Looking for other proof of expanding universe.

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The discussion centers on the evidence for an expanding universe, primarily using Cepheid stars and type Ia supernovae as key indicators. While the change in wavelength from Cepheid stars suggests expansion, some participants argue that alternative methods should be explored to confirm this theory. Type Ia supernovae are highlighted for their consistent intrinsic brightness, allowing astronomers to correlate brightness with redshift, reinforcing the expansion model. The conversation also touches on misconceptions about the nature of cosmic expansion, emphasizing that it is not merely an explosion but a fundamental property of space itself. Overall, the consensus leans towards the validity of the expansion model, supported by extensive observational data.
  • #61
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.
 
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  • #62
Chronos said:
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.
 
  • #63
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?
 
  • #64
Drakkith said:
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?
 
  • #65
marty1 said:
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)?
 
  • #66
zonde said:
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?
 
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  • #67
zonde said:
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.
 
  • #68
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?
 
  • #69
marty1 said:
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.
 
  • #70
marty1 said:
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.
 
  • #71
Zonde, I think we are on the same page.
 
  • #72
zonde said:
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?
 
  • #73
marty1 said:
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.
 
  • #74
codex34 said:
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.

codex34 said:
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?
 
  • #75
zonde said:
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.
 
  • #76
This thread has been closed for moderation.
 

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