bangstrom

1 hour ago, Markus Hanke said:

I’m having difficulty gauging your understanding, based on what is written here.

Are you thinking that (kinematic) time dilation is merely an optical effect, and produces no measurable physical consequences other than what an observer can visually see?

I see the time dilation as genuine and not merely optical and it works both ways.

An observer at the tower sees Einstein’s moving clock as running slower due to kinematic time dilation and, likewise, Einstein sees the the tower clock as running slower since he sees the clock tower as moving away from his position.

So Einstein sees the tower clock running slower as a SR effect but the most evident change is the Newtonian Doppler effect.

4 hours ago, swansont said:

You do not have an adequate understanding of relativity to contribute here.

I am here to learn.

The question in the OP asked if it is correct that Einstein on a train moving away from the clock tower should see the receding clock running slower? I say, Yes.

The answer you gave “ The clock ticked slower because time slowed down, owing to relative motion.” makes no sense to me as an answer to the question and I understand about time dilation.

First, should Einstein see the tower clock running slower or not?

9 hours ago, swansont said:

Moving clocks actually run slow. Read what else Janus wrote. One effect in play is "Time dilation, which always has the moving source clock tick slow"

Janus is right but your answer to the question in the OP was wrong. Here is the question with your reply below.

On 5/23/2022 at 5:52 AM, swansont said:

On 5/23/2022 at 12:38 AM, MPMin said:

If I understand Einstein’s clock tower thought experiment correctly, Einstein saw himself on a train traveling away from a clock that was situated on a clock tower. From Einstein’s perspective, the hands of the receding clock would have appeared to be moving slower, hence, giving the illusion that the clock’s time had slowed down. Is this correct? 
 

No, it was not proposed to be an illusion. The clock ticked slower because time slowed down, owing to relative motion.

The correct answer to the question is: Yes, Einstein should see the hands on the tower clock moving slower because of the classical Doppler effect.

Your answer (in the expansion) makes no sense as stated. You may be thinking correctly but it came out all wrong.

If Einstein's clock is running slower, he should see the tower clock running faster than his own but this is the opposite of what he observes. Also, Einstein should see no change to the clock in his own reference frame.

Janus is correct that Einstein's clock is running slower than the tower clock but he added the caveat that you must discount the classical Doppler effect from your observation. Einstein can not observe any relativistic change from his own reference frame but he does observe the Doppler effect where the tower clock appears to be running slower.

1 hour ago, MPMin said:

 You state that both observers A and C see each other’s respective clocks ticking slower. Is that because they are effectively moving away from each other? Does the apparent slower ticking occur because the photons take longer to reach each observer, and if so, does that mean each observer is seeing fewer photons because they are arriving less frequently due to the Doppler effect, and does that mean that red shifted light is inherently dimmer than the original source?

The classical Doppler effect is the major contributor to the observations. It takes longer for light to reach the train as distances increase so the time between ticks also appears longer.

The light appears dimmer with distance because the light is emitted radially and the train captures less of the emitted light as the emission spreads. This is not a part of the Doppler effect.

The redshifting of light is a Doppler effect at relativistic speeds. It takes longer for an entire wavelength of light to be detected when the receiver is moving away causing the wavelengths appear longer and shifted more towards the red (longer wave) end of the color spectrum. The same happens with sound waves but at vastly slower speeds.

Red shifted light is not necessarily dimmer but it is less energetic than light with shorter wavelengths.

On 5/23/2022 at 5:52 AM, swansont said:

No, it was not proposed to be an illusion. The clock ticked slower because time slowed down, owing to relative motion.

Einstein should see the tower clock ticking slower because he sees the ticks arriving slower at his moving location due to the Doppler effect but the clock did not actually tick any slower.  It makes no sense to speak of time as having slowed. The observation of a slower time is real but the actual slowing of time at the tower is an illusion.

As Janus said in the quote you cited, “Do not conflate what a observers visually sees via the light arriving from a source with what that observer would conclude it happening at the source.”

3 hours ago, MPMin said:

Let’s assume the train has left clock tower A (point of origin) travelling towards clock tower B (point of destination) and has reached a constant velocity towards clock tower B, the following questions are with reference to this situation.

How does observer A (at point of origin) perceive the ticking rate of clock C (on the train)

How does observer B (at point of destination) perceive the ticking rate of clock C (on the train)

How does observer C (on the train) perceive the ticking rate of clock A (at origin), B (at destination) and C (on the train) just wondering if the observer on the train perceives any difference to the ticking rate of the clock on the train?

Observer A should see the clock on the train ticking slower.

Observer B should see the approaching clock on the train ticking faster.

Observer C on the train should see the clock at A (the origin) ticking slower. B (at the approaching destination) ticking faster. And C (on the train) should see no difference on his clock.

On 5/22/2022 at 5:57 PM, Genady said:

I know how the magnetic field was set on Earth when the other entangled electron was measured 'up'. I want to set the magnetic field here (M87) so that the electron here will definitely measure 'down'. If 'here' was in the same lab, I would set the magnetic field just parallel to the other.

The first observation establishes the orientation of both particles at the instant of observation. That is, the event is non-local. The very first observation destroys the entanglement so, if you know the orientation of the electron in your laboratory, you can’t predict the orientation at another location because the particles are no longer entangled.

On 5/23/2022 at 5:52 AM, swansont said:

No, it was not proposed to be an illusion. The clock ticked slower because time slowed down, owing to relative motion.

 

MPMin’s understanding of the problem is correct. The clock time will appear to slow from Einstein’s perspective and the clock should appear redshifted.

Einstein’s motion away from the clock can not make the clock in the tower tick slower. The clock ticks as normal, but from Einstein’s view the clock does tick slower.

Also, from the perspective of an observer at the clock tower, Einstein’s clock ticks slower. But if Einstein’s clock is actually ticking slower, he should see his clock and the tower either keeping time in sync or running faster.

There is an illusion here and no clocks are actually ticking slower. Think about it and guess again.

3 hours ago, MigL said:

That's not true.
GR does not allow for a universal reference frame, so it would not be consistant with the latter case.

Very true about GR, but relative to ‘What’ is the universe expanding? Or is it expanding at all?

I had a goldfish that grew too large for its bowel, but from the perspective of a goldfish, the bowel must have been growing too small for the fish.

When a woman puts on a pair of old pair of pants and the pants are too tight, she thinks she must be getting fat. When a man puts on a pair of old pair of pants and the pants are too tight, he thinks the pants must have shrunk.

With the universe as a whole, we don’t have a god’s eye view of events where we can view the universe from the great beyond and watch it expand or contract or remain the same so we have no external scale to tell us if the universe is truly expanding or if all the material within is growing smaller.

We are like goldfish in a bowel where our only perspective is that of what the universe looks like from the inside and our choice of absolutes is arbitrary because the laws of physics and math are blind to perspective and they do work both ways.

On 5/8/2022 at 11:11 PM, Romao Mota said:

The SMT-VSL and the expanding universe theory are equivalent.

The value of having an equivalent but alternative model to the Standard BB expansion theory is that we can compare one model with the other looking for consensus and also looking for inconsistencies that suggest there may be something wrong with our interpretation of one or both models. I think your model of shrinking matter model suggests some serious problems with the expansion theory but it works both ways.

I hope I understand how you find speed of light to be varying in your model but if you apply the same thinking the SMBB you should find that the speed of light is also varies from reference frame to reference frame in the Standard Model. If space expands while time remains the same, the speed of light must necessarily be slowing.

My understanding of this is that your model is no more a model of changes in the speed of light than is the SMBB, since in both models, the speed of light should be measured the same in each and every individual reference frame.

So how is your model any different from the SMBB? A little known mathematician named Russel Ryerson had a model of contracting matter essentially the same as yours and he said one model is the conceptual and mathematical inverse of the other. This is why they are equivalent and he called his model “Inverse Expansion.”

In the SMBB, space is expanding while time remains the same. In your model, matter is contracting, while space remains the same. I explained earlier in my comment of “little meaning” that the measured value of c remains the same in every reference frame and this should apply to your model just as it does to the SMBB. So your model is one of shrinking matter rather than a changing speed of light.

As particles in the material world grow smaller, they spin faster, and our perception of time quickens.

In the SMBB model, space expands while time remains the same and the speed of light slows from one reference frame to another. In your model, space remains the same while matter contracts and the speed of light quickens from one reference frame to another. One is the simple inverse of the other but we can't go back in time and measure light speed in these older reference frames so the variations are safely ignored.

Our observation of c remains the same in both models so neither one can be considered a model of a variable speed of light. The real difference is that the SMBB is a model of expanding space and yours is a model of quickening time.

4 hours ago, Romao Mota said:

In the first post, I said “In the SMT-VSL, the universe is the reference frame, so there is not expansion to cause redshift

It is clear that light waves are not “stretched out” in your model but I was asking if light wave emissions are growing shorter with time? That is, progressively shorter starting with the CMB and up to the present time.

6 hours ago, swansont said:

8 hours ago, bangstrom said:

The “speed of light” is a constant by definition and therefore can’t change.

That's not an actual rebuttal.

You disprove a conjecture by showing that it's not consistent with what we observe.

My statement was a comment and not an “actual rebuttal” because the OP makes sense. The “speed of light” can vary from one reference frame to another but the observed value for c should be the same in all individual reference frames.

8 hours ago, swansont said:

c=1/√(ε0μ0)

If c is a constant, then (ε0μ0) is also a constant. Separately, e0 and μ0 may be variables but their multiples and ratios should be a constant, just as when c= d/t. Distance and time may be variables but their observed ratio is a constant.

This implies that c can serve as a conversion factor for converting between units of distance and units of time. The value of c is essentially the length of a standard meter expressed in seconds.

2 hours ago, Romao Mota said:

One mistake does not justify another. In this theory, the only thing constant in the Universe is the sizes of the electromagnetic waves emitted. In this context, the only standard measure is the peak of the CMB.

If the sizes of the EM waves have remained constant, then why do present day emissions appear shorter than primal emissions from the CMB? Your model doesn’t have an expanding space to explain why light waves from distant sources have become “stretched out.” Unless, by constant you mean proportional to the shrinking atomic scale.

6 hours ago, Romao Mota said:

If matter shrinks, there must be a reason for that. Some constant would have to vary for this to happen. The “Shrinking Matter Theory with Variable Speed of Light” (SMT-VSL) presents all necessary behavior for that. 

The “speed of light” is a constant by definition and therefore can’t change. Our standard units of length and time and the ratio c are all mutually defined which makes it impossible to measure the speed of light as anything other than what it is defined to be. But you have the right idea that if matter shrinks, the nature of spacetime must change.

The value of c is a constant ratio of distance to time and not necessarily a speed. C can remain a constant if both time and distance remain as the same ratio.

The standard length of a meter is defined as the distance light travels in approximately 1/3x10^8 m/s and a light year is defined as the distance light travels in a year. Consider the impossibility of trying to measure the speed of light in meters or over the distance of a light year.

6 hours ago, Romao Mota said:

The SMT-VSL and the expanding universe theory are equivalent. If we make our world as the reference frame, the universe should expand. If we make the universe as the reference frame, matter should shrink. Laws of physics work to both theories.

This is simple logic that needs no explanation but it is impossible to explain it to anyone who doesn’t immediately find it intuitive. The more one tries to explain it, the more incomprehensible it becomes. If you haven’t discovered this yet... you will.

6 hours ago, Romao Mota said:

The Doppler shift (redshift) is well known in the expanding universe theory.

The Doppler shift is no longer considered the cause of distant redshifts. The current explanation is that space itself is expanding and light waves are being stretched out by the expansion of space which is a much different explanation but conventional thinking and calculations remain rooted in the Doppler shift paradigm.

6 hours ago, Romao Mota said:

Light speed, in this theory should grow 7.25 mm/s per year.

Light speed can vary from one reference frame to another, but within all reference frames, the value of c as a ratio of distance to time should remain the same.

The spheres are called “framboids” and here is an extensive article speculating about their possible origins. Large framboids are collections of smaller framboids rather than true crystals.

 https://www.researchgate.net/publication/313528873_Framboids_From_their_origin_to_application

16 hours ago, Genady said:

An old fable:

An old WWII RAF pilot became a commercial airline pilot when he retired from the military. The airport at Frankfort was notorious for its mix of runways and complicated landing patterns.

On the pilot’s first flight from London to Frankfort, he was having difficulty following the complicated instructions he was getting from the tower so the frustrated Air Traffic Control officer asked, “Haven’t you ever flown to Frankfort before?”

The pilot answered, “Yes, but I never had to land.”

10 hours ago, caracal said:

There is one solution for time keeping and comparing times. If there is a space vessel that has contracted by factor 1/20 and it is flying in the park and there is an ordinary man walking on the park, the man can just give gift to the space traveler: a clock that is made of ordinary matter. The man has identical clock in his pocket that is synchronized to same time. The space traveler can put this gift clock then into his pocket and every time he wants to know what is the time outside, he just look this clock.

 

Why would the space travelers 1kg mass be hardly any greater than the same mass for the man in the park? And, why would a material object, either a clock or a weight, moved from one reference frame to another not rescale to its local environment?

Also, your scenario would work better with a time traveler than a space traveler. Movement through space slows time so the two aren’t entirely different.

10 hours ago, caracal said:

Or is it so that light does not cause gravity at all and only matter causes gravity?

Light can’t be detected by any means in the space between signal and receiver so how do we know that light energy even exists in the space between? Mach asked this question as did Berkley long before him. Currently, Carver Mead along with a litany of others are convinced that energy never exists separate from matter.

1 minute ago, Genady said:

I understand that galaxies are not expanding. I'm curious, what does space expands within a galaxy mean? 

That is a matter for the Big Bang experts.  That is my interpretation of the theory so I am not the person to ask. I find it a strange idea when I think about it.

21 hours ago, Genady said:

What does it mean? (my emphasis)

How does space expand beyond the galaxies?

If matter and galaxies both were to expand along with the expansion of space, we would have no observation of an expanding universe. Since we observe galactic redshifts and interpret that as evidence of an expanding universe, the implication is that the galaxies must be remaining the same size while space expands beyond the perimeter of the galaxies. The galaxies are not expanding because they are gravitationally bound and are not affected by expanding space.

In the contracting matter theory, the universe is interpreted as being enormous in size from the beginning but not expanding. Instead of expanding space, the entire material world, from atoms to galaxies, is growing smaller so we have the illusion of expansion together with the observation of galactic redshifts because atoms are progressively growing smaller with time. Going back in time, earlier atoms were larger and emitted light in longer wavelengths proportional to their larger size.

In the BBT, space is expanding past non-expanding matter, but in the shrinking matter theory, matter is uniformly growing smaller within a background of static space while remaining proportional in size to the rest of the material world. The first is a model of expanding space and the second is a model of quickening time but the picture works the same from either perspective.

22 hours ago, joigus said:

Maybe he's somebody else's brother and she's somebody else's sister. But I think they're cousins.

https://en.wikipedia.org/wiki/John_C._Baez#Family

You are right, they are cousins. I wasn't aware that Joan Baez had such an ilustrious father.

9 hours ago, MigL said:

What we have gotten from you is that size reduction of atoms works, and mass can reduce linearly, because atoms are mostly empty space.

I said mass remains the same. I never said anything about a reduction in mass. Losing empty space increases density but no mass is lost since empty space has no mass.

9 hours ago, MigL said:

Reducing the radius of a sperical mass, while keeping density the same would result in a mass of 1/8 the original. If it weighs 1/2 the original, as you propose, then you have added/created binding energy, even if the number of constituent particles remains the same, and have effectively increased the density.

I never proposed a decrease in mass or keeping density the same. You are reading nonsense into what I wrote.

9 hours ago, MigL said:

That 'empty' space, however contains fields, such that the mass of a hydrogen atom is composed of about 2 % from the rest masses of its three quarks and one electron; the other 98 % is chromodynamic and electrodynamic binding energy.

Think about what happens in the BBT. When space expands within a galaxy while the galaxy remains the same size, the fields don’t expand with space, they remain with the galaxy.

In a “shrinking matter” theory, when matter contracts, the fields contract. The fields remain with matter.

15 hours ago, joigus said:

The quote is due to Baez.

What an amazing family! John and Joan Baez are brother and sister.

7 hours ago, MigL said:

If you were sitting on a planet 13 Billion years ago, and it underwent a linear downscaling of 1000, of the type you propose ( 1000 times smaller and 1000 times less massive ), it would now be 1000000 times more dense, and you could find yourself sitting on the event horizon of a Black Hole.
Without any cause, simply the passage of time.
IOW, physical laws are no longer invariant with the passage of time.

That would be a strange universe if physical laws could change at any moment.

I don’t see the scenario playing out that way but your conclusion is right.

In the “shrinking matter” model, at the time of recombination, planets had not yet formed but there were H atoms so let’s follow the progress of the atoms. If the atoms downscale by 1000, they would be 1000 times smaller and no less massive but with far greater densities. They would be the normal atoms we see today except that they were 1000 times larger and therefore less dense in the remote past.

In another 13 billion years, there could be some black hole issues. Normally physical laws don't change but matter itself  could be vastly different at the extremes

16 hours ago, MigL said:

You don't seem to want to address the problems pointed out by forum members.

What I have written has been largely in response to considered problems. What has not been addressed?. 

16 hours ago, MigL said:

Simply put, in a 3Dimensional space, length and mass don't scale in a way that keeps the Physics unchanged.

Are you saying they don't scale or they do scale?  I see space and time scaling in both 3D and 4D and matter scaling proportionally which is why the physics remains unchanged.

17 hours ago, MigL said:

You either have the violation of mass/energy conservation at the local level, along with ( as you claim ) violation of time symmetry ( Noether's theorem ),

Your claim is not my claim. But I do agree conservation laws hold locally because all changes remain proportional from one reference frame to the next.

17 hours ago, MigL said:

Or, you have gravitational changes at the large, or cosmological, scales, such as the laws of gravity being different at cosmological distances, such as galaxies being differently shaped or stars burning hotter/cooler, etc., yet we don't observe any of that either.

Why would the laws of gravity be any different. For convenience, we are justified in considering gravitational sources as single points. If particles become a smaller it should make no difference to gravity or changes in shape.

But it should involve all material in the universe growing hotter with time and we observe this as a rise in temperature from the primal temperature of 3.73K.

18 hours ago, MigL said:

So other than a mental exercise in "What if ?", what exactly are you hoping to accomplish ?

For a long time I thought it was simply a “What if ?” that helped my understanding of the BBT but now I see it as the answer to several problems with the Standard Model. But that is another story.

17 hours ago, joigus said:

I'll take a closer look at it later, but let me tell you physics is not just about making sense.

I wrote my response without taking time to consider it properly. That is why I asked for your expertise to take a look at it. Not because I was trying to explain away something I didn’t understand.

17 hours ago, joigus said:

I have some comments to make about this idea of observer-dependent scaling. It's akin to a slippery-slope kind of argument, but for good reasons

I favor a Machian approach to physics which tries to eliminate as many “metaphysicals” as possible and modify or remove any laws of physics that do not hew closely to experiment and observation.

On 3/9/2022 at 6:31 PM, joigus said:

 But we want some understanding at a gut level why making the electron heavier would make the hydrogen atom smaller!

That is a good matter for consideration. 

10 hours ago, joigus said:

https://math.ucr.edu/home/baez/lengths.html

You don't contemplate quantum mechanics, that's why you don't understand. The world is quantum.

ℏmc is a length. It's the length scale from which you must start making quantum relativistic corrections. You can't leave quantum mechanics out of the story. Otherwise your story is not about the real world. It's about a fantasy world.

 Does this make sense?

Caracal gave the example of two men in two jars with time varying at different rates in each jar. Neither man notices a change in his own jar but they can look out and see that their clocks are running at different rates and their units of length no longer match.

The radius r of an atom in both jars is r = ℏ2/me2 and the value of e in both jars is e=L3/2M1/2/T.

The atoms in the jar with the faster rate of time should be smaller than in the jar with the slower time because the value of e is greater where e= L3/2M1/2/T when the length L is shorter, and momentum M is greater, and the rate of time T is greater.

4 minutes ago, joigus said:

Mass scales as inverse length. By together, I didn't mean the same way.

It does for uniform solids but I don't understand this as a uniform principle.

8 hours ago, joigus said:

11 hours ago, bangstrom said:

In the BB theory, it is a given that space is expanding while time can be considered unchanging.

 

(My emphasis.)

Who gave it? And are you a co-author?

x-posted with Swansont.

In any case, mass and length scale together due to relativity and quantum mechanics, so no, you can't pull this off. Unless you explain very good reasons why ℏ and c (speed of light) are irrelevant in physics.

The “given” of an expanding universe began with the interpretation of Hubble’s observation of distant galactic redshifts as recessional velocities. Hubble himself was never convinced that the universe was expanding because he could see other possible explanations.

I am not a co-author of anything.

What do you mean by “mass and length” scale together? Did you intend to say time and length scale together?

It has never been my claim that ℏ and c are irrelevant.

4 hours ago, caracal said:

My idea assumed "equality principle", that is a statement than when there is a box or space vessel in rest or constant velocity in empty space (or in freefall in uniform gravitation field), and the whole box or vessel has been transformed, and there is a space traveler inside the vessel, he can't know whether he and space vessel has been transformed or not by doing measurements inside the vessel. He can only know that he and the vessel has been transformed if he looks outside from the window.

My interpretation is that the space traveler could know he has been transformed if he can observe an increase in the rest mass of a massive body. However, if his atoms are smaller and therefore more dense and time has quickened, there should be an increase in the objects inertial mass but he would not be able to observe the change because his rate of time is faster

When you say mass has increased, do you mean rest mass or inertial mass or both?

Also, Wetterich has a contracting model with quickening time where he claims that mass increases with time but I don’t know enough about the model to claim I understand it.

https://bigthink.com/articles/the-universe-may-not-be-expanding/

arXiv:1912.00792v4 [gr-qc] 30 Apr 2021

The great emptiness at the beginning of the Universe

“The beginning is vacuum, characterized only by average values of fields and their fluctuations. This is a very quiet epoch with only a very slow increase of particle masses. In the infinite past all particles become massless.”-Wetterich

Wetterich also has this to say,

“For standard inflationary models we find that the big bang singularity of homogeneous solutions is an artifact of a singular choice of fields.”

5 hours ago, joigus said:

I don't understand how the equivalence principle allows you to pull this off.

In the BB theory, it is a given that space is expanding while time can be considered unchanging.

With shrinking matter, it is a given that space has always remained the same while time quickens. As time quickens, our material world grows smaller relative to the space around us.

A more realistic possibility may be that space and time are changing simultaneously so space expands as time quickens but that possibility has too many variables for a single model.

Any of these models should work with the condition that distance/time always equals c. The measurements and laws of physics within each reference frame should be the same even though they may vary from one frame to the next.

On 3/7/2022 at 2:14 PM, MigL said:

So, in your 'model' if you reduced the radius of the Earth by half, it would have half the mass ?

Did you not say everything scaled accordingly so as to preserve physical laws/relationships ?

The mass remains the same. Our measurements of size scale but not mass.

14 hours ago, MigL said:

If we use your simplistic approach that actually everything in the universe has shrunk about 1000 times, that applies to everything, not just atoms.

This should apply to all measurable bits of matter and everything but space itself .

The assumption in the model is that time quickens but space does not expand. Lengths are measured as shorter as time quickens so distances appear to increase

On 3/7/2022 at 2:14 PM, MigL said:

So, in your 'model' if you reduced the radius of the Earth by half, it would have half the mass ?

We can compare this with the Big Bang model since the two models are equivalent. Doubling the radius of the universe requires that its mass increase by 8.

No, that would be a violation of the conservation of mass as would a decrease of mass in the example you gave. That would no work within the model.

15 hours ago, MigL said:

if everything shrank by about 1000 times, the the mass of planets, stars and galaxies has also decreased by about 1000 times, and that would mean they increased in density immensly.
By a million times !

 In the shrinking model, Atoms grow smaller with time, so if you run the movie backwards to the recombination era, atoms would be larger by about 1000 times in an extremely crowded universe. 

 

15 hours ago, MigL said:

Maybe you should closely consider Markus' comments about scaling.
Your theory doesn't seem to 'scale' very well.

This is a reference suggested by Markus https://en.m.wikipedia.org/wiki/Scale_invariance and the first sentence reads, “In physics, mathematics and statistics, scale invariance is a feature of objects or laws that do not change if scales of length, energy, or other variables, are multiplied by a common factor, and thus represent a universality.”

I understand this to mean we can use different scales for length, among other things, to measure objects without changing the laws of physics so long as they are multiplied by a common factor. I can explain how the common factor is the value of c later, but for now, the following is essential to understand the shrinking matter model.

Relative to the radius of the universe, the atomic scale is growing smaller. Conversely, relative to the atomic scale, the radius of the universe is growing larger.

In other words, either the universe is growing larger relative to the material within or the material within is growing smaller while the radius of the universe remains large and unchanging. The two possibilities are equivalent and neither one is impossible.

Either the universe is growing larger or we and the material world is growing smaller. Our observations should be the same either way.

3 hours ago, MigL said:

Shrinking distances by half, would result in shrinking mass to one quarter, as it depends on volume.

Mass does not grow smaller when the volume lost is empty space. The electrons grow closer to the nucleus causing the atoms to spin faster and our perception of time to quicken.