Why Does Our Universe Have Three Dimensions?

Jennifer Ouellette reports on the findings of a Japanese team’s simulation of what happened in the moments just as our universe came into existence - right at the Big Bang.

Their model tries to draw a line between a pre-Big Bang universe that consisted of nine dimensions (and time) in a strained but symmetrical state. Then it popped, and out came the three dimensions that we view as our current universe:

Imagine that you are trying to making the bed on laundry day, but the bed sheet has shrunk slightly in the wash. You manage to get it to fit around all four corners of the bed, but the sheet is stretched so tightly that it just won’t stay in place.

There is too much strain on the fabric, so one corner inevitably pops loose, causing the bed sheet to curl up in that spot. Sure, you can force that corner back into place, but again, the strain will prove to be too much and another corner will pop.

Like the bed sheet, the original ten-dimensional fabric of space-time was stretched tight in a supersymmetric state. But the tension became too great, and space-time cracked in two. One part curled up into a tight little ball, while the aftershock from the cataclysmic cosmic cracking caused the other part to expand outward rapidly, a period known as inflation. This became our visible universe.

I love the analogy of a tightly-stretched sheet. Analogies like that are the only way the biologists like me can hope to wrap our biological brains around extra dimensions. If you’re having trouble understanding “extra dimensions”, stop thinking of geometry or time-travel, and think instead of this flea on a tightrope.

At any rate, as confused as us non-string theorists might be about it all, it’s an elegant tool to simulate a universe that can’t exist as we know it today.

(via Discovery News, image of Calabi-Yau manifold via Wikimedia commons)

Source: news.discovery.com