Is time infinite?

S.Augustin, by Louis Comfort Tiffany
Lightner Museum

Since ancient times, man has been interested in the enigma of time. Even though we all experience time, time is an enigma. As St. Augustine said in his Confessions (B.XI C.XIV): What is time? If no one asks me, I know; if I want to explain it to a questioner, I don’t know.

As I said in another post, the explanations devised to solve the enigma of time are of two types: those that consider it cyclical, with or without multiple repetitions, which would allow the passage of time to be represented geometrically by a circle, and those that consider it linear, which represent it by a straight line. In turn, this last case is divided into several: one can accept, or not, that time had a beginning; and one can accept, or not, that there will be a final moment of time. Combining these two alternatives, we have four different cases. So in total there are six possibilities, which we will analyze next in the light of modern cosmology:

1.      Single cyclic time: This would correspond to a closed universe where the time between the Big Bang and the maximum expansion was the same as the time between the maximum expansion and the Big Crunch, but running in the opposite direction. There are theories supporting this, absurd as it may seem.

2.      Multiple cyclic time: This would correspond to a closed universe where each Big Crunch would bounce and become a new Big Bang that would start a new cycle. In this case, it is not necessary to assume that time does strange things during the contraction phase.

3.      Linear time with no beginning or end: This would correspond to a universe like that of the steady state theory, where there was no Big Bang, or to the multiverse of perpetual inflation (or eternal inflation, as some physicists call it, who do not know that eternity is not the same as perpetuity), where an infinite number of universes like ours would continually emerge, enormously separated from each other, some of which would be closed, but others could be open, and therefore without end.

4.      Linear time with no beginning, but with an end: This would correspond to one of those universes of the multiverse of perpetual inflation, which after starting with a Big Bang would end in a Big Crunch without rebound.

5.      Linear time with a beginning but without end: This would correspond to a universe that would have started in a Big Bang not associated with an inflationary multiverse, which were flat or open, i.e. it would expand indefinitely without ending, although at some point it would stop being favorable for life and reach thermal death. I spoke about this in another post.

6.      Linear time with a beginning and an end: This would correspond to a universe that would have started in a Big Bang not associated with an inflationary multiverse, which were closed, i.e. it would stop expanding at some point and contract until a Big Crunch without rebound.

What does modern cosmology say about all these alternatives? As we saw in the previous post, right now we do not know if our universe is flat (curvature=0), open (curvature<0) or closed (curvature>0). It seems that it is almost flat, but due to the almost we cannot eliminate any possibility.

On the other hand, theories based on the multiverse of perpetual inflation are based on pure speculation, with no real physical basis. It cannot even be said that the theories of the inflaton field and all its accessories are based on a coherent mathematical theory, because those who defend them continually change the mathematical assumptions to face the difficulties they encounter. Of course, there is no experimental observation that confirms, not just the inflationary multiverse, but even the inflation after the Big Bang, which was proposed to solve a couple of problems associated with the Big Bang theory (the isotropy of the visible universe, the fact that the universe is almost flat, and the absence of magnetic monopoles), but which has not managed to make a single surprising correct prediction that validates it.

I repeat that right now it cannot be said that there is a coherent mathematical theory of perpetual inflation. Its defenders can say what they like, but one cannot help feeling that this is a desperate attempt to eliminate the Big Bang as the origin of the universe and thus escape the need for God, which they believe is associated with that origin.

Case 2 (multiple cyclic time) also presents difficulties. According to the calculations made, the bounce from a Big Crunch to a new Big Bang would probably be damped, so that it would not be possible for the number of previous bounces to be infinite, and after a certain number of bounces the universe would become open, with time becoming linear. This implies that this type of universe would have to have a beginning.

Theoretical physicists have a lot of fun inventing worlds, but I think they should leave that to science fiction writers. Right now, based on what we know, and disregarding unsupported speculation, our universe is most likely a type 5 or 6 universe, having started in a Big Bang and ending either in the thermal death or a Big Crunch, after which we can’t predict anything.

The same post in Spanish

Thematic Thread about Time: Previous Next

Manuel Alfonseca