a few milliseconds or over a few millennia. We can only perceive our bit in the middle. That’s why computers can do so much and part of why they seem so mysterious. They can do what they need to do in tiny amounts of time, so they can get on with it and finish amazingly complex tasks before we perceive any time passing. Computers continue to get faster, but we can’t perceive why, because both a millionth and a billionth of a second are the same to us: too fast to notice. But that doesn’t mean the distinction isn’t significant.
What you see depends on the timescale on which you are looking. To grasp the contrast, let’s compare the speedy and the ponderous: a raindrop and a mountain.
A large raindrop takes one second to fall 20 feet, the height of a two-story building. What happens to it during that second? This raindrop is a jostling cluster of water molecules, each one held firmly in the grip of the group, but constantly shifting its allegiances within that group. A water molecule, as we saw in the last chapter, consists of an oxygen atom accompanied by two hydrogen atoms on either side, the trio forming a “V” shape. The whole molecule can bend and stretch as it hops through the loose network formed by billions of identical others. In that one second, this molecule may hop 200 billion times. If our molecule reaches the edge of the multitude it will find that there’s nothing outside the droplet that can compete with the huge attraction of the masses, so it’s always pulled back to the center. The cartoon raindrop shape is a fiction: Raindrops have lots of shapes but none of them have sharp points. Any pointed edges will be rapidly smoothed away, because individual molecules can’t resist the pull of the mob. But despite the strength of that pull, the perfect shape is never reached. There is constant readjustment in response to the buffeting of the air. A drop may be squashed flat, but will then pull itself back together, overshoot, become stretched into a rugby ball shape and then back again, 170 times in this one second. The globule is constantly wobbling and reinventing itself, a battleground between the external forces trying to tear it apart and the fierce pull of the mob keeping it together. Sometimes a raindrop flattens into a pancake, then stretches into a thin umbrella, and then explodes into an army of tiny droplets. All of this happens in less than a second. We can’t see any of it, but that droplet has transformed itself a billion times in the blink of an eye. Then the droplet splats down on to bare rock, and the timescales shift.
This rock is granite. It has not moved or changed in human memory. But four hundred million years ago there was a giant volcano in the southern hemisphere, and magma from below squeezed into the gaps in the volcanic rock. Over the following millennia the magma cooled, separating slowly into crystals of different types, and became hard unyielding granite. As more time has passed, the rocky leviathan has been ground down by ice ages, chipped away by plants and ice, polished by rain. While the volcano was wearing away, it was also traveling. Since the giant explosion that finished it, this chunk of continent has been creeping north. On top of it, species and geological eras came and went as the machinery of the planet shunted the ill-fitting jigsaw pieces of its surface together and apart. Today, a tenth of the total lifetime of our planet later, all that is left of the original dramatic volcano is the sorry remains of its exposed guts. We call it Ben Nevis, the highest mountain in the British Isles.
When you and I look at either the mountain or the raindrop, we notice very little change. But that’s just because of our own perception of time, not because of what we’re looking at.