Looking for other proof of expanding universe.

[marty1]

This is just a question I thought of reading these posts. Could the increasing distance between galaxies and decreasing gravitational tension between them lead to a non-linear increase in the time needed to travel between them--acceleration even though they are independently at constant velocity locally?

 

[Drakkith]

This is just a question I thought of reading these posts. Could the increasing distance between galaxies and decreasing gravitational tension between them lead to a non-linear increase in the time needed to travel between them--acceleration even though they are independently at constant velocity locally?

What? I mean, they are already moving away with an increasing acceleration, and it's an expansion, so the distance increases faster than linear.

 

[zonde]

That's ridiculous, you can't claim the 1st thing and then right after claim the 2nd thing as evidence.

Not sure I understand what you are saying here. So let's see if we agree when I formulate it this way:
If you use some fact to arrive at hypothesis then you can't use the same fact as confirmation of your hypothesis.

Luckily we get around these circular arguments by empirical evidence and making models! We say "What happens if we assume that redshift is the result of expansion?" and then do some math and make some observations. It turns out that every result so far has turned out to be in support of expansion. The distribution of matter, the CMB, and a multitude of other things only make sense if we view expansion as being correct.

"makes sense" is subjective criterion and it is not exactly what we call scientific test.
You left out very important thing - prediction. It's not enough to do some math. It has to result in some predictions.

The FACT is that we know several things that cause redshift. We can verify them in the lab.

You mean, we know two things - recession of source from receiver and time dilation, right?
As there are no broad range wavelength converters, right?

When we apply it to cosmology the result is that things are moving away from us.

Yes, basically that's what I said about straight forward interpretation of redshift.

Using GR we interpret this recession to be due to the expansion of space for a number of reasons.

And that's the exotic part.

 

[Drakkith]

Not sure I understand what you are saying here. So let's see if we agree when I formulate it this way:
If you use some fact to arrive at hypothesis then you can't use the same fact as confirmation of your hypothesis.

Of course you can. You just can't use it as the only confirmation.

If I hypothesize, for whatever initial reason, that the universe is expanding then redshift is exactly the kind of thing we would expect. It doesn't matter if I observed it before I made the hypothesis or not. I make my hypothesis, make predictions, gather other evidence in addition to redshift through observations and tests, and then form my theory and model. If everything fits together and passes further tests and predictions, and no other competing theory can explain it as well and as simple as mine then it can be considered to be valid.

"makes sense" is subjective criterion and it is not exactly what we call scientific test.
You left out very important thing - prediction. It's not enough to do some math. It has to result in some predictions.

Exactly.

 

[marty1]

What? I mean, they are already moving away with an increasing acceleration, and it's an expansion, so the distance increases faster than linear.

What I am asking is whether you could be fooled into thinking you are accelerating if the time it took for light to travel between you and a reference point increased at a rate greater than would be calculated classically from your actual velocities you knew you left each other at some point in the past. Time dilation caused by the lower and lower gravitation tension in that empty space between you and the object you measure the distance to. Since the speed of the light can't change the extra time is expresses itself as a change in wavelength; in this case a red shift.

We interpret travel time as distance only because we know the speed of light is constant. If the travel time of light increases your only choice would be to say that the distance has increased even though it could be the time that is dilated and there is in fact no acellerative force being applied to either the source or the object.

What I am asking is whether there is any evidence that the amount of ambient gravitational field in an large empty area over a large empty space would cause a non-linear dilation of time as the area became less dense even though the objects vacating that region were moving at constant velocity. I think you would be forced to interpret the situation as acelleration if the travel time between 2 objects increased non-linearly even if the classical distance calculated from velocity over time was linear.

 

[Drakkith]

What I am asking is whether there is any evidence that the amount of ambient gravitational field in an large empty area over a large empty space would cause a non-linear dilation of time as the area became less dense even though the objects vacating that region were moving at constant velocity. I think you would be forced to interpret the situation as acelleration if the travel time between 2 objects increased non-linearly even if the classical distance calculated from velocity over time was linear.

No, if anything there would be a blueshift, not a redshift.

 

[marty1]

No, if anything there would be a blueshift, not a redshift.

Even if I reversed my assumptions on the dilation? If the time between was less than the classical distance would calculated (more efficient to travel through space with less ambient gravity)?

 

[Drakkith]

Even if I reversed my assumptions on the dilation? If the time between was less than the classical distance would calculated (more efficient to travel through space with less ambient gravity)?

I'm trying hard to understand what you are asking, and unlike Marcus or Chronos, I don't have enough knowledge and experience with GR and Cosmology to give you detailed and specific answers for all your questions. Still, I'm pretty sure that what you are asking is simply not the way it works. Perhaps someone with a bit more knowledge could answer it, as I don't feel I am knowledgeable enough to answer this without really stretching my basic understanding.

 

[zonde]

Of course you can. You just can't use it as the only confirmation.

And if you use it as the only confirmation then you can't consider your hypothesis confirmed, right?

If I hypothesize, for whatever initial reason, that the universe is expanding then redshift is exactly the kind of thing we would expect.

If you hypothesize that the universe is expanding for the very reason that we observe redshift then it is kind of ridiculous to say that redshift is exactly the kind of thing we would expect.

It doesn't matter if I observed it before I made the hypothesis or not.

It matters. Read about hindsight bias.

 

[Drakkith]

Sorry Zonde, I'm not going to argue with you any more. It isn't as simple as you are making it out to be. Redshift IS evidence for expansion when you take the whole model into account. Look at the whole picture, not just the part you want to see.

 

[Chronos]

marty1, whatever point you were trying to make has become too illogical to even merit a comment. Apparently zonde has attempted to 'rescue' whatever it was you thought you 'discovered'. It's flat wrong, so, just get over it.

 

[marty1]

marty1, whatever point you were trying to make has become too illogical to even merit a comment. Apparently zonde has attempted to 'rescue' whatever it was you thought you 'discovered'. It's flat wrong, so, just get over it.

It was a question. Questions cannot be wrong. Only your answer can be right or wrong.

 

[marty1]

Please allow me to simplify my question then. How can an observer using only the one way travel of light from a distant source distinguish between the acceleration of the source from a relativistic dilation of length and time that varies over time?

 

[zonde]

Sorry Zonde, I'm not going to argue with you any more. It isn't as simple as you are making it out to be.

To have any meaningful discussion we have to have some common base that we accept without doubt. In science this common base is scientific method.

Certainly you agree with that, right?

 

[zonde]

Please allow me to simplify my question then. How can an observer using only the one way travel of light from a distant source distinguish between the acceleration of the source from a relativistic dilation of length and time that varies over time?

You want to compare absolute (flat) source in flexible spacetime with flexible source in flat spacetime?
Or are you talking about ordinary acceleration of source like with applied force and everything (and flat spacetime)?

 

[marty1]

You want to compare absolute (flat) source in flexible spacetime with flexible source in flat spacetime?
Or are you talking about ordinary acceleration of source like with applied force and everything (and flat spacetime)?

No, not compare, receive a signal and know how much each of those two extremes contributed to changing it from what left the source (one way).

How do I distinguish the effects of the intervening and changing (important part) curved space-time over vast distances from the acceleration of the source?

 

[Drakkith]

To have any meaningful discussion we have to have some common base that we accept without doubt. In science this common base is scientific method.

Certainly you agree with that, right?

Yes.

 

[codex34]

Can I just point out that the distance to redshift relationship is inferred, it isn't an actual observation.
The magnitude versus redshift is the best fit relationship and distance is inferred from this and other assumptions.
There is also an Angular size to redshift relationship, which fits non expanding euclidean space!
http://www.wissenschaft-in-not.de/kosm003e.htm

The magnitude, luminosity, angular size, and distance relationships all have their problems with assumptions, such as the magnitude being an average of luminosity in watts/area, which doesn't account for an objects shape.
You can't say redshift is PROOF of anything, the method of measurement used to produce the redshift is archive based, a comparison against other observations, it's relationship to anything else is inferred.

I recently read a paper that measured the velocity field for certain edge on galaxies, one small statement really stood out, 'on turning the slit 90° no velocity field was found' - WHY? Isn't the shift in spectrum embedded in the light?

The statement that expansion is the only correct model shouldn't be made, it is simple our current model, we have other things to investigate and bigger telescopes to build before making such statements.

How many people know what a parabolic caustic is?
How many people can calculate them?
How many people think light is parallel?, or as effectively parallel to ignore any angle?

 

[Chronos]

No, not compare, receive a signal and know how much each of those two extremes contributed to changing it from what left the source (one way).

How do I distinguish the effects of the intervening and changing (important part) curved space-time over vast distances from the acceleration of the source?

OK, will give it another shot. Accrleration is irrelevant in special relativity. This is generally referred to as the 'clock principle'. Despite some lingering controversy, that postulate appears sound based on experiments to date. Causality is another important consideration. In deep space there are only two effects believed to be of any significance - gravity and expansion. Everything else is too weak to merit consideration. You need a mechanism, and any mechanism outside of gravity and dark energy is not yet well received by the scientific community. Any effect due to variation in curvature of spacetime demands a mechnanism. Light passing through a large cluster, or void, in deep space is subject to the integrated Sachs-Wolf effect. Beyond that, you enter the realm of unicorns and magic.

 

[zonde]

No, not compare, receive a signal and know how much each of those two extremes contributed to changing it from what left the source (one way).

How do I distinguish the effects of the intervening and changing (important part) curved space-time over vast distances from the acceleration of the source?

Hmm, I believe there can't be sustained acceleration for very long time. It requires some change in situation.

But if you want to know if redshift has some additional property that would allow us to distinguish one redshift from another redshift then we know of none such property and there is no reason to believe that there could be such a property.

 

[Chronos]

Zonde, I think we are on the same page.

 

[marty1]

Hmm, I believe there can't be sustained acceleration for very long time. It requires some change in situation.

But if you want to know if redshift has some additional property that would allow us to distinguish one redshift from another redshift then we know of none such property and there is no reason to believe that there could be such a property.

So could it be equally "correct" to conclude that the light we are receiving from a distant source is climbing from greater to lesser gravitation? That would cause a red shift as well. Since it did come from the distant past, when the universe was more dense, this would make sense and gravitational fields do not fall of linearly with linear expansion (a mechanism). Why conclude that the expansion is accelerating at all based on red shift?

 

[zonde]

So could it be equally "correct" to conclude that the light we are receiving from a distant source is climbing from greater to lesser gravitation? That would cause a red shift as well. Since it did come from the distant past, when the universe was more dense, this would make sense and gravitational fields do not fall of linearly with linear expansion (a mechanism). Why conclude that the expansion is accelerating at all based on red shift?

Well, you can't really conclude just from redshift that expansion should be accelerating. You need luminosity too. Because luminosity (of standard candle) tells you about distance (after you factor out relative velocity) so that you can find relative velocity/distance relationship.

 

[zonde]

Can I just point out that the distance to redshift relationship is inferred, it isn't an actual observation.

Can I point out that there is no such thing as actual observation.
There are layers of interpretation and we are not even conscious about the very first layers of interpretation.

There is also an Angular size to redshift relationship, which fits non expanding euclidean space!
http://www.wissenschaft-in-not.de/kosm003e.htm

Yes, angular size is another thing that we can observe. As I understand in the link you gave it is argued that explosion type expanding gives different predictions for angular size/redshift relationship, right?

 

[codex34]

Yes, angular size is another thing that we can observe. As I understand in the link you gave it is argued that explosion type expanding gives different predictions for angular size/redshift relationship, right?

You'll have to make your own mind up about that, angular size is angular size, it has absolutely no bearing on distance unless you make certain assumptions about the objects you observe, within the model you choose to use. You could probably model a shrinking universe and get angular size to fit the model.
There are more studies than just this one, some are presented as a collection of data for you to interpret, some attempt to interpret it for you.
We need more model independent studies like these.

From the redshift/distance curves I've seen fit to the accelerating expansion (not up to date on this though), it looks like the z~1.25 is approximately the point of inflection in the log curve used for the magnitude/redshift, which is too weird.

I think the objects shape is a big problem in ALL the models, for example on edge on galaxies, what angular size are we referring to? the longest distance, the shortest distance, an average? emitted light?, reflected light?, both?

It is possible that a proportion of redshift, if not it's entirety, is a phantom presented by our lack of understanding of our instrumentation and the naive assumptions we have made.

 

[George Jones]

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