About the Size of It
Our human brains evolved in the space between a gnat and a mountain. If it were smaller than a gnat or larger than a mountain, our prehistoric ancestors didn’t have to worry about it. So these are the natural limits of our perception. If you try to picture something outside of that range, your imagination begins to fail you. How much smaller than a gnat is an atom? How much larger than a mountain is the planet Earth?
A good way to get a handle on these questions is to play around with the sizes of everything – shrinking everything down or expand it all up until the objects we’re looking at end up within our gnat-to-mountain range of perception.
A good example of that strategy are those diagrams depicting the planets of the Solar System, which you can find everywhere from elementary school classrooms to the kids’ placemats at Denny’s. Those merry little planets swarming around the Sun in tightly-packed concentric rings.
Of course, on a Denny’s placemat, scientific accuracy isn’t really the goal. Even so, many reasonable adults go through their entire lives imagining the actual Solar System looks more or less like this.
They are, of course, wrong. Everything is wrong here, from the comparative sizes of the planets, to the distance between them, to the shape and paths of their orbits. The truth is much, much more interesting.
Here is a much more accurate comparison: if we shrunk down the entire Universe until the Sun was the size of a basketball, then the Earth would be the size of the inside of this lower- case “o." Of course, you can’t depict a size difference that large on a placemat, which is why Denny’s doesn’t even try.
But the real stunner is the distance between them. How far apart do you imagine our basketball Sun and our letter-o Earth would be from one another? A foot? A yard? Three yards? Ten?
On this scale, the actual distance between the Sun and the Earth would be 28 yards – almost the length of a basketball court, hoop to hoop.
Now, imagine yourself standing under a basketball basket. Peering across the court, you see your friend under the other basket, and . . . what’s that he’s got in his hand? Looks like a tiny bead.
If you can imagine how hard it would be to spot a bead across a basketball court, then congratulations: you now have your first clear idea of the size of the Earth compared to its distance from the Sun.
Now forget everything – the gym around you, the hoop above you, the floor under your feet – and picture just you and your friend floating in open space. The only things that exist are the two of you and the space in between. And that space is empty.
Almost empty. Sometimes, floating in the open space in front of you, you might catch sight of another bead and a grain of sand. The bead is the planet Venus and the sand grain is the planet Mercury.
That’s a very tiny collection of stuff for such a comparatively wide space. But the inner Solar System is practically a traffic jam compared to the vast emptinesses of interstellar and intergalactic space.
Compare once again the bead in your friend’s hand to its distance away from you. Now ask yourself: on this scale, how large would a human being be?