At Rest with our Hubble view

[Layman]

You are mistaking the map for the territory, the Universe is only flat in the calculations of topology, it is a two dimensional chart that has edges only because it leaves out two whole dimensions, it is not the 4D reality.

I am doing no such thing, I am just repeating some reasons on how the universe simply looking flat doesn't prove that it is actually flat. Without knowing the total size of the universe it leaves open this possibility.

And open or closed is simply about whether the Universe will collapse back into a Big Crunch(closed), eventually reach stasis(flat) or expand forever more(open), it says nothing about what shape or size the Universe is. The shapes of topology do not represent reality, just certain aspects of it.

Yes, but in order for the universe to be closed it would have to have more than the critical mass in order to make it that way. The critical amount of mass needed to make a closed universe would then create enough force of gravity to create enough curvature for it to be closed. But, the amount of mass in the universe is very close to it just being flat or right at the critical mass, and then they discovered that the rate of expansion of the universe is just slightly over what is needed for it to be open, so then a slightly open universe would imply that there is negative curvature. Gravity is losing the battle with inflation. It is just that the universe is so big that we were not able to notice before.

The Universe has no edge, there is nothing "beyond" the Universe, nothing outside of the Universe for there to be an edge between it and something else, the Universe is not expanding into anything, it IS everything. And curvature can never lead back to the same point, that is simply wrong.

If you curve a line it will eventually make a circle, if you curve a plane it will eventually create a sphere. If you curve a coordinate plane it will eventually create a hypersphere. I see no reason why high dimensional geometry should be different than lower dimensional geometry. Then if the universe IS everything then it would seem that it would then have to be infinite.

Even if you got back to the point of origin it would be far in the future in the dimension of time, everything you left behind would no longer exist. But you cannot make the trip, you can never reach most of what you see in the Universe, as most of what you see no longer exists and is way too far away in time and space. See, it's hard to think in 4D, we're really not cut out to understand a hypersphere, much less when you add the dimension of time.

You can use lower dimensional examples from geometry in order to try and understand the properties of a hypersphere. It would curve in a higher dimension that is 45 degrees from the other three dimensions. It would be like trying to fold a block onto itself, but then you cannot imagine what direction that you then make this bend. It does not mean that a bend will not be there.

The Universe is finite in size, but that does not mean what we think of as a finite size or shape within the Universe, it adds another whole dimension(time), but it is finite, nonetheless. And there are no edges to spacetime except the leading edge of travel through time(the now), every point exists on the leading edge of time and the only geometrical point we can identify is dead center to the entire thing, every point still dwells at that center and always will. The Universe must be finite in size(no infinite time or speed at any time in the past, it had a beginning, therefore not infinite in either space or time), and it also must be unbounded(there's nothing the Universe can have an edge with, an edge is a boundary between two things, the Universe is the only thing there is, so there is no boundary, thus it is unbounded).

What if I had two balloons that where already blown up and they where of equal size. Then I looked over at the table and noticed that there where two different size balloons of different sizes. How could you then know what size balloon was which that was already blown up? Both size balloons could be blown up to equal sizes, then it gets worse. What if the balloons where blown up so big that you couldn't even see around them. How could you ever know what size of balloon it was you started with? Both balloons could give you a balloon that is the size of the balloon that was blown up, there would be no way to tell. Claiming that you can tell actually makes you worse than pop physics, at least they can admit that they don't know something for sure, if you could prove it you would be one of the best physicist of all time. But, then I don't think the word prove is in your vocabulary. Scientist have not been able to pin down an exact set of starting conditions that can only lead to what we observe now in the universe, so then every conceivable condition then has to be considered.

The actual shape or size of a Universe that meets all these conditions is not something human minds can grok. We live within the Universe, we are missing a dimension in our experience, this is much harder to visualize than simple Relativity, but it MUST be true, there's nothing else that can be true. The geometry of the Universe is not the same as the geometry of things within the Universe, everything in the Universe has the rest of the Universe to have a boundary with, the Universe cannot have a boundary, there's nothing there to have a boundary with. The Universe has no edge, it only has a center, and every point is at that center from it's own frame of reference, surfing on the leading edge of time.

How do you know that it is not just the limitations of your own mind that cannot visualize an end to the universe? It seems like you hold to all these assumptions just because you cannot visualize infinity. Say you had a graph of an imaginary number, you could look at the edge and then see that it increases in detail infinitely, but then you notice that there is a black spot in the middle of this edge. The edge goes on forever to infinity to more detail, but then that doesn't mean that it has to fill the entire black spot in the center of the graph. You could never reach the true edge but then it does not go on into everything that is there, and imaginary numbers represent higher dimensions (square root of a negative number is not on the real number line, there would have to be another axis that when you multiply by itself it then becomes negative). It has an edge but then the final aspect of that edge can never be reached.

 

[brucep]

I don't see why Grumpy should be able to post his nonsense, when anyone else in these forums would stand to correct someone else for doing so. I think a lot of people here just don't have the background to know how ridiculous his claims are, and it is not my fault that science has not been able to prove one way or the other. But, I have mentioned specific well known scientist that are leaning to just the opposite of what Grumpy claims, but you are right no body knows one way or the other. They where unable to prove that there was any type of curvature even from finding a closer value of the cosmological constant. They only found that it still looks to be flat, but it most likely may be that it just wasn't accurate enough to determine this.

I thought it should be clear by now that I have read a lot of pop physics books, and this is a topic that a lot of them talk about. They are all in agreement that they do not know one way or the other, that is what has become mainstream physics. That is what is said in all the books written about it.

For the same reason you get to post all the delusional 'nonsense' you've been spouting since you showed up. I haven't read what Grumpy said but I'm absolutely sure you're full of crap.

 

[Layman]

For the same reason you get to post all the delusional 'nonsense' you've been spouting since you showed up. I haven't read what Grumpy said but I'm absolutely sure you're full of crap.

Then I am absolutely sure that you have no background or knowledge of the subject to base your judgments on. This is just obvious trolling.

To fill you in since you where to lazy to read the discussion before your brilliant line of input, Grumpy thinks he has solved the problem about describing the universe as a whole. That he knows for a fact that it is not infinite, and that it curves back on itself. I am saying that there is no way he could really know this for certain, and it is not scientifically accepted that we do, contrary to Grumpy's claims. That again shows that you have no knowledge of this either or have never even looked into it, just like you say you didn't even have to look what Grumpy even said.

So then basically you have just said that Grumpy has solved one of the biggest riddles in theoretical physics since Einstein and will bring a new dawn to how we think of the universe as a whole. Someone will just have to be able to talk him to providing some type of proof that he doesn't believe is necessary for advancements in science.

Why don't you just face it, and admit that since you have no knowledge of this that you can only then agree with Grumpy and his delusions since you are biased against me and anything I say. Just like you are biased that Hawking Radiation is a well accepted theory, because it came from a well known physicist Stephen Hawking. That for some reason you think is no longer open for debate, I still find it hilarious that he even thinks he has to show how energy is conserved from a quantum mechanical principle that then violates conservation of energy and then shows how energy is conserved saving the laws of thermodynamics with a principle that then violates it. You just don't see this because again you just don't know enough about the subject.

 

[AlexG]

For the same reason you get to post all the delusional 'nonsense' you've been spouting since you showed up. I haven't read what Grumpy said but I'm absolutely sure you're full of crap.

How can that be? Layman gets his information from a 1960 radar tech manual that he half remembers reading. Can't ask for a better source than that, can you?

 

[Layman]

How can that be? Layman gets his information from a 1960 radar tech manual that he half remembers reading. Can't ask for a better source than that, can you?

There is explicit symmetry breaking in the fact that photons only come from charged particles when the Higgs Boson emits two photons. The Higgs Boson breaks this law of physics. Why did we even call it the God Particle if we would also just deny what God is trying to tell us? If we searched for the Higgs Boson to find what was wrong in physics and then something comes up wrong and then we just deny it, then it would seem that the search for this particle was in vain. Surprise, surprise, scientist have denied their own God.

 

[AlexG]

Why did we even call it the God Particle if we would also just deny what God is trying to tell us?

A reporter named it that. Higgs was not pleased with the name, but it caught on among the general, ignorant public.

 

[Grumpy]

Layman

Originally Posted by Grumpy
The Universe has no edge, there is nothing "beyond" the Universe, nothing outside of the Universe for there to be an edge between it and something else, the Universe is not expanding into anything, it IS everything. And curvature can never lead back to the same point, that is simply wrong.

If you curve a line it will eventually make a circle, if you curve a plane it will eventually create a sphere. If you curve a coordinate plane it will eventually create a hypersphere. I see no reason why high dimensional geometry should be different than lower dimensional geometry. Then if the universe IS everything then it would seem that it would then have to be infinite.

You are still stuck with thinking about how geometry works WITHIN the Universe. Everything within the Universe has something to have a boundary with, something "not it". The Universe has nothing it can have a boundary with, there is no "not it", thus no edge, thus unbounded. Just facts.

And, once more, no infinite time and no infinite speed of expansion means finite in size, it can be nothing else(not if it had a beginning, good luck finding a scientist that thinks it doesn't).

We can argue about the size and flatness, but there is no possibility that the Universe is infinite(it had a beginning)and there is nothing for it to have a boundary with, therefore it MUST be finite and unbounded. Isn't logic wonderful?

This is where you are wrong.

XXXI. The Possibility of a “Finite” and Yet “Unbounded” Universe

Clearly Einstein thought the universe was "Finite" and Yet "Unbounded". This means that it isn't infinite in size and that it doesn't curve back around on itself as a type of sphere.

Einstein was working before we knew of the expansion of the Universe, up until Hubble found that Einstein worked toward establishing a static, infinite Universe(his Cosmological Constant was meant to maintain the stasis, which otherwise would have already collapsed). He was wrong. He did not think the Universe was finite, he did say it was unbounded, but that follows automatically with infinite size. Today we KNOW the Universe is finite in size, it is unbounded because because of it's geometry, there is nothing that isn't the Universe for it to abut, sit next to, expand into, have a boundary with or have an edge with the Universe on one side and something not the Universe on the other. This is part of the geometry of something that contains itself, there can be no edges, there can only be a center, and every point can only be at that center(give or take the movement it experiences in local spacetime)from it's own frame of reference. Each point sees every other point some distance away from it in TIME, which is a distance in Cosmology. The further away in time, the further away from it's frame. When we look out into the Universe we are seeing the history of spacetime, the further away in distance, the further away in time(and vice versa). The center is relative to every point in space, no point could possibly be closer to the edge as there is no edge. And if you are having so much trouble with 4D, we'll avoid discussing the 7 other dimensions that current theory seems to indicate exist.

It seems like you hold to all these assumptions just because you cannot visualize infinity.

Name one infinity that actually exists outside of math. Even the infinite density of BHs is an assumption, it's gravity certainly never reaches infinity. Infinity is science's way of telling you that you've made a mistake, an invalid assumption or lack understanding of the system. NOONE can visualize infinity, you are incapable of even visualizing a light year, or a million years and a whole slew of things in the Universe. Our minds are not wired to deal with these things instinctively. And there are no actual infinities in this Universe.

I don't see why Grumpy should be able to post his nonsense, when anyone else in these forums would stand to correct someone else for doing so.

Grumpy taught young minds full of mush in High School Physics and Chemistry classes for over 30 years. He's spent his whole life investigating what science tells us about the Universe. Grumpy knows something about the subject. You don't seem to get even the simplest things. Grumpy is not perfect, he's also old and suffereing memory problems, but he STILL knows more than you do.

Grumpy

 

[PhysBang]

Our conversations on that mirror conversations you see elsewhere, such as on arXiv. I would encourage you to look into this. Search arXiv on VSL and variable speed of light and varying speed of light. Also see this Baez article and note the contradiction within the GR section.

Only the most short-sighted and the ignorant of GR could say that there is a contradiction in that article. There is no change in the speed of light at the level of infinitesmal distances on a manifold. However, one is free to assign all sorts of things the name "speed of light" and in these senses, the "speed of light" can be anything one wishes. If one wants to do physics, then one has to be very careful what one chooses to use.

 

[PhysBang]

If we can still see the CMB(and we can)we are seeing the entire Universe as it was then.

No, we are seeing (almost) a two-dimensional surface, a particular section of the universe at a particular time. Not all the light from the universe can reach us at the same time because of the time it takes for light to reach us. The light from the CMB is the light from a particular cosmological era, and we can only see the light of that era at a certain distance, not anything of a lesser distance nor anything at a farther distance.

You are mistaking the map for the territory, the Universe is only flat in the calculations of topology, it is a two dimensional chart that has edges only because it leaves out two whole dimensions, it is not the 4D reality. And open or closed is simply about whether the Universe will collapse back into a Big Crunch(closed), eventually reach stasis(flat) or expand forever more(open), it says nothing about what shape or size the Universe is.

On the contrary, whether the universe is open or closed says something about the overall geometry of the universe and not whether or not the universe will continue to expand or whether it will collapse. These two aspects of the universe are actually equivalent in a universe dominated by matter density. The presence of a cosmological constant (or dark energy) means that the final fate of the universe (so to speak) is somewhat independent of the overall matter density and the overall geometry. The consensus model has a flat universe with continued accelerated expansion into the future. (See WMAP website.)

 

[Layman]

You are still stuck with thinking about how geometry works WITHIN the Universe. Everything within the Universe has something to have a boundary with, something "not it". The Universe has nothing it can have a boundary with, there is no "not it", thus no edge, thus unbounded. Just facts.

A universe that curves back on itself would not have an edge. A universe that doesn't curve back on itself would seem like it would have an edge. The science behind this problem has gone nowhere since they found the value of the cosmological constant. I think this is because since it was going to continue to expand then it should have negative curvature, but then they didn't find that curvature and said that the experiment just showed that it was still flat. So then this confuses matters, how could the universe be flat and then be open and not have negative curvature, when it was predicted that it would have negative curvature if it was open.

And, once more, no infinite time and no infinite speed of expansion means finite in size, it can be nothing else(not if it had a beginning, good luck finding a scientist that thinks it doesn't).

I wouldn't have to go very far, all I would have to do is pick a book out of my local library and then look up the author, then I would know that they don't think that they know for sure that the universe is truly finite. Frankly cause I have read most of them and none of them claim to know for a fact that it is true. I imagine even the ones that make predictions based on finding the cosmological constant are still scratching their heads wondering why the universe is open but then looks to remain flat.

We can argue about the size and flatness, but there is no possibility that the Universe is infinite(it had a beginning)and there is nothing for it to have a boundary with, therefore it MUST be finite and unbounded. Isn't logic wonderful?

It would be wonderful if logical rules applied to infinity. The Big Bang event could have just been infinite in size, there are more recent theories like this that have taken the idea that Big Bang event was everywhere too literally. This meaning they think that the Big Bang event was an infinite in size universe already. They no longer think that the Big Bang happened everywhere just because of some higher dimensional geometry, it could be that there was already stuff everywhere and that stuff just inflated. I think there would be a problem with it creating a closed singularity, but then again no one has really showed how any type of Big Bang event could escape a singularity. (mainly why I think the early universe was made of only energy)

Name one infinity that actually exists...

In the image I put up of an imaginary number, what is the distance of the edge from the colored section to the black section? If you zoom in on the image you will find that it continually grows and becomes more complex. The distance you would have to navigate around it would then be infinite. So then a flatlander in the colored area could say that the boundary was infinite in size. Then this is only a simple graph of a number that could exist in higher dimensions. There is an edge, but then that edge would be infinite in size, then the area inside of that border would be infinitely large. So then in order to imagine a border that is infinite in size that has a boundary, all you would have to do is think of a graph of an imaginary number that is lower dimensional depiction of a higher dimensional system. The graph itself is mathematical proof that there can be boundaries of infinite size, and that just so happens to be a graph of a higher dimensional number.

 

[Layman]

A reporter named it that. Higgs was not pleased with the name, but it caught on among the general, ignorant public.

Even so there was a lot of hope that it would better our understanding of physics. I thought it actually got its name from the book The God Particle, where it is actually described with some sort of demon like properties like icy tentacles that stretch all across space itself.

 

[Grumpy]

Layman

A universe that curves back on itself would not have an edge. A universe that doesn't curve back on itself would seem like it would have an edge

With what? An edge is a boundary between two different things. We know the Universe exists, what other thing exists to form a boundary?

Again, the curve you are speaking of only represents certain aspects of the Universe. Like the rubber sheet, it is not really there, it is a simplification so we can understand a reality we cannot even visualize. Like I said, you cannot even visualize a hypersphere, much less if you added one other dimension. A Klein jar is a 2D representation of a 4D Universe that contains itself. Your mind(and mine)are hopelessly out of our depth trying to visualize that. We can see the Klein jar, or a Mobius loop and they do hint at the characteristics of the reality, but only at two steps back, and they are totally inadequate and misleading when applied to the whole.

The science behind this problem has gone nowhere since they found the value of the cosmological constant.

I could care less about the flatness of the Universe, that has no bearing on it being finite and unbounded. They are two different and unrelated questions. The Universe is finite because it had a beginning(thus it will never be infinite in duration), it never expanded at infinite speed(thus finite in size) and it has nothing to generate any edges with, you cannot have an edge without two separate things to form a boundary between and the Universe is all there is(thus it MUST be unbounded). The geometry of a Universe that contains itself is not the geometry of something in that Universe. A consequence of that is that every point is at the center of the Universe. Not only does it appear that way, it is that way.

It would be wonderful if logical rules applied to infinity.

What infinity. Infinity does not exist except in our math or as a concept in our minds. Again, name one single infinity. Time is not infinite, it began and has had a specific, finite duration to now. Speed is not infinite, lightspeed is a hard, finite limit. Even during inflation the speed was very, very high, but not infinite, and it had a finite duration, leaving a very large(but not infinite)expanding Universe. BHs may be infinitely dense, but may not be due to quantum effects, we will never know. Their gravity is not infinite. Even protons and electrons have a slight(but non-zero)chance of spontaneous disintegration, so they have no infinite duration, either. Go ahead, name a single actual infinity. So where does logic go with things that just don't exist.

The Big Bang event could have just been infinite in size, there are more recent theories like this that have taken the idea that Big Bang event was everywhere too literally.

What do you think every point being in the center of the Universe means? It means every point(everywhere)was at the center of the Big Bang(and still is). Just like I've been telling you. But it started almost infinitely small and expanded at non-infinite speeds, for a non-infinite duration, so it is non-infinite(finite)in size.

In the image I put up of an imaginary number, what is the distance of the edge from the colored section to the black section? If you zoom in on the image you will find that it continually grows and becomes more complex. The distance you would have to navigate around it would then be infinite.

Wrong. The length of the edge of a Mandelbrot series is very large, but it isn't close to infinite. No matter how large, it can always be bigger, and more complex. Infinite means (never ending), Mandelbrot series are not infinite(neither is anything else). Even a Mandelbrot the size of the Universe could never be infinite.

PhysBang

No, we are seeing (almost) a two-dimensional surface, a particular section of the universe at a particular time.

We see the entire Universe as it was at about 300,000 years, when the Universe became clear and the radiation of the BB was released, everything else we see is at smaller distances in time, the CMB is the furthest thing it is possible to see. We see it as it was(it's bigger now), but since we can see the furthest thing it is possible to see, we are seeing the entire history of the Universe(in principle, the practice needs more work). We see it in two spacial dimensions and one of time.

The light from the CMB is the light from a particular cosmological era

Yes, the very first era, the era the furthest distance from us in time, and all eras from then to now. We cannot see the whole Universe as it is today, but we can see the entire history of the Universe. Strangely enough it is the eras closest to us that we can see the least history of. We cannot see all eras at the same distance in time, but we can see all areas of the Universe at different distances in time.

On the contrary, whether the universe is open or closed says something about the overall geometry of the universe and not whether or not the universe will continue to expand or whether it will collapse.

Wrong, open or closed is just about whether the Universe will expand forever or collapse(or somewhere in between) it says little about the geometry overall, just it's curvature on a graph. But even that is misleading, curvature does not mean you could conceivably travel far enough to return to the same place, the place in question will be displaced through the time dimension. There is no return to the same point, there is a spiral through spacetime at best.

The consensus model has a flat universe with continued accelerated expansion into the future. (See WMAP website.)

The consensus is that the Universe started out almost perfectly flat(when it was gravity dominated)and Dark Energy has pushed it open(the definition of an open Universe is continued expansion into the future).

Grumpy

 

[Layman]

With what? An edge is a boundary between two different things. We know the Universe exists, what other thing exists to form a boundary?

I don't know, nothing I guess. Just because something cannot be conceptualized doesn't mean that it is not true, it only means that you are not smart enough to visualize it.

Again, the curve you are speaking of only represents certain aspects of the Universe. Like the rubber sheet, it is not really there, it is a simplification so we can understand a reality we cannot even visualize. Like I said, you cannot even visualize a hypersphere, much less if you added one other dimension. A Klein jar is a 2D representation of a 4D Universe that contains itself. Your mind(and mine)are hopelessly out of our depth trying to visualize that. We can see the Klein jar, or a Mobius loop and they do hint at the characteristics of the reality, but only at two steps back, and they are totally inadequate and misleading when applied to the whole.

Take for example a sheet of paper that you then want to turn into a sphere or place on the surface of the sphere. You wouldn't be able to place the sheet of paper on it without getting any kinks or folds. It wouldn't be able to be placed on it without then altering something in the two dimensions of the paper. You could cut slits in it, but then still you would have altered the paper, the two dimensions. Same way with a string, if you form a circle with it the string would then be curved, it would cringed on one side and then be stretched out on the other. So then it should be clear that curvature in a higher dimension would then alter things in the lower dimensions. Then again there is no reason why this type of behavior should be different in higher unknown dimensions.

I could care less about the flatness of the Universe, that has no bearing on it being finite and unbounded. They are two different and unrelated questions. The Universe is finite because it had a beginning(thus it will never be infinite in duration), it never expanded at infinite speed(thus finite in size) and it has nothing to generate any edges with, you cannot have an edge without two separate things to form a boundary between and the Universe is all there is(thus it MUST be unbounded). The geometry of a Universe that contains itself is not the geometry of something in that Universe. A consequence of that is that every point is at the center of the Universe. Not only does it appear that way, it is that way.

If we are not able to detect any curvature in our three dimensions of space and dimension of time, then there would be no reason to conclude that there is actually curvature in higher dimensions. Curvature in higher dimensions would have effects on the lower dimensions. An ant traveling along a string that forms a circle would notice that one side of the string is more crunched than the other, it would effect the first dimension by curving it around in the second dimension.

If by scientific experiments it is found that space is just flat, then it would be reasonable to assume that the universe just does not curve back on itself. A simple hypersphere just would no longer be good enough to describe the universe. It would be more like Pac-Man where the universe is flat but then Pac-Man just magically pops out the other side when it leaves the other. In this type of situation it wouldn't be simply addition of gravitational curvature that has added up over distance to then eventually curve spacetime back on itself.

Even worse is the possibility that you just can't go around the universe and then we would have to learn to deal with the fact that there is some kind of actual boundary to absolutely nothing that has been joked about in science fiction. :bawl:

What infinity. Infinity does not exist except in our math or as a concept in our minds. Again, name one single infinity. Time is not infinite, it began and has had a specific, finite duration to now. Speed is not infinite, lightspeed is a hard, finite limit. Even during inflation the speed was very, very high, but not infinite, and it had a finite duration, leaving a very large(but not infinite)expanding Universe. BHs may be infinitely dense, but may not be due to quantum effects, we will never know. Their gravity is not infinite. Even protons and electrons have a slight(but non-zero)chance of spontaneous disintegration, so they have no infinite duration, either. Go ahead, name a single actual infinity. So where does logic go with things that just don't exist.

I don't care if there is no infinity that we can get our hands around. I don't think this line of reasoning is logically sound. Like I said, I don't have a basket of oranges, therefore baskets of oranges DNE. If you applied this logic to anything you would never always get the correct answer. Wait I think I got one, how about the universe? The multiverse even? The number of different solutions to string theory?

What do you think every point being in the center of the Universe means? It means every point(everywhere)was at the center of the Big Bang(and still is). Just like I've been telling you. But it started almost infinitely small and expanded at non-infinite speeds, for a non-infinite duration, so it is non-infinite(finite)in size.

That is not the point. I am telling you that there are more recent theories that assume that the universe is infinite, and the size of the universe at the moment of the Big Bang was also infinite. Maybe you should ask them, "What do you think every point being in the center of the Universe means?", they think it means that it was just always that big.

Wrong. The length of the edge of a Mandelbrot series is very large, but it isn't close to infinite. No matter how large, it can always be bigger, and more complex. Infinite means (never ending), Mandelbrot series are not infinite(neither is anything else). Even a Mandelbrot the size of the Universe could never be infinite.

Oh yes, and how convenient that the wiki especially focuses on explaining how it is not infinite. This being said even though it is widely known that it continues to have increasing amounts of detail all the way down. It goes all the way down to infinity. It then has an edge the whole way down. It has infinite detail, there's one. I don't think you could deny that it has infinite amount of detail.

 

[Farsight]

I think one way to think about a non-infinite flat universe is to imagine a spherical droplet of water. A wave inside the droplet can't go out past the surface of the droplet. Instead it undergoes total internal reflection.

Try applying that to an electromagnetic wave in space, and take a look at the Hubble ultra deep field. Find a prominent galaxy, then look across to the right and down a little. There's another galaxy that somewhat resembles it. This is probably pure accident, but it gets across what the "edge of space" might look like. A perfect mirror. So perfect that you can't actually see it, all you see is space extending onwards.

 

[Markus Hanke]

Yes, the deflection we see is not frequency-dependent.

Precisely. That explicitly rules out any inhomogeneities in terms of permittivity and permeability, because that would contradict observation.
In short - inhomogeneous flat space ( varying speed of light ) is not physically equivalent to curved space-time.

Our conversations on that mirror conversations you see elsewhere, such as on arXiv

Actually, I wasn't talking about mirrors, only about whether or not "inhomogeneous space" is equivalent to "curved space-time". Clearly, it isn't, for reasons explained above.

 

[Grumpy]

Farsight

I think one way to think about a non-infinite flat universe is to imagine a spherical droplet of water. A wave inside the droplet can't go out past the surface of the droplet. Instead it undergoes total internal reflection.

Try applying that to an electromagnetic wave in space, and take a look at the Hubble ultra deep field. Find a prominent galaxy, then look across to the right and down a little. There's another galaxy that somewhat resembles it. This is probably pure accident, but it gets across what the "edge of space" might look like. A perfect mirror. So perfect that you can't actually see it, all you see is space extending onwards.

The thing is that no point in spacetime can be closer to an edge than any other. There is only one edge in the Universe and that is the now in the time dimension, so all things in the Universe are surfing on the leading edge of time. The appearance of being in the center is the reality of being in the center. If you measure the distance to the CMB in all directions you will find that it is very precisely equal in all directions. This is true no matter where you are in the Universe, every point see exactly the same situation, we are not unique or special. What you are measuring is a distance in time, you cannot see that distance in space because each point along that line is at a different time and what you are seeing is no longer there, it is much further away. It is true that we cannot see the entire Universe as it exists today, but we can see the entire Universe as it was in the past(the further away, the further in the past). We can see every area in spacetime, but we see them as they were, not as they are now. It is likely that many of these areas are now so far away that we will never see the light they emit today.

Grumpy

 

[PhysBang]

Farsight



The thing is that no point in spacetime can be closer to an edge than any other. There is only one edge in the Universe and that is the now in the time dimension, so all things in the Universe are surfing on the leading edge of time. The appearance of being in the center is the reality of being in the center. If you measure the distance to the CMB in all directions you will find that it is very precisely equal in all directions. This is true no matter where you are in the Universe, every point see exactly the same situation, we are not unique or special. What you are measuring is a distance in time, you cannot see that distance in space because each point along that line is at a different time and what you are seeing is no longer there, it is much further away.

While this is part of the standard cosmological model, it is essentially an assumption that our position in the universe is not particularly different from other positions in the universe. It is possible that there is some edge to spacetime.

What Farsight needs to do in order to be even close to plausible is show that there is a solution to the Einstein Field equations that matched his raindrop universe. Once he has this, he can then work to show that it matches any of the cosmological observations. He has done neither step. He will not do either step, nor will he retract his claims, because he cares about his internet persona, not physics.

It is true that we cannot see the entire Universe as it exists today, but we can see the entire Universe as it was in the past(the further away, the further in the past). We can see every area in spacetime, but we see them as they were, not as they are now. It is likely that many of these areas are now so far away that we will never see the light they emit today.

Why do you persist in this? It cannot possibly be true. Even if we could receive light from every part of the universe, we could only receive light from those regions that are exactly the right distance away that a photon could travel from that location to us in the amount of time that the universe has been around. This means that there is an upper and lower limit to viewing the past, even with the possibility of superluminal inflation in the early universe. Given that the CMB exists as an upper bound, then we clearly cannot see any distance in space beyond the location of the particles emitting the CMB.

 

[Grumpy]

PhysBang

While this is part of the standard cosmological model, it is essentially an assumption that our position in the universe is not particularly different from other positions in the universe. It is possible that there is some edge to spacetime.

Which is more likely...That we are special and in the ONLY place in spacetime where that appears to be in the center, or that we are not special and all points see the same thing? I think the possibility that we are unique in the Universe is incredibly small. Edges imply there is something to have a boundary with. What is that something? If you cannot answer, your possibility isn't.

Why do you persist in this? It cannot possibly be true.

It can't possibly NOT be true.

Even if we could receive light from every part of the universe, we could only receive light from those regions that are exactly the right distance away that a photon could travel from that location to us in the amount of time that the universe has been around

Well, Duh! That's exactly what I mean by time being a distance. And what is the furthest distance we can see? The CMB. When is that? The beginning of time(well, 300,000 years after). So all time is visible today, all the way back to the very beginning of time. All areas of the Universe are visible, each is visible at a certain distance in time. We cannot see the Universe as it is today, but we can see every single area(in principle), we just see each at it's own distance in time, not at it's present distance in space.

This means that there is an upper and lower limit to viewing the past, even with the possibility of superluminal inflation in the early universe

The upper limit is now, the lower limit is the beginning of time(or vice verse, depending on what you mean by upper and lower). If we can see the beginning and the end(now)of all the time that has ever passed, we see the entire history of the Universe(after the first 300,000 years). To illustrate time as a distance, it takes 8 minutes for light to travel from the sun to the Earth. The distance in time to our sun is 8 light minutes, it is also 93 million miles away in space. This distance is close enough that the difference between the two is visible in real time. The closest star to our sun is Proxima, about 4 light years away, we see it as it was 4 years ago, it is 4 ly away in time. If it blew up today, it would be 4 years before we knew it. That is a distance in time that is too large to see in real time. Distance in space is not visible in real time, distance in time is all we can see, the further away the greater the difference between distance in time and distance in space. Once past about 75 light years or so, we can no longer see distance in space in one lifetime, we can only see distance in time. Once you are some billions of light years away it is likely we never will see the real distance in space, as what we can see in distance in time today is already over our light horizon in distance in space and the light it is emitting today will never reach us. It is this that scientists talk about as not being able to see the whole Universe. But we can see the entire Universe in time, as we can see all the way to the beginning of time.

Given that the CMB exists as an upper bound, then we clearly cannot see any distance in space beyond the location of the particles emitting the CMB.

There is nothing beyond the CMB but plasma and the BB, which are not visible because space was opaque then. And I have always been careful to distinguish between distance in time and distance in space. Our light horizon is much closer to us in distance in space than the current distance to the CMB, it is currently far beyond where we will ever see it as it is today. But, again, the entire history of the Universe is visible in distance in time, we can see every point as it used to be, we have no light horizon in distance in time, the furthest things are not expanding away from us at light speed(yet).

Grumpy

 

[PhysBang]

Which is more likely...That we are special and in the ONLY place in spacetime where that appears to be in the center, or that we are not special and all points see the same thing? I think the possibility that we are unique in the Universe is incredibly small. Edges imply there is something to have a boundary with. What is that something? If you cannot answer, your possibility isn't.

I don't know how to answer this question of probability. However, I can say that by adopting the assumption that space is roughly homogeneous, we are able to turn observations about the universe into evidence that we can evaluate to a greater extent than we can do otherwise.

It can't possibly NOT be true.

Well, if you are going to be dogmatic, fine.

Well, Duh! That's exactly what I mean by time being a distance. And what is the furthest distance we can see? The CMB. When is that? The beginning of time(well, 300,000 years after). So all time is visible today, all the way back to the very beginning of time. All areas of the Universe are visible, each is visible at a certain distance in time. We cannot see the Universe as it is today, but we can see every single area(in principle), we just see each at it's own distance in time, not at it's present distance in space.

You seem to be making the claim that we can see all points of space of the universe, just at different times. Even including expansion, we can see only as far as the speed of light allows. If there is a space beyond this, we cannot see it. Do you find a problem with this reasoning? If so, what?

And I have always been careful to distinguish between distance in time and distance in space.

Not careful enough, as I am still not clear about your claims.

we can see every point as it used to be,

By "point", do you mean "cosmological era" or "location in space". The former is true (back to the origin of the CMB) and the latter is false.

we have no light horizon in distance in time

Except the origin of the CMB.

the furthest things are not expanding away from us at light speed(yet).

Except that they are.

 

[Grumpy]

PhysBang

Edges imply there is something to have a boundary with. What is that something? If you cannot answer, your possibility isn't.

Answer that question before you say anything more about edges.

You seem to be making the claim that we can see all points of space of the universe, just at different times.

Yes. We see the CMB and that is the furthest point in time it is possible to see, so everything else in the Universe is between us and the CMB IN THE DIMENSION OF TIME. Time is a distance in Cosmology, we cannot see the current distance in space because there has not been time for those photons to reach us. But that doesn't matter, we see the Whole Universe in the dimension of time(distance away from us is distance back in time). Additionally, every point in space is the place where the BB occurred, and every point sees all other points expanding from that center in the dimension of time, and since every point is 13.7 billion years from the first thing(the CMB)in all directions, they all see themselves as the center of the Universe. The CMB is 13.7 billion years from us, everything else in the Universe is closer to us in time. Until you get that time is a distance you will not understand this point.

Even including expansion, we can see only as far as the speed of light allows.

And that distance is 13.7 billion years in the dimension of time, there is nothing further away in time, as the furthest thing is at that distance(the CMB). Today the CMB is much further away in space, but we will never see it at that distance, in the future the CMB will not be visible at all.

By "point", do you mean "cosmological era" or "location in space"

Location in space. We see them all, but the further away from us they are the further back in time we see that point. We do not see all the points in the same era, we can not see all points as they are today, for example, nor do we see all points as they were 10 billion years ago. We do see all the points spread across the distance of time back to the very beginning, however. Some we see as they were 8 minutes ago(the sun), some 30 hours ago(Jupiter, I think), 4 years ago(Proxima),....and 13.7 billion years ago(the CMB). Their apparent distance in space is an illusion, they are actually much further away today. But their appearance in time covers the whole history of the Universe back to the very beginning and includes everything in the Universe at one time or another.

the furthest things are not expanding away from us at light speed(yet).
Except that they are.

Depends on if you are speaking about distance in time, or distance in space. In time the furthest things do not appear to have exceeded the speed of light due to expansion(I think the furthest things have been measured at .8 C), in reality(which we do not see)the furthest things are probably well beyond our light horizon. What we see is not the reality of the Universe today, what we see is the reality of a certain point as it was at a specific time in the past.

Grumpy