Before the Big Bang (Kindle Single) by John Gribbin

Author:John Gribbin [Gribbin, John]
Language: eng
Format: azw3
Published: 2015-02-02T16:00:00+00:00

Three

Inflation

Alan Guth recalls that the flash of insight came to him late in the night of 6/7 December 1979. Among pages of calculations in the notebook he was using that night there is a dramatic sentence: “This kind of supercooling can explain why the universe today is so incredibly flat.” He had realised that a process called symmetry breaking, involving a phase transition not unlike the way steam gives out latent heat when it condenses to form water, could have poured out energy in the first split-second of time, pushing the Universe through a phase of rapid expansion which he called inflation and ending up with the Big Bang. Using Guth’s own analogy, in appropriate circumstances water can be “supercooled” to temperatures below 0 oC without freezing. As the cooling continues, the water will eventually freeze suddenly into ice, releasing its latent heat of fusion in the process of changing from the water “phase” to the ice “phase”. But the equivalent phase change process in the very early Universe was much more dramatic, affecting the fabric of space itself.

During inflation, the size of the Universe increases exponentially, doubling in size once every hundredth of a trillionth of a trillionth of a trillionth of a second (10-38 sec). On this picture, everything we see in the observable Universe today was inflated from a seed less than a billionth the size of a proton to about the size of a basketball within about 10-30 sec (another analogy is to imagine inflating a tennis ball up to the size of the visible Universe in a comparably short time). Only then did the Big Bang take over. The Universe we see around us is so uniform because it has been inflated from a seed so small that there was no room for any variations in density within it. This also resolves the flatness problem, because inflation flattens the Universe in the same way that the surface of an expanding balloon, or any other expanding sphere, is flattened when it is inflated. A tennis ball is very obviously curved; but if that tennis ball were inflated to the size of the visible Universe, and you could somehow move about on its surface, any measurements you could make would show that it was indistinguishably close to being flat, just as the real Universe is (but in three dimensions, not two). It also solves the horizon problem, because regions of the Universe that are now widely separated used to be in contact, but were ripped apart by the superfast stretching of space. This stretching occurs, in a sense, faster than light, but nothing moves through space faster than light. The origin of the “seed” itself would have been a so-called quantum fluctuation, a tiny disturbance in the fabric of spacetime blown up by inflation before it could disappear.

As cosmologist Max Tegmark has quipped, rather than being a hot Big Bang, the birth of the Universe involved a “Cold Little Swoosh” in which what became the observable Universe

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