AbstractDreamer

"In physics, a redshift is an increase in the wavelength" https://en.wikipedia.org/wiki/Redshift

"One interpretation of this effect (cosmological redshift) is the idea that space itself is expanding." https://en.wikipedia.org/wiki/Redshift

"In physics, spacetime is a mathematical model that combines the three dimensions of space and one dimension of time into a single four-dimensional manifold" https://en.wikipedia.org/wiki/Spacetime

Why do we use classical physics and not GR to interpret cosmological redshift as an increase in wavelength and not a decrease in frequency?

Why do we allow the metric of space to expand, but not the metric of time, when interpreting cosmological redshift as space expansion?

What are the other interpretations of cosmological redshift where something else is happening other than space expanding?

11 minutes ago, exchemist said:

For that wouldn't you need evidence of phenomena that can't be predicted by existing physics? Though I suppose dark energy might be a candidate.

But there are plenty of different kinds of mechanics: quantum, statistical, Newtonian, Hamiltonian........

 

Yes, I had dark energy or space expansion phenomenon in mind.

Perhaps "mechanics" is confusing the issue.  I had in mind the concept of "micro" vs "macro", or "quantum" vs "classical" as in the OP, when thinking about categories of which there are only two and not three.  The introduction of the word "mechanics" open up the number of categories to any number really.

Why do we only categorise only two perspectives of reality, "micro" and "macro".   Is that because of the difference between QM and GR?  If we can say decoherence makes observations lose their quantum properties (not sure if we can say this), can we also say a fully coherent observable is "beyond the limit of QM"?

Why is there not three (or more) mechanics?  If there was a third, I would guess it would lie beyond the macro mechanics, "super-macro" rather than beneath the micro, "sub-micro".  It would have to describe phenomena that is beyond the limits of GR, such as the local referenced limit of speed and the apparent superluminal recession speeds at very large distances.  

Is it possible we need a third set of mechanics to describe observable physics at the super-macro scale, but still within our observable or future observable envelope.   Or is the scale of all observations complete with just two mechanics?

On 9/13/2022 at 9:06 AM, Markus Hanke said:

 

I can make an educated guess though - given the right wavelengths for your gravitational radiation, the event horizon of your BH would begin to oscillate and ‘vibrate’ (like a bell) and eventually achieve a state of resonance with the external wave field. But this also means that the BH itself becomes a source of gravitational radiation - so it would essentially reflect some of the radiation back out. I don’t know if it would re-radiate all of the energy, or absorb some of it and grow in mass; one would have to run the numbers to find out.

What’s more, the re-radiated waves will interfere with the incoming background waves in complicated non-linear ways, changing the wave field in ways that I can’t predict here now. 

And to go even further - if you were to ‘turn off’ the external wave field somehow, the BH will slowly ‘ring down’ like a bell, and eventually become stationery; however, the surrounding spacetime will remain permanently altered by all these waves having gone through it. It’s called the gravitational memory effect.

This is a really complicated scenario, but very interesting.

What kind of oscillation do you mean?   Do you mean a physical oscillation, that is, this EH boundary's location/position in space wobbles with some frequency?  Or do you mean oscillation in the values of a BH's properties, such as mass, angular momentum and charge?

If the position of the EH can "wobble", is it possible the wavelength of this is large enough to allow energy to escape?  For example if you were a photon just within the EH, but moving with 99.99999% of your speed directly away from the point of singularity, such that your geodesic is almost parallel with the EH boundary (you are still falling in just very very slowly).  If the boundary then wobbles sufficiently, is it possible to wobble "behind" you and momentarily wobble you outside the EH?   While it is likely you will wobble back within the EH on the next phase, is it possible to permanently leave the EH in this way?

"... the photons instead increase in wavelength and redshift because of a global feature of the spacetime through which they are traveling. One interpretation of this effect is the idea that space itself is expanding."

https://en.wikipedia.org/wiki/Redshift

Wiki even states that space expansion is only ONE interpretation. 

I am guilty of entertaining another interpretation.  Yet despite all your responses you have repeated failed to address the important points; either due to a failure to understand my point, or you are blinded by a desire to be right and steadfast refusal to be helpful.   

9 hours ago, swansont said:

You ask as if you don’t know the answer, despite it being given multiple times.

YOU DON’T HAVE EXPANSION WHEN THE CURVATURE IS LARGE ENOUGH.

I wouldn't ask if I knew the answer.  That's the nature of asking questions.   You answer as if you aren't reading the question, despite it being asked multiple times.  Hubble's law

	=	recessional velocity
	=	Hubble's constant
	=	proper distance

Where is the effect of curvature on recessional velocity?  In this equation that shows the direct relationship between recessional velocity (cosmological redshift interpreted as spatial expansion) and distance, where does gravity come into the picture?   

10 hours ago, swansont said:

Make up your mind. At the very least you need to be consistent.

Apparently you believe it too. At least some of the time.

I've been very consistent. There is nothing I can do about other people choosing to be inconsistent with understanding what I'm saying.   It's about whether or not cosmological redshift can have an interpretation that includes a temporal contraction/expansion.   It's NOT about if I believe that it does or does not.  What I believe is irrelevant.  Science is not about faith.

10 hours ago, swansont said:

You didn’t ask about redshift. I didn’t answer about redshift. You asked about negating expansion.

I never asked about negating expansion.  You answered that gravity negates expansion. 

On 9/29/2022 at 12:25 PM, swansont said:

We observe that gravity negates the expansion; there is no corresponding redshift. 

Your answer was in response to my supposition that gravity affects space expansion... which was simply a juxtaposition of your previous question about gravity affecting time, which to me seemed to carry an implicit meaning that gravity DID indeed affect space expansion, which I didn't know then and latter asked about.

On 9/29/2022 at 10:09 AM, swansont said:

Do we independently observe gravity affecting time (or not affecting time) in this manner?

On 9/29/2022 at 11:33 AM, AbstractDreamer said:

On the other hand, we have the observation that gravity affects space expansion.

You are looking at the FLRW metric model and the evolution of the Universe as a whole; a model that assumes a spatial expansion interpretation of comoslogical redshift and a flat time metric, to explain why gravity negates spatial expansion and not the time metric, and describe how the universe evolved.   You're using a theory to justify its assumptions.  That is a logical fallacy.

Not only that, I'm asking specifically about cosmological redshift interpretation, not gravitational or relativistic redshift.

10 hours ago, swansont said:

String theory at least has math and a theoretical basis.

The point was about testability or non-testability.   Are you conceding that your argument that my proposal is untestable is moot at this stage?

In response to my lack of maths, I'm not denying that.   I don't think it is a reason to dismiss the idea entirely at such an early conceptual stage.

In response to a theoretical basis, your arguments thus far have largely missed the mark.  I'm questioning the completeness of a spatial expansion interpretation of cosmological redshift.  Your arguments supporting spatial expansion are all premised on that interpretation.  You cant use a theory to justify its premises.

OK yes, the slits themselves do not have to be entangled.   I guess you cant actually entangle a hole.  But perhaps you can have two microscopic holes that are blocked by an entangled pair of particles.  For the sake of clarity, lets just call it an entangled slit.

But this raises another question.  What happens if the two slits are not exactly perpendicular to the wave?  So when the wave reaches one slit first, it would instantaneously close the other before the wave reaches the second slit, thus showing no interference on the detector, as the 2nd slot is closed by the time the wave arrives.

Is this a matter of precision?  Could we position the two slits accurately enough to ensure the wave passes both slits simultaneously?   So accurate as to match the instantaneous decoherence of the entangled slots?   Lets say the wave managed to reach both slits instantaneously.  Would the wave managed to pass through both slits before either of the closed and we see interference, or will the slits close before the wave gets through and we see no interference.  

Does the wave function of a quantum system preserve quantum entanglement in another system it encounters.

On 9/29/2022 at 4:40 PM, swansont said:

In Newtonian terms it’s an attractive force.

Space expansion is not modelled in Newtonian physics.  In Relativistic physics, gravity is a curvature of spacetime 4d manifold, and space expansion is a stretching of only the 3d space metric.   How does curvature affect spatial expansion?

On 9/29/2022 at 4:40 PM, swansont said:

So it’s an even weaker claim, since you acknowledge that expansion happens.

How exactly is it an even weaker claim, even if I acknowledge that expansion happens?

And No.  I don't acknowledge that expansion must happens.  I acknowledge cosmological redshift is measured.  I acknowledge spatial expansion it is a viable interpretation of redshift.  It is apparent you are the one that adamantly believes it expansion happens, and perhaps evidentially so.  But you need to separate your beliefs, from mine. 

On 9/29/2022 at 4:40 PM, swansont said:

So how does gravity eliminate redshift?

Space expansion is a proposal - an interpretation - based on cosmological redshift not relativistic or gravitational redshift.  Your answer, that gravity is an attractive force under Newtonian physics is nonsense when talking about cosmological redshift.  There's no effect of gravity in cosmological redshift.

Hubble's Law describes cosmological redshift is related to proper distance and time (Hubble parameter), and NO gravity factors.   The FLRW metric describes space expansion is due to proper distance and time, and again NO gravity factors   Time metric contraction is related to distance not gravity (me).   

On 9/29/2022 at 4:40 PM, swansont said:

So we can measure expansion, owing to redshift but not time effects? 
 

No. Ill say it again as pedantically as possible, might just work eventually.

IF we interpret the cosmological redshift effect as spatial expansion and zero temporal expansion, then the cosmological redshift effect is all due to spatial expansion, according to Hubble Law and FLRW metric.  In this case the redshift represents only spatial expansion, and as such it is a measurement of spatial expansion.

IF we interpret the cosmological redshift effect as partial spatial AND partial temporal expansion, then the cosmological redshift effect is NOT all due to spatial expansion.   In this case cosmological redshift represents more than just spatial expansion, and as such its measurement cannot wholly be attributed to spatial expansion.

On 9/29/2022 at 4:40 PM, swansont said:

If it’s not testable, it’s not science.

Like I said before.  We can argue whether or not its testable later.  We don't know if its untestable right now.  Lack of testability hasn't stopped ideas in String Theory.

I'm sure this has been asked multiple times, but I couldn't easily find a answer.

So in the double slit experiment, with steady source of emission through two slits, we see an interference pattern on the other side that suggests the emission is wave like as it passes the slits.  The emission appears to acknowledge and pass through BOTH slits, while its waveform remains uncollapsed.

What happens if the two slits are entangled such that when one slit is open the other is instantaneously closed, for each emission.   Would the entanglement of the slits cause the waveform of the emission to collapse, or would the waveform cause the slits to decohere?  How would a partial decoherence of the slits affect the probability distribution of where the particle might end up being detected?

Just now, swansont said:

We observe that gravity negates the expansion; there is no corresponding redshift. Gravity is an interaction that is experimentally confirmed. 

How exactly does gravity negate expansion, knowing that expansion is a change in the metric and gravity is not?

1 minute ago, swansont said:

You claim is that the effect on time is measurable as it is responsible for the redshift. 

No.  My claim is that redshift could be due to BOTH a spatial AND temporal adjustment.  If there was no spatial adjustment, then yes, perhaps you can deduce the redshift is entirely due to a temporal change, and to this end, it might be measurable.  But I'm not claiming exactly how much of the redshift is due to spatial or temporal expansion.  My claim is that some of the redshift could be due to change in the temporal metric, and why is that not a possibility.

My claim is also that a change in the metric of time could be measured, if there is a way to "untrap" a frame of reference from the same moment of time as the observation, or vice versa.  Which AFAIK is not possible, but I dont know what might be possible in the future.

10 minutes ago, swansont said:

So why isn’t the time metric contracting uniformly, if there is no change in scale?

I'm not claiming there is no change in scale.

13 minutes ago, swansont said:

How does GR support the static (or contracting) universe that must result?

We find solutions where redshift can be explained via not just a spatial expansion, but a spatial AND temporal expansion.

The term time-metric-contraction might be imprecise.  I simply used the word "contraction" to conceptualise a rotation that is symmetrical to expansion.

8 hours ago, md65536 said:

It doesn't violate GR. It is a prediction of GR given the values of several measured variables.

Ok I accept that apparent super luminal recession is a prediction of GR given the FLRW solution, and not a violation of GR under that interpretation.  And that solution allows the metric of space to expand at any speed.

The cosmological constant was supposed to provide a static solution to the field equations.  Redshift was then discovered in spiral nebulae. Lemaitre proposed a spatially expanding universe, deriving the Friedman equations with a parameter for the scale factor of expansion, and calculating Hubble's law.  Hubble then provided experimental observation evidence to support Hubble's law describing a relationship between the redshift measurements and distance from Earth.

Why have we not proposed a spatially and temporally expanding universe to explain redshift?  I dont see why it's unreasonable. 

You cant use the FLRW solution to explain why the universe expands only spatially, because the FLRW solution IS the interpretation of a universe that expands only spatially.  If you question the premise of a universe that expands only spatially, you cant use FLRW solution to falsify that question.

1 hour ago, swansont said:

Do we independently observe gravity affecting time (or not affecting time) in this manner? Is there a theoretical basis for this? If not, you’re basically saying it’s magic.

No, because it's an affect on the metric of time is not measureable (AFAIK).  

On the other hand, we have the observation that gravity affects space expansion.  Under what mechanism?  Magic?  Space expansion is a stretching of the metric.  Gravity, AFAIK, affects the curvature and coordinate values of spacetime, but does not stretch the metric.  Hence why gravity is bounded by causality and the speed of light, and space expansion is not.

Lemaitre's theoretical basis for space metric expansion was redshift measurements

My theoretical basis for time metric contraction is redshift measurements.

Sure he managed to derive actual solutions.

1 hour ago, swansont said:

Except it’s not dependent upon distance when the distance is small.

Then neither is a change in the time metric.

1 hour ago, swansont said:

Testability is a requirement for it to be scientific 

Then String Theory is not scientific, but it still being explored.

1 hour ago, swansont said:

Gravity. As has repeatedly been explained.

Then gravity is also the mechanism why there is no observed change in the time metric where gravity is significant, as I have repeatedly explained through inheritance.

1 hour ago, swansont said:

Nothing in science has definitive proof, so this is an artificial objection.

Then a falsification will suffice.

3 hours ago, swansont said:

Because our model of space expansion has a caveat for gravitationally bound systems - an interaction that depends explicitly on distance. But not time. So you can't just swap them.

And I will keep pointing out that this is meaningless without an actual model that tells us what is supposed to be happening, and why we only observe it happening with objects that are not close to us.

In the same way that space expansion is explicitly dependent on distance, so too could the proposed time-metric-contraction equivalent - that is, dependent on distance not time.  There is no requirement that the dependency needs to be swapped.

In addition, is it not true that distance is explicitly intertwined with time?  The coordinate system for GR describes a spacetime value, not just a space value or a time value.  Anything that is far away in distance is ALSO far ago in time.  Something that is 10 lightyears away in distance is also a year away in time.  Something that is 20 lightyears away in distance is also twice the time away than something 10 lightyears away in distance.  Something that is 1 year ago has some value of distance away based on its motion and potential and background curvature.  Anything explicitly dependent on distance is also explicitly dependent on time, and vice versa.

So if space expansion is explicitly dependent on distance, is it not also possibly explicitly dependent on time under a specific coordinate rotation?

3 hours ago, swansont said:

Without a model as guidance, you can't come up with tests.

The concern for testability is not a reason to dismiss an idea before consideration, at least not before even a model is framed.  Once we have a model, you can argue it cant be tested.  Before that, we should be allowed to create a model.  Unless you already have all the answers.

3 hours ago, swansont said:

No, as previously discussed, we know why no expansion is observed in those cases. We have a mechanism.

Please elaborate what this mechanism is.  Is there any definitive proof why it must only stretch the spatial axes but the temporal axis must remain constant?

20 hours ago, swansont said:

Again, without a model, you can't guarantee this.

I am using a principle of inheritance to say that without a model.   If you can demonstrate that you can drink a glass that is half full in one gulp, then the same glass that is half empty can also be drunk in one gulp without necessarily needing to demonstrate it - because the latter inherits all the properties of the former.   If a space expansion explanation of cosmological redshift does not affect the fine structure constant, then neither would a time-metric contraction explanation nor even a massless invisible gorilla explanation affect the fine structure constant.

20 hours ago, swansont said:

We know the speed of light is invariant - we have physics that tells us this. We see changes in light that occur with an invariant c and space expansion - a redshift that only occurs in regions that are not gravitationally bound. So if you want to propose that this is an effect on time you would need to explain why there is no time shift for gravitationally bound entities, where the redshift is not observed.

I beg for precision.  We know the speed of light is invariant with a constant metric of time.  We know the speed of light is invariant using any frame of reference at the same moment as the measurement of that speed.  These premises are fundamental and intrinsic to the physics of GR.  You cant use a theory to prove its own premises!

In the same way we cant explain why there is no (or insignificant) space expansion in volumes of curvature.  It's just an observable the redshift only occurs in "flatter" volumes.  Anything you can say about why space expansion is observed the way it is can be similarly attributed to any alternative explanation of redshift.

I have wildly speculated previously, the measuring of wavelengths are "trapped" in time with the waves themselves.   We literally cannot measure something yesterday or tomorrow.  We can measure something that was emitted yesterday and travelled a lightday through space to reach us.  But we can only measure it "right now".  If we did measure it yesterday,  it was measured "right then" and not "right now".   We cannot measure something "right now" as it was or will be at any other time than "right now".   The "fixing" of this time moment requires that the observer and the object be in the same moment.   

But I propose that redshift is due to the continuum being stretched -  not just the space part.  It looks like the only the space part (wavelength stretching redshift) is changing because our observations are fixed in time with our objects.

9 hours ago, md65536 said:

I don't think anyone said it cannot fit? Just that it is meaningless. In fact there are published papers that propose exactly what you're saying, they're just not accepted as mainstream science, mainly because they don't account for everything that the accepted science does. Accepted science is always changing (usually slowly) but it changes to better account for actual observations, not imagined alternatives (unless it's a useful improvement). A lack of evidence doesn't prove your alternative doesn't fit, just that it doesn't improve anything.

What exactly does a constant metric of time account for that a non-constant metric of time doesnt?  AFAIK, GR doesn't even model the metric of time.   It just assumes that time over time is constant.  It is a fundamental premise of its theory, despite not explicitly stating it. The consequence of this assumption is that it effectively "normalises" the theory to a state where it works where time over time is constant - which of course suitably matches all observations because all observers are trapped in time with their observees.   Would a more fundamental model be one that includes a metric of time, albeit one that only matches observations when a solution to the metric of time for the observer is the same as that being observed.

Such a model could then interpret redshift as potentially also a stretching of the temporal axes, and not just the spatial axes.  While I agree it wont necessarily help with observations and won't be easy to test, its just an interpretation, like the Copenhagen vs Many Worlds interpretation of QM.

9 hours ago, md65536 said:

What it looks like to me, is that you're suggesting the possibility that instead of using GR to account for the universe as we observe it (where it fits very well for cosmology and large scales), we use it to account for something different than what we observe, and add in your proposals to account for the difference.

I'm saying that GR absolutely accounts for the universe we measure, because all measurements are trapped in time with whatever they are measuring and therefore it does not need to model a metric of time.   The universe we experience is one that measureably has a constant metric of time. 

Should it (GR) account for something different than what we observe (measure)? Possibly, but that would be an end-result or a consequence that follows perhaps, rather than the reason to believe so.  The reasoning is that GR models spacetime as a single manifold with four dimensions, and with the discovery of redshift measurements, we accommodate this discovery by declaring that the spatial metrics are variable and the temporal metric is constant  - for (to me) no apparent evidence, knowing that those redshift measurements by necessity have the same time metric value as the EM waves being measured, which would allude to a constant metric time but not eliminate one that is non-constant.

Why should our measurements (of redshift) necessarily be accounted for only by expansion of space because the limitations in GR on the speed of light and the implicit invariant metric of time.  That is, the redshift shows that the receeding exceeds the speed of light, which violates GR, so there must be another mechanism at play; and implicitly, this moment of measurement of redshift is trapped in time with the EM waves themselves, which is a premise of GR.

I previously asked the question is there anything that exists that is observable but not (directly) measurable.  Perhaps it is possible the universe is more than just what can be measured? Or should we straight up dismiss it because it might not ever pass scientific methodology - "If it cant be seen today, it won't ever be seen in future and so its not there?"  That's some fallacious reasoning there.

We cant see the extra dimensions of string theory, let alone test them, yet I don't see us outright dismissing string theory.  Why should we dismiss a metric of time idea before we even have a mathematical model and before we know whether or not we can falsify it?  Surely that is more unscientific than a wild speculation with even just the slightest of reasoning.

54 minutes ago, swansont said:

A problem is that you can't make the claim of paragraph 1 if paragraph 2 is the case.

I cant prove my claim, but I have asked you to falsify it and you haven't yet conclusively.  And it is not totally unreasonable like a massless invisible gorilla.  It relates directly to the spacetime continuum and why we allow the space-metric to stretch but not the time-metric.  It is a claim with sufficient reasoning to ask for a falsification before a complete proof is made.

55 minutes ago, swansont said:

If the idea isn't falsifiable it's not science.

In contrast, I have asked you show me evidence why we assume the metric of time is constant.  This idea is not falsifiable either, yet its science.   And you have not given me a sufficiently adequate answer yet.

On 9/23/2022 at 11:38 AM, swansont said:

As far as expansion goes, it's what is predicted by a wildly successful theory called General Relativity, and what agrees with the evidence, such as the redshift and the microwave background radiation, and the confirmation that the universe is, to a large degree, isotropic and homogeneous 

This is the closest answer you have given me, which I have addressed previously as inappropriate for the question of specifically evidence for/against space metric expansion vs time metric contraction.  You need to give me another answer that proves space metric expansion AND NOT time metric contraction is the only viable and correct interpretation. 

Either proof that my claim is refuted, or proof that the space-metric-expansion is the only correct interpretation of cosmological redshift.   If you can prove neither, then I would argue my claim has viability - without a full mathematical model.

54 minutes ago, swansont said:

Except you aren't because you have no math to present.

Can you show me the maths in the GR field equations for space-metric-expansion as starting point please?

54 minutes ago, swansont said:

We have measured the fine structure constant. There is no effect from space expansion, because it's not dependent on space. But changing time? Does that affect the speed of light? One might imagine it does since the distance is the same but time is changing, but we don't know, because you don't have any science to point to that would give us a clue.

 

If there is no effect from space expansion, and as the proposal of time-metric-contraction is an interpretation of space-metric-expansion, then it would inherit the same answer.  "There is no effect of time-metric-expansion on the fine structure constant".   

I would argue one might imagine it does NOT affect speed of light as measured using any frames of reference that are trapped in the same time moment.   

On 9/23/2022 at 4:53 PM, swansont said:

One has to look at the evidence, though. What would a contracting universe look like? (as we've ruled out a stable one)

 

A problem here is the claim that the interpretation can agree with the evidence, but you have not provided an actual model to test. That's incredibly thin.

 

You have to show that the alternative fits. One cannot say it does based on waving of hands, it requires a quantitative analysis to be able to say it fits. You would not just be getting rid of some parts of GR with your conjecture. How does your idea affect the fine structure constant, for example?

And just how much of GR are you dispensing with? GR makes predictions other than expansion.

A universe like ours that experienced and experiences an adjustment of the metric of time instead of the metric of space in space expansion, could look exactly like how ours started and evolved to what it is today.

I'm not competent enough to provide an actual model, at least one that would satisfy actual physicists. I just have a obscure idea that I'm struggling to find words to describe, without every other response misunderstanding my meaning.  For analogy, its like I'm asking why glass is not half empty instead of half full, and some responses are because the water is half the volume of the glass.  The answer is missing the point.

I cannot show the alternative fits.  I'm asking why it cannot fit.   I'm not necessarily getting rid of any parts of GR.  I have no idea how it affects the fine structure constant.  How does space expansion affect the fine structure constant?  Is the fine structure constant different at two locations separated by a distance large enough to measure cosmological redshift?  I doubt we have any evidence of such measurement.

I'm not dispensing of anything within GR.  Whatever mathematics are used to describe space expansion, such as the scale factor of expansion, or the cosmological constant, I am re-interpreting what some of the variables actually represent, rather than the  equations themselves.

On 9/24/2022 at 12:57 AM, swansont said:

Are you suggesting we don’t routinely compare clocks with each other? I can assure you we do. For normal timekeeping, and also for tests of relativity

We have never compared at a single moment in time, a clock ticking at that moment, with it's historical ticking at the same moment (future moment relative to the historic clock).  Any measure of the clock historically has also been made at the historic time of measurement.  The time of measurement is trapped in time with the clock ticking.  So, while we routinely compare clocks, we are not exhaustively eliminating all possible variables in any of the comparisons, such as the potential variability of the metric of time.

On 9/23/2022 at 7:59 PM, MigL said:

The fact is, the universe is only expanding at certain scales; below those scales, galaxies may actually be coming together, such as our galaxy and Andromeda, because the gravitational coupling exceeds the 'dark energy' of the expansion.

IOW, expansion is distance ( scale ) dependent.

But this does not refute an idea of time metric contraction.  The whole point of this alternative perspective is to re-interpret cosmological redshift as a time metric contraction instead of space metric expansion.  Any/all characteristics, such as dependency, is automatically inherited.  That is, if expansion is distance dependent, so too is time metric contraction.

On 9/23/2022 at 7:40 PM, NTuft said:

They are bound together in the spacetime paradigm, and I do think that time is presumed to be constant unless there is a relative acceleration that causes a dilation or contraction; similarly distances are contracted or dilated under a relative acceleration. my inference here I think is that it could go both ways assuming some deceleration; officially it may be length contractions and time dilations.

Specifically, I want to distance this topic from time dilation due to motion and gravitational potential.   This time-metric-contraction idea is a separate entity and relates only to cosmological redshift observations.   In the same way that space expansion is a separate entity to curvature.

12 hours ago, Bufofrog said:

You said, "All we have are measurements of spectral emission lines from type 1a supernovae".  The spectral emission lines are from the galaxy not the supernova.  The type 1a supernova have the same absolute magnitude.  By comparing the apparent magnitude to the absolute magnitude you can calculate the distance to the galaxy.  So therefore you can then relate the redshift (recession speed) of the galaxy to the distance of the galaxy calculated from the supernova.

So its still redshift measurements is all we have as evidence for space expansion?

4 hours ago, swansont said:

I was referring to your analogy, and claim that that '"self-arranging atoms" decide to spontaneously form banana peels directly from thick air makes more sense'

(you can tell I was referring to this because it's what I quoted with my response)

You offer this and them make a ludicrous claim about banana peels forming spontaneously as if this is a reasonable analogy.

The analogy was to show that space expansion as a theory for explaining cosmological redshift is no more sensible or no less ludicrous, to me, as time contraction; that massless invisible gorillas are as ludicrous/sensible as self arranging atoms.  The analogy goes no further than that.  It is a perfectly reasonable analogy for this purpose.

Hence why I consequently asked what makes space expansion compelling and make more sense.

4 hours ago, swansont said:

As far as expansion goes, it's what is predicted by a wildly successful theory called General Relativity, and what agrees with the evidence, such as the redshift and the microwave background radiation, and the confirmation that the universe is, to a large degree, isotropic and homogeneous 

I disagree that space expansion is predicted by GR.  GR predicts a static universe cannot be stable.  It is cosmological redshift observations that are interpreted as galaxies are moving away from us over distance that we then conclude  the universe is (currently) in a state of spatial expansion; and that is then used by GR, with tuning, to model its history to explain such expansion.   

I am proposing a time contraction interpretation of cosmological redshift, where galaxies are not necessarily ONLY moving away from us spatially, but also temporally.    This interpretation can similarly agree with the evidence, such as redshift, MBR and that the universe is to a large degree isotropic and homogeneous, with the right metric and right tuning.   

Essentially what this boils down to is why we prefer that the spatial metric is variable and that the metric of time is linear; and why we reject a linear spatial metric and a variable temporal metric.

The answer "because it fits" simply does not apply, because the alternative also fits

4 hours ago, Bufofrog said:

That is imprecise and incorrect.  It would seem to me that you should have a good understanding of a theory before you dismiss it.

Feel free to be helpful and explain where I'm wrong.

1 hour ago, swansont said:

You would need a compelling model, and evidence to support it, that explains why this makes more sense.

The evidence is cosmological redshift.  Can you explain why space expansion is a compelling model and makes more sense?

3 hours ago, swansont said:

In what way is the receding of galaxies not measurable?

I can't think of anything that is observable that is not measurable in some way.

 

Sorry, I was imprecise.  The receding of the galaxies is not a measurable it is the conclusion.  All we have are measurements of spectral emission lines from type 1a supernovae which indicate non-linear distance-redshift relationship at very large distances. 

Afaik, that there is no other measurable (besides cosmological redshift) that is explained by space expansion.   And space expansion is not directly measureable or testable at shorter distances.   Going out on a limb, how can we ever directly test for space expansion, without an experiment that spans a distance where such expansion might be evident?

3 hours ago, swansont said:

 The interaction is that they eat bananas and render them invisible, and leave the peels behind.

We all agree there are peels on the floor.  But instead of massless invisible gorillas, we decide that "self-arranging atoms" decide to spontaneously form banana peels directly from thick air makes more sense.   For this analogy, the peels are the red-shifted measurements; time contraction is the ludicrous massless invisible gorillas theory; and space expansion is the spontaneous banana-forming self-organising atoms theory.  From my perspective both are viable, but why do we choose one and reject the other?

3 hours ago, swansont said:

What you need to do is find some effect that the non-constant time would have. What is the variable time equivalent of the banana in that scenario?

Space expansion is such an effect - or more precisely cosmological redshift.   Space does not need to expand to cause redshift.  If time contracts, we can achieve the same result.  The experience of contracted time for the photon is "baked" into the wavefunction of the photon during the experience, which results in two perspectives: either a lengthening of the  wavelength as measured by an observer "trapped" in the same time as the photon (me and you and most everything else in the universe trapped in time); or an unstretched wavelength as measured by an observer "outside" the influence of time (neither me or you or most things in the universe)

3 hours ago, swansont said:

Is this consistent with all distance measurements, like supernovae, cepheids, parallax, etc.?

In the same way the FLRW metric is tuned to BE consistent with such measurements, there might be solutions to metric of time contractions that are equally consistent.  Perhaps preserving the uniform axes of space, but not necessarily so for other solutions.  The counter argument where we could wildly choose functions of time is absurd; of course it would have to fit cosmological red shift measurements.  Just like wildly choosing solutions to the field equations does not mean fitting solutions like the FLRW metric cant be found.

On 9/15/2022 at 4:42 PM, swansont said:

If there isn't any measurable effect, then time changing doesn't matter - there is no effect. I will borrow and analogy I've read elsewhere: if you propose that there is a massless invisible gorilla in the room, and there are no gorilla effects that can be detected, then your proposition is not a scientific one. It's meaningless.

What people investigate is whether dimensionless constants change over time, such as the fine structure constant. And the limit on how much that might have changed is quite small (a part in 10^17 per year as an upper bound)

What if the effect is not measurable, but observable, such as the receeding of galaxies very far ago?

What if I propose a massless invisible gorilla in the room that cannot be measured, but I point at the banana peels on the floor as an observation? 

On 9/15/2022 at 3:33 PM, MigL said:

So, since the metric is a function of time, then time itself has to be a function of time ???

I don't follow your reasoning.

As far as understand the metric assumes a time over time is flat with uniform axis, and that it is space over time that is allowed to have axes that stretch.  Why one and not the other?

red, but I point at the banana peels on the floor as an observation? 

On 9/15/2022 at 3:33 PM, MigL said:

So, since the metric is a function of time, then time itself has to be a function of time ???

I don't follow your reasoning.

As far as understand the metric assumes a time over time is flat with uniform axis, and that it is space over time that is allowed to have axes that stretch.  Why one and not the other?

So we notice that the wavelength of photons are redshifted cosmologically, and for far ago galaxies they are receeding faster than the speed of light, and we say that is possible as the space between us is expanding. 

Nothing wrong with this logic at all, but there is no basis other than "it seems obvious" to allow space to expand to explain the red shift - and that FLRW metric expansion of space has been arbitrarily tuned to agree with observations.   But what is wrong with this interpretation:

So we notice that the wavelength of photons are redshifted cosmologically, and for far ago galaxies they are receeding faster than the speed of light, and its possible that time between us is contracting.

So the cosmological redshift might not be not further away in distance due to space expansion, but further away in time due to time contraction.  A metric contraction of time.

On 9/13/2022 at 8:53 PM, md65536 said:

If it's made up and can't be measured, how can you possibly draw a useful conclusion from it? What's stopping you from imagining it to be something where the rate of time varies wildly relative to what we measure, and someone else imagining it to be something where the two measures are the same?

Its made up in the same way that we assume time is constant over time.   Any observations or experimental evidence that is itself "trapped" in time can neither support or disprove either that time is constant or non-constant.     And yet we are happy, without evidence or measurement, to assume it is constant; and draw as a useful conclusion, the FLRW metric to describe a Universe that changes over time - it "looks different at different moments in time".  Is this not in contradiction with its OWN premise of homogeneity of the Universe?

If spacetime is a continuum, and space has been observed to expand, why is it not described as time contraction?  Why must the constancy and consistency of time be preserved?  What makes the immutability of time more sacred than space?

10 minutes ago, swansont said:

If you have no way to test it, then it can’t have any measurable effect. 

 

While this is a sensible statement rooted in logic, it's not a universal law or principle afaik.  Is there any way to test Hawking Radiation at the event horizon on the black hole?  Does it have a measurable effect?   Is there any way to test space expansion at the edge of our observable universe?  Does it have a measureable effect?

11 hours ago, md65536 said:

1. Time is what clocks measure, by definition.
2. The only way to measure or reason about the rate of time, is to compare time measured by one clock to that of another clock.
3. A clock will always tick at 1 s/s compared to itself, there's simply no room for a clock to disagree with itself.

AbstractDreamer, I can't make sense of what you're saying without knowing what definitions you're using or where you disagree with these 3 things.

 

Ha!  I honestly struggle making sense of it myself, definitions in words is very difficult, and my maths is school boy level so I cant model anything.

But I think overall we are grasping at the same concept.

Let's say that this notion of "time over time" is NON-constant.  What I mean by this is that the "rate that time propagates" is different at two different values of time, relative to a theoretical frame of reference that is "outside" or "independent" of time.  Now clearly there is no such frame of reference in reality.  Everything in our spacetime is intrinsically bound within time.  Hence it is a theoretical, or imaginary frame of reference.  But that the frame is suitably "static" relative to both events in time.

So let's say that one second, today at time t=13.8B years, is defined by caesium frequency of caesium atoms that exist at time t=13.8B years.  Let's imagine at time t=1 year that caesium atoms exist, and 1 second is again defined by caesium frequency of caesium atoms that exist at time t=1 year.     

So then you measure the speed of light in units of "distance per caesium frequency".   Assuming distance is constant (this is another problem), then both today and at t=1 year, both measurements would arrive at the same result - relative to the caesium frequency of that time. 

But if somehow you compared the two caesium frequencies, using a measure and a frame of reference independent of both time today and time 1 year, then a "non-constant time over time" would allow the two frequences to differ -  and yet nothing need be violated for either of the two events, within their respective time.

I'm really not sure how to respond to those three points and how they might relate and where I might disagree.  Those three points are total valid, but there are practical limitations implied within them.  Point 2 is about measuring time.  My point accepts that measuring is currently experimentally impossible.   Point 3 is about using the clock as its own frame of reference.  This is different to a frame of reference independent of time.

Thank you for such precise answers to my questions!  I shall digest them thoroughly.  My biggest enlightenment was learning that a Schwarzschild BH have very exact requirements... can I argue it is a physically improbable in our real universe -  to have a black hole that exists in perfectly flat, albeit possibly hyperbolic, spacetime?  Is it also true that flat Minkowski space is similarly improbable in our real universe?