B Is the center of the universe empty?

[jbriggs444]

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.

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.

When you take an idealized extrapolation which features a singularity, that extrapolation takes the form of a "manifold". A manifold models space time as a continuum in which every part can be described with an n-dimensional cartesian coordinate system in which Newton's laws hold good -- locally. That "locally" part is important. It means that for any accuracy you specify and for any event in space-time you select, one can always find a neighborhood around that point which is small enough so that Newton's laws hold good throughout that neighborhood to the accuracy specified. As you approach the edges of the region that is covered by the coordinate chart, you may find that things get more and more extreme. The neighborhoods you have to pick so that Newton's laws are upheld may get smaller and smaller as you approach the edge.

You may find that even though you can get closer and closer to the edge, you can never succeed in extending a coordinate system all the way to (and past) the edge. In that case, the edge is a singularity. All points up to the edge are part of the manifold. But the edge itself (aka the singularity) is not part of the manifold.

To say it briefly: "If there is a singularity in the model at t=0 then t=0 is not part of the model".

 

[maroubrabeach]

To say it briefly: "If there is a singularity in the model at t=0 then t=0 is not part of the model".

I agree, as I said to Drakkith in the following...

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.

Perhaps I have not put it clearly enough, and my use of extrapolation back to t=0 was wrong.

The "BB model" does not go anywhere nearly that far back

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?.
Direct observations as far as I know, will never be possible further back then 380,000 years post BB, or when temperatures had dropped far enough to allow electrons to be captured by atomic nuclei.

 

[Drakkith]

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.

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

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.

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.

 

[nikkkom]

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...

When the math of your theory stops working, you cannot rigorously extrapolate past that point. The rigorous answer to "what was before this point according to your theory?" is "I don't know".
(If course, people can, and do embark on various handwavey explanations past that point, but this is not real knowledge).
In particular, it may well be so that with a better theory, past that point there is an infinitely long past, not a "beginning of spacetime". Many eternal inflation models are like that.

 

[maroubrabeach]

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

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.
I like to speculate myself that the BB is simply the back end of a BH from another universe, or a White Hole.
The BB theory though while only being a theory of the evolution of space and time from t+10-43 seconds, as distinct from telling us how or why, or anything else about the quantum/Planck realm, is still the overwhelming supported theory.
The BB theory also arose from the theory of dynamic spacetime as predicted by GR, and all mathematical conclude with t=0 and a singularity where all our solutions and knowledge break down.

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.

Hmmm, OK, I'm sure I've seen it in reputable sources as I have detailed.
Thanks for an interesting debate anyway...given me stuff to think about.

 

[maroubrabeach]

When the math of your theory stops working, you cannot rigorously extrapolate past that point. The rigorous answer to "what was before this point according to your theory?" is "I don't know".
(If course, people can, and do embark on various handwavey explanations past that point, but this is not real knowledge).
In particular, it may well be so that with a better theory, past that point there is an infinitely long past, not a "beginning of spacetime". Many eternal inflation models are like that.

You are speaking of t+10-43 seconds?
Again, speculation as I said in my previous post, although I like the idea of eternal Inflation, but as yet still speculative.

What do you guys think of the following scenario...
https://www.astrosociety.org/publications/a-universe-from-nothing/

A Universe from Nothing
by Alexei V. Filippenko and Jay M. Pasachoff

Insights from modern physics suggest that our wondrous universe may be the ultimate free lunch.

Adapted from The Cosmos: Astronomy in the New Millennium, 1st edition, by Jay M. Pasachoff and Alex Filippenko, © 2001. Reprinted with permission of Brooks/Cole, an imprint of the Wadsworth Group, a division of Thomson Learning.
In the inflationary theory, matter, antimatter, and photons were produced by the energy of the false vacuum, which was released following the phase transition. All of these particles consist of positive energy. This energy, however, is exactly balanced by the negative gravitational energy of everything pulling on everything else. In other words, the total energy of the universe is zero! It is remarkable that the universe consists of essentially nothing, but (fortunately for us) in positive and negative parts. You can easily see that gravity is associated with negative energy: If you drop a ball from rest (defined to be a state of zero energy), it gains energy of motion (kinetic energy) as it falls. But this gain is exactly balanced by a larger negative gravitational energy as it comes closer to Earth’s center, so the sum of the two energies remains zero.

The idea of a zero-energy universe, together with inflation, suggests that all one needs is just a tiny bit of energy to get the whole thing started (that is, a tiny volume of energy in which inflation can begin). The universe then experiences inflationary expansion, but without creating net energy.

What produced the energy before inflation? This is perhaps the ultimate question. As crazy as it might seem, the energy may have come out of nothing! The meaning of “nothing” is somewhat ambiguous here. It might be the vacuum in some pre-existing space and time, or it could be nothing at all – that is, all concepts of space and time were created with the universe itself.

Quantum theory, and specifically Heisenberg’s uncertainty principle, provide a natural explanation for how that energy may have come out of nothing. Throughout the universe, particles and antiparticles spontaneously form and quickly annihilate each other without violating the law of energy conservation. These spontaneous births and deaths of so-called “virtual particle” pairs are known as “quantum fluctuations.” Indeed, laboratory experiments have proven that quantum fluctuations occur everywhere, all the time. Virtual particle pairs (such as electrons and positrons) directly affect the energy levels of atoms, and the predicted energy levels disagree with the experimentally measured levels unless quantum fluctuations are taken into account.

Perhaps many quantum fluctuations occurred before the birth of our universe. Most of them quickly disappeared. But one lived sufficiently long and had the right conditions for inflation to have been initiated. Thereafter, the original tiny volume inflated by an enormous factor, and our macroscopic universe was born. The original particle-antiparticle pair (or pairs) may have subsequently annihilated each other – but even if they didn’t, the violation of energy conservation would be minuscule, not large enough to be measurable.

If this admittedly speculative hypothesis is correct, then the answer to the ultimate question is that the universe is the ultimate free lunch! It came from nothing, and its total energy is zero, but it nevertheless has incredible structure and complexity. There could even be many other such universes, spatially distinct from ours.
::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

Professor Lawrence Krauss, as you probably know, also has a book out entitled "A Universe from Nothing"

 

[Chronos]

This is obviously a BS parade, you cannot assert something originated from nothing without violating every known law in the universe. W e either need new laws or a broader definition of 'reality ',

 

[maroubrabeach]

This is obviously a BS parade, you cannot assert something originated from nothing without violating every known law in the universe. W e either need new laws or a broader definition of 'reality ',

Hi Chronos:
What speculative scenario do you suggest to explain why the universe exists, or for that matter, why we exist, also?

http://www.phys.utas.edu.au/physics/aip_tasbranch/program/Abstracts/2012f%20Krauss-9August2012c.pdfI'm not saying the speculative comments of Alex Filippenko or Lawrence Krauss are necessarily correct, just that they are scientific answers to the eternal questions man has forever been asking.

 

[jbriggs444]

This is obviously a BS parade, you cannot assert something originated from nothing without violating every known law in the universe.

You seem to be arguing against a position that no one is taking. Or making assumptions that are not needed. However, it is difficult to be sure since you have not identified a statement with which you disagree.

 

[fresh_42]

Thread locked.

The debate appears to have lost its B-level and the focus on the OP's question.

Well, thank you everyone. Even though most of it is over my head I did learn somethings. I have no formal education in physics but watch every science program on cable including Brian Cox's recent series. He loves saying billionths of billionths...of a second after the start of the universe everything was say 100 feet wide which reinforces the idea of a center.

The basic difficulty here is not to imagine the universe as something placed in somewhere. The universe itself is already the somewhere and we haven't a clue of its actual topological shape. Only evidence that it seems to be almost perfectly flat, so it's either really flat or so big, that its curvature cannot be taken to get an idea of the overall shape. Since we are limited to a three dimensional imagination and surfaces, which are embedded in a three dimensional Euclidean space, it is difficult for us to imagine something without being embedded anywhere. The best picture to come up with, is in my opinion the surface of the earth. If this surface were all that the universe is made of, what is its center? And standing on a prairie in Kansas or Kazakhstan might well lead to the observation, that Earth is flat. It's similar with the universe, only on a higher dimension.

What this forum could use is a 'For Dummies' section that explains these ideas to folks with no physics background.
Thanks again,
Ed.

... so the purpose of this thread is fulfilled?

I don't want to stop the debate, but it might be a good idea to start a new thread and eventually based on some publications to find a common ground.