It's assumed that if it is infinite then it was always infinite. In any case, it was never a single point.outremer said:If the universe is infinite and if it started out of a finite singularity, how did it make this step ? From finite to infinite ? This looks a hard thing to do ?
It didn’t. At least not according to current cosmological models.outremer said:If the universe is infinite and if it started out of a finite singularity,
outremer said:If the universe is infinite and if it started out of a finite singularity, how did it make this step ? From finite to infinite ? This looks a hard thing to do ?
Careful here, our Observable universe is finite. It can originate from a portion of an infinite universe. We can't forget the universe is far larger than our Observable universe.PeroK said:It's assumed that if it is infinite then it was always infinite. In any case, it was never a single point.
I'll make cerrtain never to do that.Mordred said:Careful here, our Observable universe is finite. It can originate from a portion of an infinite universe. We can't forget the universe is far larger than our Observable universe.
Indeed. This is perhaps true in math, but there's no evidence that this is possible in the physical universe.Hornbein said:There is a way to get from finite to infinite. Increase size by X percent in a second. Do it again in a half second. Again in a quarter second. Etc. This however seems nonphysical.
However, I seem to understand that in this video Alan Guth is implying that there is a way in which a finite universe can become infinite.Mordred said:A finite universe will not become infinite.
The words I heard him use at about 2:10 were "begins in a very small region which we can model as a point".Jaime Rudas said:However, I seem to understand that in this video Alan Guth is implying that there is a way in which a finite universe can become infinite.
In large-scale cosmology, a galaxy or even a galaxy cluster can be modeled as a point!jbriggs444 said:The words I heard him use at about 2:10 were "begins in a very small region which we can model as a point".
That is not an argument that something finite can become infinite.
We model the tip of a pencil as a point. That does not make it one.
Yes, but at 2:50 he says: "[...] at any given time the bubble is finite [...] the space-time is tremendously distorted inside this bubble compared to what looked like outside and inside the bubble you really have what is equivalent to this infinite model of the universe that we talked about earlier, this open model [...]"jbriggs444 said:The words I heard him use at about 2:10 were "begins in a very small region which we can model as a point".
That is not an argument that something finite can become infinite.
We model the tip of a pencil as a point. That does not make it one.
This is an issue of a coordinate transformation and what you call "time", which defines the simultaneities inside the bubble. In the same sense you could say that the light cone of an event in special relativity is spatially infinite because if you go to Milne coordinates then the spatial hypersurfaces of constant Milne time become infinite. Would most people conclude that the light cones are spatially infinite? I would not think so.Jaime Rudas said:Yes, but at 2:50 he says: "[...] at any given time the bubble is finite [...] The space-time is tremendously distorted inside this bubble compared to what looked like outside and inside the bubble you really have what is equivalent to this infinite model of the universe that we talked about earlier, this open model [...]"