Wednesday, February 15, 2012


I've been thinking about weighty things lately: Gravity. Outer space. Human brains. The Universe.

I've mentioned before on this blog how our tiny little human brains can't really fathom time and space. I've also talked about how are brains aren't built for number, time, or space calculation.

So I was fascinated to find this link on Facebook:

It shows the entire scale of the known universe, from the tiniest tiniest little imaginable segment to the (estimated) entire size of the universe.

You can see, for example, how Central Park is way bigger than Vatican City, and how a grain of salt looks like to an ant.

But what's fascinating to me is that the overwhelming majority of things on the scale are things we can't see, either because they're too small or too big (and far away.) The scale of things in the universe that we can experience with our own eyes is infinitesimal compared to the rest of it.

What's also interesting is how much wide open space there really is in the universe. "Space" is a good name for it. When I imagine the Earth and the Moon, I think of something like an orange orbiting a basketball. What I don't consider, however, is that the orange is something like a football field away from the basketball.

The Earth is the small marble on the left. That tiny little dot on the right? That's the moon. Any other dots you see is just dust on your screen.

How does gravity even work from that far away?

Gravity fascinates me.

We tend to take it for granted because it's always constantly working on us. There's never a time in your life when you don't feel its pull. But if you think about it, it must be a very weak force. Think of how incredibly huge the Earth is compared to a human. And even then, this gigantically massive thing that supports every man-made object ever made like a person "supporting" a bacteria, only exerts enough gravitational force on us that we can jump away from it. We can stand up, walk, jump, and even make machines that enable us to leave the Earth's surface for hours at a time.

The thing I have a hard time wrapping my puny little brain around is, how does a force that is so relatively weak work between objects that are as far apart as the Earth and moon? And if there's this attractive force between them, why doesn't the moon just crash into the Earth? For that matter, why doesn't the Earth and all the planets crash into the Sun? Obviously, if gravity did work like that, I wouldn't be here to ponder these questions.

But apparently, even though the Earth and moon are so far away from each other, the way gravity works is they circle each other. Or rather, the Moon (smaller object) circles the Earth (larger object), just as the Earth circles the Sun. The way I've heard it described is the smaller object "falls around" the larger object. As someone who lives with gravity every day, inside a body that evolved through millions of years of gravity, it's hard to conceptually grasp this cosmic function of gravity.

I blame images like this, which is totally NOT to scale

But it's fun to think about. I should have been an astronomer. An astronomer/architect/tennis pro!

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