Originally posted by @wolfe63
Cosmology is beyond my scope of practice. But I've sincerely enjoyed the tone and substance of this thread's discussion.

Interesting grub for thinking.

The subject is just a bit on the mind boggling scale, an entire universe banging into our or new work on the big bang saying maybe the huge uniformity seen in the CBR (now shown to be not quite uniform but giving us hidden information) but the uniformity may have happened before the BB. All speculation but there is SOME evidence which of course has to be independently verified.

Originally posted by @sonhouse
The subject is just a bit on the mind boggling scale, an entire universe banging into our or new work on the big bang saying maybe the huge uniformity seen in the CBR (now shown to be not quite uniform but giving us hidden information) but the uniformity may have happened before the BB. All speculation but there is SOME evidence which of course has to be independently verified.

"Don't sell the skin before you've caught the bear."
Speculations is everything we have. No evidences whatsoever. Please, don't use religious rhetorics.

We have no way to imagine two universes cannot collide in a space in 3 spacial dimensions. In order to do that we need more universal spacial dimensions. Where are the speculations about that?

Originally posted by @fabianfnas
We have no way to imagine two universes cannot collide in a space in 3 spacial dimensions. In order to do that we need more universal spacial dimensions. Where are the speculations about that?

Sorry, a "no" to many. I keep the 'no' but change the 'cannot' to 'can'.

Should be:
We have no way to imagine that two universes can collide within a space in 3 spacial dimensions. In order to do that we need more universal spacial dimensions. Where are the speculations about that?

Originally posted by @fabianfnas
Sorry, a "no" to many. I keep the 'no' but change the 'cannot' to 'can'.

Should be:
We have no way to imagine that two universes [b]can collide within a space in 3 spacial dimensions. In order to do that we need more universal spacial dimensions. Where are the speculations about that?[/b]

That would be because Einstein said the universe is finite but unbounded. I think that is what he said. Unbounded implies our universe is some kind of 3D bubble in a higher dimensional reference. If so, that would make it at least theoretically possible for another universe to be side by side to ours.
String theory posits 10 or 11 dimensions and there is a concerted effort to find evidence of these admittedly theoretical extra dimensions.

One of the efforts in that regard is testing the strength of gravitational attraction versus distance. They thing if there is some variation of the inverse square law of gravity, in this case, a change as two masses get closer together.

So far, no luck, they have measured the inverse square law to within 100 microns (1/10th of a millimeter) but are trying to get measurements even closer.

The theory behind that is if there are other dimensions, they may be hiding in plain site by being kind of like a magnetic line of force, that is my analogy, don't know how accurate that is but the idea is at very close distances, a change in the inverse square law would be the result of an interaction between gravity and those other dimensions.
News at 11🙂

Don't know how close they can eventually come with that measurement and how they would interpret a lack of change say even down to an angstrom distance. I think if they ever get down to that distance, there will be interference with that measurement because of Casimir effect, where the force of virtual particles causes an attraction of say, two plates as they get very close, like angstrom distances apart.
That is a real effect due to the pressure on one side of a plate where virtual particles pop into and out of existence more frequently on the outside of the two plates because the presence of the plates on the inside separation somehow blocks or slows down the existence of virtual particles so there is a difference in the force leading to an attraction of the plates together independent of gravity, strong or weak or van der waal forces, electric or magnetic fields.
So that would have to be taken into account if they ever were able to measure gravity at anstrom distances.
But the actual gravity measurement as you get closer together to measure possible changes in the inverse square law, those measurements get progressively more difficult to achieve.
I think they are working on the measurement at about 50 microns but that is way too far apart for interference from Casimir effects.

Originally posted by @sonhouse
That would be because Einstein said the universe is finite but unbounded. I think that is what he said. Unbounded implies our universe is some kind of 3D bubble in a higher dimensional reference. If so, that would make it at least theoretically possible for another universe to be side by side to ours.
String theory posits 10 or 11 dimensions and there is ...[text shortened]... would be the result of an interaction between gravity and those other dimensions.
News at 11🙂

Well, when you see the Universe as a bubble in an supradimensional environment, then you are led wrong. You cannot ever see the universe from outside. As universe is everything in our 3-dimensional space, you are always inside it.

We always see the event of BigBang as an explosion in popular scientific books for children or adults, as we could witness from outside, we are taught that this is correct view of the Universe. It isn't. Don't fall into this trap!

You see our Universe as a bubble among other bubbles. Here and there there are universes colliding. This is a false picture. This could not happen within our three dimensions. And there are no more dimensions that are Universal. No observations support this.

There are a bunch of dimensions according to the M-theory, but they are on the microscopic level and not relevant in the Universal distances. So the Universe has three dimensions. If you believe in a fourth one, then show me the direction perpendicular to our normal three ones, and I will believe you.

You have to rethink your view of the Universe from the beginning, avoiding the traps, and come into a truer picture of the Universe. I can lead you if you want, but it takes some mind twisting thoughts if you are prepared.

Originally posted by @fabianfnas
Well, when you see the Universe as a bubble in an supradimensional environment, then you are led wrong. You cannot ever see the universe from outside. As universe is everything in our 3-dimensional space, you are always inside it.

We always see the event of BigBang as an explosion in popular scientific books for children or adults, as we could witness ...[text shortened]... verse. I can lead you if you want, but it takes some mind twisting thoughts if you are prepared.

The curvature of the universe suggests a bubble. It takes a higher dimension to be able to make the universe at once finite but unbounded as big Al says. The thinking about the size of the universe is it may be about 50 billion light years across, which is finite. Don't sell higher dimensions short and of course we have no solid verifiable proof of other dimensions yet. The universe gets bigger every second and in fact is in total expanding at a speed greater than light right now. Which is why we suggest the universe is about 3 or 4 times bigger than that which we can see in telescopes, the bits have blown away from us at a rate we can NEVER see directly since it outran light getting to whatever size it is right now.

I was present at a talk given by Alan Guth at Bell Labs many years ago and he mentioned some figures of the inflationary era of the BB, I did a bit of calculating and came up with the idea at the earliest epoch the universe expanded at a velocity 10^22 times the speed of light and I was able to ask him how that could be in light of Einstein's speed limit of c.
He said "You got your arithmetic right''🙂 and said it was because space expanding, not actual matter so matter just comes along for the ride and space can contract or expand at whatever speed it wants to as a result of the forces that drives it.

Originally posted by @sonhouse
The curvature of the universe suggests a bubble. It takes a higher dimension to be able to make the universe at once finite but unbounded as big Al says. The thinking about the size of the universe is it may be about 50 billion light years across, which is finite. Don't sell higher dimensions short and of course we have no solid verifiable proof of other d ...[text shortened]... e can contract or expand at whatever speed it wants to as a result of the forces that drives it.

Here is a piece on the idea of the universe containing ten dimensions. I am not advocating for this, I am just presenting it as evidence of human work being done on the subject:

https://phys.org/news/2014-12-universe-dimensions.html

The problem with string theory is there is very little that can be tested in a way that could pass muster like the falsifyability test of Popper.

That said, there is much that string theory seems to address in ways that seem to show the answers of string theory account for much of what we see in the universe.

It has been claimed string theory is 23rd century physics showing up in century 20.

Which may be part of the problem since our technology is just a few steps up from in fact 20th century technology and as such our technology of instrumentation is just not strong enough to find positive evidence of the truth of string theory.

So it might be decades or centuries before such issues can be verified or refuted.

Originally posted by @sonhouse
Here is a piece on the idea of the universe containing ten dimensions. I am not advocating for this, I am just presenting it as evidence of human work being done on the subject:

https://phys.org/news/2014-12-universe-dimensions.html

The problem with string theory is there is very little that can be tested in a way that could pass muster like the fals ...[text shortened]... ng theory.

So it might be decades or centuries before such issues can be verified or refuted.

Those extra dimensions are small, very small, far smaller than a proton.
You cannot use them in any discussion regarding the size of the Universe.

Originally posted by @fabianfnas
Those extra dimensions are small, very small, far smaller than a proton.
You cannot use them in any discussion regarding the size of the Universe.

Sure, it they exist at all which has yet to be shown but just finding there there are these soda straw dimensions would be a revelation of the highest order for physics.

I would not be surprised if other ways to show the reality of these dimension but for now I think the only way we see to do that is the search for variance in the inverse square law at close distances.. From what I read, the tech to do that at closer and closer distances, now looking at distances apart of the weights or masses used, now at 100 microns apart, 1/10th mm and it is exponentially more difficult the closer you try to go and at least in part because of the force of virtual particles which has nothing to do with all the forces we know about so the closer you get the larger the Casimir force gets so large compared to gravity, electric, magnetic forces and the like. It might be that you need to do that kind of experiment at sub pico meter distances and I don't think anyone has even a clue as to how to get a reading of inverse square law at those distances.

Originally posted by @sonhouse
Sure, it they exist at all which has yet to be shown but just finding there there are these soda straw dimensions would be a revelation of the highest order for physics.

I would not be surprised if other ways to show the reality of these dimension but for now I think the only way we see to do that is the search for variance in the inverse square law at ...[text shortened]... hink anyone has even a clue as to how to get a reading of inverse square law at those distances.

But now you're off topic.

Originally posted by @fabianfnas
But now you're off topic.

It's just that at this point in time, the inverse square law investigation is the only game in town to even TRY to detect the theoretical presence of these curled up dimensions. Presumably the curled up part, if true, would be how you prevent interference from these extra dimensions from effecting our 4 dimensional universe by compacting them down to Planck size. I don't have a clue as to how that would happen though. The answer to that question will probably be left for a much more advanced scientific society than exists now.

Like 24th century science assuming we can maintain a thriving scientific civilization for that long.

Originally posted by @sonhouse
It's just that at this point in time, the inverse square law investigation is the only game in town to even TRY to detect the theoretical presence of these curled up dimensions. Presumably the curled up part, if true, would be how you prevent interference from these extra dimensions from effecting our 4 dimensional universe by compacting them down to Planc ...[text shortened]... 24th century science assuming we can maintain a thriving scientific civilization for that long.

There is no chance that any information can survive the first plank time unit after the BigBang at t=0. We can dream about it, we can speculate about it, we can even write Science Fiction books about it, but there is not even a snowball from hell that we can observe anything about it.

Let's wait and see until anything non-speculative ideas turns up, but until then - only dreams.

Originally posted by @fabianfnas
There is no chance that any information can survive the first plank time unit after the BigBang at t=0. We can dream about it, we can speculate about it, we can even write Science Fiction books about it, but there is not even a snowball from hell that we can observe anything about it.

Let's wait and see until anything non-speculative ideas turns up, but until then - only dreams.

For now that is about all we can do. I do hope however that at some point the experimentalists find some variation from IV square law.

Here is one such from 2012, I think there are newer closer distance work because this one shows no deviation at the 400 micron level, 0.4 mm separation of masses.

There was an article in Scientific American that reported no deviation of inverse square law down to 100 microns, four times closer distance of masses than this abstract:

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.108.081101

Originally posted by @fabianfnas
Those extra dimensions are small, very small, far smaller than a proton.
You cannot use them in any discussion regarding the size of the Universe.

The additional dimensions in Brane worlds are not necessarily compactified. In these theories, with large additional dimensions, the universe is a four-brane embedded in a bulk (as it is known), with the rule that fields on the Brane are restricted to it - they do not extend into the bulk.

There is no evidence (except theoretical consistency) either for or against large (i.e. infinite, or as good as) additional dimensions. I'd say that that one's open.

Since the intrinsic curvature of a space is the same whether it is embedded in a higher dimensional one or not, I don't think there is a big problem with imagining the universe as embedded in a higher dimensional space.

Originally posted by @deepthought
The additional dimensions in Brane worlds are not necessarily compactified. In these theories, with large additional dimensions, the universe is a four-brane embedded in a bulk (as it is known), with the rule that fields on the Brane are restricted to it - they do not extend into the bulk.

There is no evidence (except theoretical consistency) either ...[text shortened]... nk there is a big problem with imagining the universe as embedded in a higher dimensional space.

The question then would be if we ever developed the capability of bouncing to higher dimensions, could we find a universe like ours with its own set of galaxies strung out like Christmas beads and each galaxy with a pantheon of stars and planets some of which are exactly like Earth, in that it is in the goldilocks zone, has lots of water and a diverse living ecosystem. We might then travel on a dimensional elevator which two flights up, we are in a totally different universe when we step out, then get back in and go 30 flights up and find a totally alien universe.

Maybe in a few hundred years.....