Why We're All Trapped In 3-D

Jun 7, 2016
Originally published on June 21, 2016 3:01 am

You are trapped in space. Seriously. You're captured, cornered, mired. You're totally stuck and there's not a damn thing you can do about it.

You're trapped in space and what that really means is you're trapped in three dimensions.

To get a gist of what I'm talking about, imagine for a moment you're walking through the woods and a bear magically appears in front of you.

To escape this angry bear, which direction would you run?

You could bolt to the left or to right. That would be a good idea. You could also run straight ahead into the bear (that would be dumb) or you could run straight away in the other direction.

If there were a cliff nearby, you could jump off it and escape by falling downward. And, finally, if you had a jet-pack you could fly straight upward (which would be totally awesome).

So, there we go: left/right, forward/back, up/down. For physicists, each of these pairs constitutes a dimension.

Now, let's get really simple for a moment to really see what this idea of dimensions really means.

If forward and back were all that existed, you'd be living in a 1-dimensional world. In a 1-D universe, everyone lives along a single line. But if you added left and right to the line, suddenly everyone gets more room. There would, literally, be more space to inhabit. This expanded 2-D world would be planar like an infinite sheet of paper.

But "up" and "down" still wouldn't exist for inhabitants of this 2-D world. In fact, it would take a pretty creative 2-D citizen to even imagine the possibility of a third dimension.

So can you see where I am going with this?

We, of course, know about up and down because we inhabit a 3-D world. For us moving in three dimensions — forward/back, left/right and up/down — is obvious.

It's natural.

But who's to say there can't be a forth, fifth or even sixth dimension to travel in? Maybe, just like those 2-D planar creatures, we're trapped in our 3-D space and can't even picture the other directions.

Albert Einstein showed us that time can be thought of as a fourth dimension. Just like you can drive from east to west along Interstate 80, all of us are constantly traveling from the past to the future through time. Of course, the weird thing about time as a dimension is you can only travel one way. You can drive back west along I-80, but you can't go backwards in time.

These days, a lot of physicists are going beyond Einstein in their thinking that there might be extra dimensions of space that we just don't experience. One of the great frontiers of physics is pushing the boundaries of experiments to find evidence of these extra dimensions.

That would be pretty cool.

If we found them, suddenly there would be extra directions to travel in — and more space to fill.

But for now, we're all just stuck in 3-D.


Adam Frank is a co-founder of the 13.7 blog, an astrophysics professor at the University of Rochester, a book author and a self-described "evangelist of science." You can keep up with more of what Adam is thinking on Facebook and Twitter: @adamfrank4.

Copyright 2018 NPR. To see more, visit http://www.npr.org/.

ARI SHAPIRO, HOST:

We are all trapped in space, the space of three dimensions. Sounds abstract, but NPR blogger and astrophysicist Adam Frank can explain. First he says imagine a bear right in front of you.

ADAM FRANK, BYLINE: To escape this angry bear, which direction would you run? You could bolt to the left or right. That would be a good idea. You could also run straight ahead into the bear, which would be dumb, or you could run straight away in the other direction. If there was a cliff nearby, you could jump off it and escape by falling downward. And finally, if you had a jetpack, you could fly straight upward, which would be totally awesome.

So there you go - left, right, forward, back, up, down. For physicists, each of these pairs constitutes a dimension. If forward and back were all that existed, you'd be living in a one-dimensional world. In a 1D universe, everyone lives along a single line.

But if you added left and right to that line, suddenly everybody gets more room. There would literally be more space to inhabit. This expanded 2D world would be planar, kind of like an infinite sheet of paper. But up and down still wouldn't exist for inhabitants of this 2D world. In fact, it would take a pretty creative 2D citizen to even imagine the possibility of the third dimension. We, of course, know all about up and down because we inhabit a 3D world. Maybe just like those 2D planar creatures, we're trapped in our 3D space and can't even picture the other dimensions.

It was Einstein who showed us that time can be thought of as a fourth dimension. Just like you can drive from west to east along Interstate 80, all of us are constantly traveling from the past to the future through time. Of course the weird thing about time as a dimension is you can only travel one way.

These days, a lot of physicists are going beyond Einstein and think there might be extra dimensions of space that we just don't experience. If we found them, suddenly there'd be extra directions to travel in and more space to fill. But for now we're all just stuck in 3D.

SHAPIRO: That's NPR blogger Adam Frank. Transcript provided by NPR, Copyright NPR.