From my studies in Cosmology I've come to the conclusion that, in line with the first law of thermodynamics, that the universe was not created, or caused if you like. I believe that before the universe arrived at it's present form of matter and energy, it existed timelessly in the form of vacuum fluctuation energy. I don't have a complete understanding of the subject, and any further insights, especially by experts, would be greatly welcomed.
The idea is that over giant spans of time, the universe loses a scale for spacetime. The scale is created by mass, and the (speculative) idea is that eventually, mass disappears.
So without a scale, there is a new Big Bang!
What's wrong with a universe that's temporally finite? We're talking about absolute fundamentals, so it seems to me that assuming a beginning is no more outlandish than assuming no beginning.
There have been plenty of speculations about how the universe came to begin, but they remain utter speculation; we have no basis for determining what happened before the Big Bang. It is theoretically possible that we might be able to detect asymmetries in the structure of the universe that might suggest something about the first instant of the Big Bang, but in general I think discussions of the universe prior to the Big Bang are entirely speculative.
discussions of the universe prior to the Big Bang are entirely speculative.
Roger Penrose described ways of testing his theory in Cycles of Time. It's very important for a physics theory to be testable.
He gave a talk on his theory, "Before the Big Bang", which can be found on Youtube.
Mr. Penrose is certainly one of our most brilliant physicists, but he, like many other great minds, sometimes plunges into, shall we say, strange territory. His claims that consciousness was due to quantum gravity have been politely but firmly rejected by the larger community of physicists. I don't want to denigrate Mr. Penrose, because the wanderings of minds such as his are worthy of respect even when they're wrong. On the question of a pre- Big Bang universe, it is indeed theoretically possible that we might eventually obtain data permitting some analysis of such a possibility. The general notion of a cyclic universe has been around for a long time and has taken many guises, Mr. Penrose's being one. At this time discussions of this subject are enjoyable speculations. I don't want to stomp on such discussions, but I think we should all be aware of the fact that, until more data is obtained, this remains a topic in which there is little in the way of information to guide us.
OK, I thought when you said it was entirely speculative, you meant not even theoretically testable. This is not the case with Roger Penrose's cyclic universe theory. Nor necessarily with other models of what happened before the Big Bang.
His theory is certainly a wonderful idea, but as I said in my review, we don't yet have a theory that predicts the disappearance of mass over vast eons of time. Such a theory would require integrating quantum mechanics with de Sitter spacetime, which is the universe with accelerating expansion that we apparently are in.
I agree, his quantum consciousness theory is quite dubious, and I also found the argument he made for it in his popular book The Emperor's New Mind, unconvincing. I felt reading it that he's better off sticking to mathematical physics :)
But who knows - maybe his quantum consciousness theory will be validated someday.
By the way, Penrose also came up with quasi-periodic tilings of the plane with 5-fold symmetry, and crystal(s) with a 5-fold diffraction pattern have been found - implying they have quasi-periodic symmetry. I used to wish when I was a kid, for a dodecahedral or icosahedral crystal, I suppose the reason why I didn't find any was that there aren't 3D space groups with 5-fold symmetry. But maybe there are some :) although rare.
I confess that I haven't read the book; I've only rummaged through various discussions about it. There's one point that I find confusing. Apparently Mr. Penrose seems to think that the low entropy of the early universe is puzzling. I find such a position so counterintuitive that I find it hard to believe that Mr. Penrose actually wrote this. Could you clarify for me his writing on the evolution of entropy of the universe?
What's puzzling about the low entropy of the Big Bang is, where did it come from? With the usual model of a collapsing universe, the singularity at the end of the collapse is very high in entropy - or Weyl curvature, which is the gravitational version of entropy.
Roger Penrose thinks that some of the entropy disappears in black holes. Over vast stretches of time, some of the matter in the expanding universe (I'm not sure how much) disappears into black holes. Eventually, over further huge stretches of time, the black holes disappear by Hawking radiation. I think Penrose feels that when the black holes disappear, some of the entropy in them disappears.
I think entropy disappears during the extremely radical process where the universe loses the scale of spacetime, but I don't remember if Penrose discusses that in the book.
So that would explain the very low entropy of the Big Bang.
It seems to me that there's a ridiculously simple explanation for the low entropy of the original universe: Second Thermo. Apply 2T to the universe and its entropy has to increase; therefore the entropy of the original universe will be lower than its current entropy -- MUCH lower, I should think.
Does Mr. Penrose address this point?
Of course he knows that. But, where did the low-entropy Big Bang come from? That's the puzzle.
It wouldn't come from a previous universe that collapsed, because the singularity resulting from a collapse would have very high entropy.
I'm still confused. When Mr. Penrose asks, "Where did all that negentropy come from?" isn't he presuming that it came from somewhere, that is, some universe that existed prior to the Big Bang? He seems to be saying "That negentropy could not have come from nowhere; therefore it must have come from something before the Big Bang; therefore, there was a universe before the Big Bang." There's something tautological in this; why must we believe that negentropy must have come from somewhere? The whole idea behind the Big Bang is that all this mass-energy suddenly appeared at time = 0, and we don't know where it came from; it just appeared. Why can't we say the same thing about negentropy?
So far as I know, negentropy is something that applies to systems that lower their entropy by exporting it.
Penrose isn't talking about negentropy - he's trying to explain where the very low entropy state at the Big Bang, came from.
The Big Bang theory doesn't assume that the universe just appeared suddenly, with nothing before it and no cause.
People don't know what came before the Big Bang. They may not even be sure there had to be a "before". Stephen Hawking proposed a theory where there is no "before" the Big Bang. I'm not sure what the current opinion about his theory is.
Quantum mechanics hasn't yet been integrated with curved spacetime. In other words, there isn't yet a theory of quantum gravity. And quantum gravity is important to understand the Big Bang itself, because the Big Bang would be extremely dense and on an extremely small scale (infinite density might be avoided in a theory of quantum gravity).
So theories about "before the Big Bang" are at the frontier of physics. Nobody really knows.
Theists love the idea that the universe suddenly popped into existence with the Big Bang, because it suggests to them a Creator who made it. Penrose refers to that when he has cartoons of the Big White Man in the Sky, with a pin poking at the tiny tiny spot of state space where the Big Bang was.
There are a huge number of possibilities for the Big Bang singularity, in other words, and they would almost all have had higher entropy than the actual Big Bang. So the question is, why did the Big Bang have such low entropy?
When there's an apparent extreme coincidence in physics, it usually means there's something we don't understand. So Penrose is trying to explain it.
Luara, I think you and I speak different languages. In my language, negentropy is merely the opposite of entropy. Where entropy is disorderliness, negentropy is orderliness. Switching between the two is merely a matter of making an expression least confusing. What does negentropy mean in your language?
When I was in grad school, many years ago, the current thinking was that the laws of physics cannot be extended through the singularity at t=0; therefore, any discussion of events in t<0 was meaningless. I realize that much has happened since then, but the failure of any theory in the last 30 years that attempts to explain anything prior to t=0 certainly lends support to that old thinking. My understanding was that the Hartle-Hawking thing was simply a formalization of what we already suspected.
The fact that theists like the idea of a creation of the universe has zero bearing on this discussion; some theists like chocolate ice cream but that has zero bearing on the qualities of chocolate ice cream. In fact, I'll point out that Big Bang has always suffered from a preference for a "nicer" universe, in which there is no beginning and no ending, just an endless parade of new things. I have no feelings whatever regarding this question; if the universe will end as a cold, empty expanse of highly rarified fundamental particles, that's fine with me. If it will go through cycles, that's fine with me. I don't wish to impose my notions of happy endings (or happy beginnings) on my understanding of the universe.
The only solid arguments I have seen regarding the possibility of discovering anything about t<0 concern the possibility of finding large-scale asymmetries in the structure of the universe. If it's lopsided, then it had to start lopsided, which strongly suggests that it came from something.
I have come to think of the physical universe in terms of information. The universe started off with a finite supply of information, and a kind of "conservation of information" has required its expansion and Second Thermo at the macro level and Uncertainty Principle at the micro level. However, I leap to point out that this is my personal speculation, and I have some serious reservations about it.