If the universe was infinite in extent at the beginning then it would have had an infinite amount of matter/energy. Had this not been the case, then it is incredible hubris to think that WE happen to be in the one part that had matter/energy. The Anthropic Principle, of course, can be used to say that well of course we have to be in that part, but I think that's a cop-out.JonathanCollins said:I have read it again and still reach the same understanding. To clarify at what point and under what circumstances are you saying that there would have been an infinite amount of matter/energy?
JonathanCollins said:What is your opinion on the existence of anything external to the singularity (matter, energy, space et al) at the moment of the big bang?
Jonathan I'd like to invite you to take a break from arguing matters of opinion at this point and try imagining a finite volume that has no boundaries.JonathanCollins said:... is still expanding it cannot be infinite. ...
That's a nonsensical, self-contradictory question. "Singularity" just means "what the hell ever existed at the point in time which we call t=0 when extrapolating back so far the math model gives unphysical results". "What the hell ever existed ... " includes everything, whatever it was.JonathanCollins said:What is your opinion on the existence of anything external to the singularity (matter, energy, space et al) at the moment of the big bang?
Murdstone said:Ten or fifteen years ago the prevailing theory was one of point expansion - existence happen at a finite point and expanded outward.
The question is no more nonsensical and self-contradictory than the mathematically extrapolated notion of a singularity existing within nothing and I assume from your response that you are simply puzzled by the paradoxes that follow. The theoretical singularity at the centre of a black hole is surrounded by a galaxy so by analogy with the theoretical singularity from which our observable universe was spawned it is rational to assume something outside of that theoretical singularity. Indeed it is irrational to envisage a singularity that exists within nothing. Since current maths and physics break down at the singularity the state of the universe at that time is currently open to debate and interpretation.phinds said:That's a nonsensical, self-contradictory question. "Singularity" just means "what the hell ever existed at the point in time which we call t=0 when extrapolating back so far the math model gives unphysical results". "What the hell ever existed ... " includes everything, whatever it was.
rootone said:BBT is a theory applicable to the observable universe, which is not infinite.
The entire universe may or may not be infinite and as far as I know, BBT doesn't have a lot to say about it.
Hi Marcus, yes I have come across these concepts many times and despite possessing a very fertile imagination I can't imagine being a 2D creature and I don't believe it is really possible to do so other than merely having faith in it as an idea in order to avoid the troubling paradoxes that present themselves when attempting to explain the observed evidence with known physics.marcus said:In my experience over the years with the PF Cosmo forum the people who can think visually in new ways and want to learn tend to stay around and people who want to debate matters of verbal opinion tend to go away.
Jonathan I'd like to invite you to take a break from arguing matters of opinion at this point and try imagining a finite volume that has no boundaries.
Nothing outside or inside it, just it.
Analogous to a balloon surface with all existence concentrated on the 2d surface---nothing inside or outside of it. No boundary because closed around on itself. Like a circular ring has no boundary.
Can you picture the analogous 3d volume?
Also Jonathan can you imagine the experience of being a 2d creature living in the zero thickness 2d surface of the balloon?
Say it is expanding. It is not expanding INTO anything, because there is no external space. All existence is concentrated in that finite area.
How do you experience the expansion? You and your family and your 2d house stay the same size but larger scale distances (like between disconnected galaxies) grow.
Can you imagine living in an infinite volume space that is expanding? It is not expanding INTO anything because there is no outside of it either. What would its expansion look like for someone dwelling in it?
Just because I'm encouraging you to exercise your visual imagination doesn't mean I'm trying to *convince* you of anything. the issue is suppleness of visual imagination, not opinion.
In fact I personally prefer to imagine the cosmos as having no boundaries and a FINITE spatial volume. But some people prefer to think of it as spatially infinite, and we never argue about this because so far the question has not been resolved. It may be resolved in the future, with more and more precise observations (or it might never be resolved...)
But you say so yourself that there actually is no singularity -- that it is a place at which the physical reality ceases to be accurately described by the mathematical model. Indeed, the physics of the big bang itself -- the event at t=0 -- is unknown (you can interpret and debate all you like, but that's not science). That said, cosmological observations do not support the idea that a point-source was the originating event; in other words, there was no pointlike singularity that exploded into the universe. Rather, the big bang effectively happened everywhere at once, perhaps in an already infinite universe. Because of this, it makes no sense to puzzle about things external to the big bang, as if it occurred in a pre-existing ambient space. That's simply not consistent with the observations, and it's not theoretically necessary.JonathanCollins said:The question is no more nonsensical and self-contradictory than the mathematically extrapolated notion of a singularity existing within nothing and I assume from your response that you are simply puzzled by the paradoxes that follow. The theoretical singularity at the centre of a black hole is surrounded by a galaxy so by analogy with the theoretical singularity from which our observable universe was spawned it is rational to assume something outside of that theoretical singularity. Indeed it is irrational to envisage a singularity that exists within nothing. Since current maths and physics break down at the singularity the state of the universe at that time is currently open to debate and interpretation.
Marcus is trying to get you to use a lower-dimensional analogy to better understand our 3D universe! He's not literally entertaining the possibility of 2D beings...surely you understand this? Surely you understand that the balloon analogy is not meant to actually convey that the universe is made of rubber and has a tiny thickness? You say you've entertained these ideas with your "fertile imagination" but I think maybe you've missed the point of the lesson.JonathanCollins said:Hi Marcus, yes I have come across these concepts many times and despite possessing a very fertile imagination I can't imagine being a 2D creature and I don't believe it is really possible to do so other than merely having faith in it as an idea in order to avoid the troubling paradoxes that present themselves when attempting to explain the observed evidence with known physics.
Interesting though the topic is to my knowledge no evidence exists to support the notion of extra dimensions so they currently remain the domain of science fiction.
Nobody is talking about extra dimensions.The potential existence of an extra dimension that is "too tightly wrapped up on itself to be visible" can be disproved by considering a line of thickness equal to the size of the dimension passing through it and thus causing its existence as a separate dimension to collapse.