At Rest with our Hubble view

[quantum_wave]

At rest with our Hubble view

What is wrong with the concept of "at rest" relative to the separating galaxies and generally constant microwave background radiation?

We observe the galaxies moving away from each other in all directions at an accelerating rate, and we measure the microwave radiation coming at us from all directions at a nearly constant frequency. These observations should be the same from any point in our Hubble view.

Given those two observations made from any point in space within our Hubble view, can we say that relativistic motion can be quantified relative to any point within the Hubble view?

 

[Farsight]

That's just saying motion is relative to us, quantum-wave. You'd be better off referring to the CMBR, see CMBR dipole anisotropy.

 

[quantum_wave]

Not exactly, as your link, with which I am familiar, points out. We are moving, and I am saying that if we were to take our loction at a point in time, say now, wouldn't we be able to plot our motion relative to that point, given the concept of "at rest" relative to the average recession of the galaxies from us and relative to the constant CMBR temperature in all directions from us at that point?

 

[Farsight]

We could plot our motion with respect to the CMB rest frame. Like the article says, we're "moving at 369±0.9 km/s relative to the reference frame of the CMB (also called the CMB rest frame, or the frame of reference in which there is no motion through the CMB) in the direction of galactic longitude l = 263.99±0.14°, b = 48.26±0.03°". Note though that this isn't the same thing as the recession of galaxies from us. Some guy in 8C1435+635 will measure a CMB dipole anisotropy of say 600 km/s in some direction, even though his recession velocity with respect to us is 0.93c.

 

[andy1033]

For all it matters to our lifes really, does it matter what is outside our galaxy?

I can understand saying in our galaxy things may be important, but outside of it, why?

 

[quantum_wave]

Nothing that really affects us, like you say, but it has implications. If the entire Hubble view is causally connected, then within it, can motion be quantified relative to any point in it?

 

[quantum_wave]

We could plot our motion with respect to the CMB rest frame. Like the article says, we're "moving at 369±0.9 km/s relative to the reference frame of the CMB (also called the CMB rest frame, or the frame of reference in which there is no motion through the CMB) in the direction of galactic longitude l = 263.99±0.14°, b = 48.26±0.03°". Note though that this isn't the same thing as the recession of galaxies from us. Some guy in 8C1435+635 will measure a CMB dipole anisotropy of say 600 km/s in some direction, even though his recession velocity with respect to us is 0.93c.

I can see your point, that depending on your point of reference, you will be moving relaive to the CMB rest frame if your are in a galaxy that is in relative motion to that rest frame, and it would seem that all galaxies would have that kind of motion. Is that what you mean?

What I am asking though, is given the fact that the observable universe is all in fairly consistent expansion motion as indicated by the raw redshift data, and given that there is microwave energy (~2.7K) coming toward all points in space from all directions, can we establish a fixed point in space relative to all of the galactic motion and microwave energy?

For example, if we measure the CMB in all directions from that point and adjust our position to keep it at ~2.7K in all directions, then are we at a fixed point in space? And can we then confirm that we are not in motion relative to the recession of the distant galaxies by verifying that the redshift data shows no relative motion compared to the constant rate of recession of those galaxies, theoretically?

 

[leopold]

there are 2 models that make reasonable sense:
1. the universe has always existed.
2. the universe along with time "unfolded" into existence.

in my opinion the universe did not "explode" into existence.

 

[leopold]

For all it matters to our lifes really, does it matter what is outside our galaxy?

I can understand saying in our galaxy things may be important, but outside of it, why?

it really doesn't matter what is on top of everest either but many have died trying to get there.

 

[Farsight]

I can see your point, that depending on your point of reference, you will be moving relaive to the CMB rest frame if your are in a galaxy that is in relative motion to that rest frame, and it would seem that all galaxies would have that kind of motion. Is that what you mean?

Yes. Go back to the raisins-in-the-cake analogy. Our galaxy is like a raisin that is moving away from all the other raisins as the cake rises and get bigger. Hence the Hubble redshift. But our raisin is also moving slowly through the cake, hence the CMB dipole anisotropy. All the other raisins are doing that too.

What I am asking though, is given the fact that the observable universe is all in fairly consistent expansion motion as indicated by the raw redshift data, and given that there is microwave energy (~2.7K) coming toward all points in space from all directions, can we establish a fixed point in space relative to all of the galactic motion and microwave energy?

Not with any certainty at present. To do that we have to know where "the edge of the cake" is. Cosmologists like Neil Cornish have grappled with this, but with no definitive success. What they're looking for is a "hall of mirrors" universe, which is why I take an interest in say the Hubble Ultra-Deep Field. But nobody has found anything conclusive or even indicatory.

For example, if we measure the CMB in all directions from that point and adjust our position to keep it at ~2.7K in all directions, then are we at a fixed point in space?

No. We're just at a some point in the rising cake, which moves away from other points as per Hubble redshift.

And can we then confirm that we are not in motion relative to the recession of the distant galaxies by verifying that the redshift data shows no relative motion compared to the constant rate of recession of those galaxies, theoretically?

No. We know that "our raisin" is drifting through the cake as it expands, but we also know that this is very small compared to the Hubble recession. It's like 500km/s as compared to 0.93c. The motion of our galaxy through the expanding universe, and the motion of other galaxies through the expanding universe, is just lost in the wash.

 

[Pete]

At rest with our Hubble view

What is wrong with the concept of "at rest" relative to the separating galaxies and generally constant microwave background radiation?

Nothing. It is just as valid as the concept of at rest relative to the ground, relative to the Sun, or relative to anything else. It's a useful reference frame for some things, not so much for others.

We observe the galaxies moving away from each other in all directions at an accelerating rate, and we measure the microwave radiation coming at us from all directions at a nearly constant frequency. These observations should be the same from any point in our Hubble view.

Given those two observations made from any point in space within our Hubble view, can we say that relativistic motion can be quantified relative to any point within the Hubble view?[/QUOTE]

 

[quantum_wave]

there are 2 models that make reasonable sense:
1. the universe has always existed.
2. the universe along with time "unfolded" into existence.

in my opinion the universe did not "explode" into existence.

The raw redshift data is certainly good evidence of expansion, and back tracking the expansion pretty logically takes us back ~13 billion years or so, depending on the geometry and math, but then the conditions or preconditions aren't so clear to me. I agree with you about choice #1 vs. #2, but this is another topic, and if we can establish a fixed point in space relative to the red shift and the CMB, it should have been possible to do that in the early galactic epoch as well, as long as expansion was taking place.

I guess my question applies to the separation of galaxies occurring back then too. Certainly the background radiation was much hotter, but still coming from all directions at a pretty consistent temperature, or maybe I should say frequency, becaue it would not have been microwaves back then, would it? Wouldn't the anisotropy, meaning the observation of a directional temperature or frequency difference, indicate relative motion to the background back then too?

 

[quantum_wave]

...

Not with any certainty at present. To do that we have to know where "the edge of the cake" is.

I guess that is true if you take me literally, meaning relative to the observable and unobservable galaxies. But I'm just talking out what we observe, and like you say, we see not edge.

Cosmologists like Neil Cornish have grappled with this, but with no definitive success. What they're looking for is a "hall of mirrors" universe, which is why I take an interest in say the Hubble Ultra-Deep Field. But nobody has found anything conclusive or even indicatory.

Was Cornish talking about the mapping of the CMB, WMAP and more recent surveys?

No. We're just at a some point in the rising cake, which moves away from other points as per Hubble redshift.

I'm not sure you are acknowledging that I said, "and adjust or position". I acknowledge that if we start with the relative motion of Earth to the background, to come to rest we would have to do some course corrections, i.e. adjust our position.

No. We know that "our raisin" is drifting through the cake as it expands, but we also know that this is very small compared to the Hubble recession. It's like 500km/s as compared to 0.93c. The motion of our galaxy through the expanding universe, and the motion of other galaxies through the expanding universe, is just lost in the wash.

I can see that from the perspective of being a raisin in the rising dough, but my question is relative to the raw redshift data and observed isotropy, and asking if we can theorize coming to rest realtive to both. Perhaps being at such a point, with no relative motion to the redshift and background, would be impractical to find under existing technology, so I guess I am asking from a more theoretical perspective.

 

[quantum_wave]

Nothing. It is just as valid as the concept of at rest relative to the ground, relative to the Sun, or relative to anything else. It's a useful reference frame for some things, not so much for others.

I appreciate you confirming the concept.

If it is possible to be at rest in that regard, then there are some other questions about the relationship between multiple rest points. If there were two such points, is there any reason that the distant between them couldn't be measured? Maybe there could be multiple measurements at some time interval? What would we be likely to find if we could do those measurements?

 

[Pete]

What rest points do you mean? There are infinitely many points at rest with respect to the CMBR average frame.
Yes, of course you can measure the distance between two points.

 

[quantum_wave]

What rest points do you mean? There are infinitely many points at rest with respect to the CMBR average frame.

You are right, and if we were to pick any two of those points right now, those could be the points I mean, as long as they are both at rest with both the generalized separation motion of the galaxies and the directional temperature of ~2.7k of the background radiation at the time we select them.

Yes, of course you can measure the distance between two points.

The thing that makes these points "at rest" is their lack of motion relative to the CMB, and relative to the redshift. The redshift is established by galaxies moving away from us, and the temperature we measure in all directions in the CMB is radiation coming to us from all directions.

I guess at this point I am asking, if we theoretically have the ability to remain at rest by continually adjusting our position relative to those two observables, will we be frustrated because the galaxies have accelerating separation motion that doesn't correspond directly to the rate of change in the CMB temperature over time, meaning we could stay at rest relative to either the redshift or the background temperature, but not both?

 

[Pete]

At large enough distances that cosmic expansion is relevant, things become more difficult than I can handle.

I'll note that if you want to remain at rest relative to the CMB average, then the thing to do would be to adjust your velocity so that you measure no CMB dipole.

meaning we could stay at rest relative to either the redshift or the background temperature, but not both?

I'm not sure what you're thinking. I don't think that "at rest relative to the background temperature" means anything.

 

[brucep]

You are right, and if we were to pick any two of those points right now, those could be the points I mean, as long as they are both at rest with both the generalized separation motion of the galaxies and the directional temperature of ~2.7k of the background radiation at the time we select them.
The thing that makes these points "at rest" is their lack of motion relative to the CMB, and relative to the redshift. The redshift is established by galaxies moving away from us, and the temperature we measure in all directions in the CMB is radiation coming to us from all directions.

I guess at this point I am asking, if we theoretically have the ability to remain at rest by continually adjusting our position relative to those two observables, will we be frustrated because the galaxies have accelerating separation motion that doesn't correspond directly to the rate of change in the CMB temperature over time, meaning we could stay at rest relative to either the redshift or the background temperature, but not both?

The cosmological metric models observers as co-moving in local proper frames where 'tick rate ratio' [1/1] and all measurements are invariant. Makes sense for making measurements associated with cosmological physics. Such as the CMBR.

 

[quantum_wave]

The cosmological metric models observers as co-moving in local proper frames where 'tick rate ratio' [1/1] and all measurements are invariant. Makes sense for making measurements associated with cosmological physics. Such as the CMBR.

Yes, it does; I have to familiarize myself with the "tick rate ratio" but I know that various models address this concept. Right now I'm asking about the concepts of "at rest" at the same time relative to two major observations that have cosmological implications, raw redshift data and the nearly isotropic background temperature.

At large enough distances that cosmic expansion is relevant, things become more difficult than I can handle.

I'll note that if you want to remain at rest relative to the CMB average, then the thing to do would be to adjust your velocity so that you measure no CMB dipole.

Yes, that is the concept . It isn't a practical thing to consider doing, but if we theorize it, that brings us to the other cosmological observation that is used for back tracking to close to the period when galaxies began to form, i.e. the raw redshift data. I'm asking if we should be able to take a position in space and adjust to keep us at a point where the generalized redshift is the same in all directions?

"Generalized" would mean that we use a set of distant galaxies or objects in them like quasars as "candles", ignoring certain galaxies that are moving within galaxy groups, and ignoring galaxies and galaxy groups that don't fit the generalize scheme. Not all are moving away from us, some groups are moving toward us, and some galaxies in other groups can show blue shift while the group as a whole is redshifted, and apparently the generalized scheme shows separation at an accelerating rate.

I'm wondering, if we theorize both types of "at rest", i.e. a rest relative to the CMB, and at rest relative to the generalized redshift as indicated by those so called candles, if our selected "dual rest states" could be maintained by adjusting to hold those positions?

I'm not sure what you're thinking. I don't think that "at rest relative to the background temperature" means anything.

It does if you are discussing the subject among friends, because the "at rest" relative to the cosmic background radiation is achieved if you measure the background temperature at the same approximately 2.7K temperature in all directions. If you have motion in any direction, the measured temperature in that direction goes up, and so you know you are not at rest.

 

[PhysBang]

I guess at this point I am asking, if we theoretically have the ability to remain at rest by continually adjusting our position relative to those two observables, will we be frustrated because the galaxies have accelerating separation motion that doesn't correspond directly to the rate of change in the CMB temperature over time, meaning we could stay at rest relative to either the redshift or the background temperature, but not both?

If the standard cosmological model is correct, the separation exactly corresponds to the change in CMB temperature over time.