How Big is Your World?
Is the universe really so big, or are we just very, very small?
Okay, I admit it, this is a question I've toyed with for a very long time—since sometime back in childhood. It all started around the time I had my first exposure to the idea of scale, and the vastly different scales between the cosmological and the subatomic, with us humans fitting in somewhere between.
Since we're indigenous to the realm of scale we developed in, naturally things in our immediate experience are regarded as "normal" in size. But take a short journey into the realms of scale above and below our own, and things start to seem very, very—well, mind-bending.
On the cosmic side we find galaxies: structures that contain hundreds of billions of stars and measure so far across that light traveling at its almost unimaginably zippy velocity of 300,000 kilometers per second take tens of thousands of years to span. Our own Milky Way galaxy is 100,000 light years across.
On the subatomic side we have atomic nuclei, where most of an atom's mass is packed away. An atomic nucleus is so small that even if the entire atom (nucleus, orbiting electrons, and all the empty space between—about 1 ten-billionth of a meter) were upscaled to the size of a basketball, the nucleus would still be too small for the human eye to perceive. An atomic nucleus is roughly 1 million-billionth of a meter across.
Galaxy: 100,000 light years or almost a billion trillion meters. Atomic nucleus: one million-billionth of a meter. Human being: one or two meters. Here we exist in a vast universe that is much larger than us, and we—and the vast universe, for that matter—are composed of particles that much smaller.
But why are these numbers important to me? Apart from the revelation in these numbers that we humans, as objects that take up space, exist betwixt these realms of scale, the entire notion that something like a galaxy ultimately owes tribute for its physical and dynamic properties to such ultimately miniscule bits is….
Though in our everyday awareness we do not perceive atoms and galaxies, we do spend our lives dealing with things that are either much smaller or much larger than we are—the broken dishwasher or those few people who are truly our own size notwithstanding.
We are sustained by a planet-sized life support system, on which we stand. We are aided, and afflicted, by microorganisms (some of which depend on us for life support). Some of us worry about asteroids crashing into the Earth (I don't personally), while others look to them as a possible source of needed natural resources. And did you know that statistically, you're never more than a few feet away from a spider?
But even the planet we stand on or a microorganism we depend on still don't figure much into our immediate awareness, each being slightly beyond the thresholds of scale we most readily perceive. The day-to-day universe that we perceive—that we functionally live in—is a lot smaller than the big one…and a heck of a lot larger than what it is built on.
What is the size of your universe?