You are unaware of how many changes would actually be needed to restore those proportions. Swapping out the lengths in a simple inversion would not be enough. A laundry list of other fundamental constants would also have to be changing at just the perfect rate to synchronize with the shrinking.
We have no external god’s eye view of the universe to tell us if the universe is expanding or if the entire material world is growing smaller and it really makes no difference since the two possibilities are physically equivalent.
They are not physically equivalent. I have explained why they are not now three times in this thread.
Emissions from distant galaxies appear redshifted relative to local emissions which can mean that either space is expanding or matter is contracting on the atomic scale.
No. It cannot mean either of those. This is wrong and I have already explained why. The two scenarios you present here would produce completely different experimental results that would be easily measured as different.
If atoms were larger many eons ago and emitted light in wavelengths proportional to their size, then the light we observe now should appear redshifted relative to modern light even if the universe is not expanding.
Atoms being larger in the past entails a
change in the local laws of physics. This change is not observed. This is a bad theory.
Being able to examine the same events from more than a single point of view gives us “perspective” in that we can compare conclusions drawn from one point of view with conclusions drawn from the other. Einstein did this quite successfully when compared the physics of gravity with the physics of acceleration as a test for the correctness of his views about gravity.
You are correct about Einstein. Engaging with physics from different perspectives was crucial to the development and history of physics.
If it is any consolation, a German physicist named Cristoff Wetterich has deeply investigated various
No-Expansion Theories. He published an article on one of those theories. He replaced spatial expansion with a local change of all mass increasing at a tiny rate over cosmic timescales. Please do read the actual paper if you can find it online. It will verify almost everything I've said about this topic so far.
How do you know (1.000000000000174 * D ) is due to the expansion of space and not contraction of the spring?
We might have to start a new thread on this system alone. In physics, when it comes to questions like "HOw do we know X?" -- things get hairy. I will admit first that this calculation models the atoms of the spring system as perfect mathematical points. That's a convenient coincidence that actually holds even in quantum field theory. With no condescension intended , you obviously
could not shrink a point. .
Anyone could be combative here and claim -- "well string theory says particles are actually strings and etc etc". Physics is very effective at modelling mechanical systems like pendulums by depicting them as perfect mathematical objects. There is no such thing in the real world, as everything here is made out of particles at a temperature. We expect a real pendulum will 'wind down' as it gives up mechanical energy to friction and sound.
In the case of cosmic expansion, this is not observed until you get to the size scales comparable to galaxy clusters. I suppose there is local expansion happening in the tiny space between molecules of a spring ; but back-napkin calcs would show it is effectively zero at such tiny distances. To make this more realistic, the spring would have to be so long that it would stretch across the distance between the sun and the orbit of Mars. In that scenario, we ignore intermolecular space expansion as being 'effectively zero' while we take into account the huge amounts of space expanding between the distant massive orbs on each ends of the spring.
I want to write more paragraphs in this direction but this might need to be forked into another thread.
{Long-story-short} we model forces as acting against the expansion. If forces are contradictory to the direction of expansion, then over time the cosmicExpansion and springForce will 'balance out'. The orbs/spring system will reach a state of stable equilibrium , but sitting motionless slightly farther away from each other.