Conformal Cyclic Cosmology: Is the end of the universe the beginning?
It is generally accepted in cosmology that around 14 billion years ago, all that existed was a singularity. A single, dense, hot point. This underwent a brief period of inflation before a subsequent expansion into the universe we know today. This process is described as the Big Bang — incidentally, a pejorative term coined by the astronomer Fred Hoyle in 1949 to describe the seemingly paradoxical appearance of reality from an explosion.
At the time, Hoyle favoured the steady-state model of cosmology, advocating for a universe that had been around forever, gradually creating more matter to fill the gaps as it expands. This model of a constant-density, eternal universe is now rejected by cosmologists. There is substantial modern evidence that suggests a finite-aged universe that started with the Big Bang and a fixed amount of matter that continually spreads out with the expansion of space.
But what if it were possible to reconcile the notions of an eternal universe with the Big Bang? Is it possible for us to have our cosmological cake and eat it too?
Our universe started in a surprisingly ordered — low entropy — state, which allowed it to fill itself with stars, galaxies, and life. As time moves on, however, the universe slowly decays into disorder — this is characterised by increasing entropy, a property that describes how energy in the universe becomes progressively less useful for doing stuff like forming stars, making vegan pizza, and existing.
Eventually, as the universe becomes more disordered, structures will decay, stars will die, and even black holes will evaporate. The increasing entropy of the universe will ultimately lead to the heat death of the universe. At this point, there won’t be much left apart from cold, dark space and the occasional photon travelling forever into the void.
It seems like a bleak picture for the universe. Compared to its apparent beginning, the ending is a damp squib. A slow fizzling out, with no possibility of anything else interesting happening. Unless, of course, you consider dark, cold, nothingness to be interesting, in which case, great (though shame you won't be there to enjoy it).