Extra Dimensions in Big Bang

String theory suggests 11 dimensions. If the Big Bang involved a sudden expansion of three of those dimensions into the space we know today, is it possible that the energy for the Big Bang and subsequent expansion was caused by the collapse of one or more of the other 8 dimensions into the tiny form they allegedly inhabit today. The form of the universe before the Big Bang is unknowable but is this hypothosis possible?
- Andrew Barron (age 54)
New Zealand

I haven't heard of any hypothetical account of the Big Bang based on M-theory or string theory in which another dimension specifically collapses to start the event. The closest I've heard to what you're discussing is the "ekpyrotic" scenario, in which a collision between 4-branes separated along one of the other dimensions triggers the expansion. The outcome of that collision would be very similar to the outcome of the hypothetical inflationary period of the more standard Big Bang picture. However, it turns out that there would be certain subtle statistical differences in the predicted cosmic microwave background radiation for these two accounts. The Planck satellite is currently measuring these properties, so we may get a glimpse back into the not-quite "unknowable" pre-bang history. Of course, at this point we aren't even sure if one these theories of extra dimensions will pan out as the quantum theory of gravity.

Mike W.

(published on 03/13/2012)