Great posts in this thread as usual Astyanax!
Originally posted by Astyanax
First of all, the damn’ thing was only infinitely massive because it had zero volume. Since anything divided by zero is infinite, its density (mass per unit volume) was infinite. As soon as it expanded to any size at all, its mass ceased to be infinite. Its energy, by the way, was zero. And remains zero.
When you say "it doesn't make sense" what you really mean is that our human brains which evolved to help us gather food as hunter-gatherers do little to help us conceive of time and dimension scales outside our human experience.
Originally posted by Illustronic
If the big bang started from a point with no volume, and expanded from there, wouldn't there be some detectable void somewhere? BTW, infinite mass with no volume doesn't make sense, even the mass we can detect to some calculable figure with no volume still doesn't make sense.
Q:.. how is it possible for something to have zero volume and infinite density?
A: This is indeed difficult to grasp. Actually at the center of a black hole spacetime has infinite curvature and matter is crushed to infinite density under the pull of infinite gravity. At a singularity, space and time cease to exist as we know them. The laws of physics as we know them break down at a singularity, so it's not really possible to envision something with infinite density and zero volume.
How can the Universe be infinite if it was all concentrated into a point at the Big Bang? ...It looks to me like the guy is making some assumptions about what's outside the observable universe. Do you know of any evidence to support his model of what's outside the observable universe? I don't. My understanding is a lot different than his. I can't prove he's wrong and I also can't prove you don't have invisible gnomes running around your back yard. I have no problem with his expanding green circle, that part I get, it's all the galaxies outside the green circle in the left hand view that I don't get.
If the big bang started from a point with no volume, and expanded from there, wouldn't there be some detectable void somewhere?
BTW, infinite mass with no volume doesn't make sense, even the mass we can detect to some calculable figure with no volume still doesn't make sense.
I don't think the big bang really means a point in space, I'm much more comfortable with it meaning a point in time.
I really don't think that kind of imagination of efforts in real science benefits anything, its a total waste of time, unless you get a nice TV gig like Michio has. Science should not be confused with philosophy.
What if since black holes suck up all matter and gas nearby, that if this mass does get taken to some no-mans-land where this matter gathers, when the universe is basically devoid of any light because all the galaxies have expanded away from each other and used up their gas to create stars, the black holes have sucked up enough mass to explode, triggering a new Big Bang, making time cyclic. If somehow the material from all the black holes was taken to one common point where they all meet, then maybe near the end of the universe after they've sucked up tons of mass, when space begins expanding to the point that it reaches the speed of light, maybe this somehow alters the laws of physics or triggers the black hole matter to explode, creating a Big Bang, re-setting the universe or creating a new universe with that matter to form the universes.
Actually it looks like he's showing the diameter of the observable universe as 78 billion light years, and Wikipedia says it's 93 billion light years. I wouldn't quibble with either of those numbers nor the difference between them, but if we assume either number could be right and the observable universe is 75-100 billion light years in diameter, I just don't see how he can show what's outside of THAT! (which is what he seems to be showing with galaxies outside of that diameter). As soon as I figure out how to disprove the invisible gnomes on your back yard, maybe I can prove him wrong, or at least show that he's making assumptions he can't prove.
Originally posted by Astyanax
I agree with you; I think Prof. Wright is making a big, unwarranted assumption. I mean, of course there are galaxies beyond the 13.9 billion light-year radius of the observable universe. The metric expansion of space, which causes very distant galaxies to move away from each other at greater than the speed of light, would see to that.
That's pretty much how I see it. What surprises me is how many supposedly credible sources seem to say it could be infinite. I tend to think as you do that if it is infinite, our model may be wrong. Then again, I'm not sure our model is completely right, it's just the best model we have at the moment. I tend to think that our model may be right in saying the universe isn't infinite, but I admit that may only be because comprehending infinity is not something I'm comfortable with. You said infinity is a concept of the human mind, though it may be slightly beyond the grasp of mine. I can write the symbol infinity, but envisioning something that truly is infinite is beyond my grasp.
But unless our current cosmological ideas are to be abandoned altogether, it’s hard to see how the universe could possibly be infinite.
That question is a bit like standing on the surface of Mars, and asking "where is the center of the surface of Mars"?
Originally posted by Alxandro
Another problem is that no one can actually point in the direction that the Big Bang originated from.
Did it come from the West or East?
Maybe North or just slightly South?
Originally posted by smithjustinb
I do support the notion of a Big Bang, but my question is, where did that unfathomably dense point of energy and mass come from?
Had it always existed?
The first something can only have come from a nothing...
What exactly is a "nothing" that can have "something"?
Why doesn't The Big Bang happen again?
I have my opinion, but I want to hear yours.