Carrion Luggage

Central Intelligence

The answer to the headline question from today's The Conversation article is, obviously: Right here where I'm sitting.

    Where is the center of the universe?  

I’ve spent decades trying to understand general relativity, including in my current job as a physics professor teaching courses on the subject. I know wrapping your head around the idea of an ever-expanding universe can feel daunting – and part of the challenge is overriding your natural intuition about how things work.

Part of the point of science is to tell us when intuition and the misnamed "common sense" fail us. Unfortunately, not everyone accepts these overrides, maybe because they're convinced they're the center of the universe. Or maybe they think the thoughts they come up with are just as valid as those who are educated and trained for this sort of thing.

For instance, it’s hard to imagine something as big as the universe not having a center at all, but physics says that’s the reality.

As with many things in general relativity, that really depends on your point of view.

And so we see the apparent contradiction there, right? On the one hand, perception of reality changes with point of view. On the other, my ignorant musings aren't as valid as a trained scientist's careful research and experimentation. If someone says "the Earth is flat," isn't that just as valid as centuries of observations supporting its roundness?

In short: no.

On Earth, “expanding” means something is getting bigger.

Like our waistlines.

This idea is subtle but critical. It’s easy to think about the creation of the universe like exploding fireworks: Start with a big bang, and then all the galaxies in the universe fly out in all directions from some central point.

Which is why calling it the "Big Bang" is compelling, but confusing. Even my preferred nomenclature, the Horrendous Space Kablooie (thanks, Calvin), is misleading.

It’s not so much the galaxies that are moving away from each other – it’s the space between galaxies, the fabric of the universe itself, that’s ever-expanding as time goes on.

When your mind gets blown, though, it is a conventional explosion. Metaphorically speaking.

A common analogy is to imagine sticking some dots on the surface of a balloon. As you blow air into the balloon, it expands. Because the dots are stuck on the surface of the balloon, they get farther apart. Though they may appear to move, the dots actually stay exactly where you put them, and the distance between them gets bigger simply by virtue of the balloon’s expansion.

As the article goes on to point out, that analogy is inadequate in a few ways. Another one I've heard is you put a raw loaf of raisin bread in the oven, and as it rises, the raisins get pushed further apart. That's incomplete, too.

The thing we think of as the “center” of the balloon is a point somewhere in its interior, in the air-filled space beneath the surface.

But in this analogy, the universe is more like the latex surface of the balloon. The balloon’s air-filled interior has no counterpart in our universe, so we can’t use that part of the analogy – only the surface matters.

It's like asking "where's the center of the Earth's surface?" If you restrict your search to the surface itself, you'll never find a center, only important points like the poles, or New York City. But none of these are an actual "center," no matter how many jokes you make about it.

One of the most mind-blowing things, though, isn't addressed by the article: that the universe is, to our limited perception, inside-out. The further away you go, the more back in time you see, until it's surrounded by the detectable remnants of the oldest matter/energy in the Universe.

A consequence of this is that we do appear to be in the center of the universe. But then, so does every hypothetical being standing on every other planet out there. And this is why appearances can't be taken at face value.