The inflationary model
Two distant objects are causally connected when they are able to communicate with a signal, provoking an effect the one to the other. The effects of this signal won’t be perceived immediately, but after some times, the higher the more distant they are because the speed of these signals, in the space, is finished. The causal horizon exactly represents the spacetime region where the two objects are connected in cause and effect.
Our Universe is made of galaxies thickenings and relatively empty regions, but in the main it appears homogeneous and isotropic isotrope (equal in every directions). How is it possible that regions so far from each other, out of the causal horizon, own such properties?
Not even the light, able to reach the highest speed, would have been able to connect casually these regions. To this question answered, since the first ’80s, the US physicist and cosmologist Alan Guth. He suggested to modify the classic Big Bang model, adding the inflation phenomenon (inflationary model). During the first instants after the Big Bang, our Universe was so narrow than its galaxies could find themselves in a cause and effect contact. In the instant t= 10-35 s it started to expand suddenly and very quickly, then, just in 10-32 seconds, it increased its dimensions of a 1050 factor. Then this expansion continued, like it had previously been described by the Big Bang standard model.
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