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Ed Lenarduzzi
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If the big bang through matter in every direction away from itself (the center) shouldn't there be a huge void there?
Chronos said:Thus, an infinite universe is the popular choice among cosmologists. A universe that is infinite now must always have been infinite, because a finite entity cannot grow to infinite size. This sums up why we believe the universe did NOT originate at any specific point within the current observable universe.
You are missing that it was NOT "packed into the size of a pinpoint prior to the big bang", if it is infinite now, it was infinite then, exactly as Chronos said.lifeonmercury said:If the universe is in fact infinite and the cosmological principle holds true, there should be an infinite amount of matter in the universe. Does this mean that an infinite amount of matter was packed into the size of a pinpoint prior to the big bang?
That doesn't seem to make any sense. What am I missing here?
"Singularity" in this context does NOT, as you seem to believe, mean "a point in space". What is means is "the place where the math model gives unphysical answers and we don't have any idea WHAT was really going on". This is perhaps the single most common misconception in cosmology and has been commented on here on PF approximately 14,000 times.lifeonmercury said:I interpreted Chronos' comment to mean that the Big Bang ‒ although not an explosion from a single point outward as often portrayed in popular science ‒ marked the beginning of the universe (and time and space) and that the universe has been infinite since its inception. Prior to the Big Bang, however, there was a singularity that is believed to have had infinite density. I would like to know if this singularity contained an infinite amount of matter.
lifeonmercury said:there was a singularity that is believed to have had infinite density
Exactly.weirdoguy said:Singularity means that the model we are discussing breaks down. It's nothing physical, so actually your question doesn't make sense.
lifeonmercury said:Does this mean that an infinite amount of matter was packed into the size of a pinpoint prior to the big bang?
lifeonmercury said:A.) Before the Big Bang, the universe didn't even exist at all so it was not infinite then.
lifeonmercury said:B.) In the very instant the Big Bang took place, the universe that was created immediately had an infinite amount of space.
C.) There is an infinite amount of matter in the universe.
lifeonmercury said:D.) It's impossible to know what was before the Big Bang and where all the matter in the universe came from.
I'm fond of saying that the BB was simply an evolution of space and time [henceforth known as spacetime] as we know them. The observable Universe we see today, arose from that.Bandersnatch said:[
At some point, as your distances go to zero, the process gives you unreasonable results: densities and temperatures trendining to infiinity. This is an indication that the extrapolation you were using enters a domain it's no longer applicable in. So you just stop using it. You don't take the infinities (i.e. the singularity) as a valid prediction of a physical state - you just accept that your theory doesn't work beyond some time in the past.
The point here is that it doesn't make sense to ask what the BB theory says about what was before what it describes.
I don't think I understand what that means.maroubrabeach said:BB was simply an evolution of space and time [henceforth known as spacetime]
Simply referring to space and time, as the accepted 4 dimensional background against which the laws of physics and GR operate and in which we exist and within which it is possible to locate events and describe the relationships between.Bandersnatch said:I don't think I understand what that means.
The BB was the evolution of space and time, as distinct from matter,[in the first instant] is the important point being made.Bandersnatch said:I understand what space-time is. I don't understand what it means for it to evolve.
If space-time is the thing being modeled then there is no time left over for it to evolve within. There is also no first instant.maroubrabeach said:The BB was the evolution of space and time, as distinct from matter,[in the first instant] is the important point being made.
I'm not sure I understand what you are inferring. As per the BB model, space and time had a beginning as we know them, and that can be applied at t+10-43 seconds. Our first fundamentals did not evolve until around t+10-33 seconds when the hypothetical Superforce started to decouple. These happened around 13.83 billion years ago.jbriggs444 said:If space-time is the thing being modeled then there is no time left over for it to evolve within. There is also no first instant.
There is no first instant because we model things using "open" sets. An open set, is like an open interval. For instance, the open interval between 0 and 1, exclusive. There is no smallest number within this interval. Similarly, there is no first instant in a space-time with an initial singularity.
maroubrabeach said:I'm not sure I understand what you are inferring.
I'm saying space and time, [spacetime ] had its beginnings as we understand them at the BB, and which we are able to reasonably describe and assign the laws of physics and GR to, at t+10-43 seconds. There is no before according to the BB.weirdoguy said:Maybe he refers to the fact that specetime does not evelove in time in the sense that you are thinking, because it does not live "next to time" the way that space does (in our everyday thinking). Spectime contains all events, the future, and the past. Everything is in it already.
maroubrabeach said:I'm saying space and time, [spacetime ] had its beginnings as we understand them at the BB, and which we are able to reasonably describe and assign the laws of physics and GR to, at t+10-43 seconds. There is no before according to the BB.
Hi Drakkith: Yes, I certainly understand that at some critical value, the maths blows up: This is at t+10-43 seconds, and the region where quantum effects take hold as I understand it.Drakkith said:My understanding is similar to jbriggs444's. The BBT models spacetime in a certain way and this model simply stops working when the density of the universe reaches some critical value and the math 'blows up'. I don't believe it describes spacetime as 'coming into existence' at this time.
maroubrabeach said:Hi Drakkith: Yes, I certainly understand that at some critical value, the maths blows up: This is at t+10-43 seconds
maroubrabeach said:Extrapolating back to the instant of the BB, is presumed as the beginning of space and time, except of course as you say, the maths blows up and we have nothing of that era...which is why I said earlier that space and time, [spacetime] as we understand them, came into existence, or evolved at t+10-43 seconds, at least that is what I have understood over the last few years.
In essence, according to the BB, there was no before and time and space [as we understand them] did have beginnings.
Perhaps I'm putting this rather poorly, or perhaps after all these years, what I have believed to be understood by the BB is wrong.
I totally agree with your statement that the BB says nothing about the how or why spacetime came into existence, or evolved, but from my understanding, and as encompassed by the BB, it does say that space and time had a beginning.Drakkith said:I think that point is t=0, not t=10-43.
I think the key point is that the Big Bang Theory doesn't say a thing about how spacetime or the universe came into existence. It merely does its job at making predictions about the conditions of the universe until it has to throw in the towel at t=0. Note that t=0 shouldn't be taken as "nothing came before this", it's just that we can't make predictions past this point as I understand it. Someone correct me if I'm wrong please.
The "BB model" does not go anywhere nearly that far back. Idealized extrapolations can go back to that neighborhood, but they have no scientific validity -- there is no experimental test that can confirm or refute their correctness in that regime. However, that is not the point that I am trying to make.maroubrabeach said:I'm not sure I understand what you are inferring. As per the BB model, space and time had a beginning as we know them, and that can be applied at t+10-43 seconds.
I agree, as I said to Drakkith in the following...jbriggs444 said:To say it briefly: "If there is a singularity in the model at t=0 then t=0 is not part of the model".
Perhaps I have not put it clearly enough, and my use of extrapolation back to t=0 was wrong.maroubrabeach said:I totally agree with your statement that the BB says nothing about the how or why spacetime came into existence, or evolved, but from my understanding, and as encompassed by the BB, it does say that space and time had a beginning.
I also understand that our understandings, maths, laws and GR fail at the quantum/Planck level, which is at 10-43 seconds after the instant of the BB. This is when as I understand it, and as you put it, "we can throw in the towel"
This is why physicists are working towards a QGT.
I also realize that the further back we go, the less certain of conditions we become, but particle accelerators such as the LHC have taken us pretty close to t+ 10-43 seconds, is that correct?.jbriggs444 said:The "BB model" does not go anywhere nearly that far back
maroubrabeach said:I totally agree with your statement that the BB says nothing about the how or why spacetime came into existence, or evolved, but from my understanding, and as encompassed by the BB, it does say that space and time had a beginning.
Cosmologist and science communicator Sean M. Carroll explains two competing types of explanations for the origins of the singularity which is the main disagreement between the scientists who study cosmogony and centers on the question of whether time existed "before" the emergence of our universe or not. One cosmogonical view sees time as fundamental and even eternal: The universe could have contained the singularity because the universe evolved or changed from a prior state (the prior state was "empty space", or maybe a state that could not be called "space" at all). The other view, held by proponents like Stephen Hawking, says that there was no change through time because "time" itself emerged along with this universe (in other words, there can be no "prior" to the universe).[5] Thus, it remains unclear what combination of "stuff", space, or time emerged with the singularity and this universe.
maroubrabeach said:Hi Drakkith: Yes, I certainly understand that at some critical value, the maths blows up: This is at t+10-43 seconds, and the region where quantum effects take hold as I understand it.
Extrapolating back to the instant of the BB, is presumed as the beginning of space and time, except of course as you say, the maths blows up and we have nothing of that era...
I have plenty of respect for Sean Carroll and his general cosmology knowledge, but speculation is just that: Nothing wrong of course in speculating as that is generally the first step to any legit scientific theory.Drakkith said:On the contrary, it says nothing of the sort. That's what jbriggs444 and I have been saying. There are, in fact, speculative models regarding the existence of the universe prior to the big bang. These would overlap with the standard BBT at some point in the past near where the BBT breaks down.
To quote from wiki: https://en.wikipedia.org/wiki/Cosmogony
Hmmm, OK, I'm sure I've seen it in reputable sources as I have detailed.Drakkith said:While it is certainly possible that spacetime had a beginning, the BBT doesn't say either way. Hence the disagreement between scientists noted in the quote.