Tlaloc_Temporal

Yes, atoms are made of smaller parts; electron orbitals change chemistry based on their distance from the nucleus, nucleons change the chances of emitting radiation based on their distance from each other, and quarks greating increase their mutual attraction based on distance.

The relative distance between fundamental particles is governed primarily by forces which don't seem to have changed much since nucleosynthesis. If expansion doesn't affect any of this, then saying things governed by forces are expanding is nonsensical.

I can see a perspective where time is slowing down, reducing the effective range of the forces and letting all matter shrink to fit the changing effective distance, and leaving unbound matter to appear to expand. However, I can't see how this would be meaningfully different from an expansion of all space, not how such a difference might be detected.

Regardless, the distances within atoms continue to behave consistently, while the distances within galactic superclusters do not.

We went over this, we observe the distance between galaxies increasing, but the distance between atoms has not.

The expansion happens everywhere, but subatomic forces massively overpower the expansion, so atoms don't expand.

Likewise, raisins are strong enough to not get pulled apart by the expanding bread. There may be slight force on them, but the bread expanding by a factor of 2 leaves the raisins the same size.

I don't understand how you think a change in distance can be detectable by light between galaxies, but not detectable by like between ends of a metre bar, or between electrons.

Well yes, that makes sense and all, but it's not nearly as fun as saying mojo is directly controlled by heart health. Or that cancer causes cell phones, or that people named Killian cause air bag recalls. They're obviously wrong and ridiculous, and that's funny.

Not thinking of cosmic expansion as a volume expanding is an interesting thought.

It does imply that the changing distance only happens at large distances though. "Faster-than-light" expansion is already non-local (I think), but all expansion being non-local is consistent with it being driven by vacuum energy. That kinda makes the rasin bread analogy stronger, as the rasins don't expand at all.

I wonder if we could detect frame-dragging at large distances. If expansion causes frame-dragging, then it's actually a change in space, not just distance.

I wonder if linear motion can even cause frame-dragging, or if it's just rotation that causes it. I do not know enough about the math to say.

This is actually a thought that some climate deniers have. "Climate change is a hoax to control you, covid was the trial run".

Unsurprisingly, the people who say that publicly tend to be funded by oil.

This does insinuate that a high-risk of heart attack causes sexlessness.

Better stock up on advil.

If there's no such thing as absolute distance, then how can you say that a metre bar (and the metre) is larger than it used to be?

If distance is relative, and matter isn't expanding relative to anything else, then matter isn't expanding.

We ultimately define distance in terms of c, and the fundamental forces agree with this. We do not observe atoms expanding, but we do observe the space between galaxies expanding. Presumably the space we occupy is also expanding, but it's such a small effect as to be irrelevant.

Back to my original question, is the boundary between irrelevantly small and detectable above or below the galactic scale?

Actually that's a good point about interferometers, the only detectable change whould be in the difference between each arm's length.

Gravitational waves do behave like EM waves, we've seen a neutron star merger simultaneously in gravity and light. If there was a difference, one observation would lag behind.

How exactly would we measure an absolute value of distance? The whole thing about general relativity is than everything is relative. If everything was scaled up such that the fine structure constant stayed the same, we wouldn't be able to measure a difference.

Which brings us back to the question I have with your model: How can a changing distance be measured by light to be the same (metre bar) but also different (redshift)? If light is scaling with the rest of the universe, it shouldn't get shifted. This in the crux of my confusion.

And yet you said that a metre bar would be larger yet measure the same. If all the aspects of the universe are expanding in lockstep such that any distance appears constant, then redshift caused by expansion is impossible.

If the increasing distance between atoms is unmeasurable, then so too must be the increasing distance between galaxies be undetectable.

LIGO can detect changes of distance on the order of 10⁻²¹, and it should be increasing in effective length by 2×10⁻¹²m/s, yet I don't see any mention of any large interferometer measuring anything but gravitational waves, and I don't see any large time-dependent components of LIGOs systemic error data.

We also can measure the increasing distance of galaxies via redshift, so unless you can explain how light from galaxies is different from the light in a large interferometer, I must conclude that the interferometers aren't expanding at the same rate as the observed expansion of the universe.

We aren't expanding like the universe is expanding.

Yes, relatively means that light appears to move at c in every inertial reference frame. That doesn't change how we measure distance in a single reference frame.

How can a metre bar be measured as a metre when it's one unit and two units long? We're measuring the bar in it's own reference frame each time, so relatively causes no change. Either c increased, or time slowed down to match the expansion of space. Either way, light doesn't get redshifted by expansion.

Help me understand, how does light appear to change speed over time in the same reference frame? How do we see a change of distance affect light between galaxies, but not between atoms?

I am aware of what redshift is. What I don't understand is how you think a metre bar can expand and the speed of light increase in lockstep with it such than we can't measure the change.

Let's say we have a metre bar that's currently one unit long, and we measure it to be one metre long. There's also a galaxy a billion light years away.

Let's say the universe doubles in size after a billion years. The metre bar is two units long, but we still measure it to be one metre long, because the speed of light has doubled (presumably). We measure the light as the same length. The light from the galaxy has now reached us, and is twice as long, but is also moving twice as fast, so the wavelength stays the same. We measure the light as the same length.

Do you see my issue with this situation? How can the measured length of light change (redshift) while the measured length of light also stay the same (metre bar)?

Either redshift isn't caused by expansion, the fundamental forces and constants are changing as we expand, or space is expanding but matter isn't. We have good corroborating evidence that redshift is caused primarily by expansion. We also have evidence that the laws of physics haven't changed significantly in at least the last 2 billion years or across the universe. And lastly, we can measure the acceleration of expansion by several corroborating methods, including redshift.

I'd love to be proven wrong here, the implications of gluons being streched by expansion is fascinating.

What is expanding in this scenario? If atoms are expanding, then either atomic forces have also scaled to match the expansion, or atoms are getting more radioactive?

I don't understand how atoms are supposed to be expanding in this model. The size of atomic nuclei and electron clouds are governed by the strength and range of the fundamental forces. If everything was expanding in lockstep such that atoms expand but don't change their properties, then there would be no observable effects. Yet we can see the distance between galaxies not just getting larger, but speeding up.

If orbits, matter, and even the fundamental forces were expanding to match, no such change in "distance" should be possible, beyond the normal movement of matter.

If our metre stick was measured as 1/299,792,458th of a light second, then a million years later it was measured as exactly the same length but was somehow dimensionally larger, then lightseconds must have become larger is lockstep.

If that were true, this expansion could not explain the redshifting of light, as c would increase in lockstep with space, leaving light the same wavelength. Redshifting only happens when the distance between waves increases in relation to the speed of light, and so a universe with redshifting must have a difference in the rate of expansion and the rate of c scaling. Such a difference should be visible as increasing distance or an increase in the flow of time, at minimum.

In your model, everything is expanding equally. Literally everything, including the speed of light, the elementary charge, and even the plank constant, are expanding in lockstep, to the point of unobservability. Is this right?