The Universe Within by Neil Turok

Author:Neil Turok
Language: eng
Format: epub, mobi
Publisher: House of Anansi Press Inc.
Published: 2012-09-11T04:00:00+00:00

A THEORY THAT PREDICTS a universe like ours a priori, without any need for anthropic selection, would seem vastly preferred. Even if anthropic selection could rescue Hartle and Hawking’s theory (which seems to me unlikely), the non-anthropic theory would be statistically favoured over the anthropic one by a huge factor, of 10 raised to the power of 10 raised to the power of 120.

For the past decade, with Paul Steinhardt of Princeton University and other collaborators, I have been trying to develop such theories as an alternative to inflation. Our starting point is to tackle the big bang singularity. What if it was not the beginning of time, but instead was a gateway to a pre–big bang universe? If there was a universe like ours before the singularity, could it have directly produced the initial ball of light, and if it did, would there be any need for a period of inflation?

Most of the universe today is very smooth and uniform on scales of a millimetre, and we have no problem understanding why. Matter and radiation tend to spread themselves out through space, and the vacuum energy is completely uniform anyway. Let us imagine following our universe forward into the future. The galaxies and all the radiation will be diluted away by the expansion: the universe will become a cold, empty place, dominated by the vacuum energy. Now imagine that for some reason the vacuum energy is not absolutely stable. It could start to slowly decay, tens of billions of years into our future. We can easily build mathematical models where it declines in this way, becoming smaller and smaller and then going negative. Its repulsive gravity would become attractive, and the universe would start to collapse.

When we studied this idea, we discovered that the pressure of the unstable energy would become large and positive, and it would quickly dominate everything else. As the universe collapsed, this large positive pressure would quickly make the universe very smooth and flat.When the universe shrunk down to zero size, it would hit a singularity. Then, plausibly, the universe would rebound, fill with radiation, and start expanding again. In fact, immediately after the bounce we would have conditions just like those in our millimetre-sized ball of light: the very initial conditions that were needed to explain the hot big bang.

Much to our surprise, we found that during the collapse initiated by the unstable vacuum energy, our high-pressure matter develops quantum variations of exactly the form required to fit observations. So in this picture, we can reproduce inflationary theory’s successes, but with no need for initial inflationary conditions.

Our scenario is far more ambitious than inflation in attempting to incorporate and explain the big bang singularity. We have based our attempts on M-theory, a promising but still developing framework for unifying all the laws of physics. M-theory is the most mathematical theory in all of physics, and I won’t even try to describe it here.

Einstein used the mathematics of curved space to describe the universe. M-theory uses the same mathematics to describe everything within the universe as well.

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