NASA/ ADBOE STOCK/ RYAN WILLS
Our universe is expanding and must have been small in the past. Certainly, rewinding the cosmological film shows that the universe has almost shrunk nearly 13.8 billion years ago. Is this when time begins? Alas, things aren’t that simple. Albert Einstein’s general theory of relativity shows that the universe’s background is space-time, a continuum of fluids that has no absolute meaning in space or time. Furthermore, in the Big Bang, space-time is distorted to points of infinite density called singularities. This is not the beginning of time, but it is simply to mark a rupture that cannot be extrapolated beyond that.
Still, some cosmologists believe there is a “front” of the Big Bang. Some have suggested that another universe precedes our universe, and that this contracted and “bounced” in the Big Bang. More fundamentally, cosmologist Roger Penrose proposes that through the dramatic “rescaling” of all spacetime, a new universe can emerge from what is not constricted.
In both these scenarios, time is eternal, but that’s just one possibility. The late cosmologists Stephen Hawking and James Hartle suggested that time was once a normal dimension like the universe, derailing into spacetime in the Big Bang. Another strange idea is that spacetime is made up of particles-like parts. If so, these can be placed at various stages, similar to steam and liquid water. Perhaps the Big Bang was the point they “condensed” into the liquid, continuous space-time, which we observe today.
Source: www.newscientist.com
