At Rest with our Hubble view

[AlexG]

It wasn't a question of the density dropping. It was the temperature. Before the recombination, the temperature was too high to allow neutral atoms to form, instead there was basically a cloud of ions filling the universe. Photons could not travel without running into free electrons. When the temperature dropped far enough, electrons and protons could form neutral hydrogen and helium atoms. (the term REcombination is a little misleading, since this was the first combination). Once the free electrons were no longer a factor, photons could travel unimpeded.

Or is expansion and stretching the same thing?

They're the same thing.

 

[quantum_wave]

...

They're the same thing.

Is stretching of space the same as "new space" being added between galaxies and galaxy groups that I have seen given as the explanation for the redshift?

 

[Layman]

It isn't a discovery, it is our present understanding in Cosmology.

You still haven't provided a source from where you are getting this from. Even all the pop physics books that people accuse me of reading are not even so bold to claim that they have ever discovered a way to know such things. Their position always is that since it is unknown which road to take, that the only way for it to be scientific is to consider both possibilities since they are unable to justify ruling out one or the other with some kind of mathematical or scientific proof.

That would be proof that you seem to be completely unaware of its use in the acceptance of discoveries in science. You have no proof to justify these claims. There is no reason anyone else should adopt these views without seeing some kind of proof.

There are many explanations of how both sides of this coin can be equally valid. I think you just lack the understanding or know how to be able to comprehend how it has been shown that the universe doesn't have to be only be considered to be finite and unbound. A infinite and bound universe could also fit the data as well, but according to some of the leading physicist they are starting to think that it actually is bound with negative curvature. This would create what they see in the Hubble View as looking deeper into space at smaller scales and then noticing the appearance of more and more galaxies. This is a view by Penrose that is trying to push this model, and I have heard this being explained by Susskind in one of his lectures in cosmology. I tend to agree with both of them as Susskind has shown in one of his lectures at Stanford that a positively curved bound universe would then appear to have bigger galaxies seen at further distances. Also they found that the universe will continue to expand based on the findings of the cosmological constant, this was an unknown in the time a lot of pop physics was written, but then they claimed that if it was discovered to continue to expand based on that value that it would have negative curvature.

 

[IncogNegro]

Does anyone know what the width of the funnel represents?

Is it the density of energy applied to a time in the univers's existence? Maybe meaning gravity is not really a concept "according to those terms"?

Can everything be written that way? Like if it helps answer a question just say your not sure of what in words and provide
A graph? Is life that easy? No way... I've got to be wrong somehow...

 

[quantum_wave]

You still haven't provided a source from where you are getting this from. Even all the pop physics books that people accuse me of reading are not even so bold to claim that they have ever discovered a way to know such things. Their position always is that since it is unknown which road to take, that the only way for it to be scientific is to consider both possibilities since they are unable to justify ruling out one or the other with some kind of mathematical or scientific proof.

That would be proof that you seem to be completely unaware of its use in the acceptance of discoveries in science. You have no proof to justify these claims. There is no reason anyone else should adopt these views without seeing some kind of proof.

There are many explanations of how both sides of this coin can be equally valid. I think you just lack the understanding or know how to be able to comprehend how it has been shown that the universe doesn't have to be only be considered to be finite and unbound. A infinite and bound universe could also fit the data as well, but according to some of the leading physicist they are starting to think that it actually is bound with negative curvature. This would create what they see in the Hubble View as looking deeper into space at smaller scales and then noticing the appearance of more and more galaxies. This is a view by Penrose that is trying to push this model, and I have heard this being explained by Susskind in one of his lectures in cosmology. I tend to agree with both of them as Susskind has shown in one of his lectures at Stanford that a positively curved bound universe would then appear to have bigger galaxies seen at further distances. Also they found that the universe will continue to expand based on the findings of the cosmological constant, this was an unknown in the time a lot of pop physics was written, but then they claimed that if it was discovered to continue to expand based on that value that it would have negative curvature.

Layman, I can't say it is nice to see you jump into my thread, because there is a history of you hijacking my threads to promote your own ideas, or to dominate the discussion as if it was your thread, and as if the others should be responding to you. On those other occasions I have asked you to start your own thread, but you just don't seem to want to for some reason. If you want to correct someone that is fine, and if you want to participate with on-topic comments about statements made, that is fine too. But you have never established yourself as an more of a reliable source of physics and cosmology than I have, let alone as someone who grasps physics and cosmology at a professional level. You post links and quotes but you show no real grasp of the science, and your latest stance can be paraphrased as "well, no body knows one way or the other".

If you want to direct the discussion start a thread, work at getting it going, lay the groundwork, and then see if anyone is interested or not. This thread may have run it course, and that is fine, but I still want to try to keep it on track.

 

[AlexG]

Is stretching of space the same as "new space" being added between galaxies and galaxy groups that I have seen given as the explanation for the redshift?

Yes. They're both imprecise ways of describing something in a language which isn't really suited for the subject.

 

[quantum_wave]

Yes. They're both imprecise ways of describing something in a language which isn't really suited for the subject.

I get that general impression. Is the stretching concept necessary to bridge the understanding gap between 3D space plus time, and spacetime?

 

[AlexG]

I don't think so. I think it's just an attempt to explain it in terms which most people can relate to. Stretching might be related to the often (mis-)used balloon analogy.

 

[AlexG]

You have no proof to justify these claims. There is no reason anyone else should adopt these views without seeing some kind of proof.

The very fact that you keep harping on the word proof shows your lack of understanding of the scientific method.

 

[PhysBang]

It wasn't a question of the density dropping. It was the temperature. Before the recombination, the temperature was too high to allow neutral atoms to form, instead there was basically a cloud of ions filling the universe. Photons could not travel without running into free electrons. When the temperature dropped far enough, electrons and protons could form neutral hydrogen and helium atoms.

Just to add:

The decrease in mass density due to the global expansion is the reason for the dropping of the temperature. Once stable neutral atoms could form, this dropped the optical density of the universe, ie. the measure of how far the average photon could travel.

Since the release of the CMB photons, the expansion is doubly responsible for the decrease in the energy associated with these photons: to the cube power due to the increase in volume and then up to the fourth power due to the expansion introducing redshift to the photon. This is reflected in the temperature of the CMB now vs. the temperature when released.

 

[quantum_wave]

Just to add:

The decrease in mass density due to the global expansion is the reason for the dropping of the temperature. Once stable neutral atoms could form, this dropped the optical density of the universe, ie. the measure of how far the average photon could travel.

Since the release of the CMB photons, the expansion is doubly responsible for the decrease in the energy associated with these photons: to the cube power due to the increase in volume and then up to the fourth power due to the expansion introducing redshift to the photon. This is reflected in the temperature of the CMB now vs. the temperature when released.

I will come back to this, but first:

My comment on the "finite and unbounded" discussion as it pertains to General Relativity, at least the Wiki version on Physical Cosmology. Einstein's model, with the Cosmological Constant, was meant to define a static universe. Even his static model with the CC was unstable due to small perturbations, and would eventually either expand or contract. But that aside, his model described gravity as a geometric property of space and time, and described space as finite but unbounded, using an analogy of the surface of a sphere.

Let me try to put that analogy in my own words to test my understanding, and to see what comments some of you will have about my view of it.

There are various shapes that the surface of a sphere can take on, and the actual "shape", the topography of the universe so to speak, is a function of the true value of the cosmological constant. For simplicity's sake, if we invoke a slightly open curved shape, it would correspond with what scientists now think.

I've seen a graphic of this shape, sort of like a saddle, and the idea is that if you take a big enough portion of the universe in three dimensions, all of the paths from one point to any other point in that patch of space follow the curve of the saddle. That means if you compare the actual distance between any two points to a straight line, the actual distance is greater. The fact of the curved topology is that going straight isn't an option because you have to follow the saddle shape when you move. You can only take a path between two points that falls on the saddle's surface.

I have to keep reminding myself, and this is a characteristic of general relativity if I understand the curved surface as it relates to any three dimensional patch of space, no matter how big or how small, natural motion occurs along the general curved topography applicable to that patch of space, and not in straight lines.

So the debate about finite and unbounded refers to the general relativity concept of "shape", and the saddle is the current view of the overall shape of the universe. It is finite because it has dimensions based on a beginning and on subsequent inflation/expansion over ~13.7 billion years, and it is unbounded as if it was a surface of a sphere that has no edges.

Is that OK, and give me some layman slack on this, lol.

 

[EinsteinHimself]

It sounds like quantum wave is saying, "What does heat and visibility have to do with how far a photon is going to travel through anything?"

Is that about right?

 

[quantum_wave]

It sounds like quantum wave is saying, "What does heat and visibility have to do with how far a photon is going to travel through anything?"

Is that about right?

Welcome. May I suggest that you use the "Reply with Quote" button at the bottom left of each post so that we can put your comments into the proper context. As it happens, you and I posted at nearly the same time, few minutes apart, and it looks like you are responding to my last post which was a little before yours, but in fact, maybe your comment applies more generally to the earlier discussion?

 

[EinsteinHimself]

It was directed toward the last post, I kinda have an affinity for this, sorry. I kinda find it annoying to reread the same quote right after another. Part of me will be reading a response and another part rereads and gets confused by the quote. But hey if you find it applies to the whole of a conversation I'm not going to doubt your perspective.

 

[quantum_wave]

You see, if your post follows directly after the post you are referring to, then no quote is necessary. I must say that your earlier response doesn't seem related to my most recent post though, and so I was the one confused.

 

[EinsteinHimself]

Oh my mistake, your all talking about the early universe as it applies to recombination. Although after reading more carefully I agree with your references to spheres and expansion. To truly have a static form it wouldn't grow isometrically in all directions. If it began as a curve, logic would perceive that it continues to curve. To add; it could be an infinite amount of curves entangled outward to still produce a static form if we were to count "entanglement" and equivalence as a statistical reduction of energy in a photon that lies in an open vacuum.

 

[Farsight]

Is stretching of space the same as "new space" being added between galaxies and galaxy groups that I have seen given as the explanation for the redshift?

Space isn't "stretching". Think of the universe as something like a stress ball. Something elastic, hence that shear stress. Squeeze the stress-ball down in your fist, then let go. Space isn't "stretching" so much as "decompressing".

The width of the funnel represents the size of the universe. A real physical size. A diameter. Do not fall for "infinite" non-answers.

 

[quantum_wave]

Space isn't "stretching". Think of the universe as something like a stress ball. Something elastic, hence that shear stress. Squeeze the stress-ball down in your fist, then let go. Space isn't "stretching" so much as "decompressing".

In post #131 I was testing my understanding of that very thing. Did you get to that post yet?

The width of the funnel represents the size of the universe. A real physical size. A diameter. Do not fall for "infinite" non-answers.

Yes, the width of the funnel represents the diameter of the universe, and the phrase "finite and unbounded" applies to the analogy used in General Relativity as the surface of a sphere. That discussion was the stimulus for post #131, but I want to go on now and pick up on the term "infinite" and the couple of statements that say it could be infinite but we don't know.

My understanding is that if you are talking about the current standard theory, Big Bang Theory with Inflation, space is finite, and there is no accommodation for infinite space within the theory. Of course there are alternative theories in which infinite space is accommodated.

 

[Farsight]

In post #131 I was testing my understanding of that very thing. Did you get to that post yet?

Yes, but I skipped it because I've missed a couple of days. I'll take a look. But later. I'm afraid I have to go now.

Yes, the width of the funnel represents the diameter of the universe, and the phrase "finite and unbounded" applies to the analogy used in General Relativity as the surface of a sphere.

The "balloon" analogy is used a lot, and Einstein talked about a hypersphere*. But the universe is flat as far as we can tell, and we have absolutely no evidence for any large-scale curvature or for any "curvature in a higher dimension". And yet people cling to that curvature, and say things like "we can't detect any curvature so the universe must be very large". Or "there isn't any curvature so the universe must be infinite". And then they come out with things like "the universe has always been infinite, and it's getting bigger, don't worry your pretty little pop-science head about it". The idea that the universe is just a sphere, a ball, and we're in it, somehow escapes their notice.

That discussion was the stimulus for post #131, but I want to go on now and pick up on the term "infinite" and the couple of statements that say it could be infinite but we don't know. My understanding is that if you are talking about the current standard theory, Big Bang Theory with Inflation, space is finite, and there is no accommodation for infinite space within the theory. Of course there are alternative theories in which infinite space is accommodated.

That's my understanding too. The universe started small**, and has been expanding for 13.8 billion years. There's no way it can be infinite. It's pseudoscience to claim that it is. Especially since it cannot expand if the "spatial pressure" is held in check by a counter-pressure at all locations.



* I've said previously that it's as if Einstein didn't believe in his own theory when it came to cosmology. I don't understand why he didn't lose the dust and stick with his shear-stress elastic space with its innate pressure, and then he would have nailed it.

** You do hear people saying the universe started as a point singularity, but "Big Bang Theory" doesn't actually say that.

 

[PhysBang]

Space isn't "stretching". Think of the universe as something like a stress ball. Something elastic, hence that shear stress. Squeeze the stress-ball down in your fist, then let go. Space isn't "stretching" so much as "decompressing".

Please don't think about this. It has no basis in physics.

The width of the funnel represents the size of the universe. A real physical size. A diameter. Do not fall for "infinite" non-answers.

I suspect that the width of the funnel actually represents what we consider the visible universe as considered in terms of coordinates co-moving with idealized galaxy clusters.

Again Farsight claims that there can be no infinite expanding universe, despite the science of his idol Einstein and despite never providing any evidence for his claim.