## The Universe in 5-D

String theorists talk alot about 6 “hidden” spacial dimensions on top of the 3 we know about. I don’t know about you, but talking about extra spacial dimensions sort of gives me a headache if I try to imagine them.

The simplest way I know to think about such things (once you get past the idea that there’s just no room in the entire universe for an extra right angle in corners), is to think in terms of analogies. If you imagine a sphere passing through a 2-D sheet of paper, what flat-worlders living on the paper experience as the 3-D sphere and their 2-D universe interact is first a point just when the sphere touches the paper, and then a growing circle as the place of contact passes through the paper, until the circle reaches a maximum and begins to get smaller again, until disappearing as a point.

By analogy, if a 4-D hypersphere were to pass through our 3-D universe, we’d experience it as first a point, then a growing sphere which would reach some maximum size and then start to shrink again until it disappeared. That’s how a finite sized hypersphere would interact with our universe.

But there are other shapes that could potentially interact with our universe. What would a hyper-cube, for instance, look like in our 3-D universe? Maybe like this? Get your red-blue 3-D glasses on before you click on the link. How about a 24 sided object? And I’m not sure what you’d call this thingy but if you’re still wearing your red-blue 3-D glasses, be sure to follow the instructions at the top – for “stereo mode” click the anaglyph choice, and click the ‘edges’ box too.

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