Matter in other galaxies would behave differently from matter in the Milky Way if fundamental constants are not always true. I argue about this sometimes. Others keep stating that the wavelengths are equal, so everything else must be.
fine-structure constant: less than 10^−17 per year
gravitational constant: less than 10^−10 per year
proton-electron mass ratio: less than 10^−16 per yearThese propositions are not mutually exclusive, the former implies the latter, right?
The https://en.m.wikipedia.org/wiki/Bullet_Cluster is pretty interesting.
These terms are mostly placeholders for things we don't understand.
There are a ton of theories to reconcile the differences, but very few are provable with our current techniques. Detecting literal dark matter is one possibility. Changes in universal constants would be another.
I don't know whether the next breakthrough in physics will be quite as relevant in our lives as quantum and relativistic physics. It would be nice if we could link gravity and E/M like we did with the strong and weak forces. Who knows what we could do if we knew how those two go together.
But, the overwhelming majority of scientists that start out asking those questions ultimately land on the mainstream theories around dark matter and dark energy being our best, most consistent, and broadest ranging answers.
If someone were to come to them with a better theory that could explain more completely the sum total of these observations they would almost certainly be open minded about it.
So... is there really dark matter and dark energy? Probably. We've got a whole lot of evidence that isn't explained better by any alternatives. But I doubt any of these scientists would say it's totally impossible.
All Einstein did, I know that conceptually this was a large leap and just saying "all he did" is doing him a severe disservice for his contributions, is note that the mass of an object is dependent upon the speed of the object. Such that for velocities that are not an appreciable fraction of c we can use Newton's laws of gravitation perfectly well.
TLDR; Einstein did not replace Newton, he tweaked him.
Depending on the constants, with significant fluctuation of them you'd expect spectral line broadening rather than the sharp lines we see in precision interferometry, violations of local Lorentz invariance, different structures in "stacked" spectra (like the Lyman-alpha forest), and instabilities in Keplerian orbits. Present measurement precision of subatomic transition spectra has really boxed you in on this: many physical constants have relative standard uncertainties on the order of 10^-10 or better.
> any measurement ... [sees only] the average
So you'd start wondering: in the limit of infinitesimal fluctuations, is a fluctuating constant just constant rather than an "effective constant"?
Where's there's still wiggle room is in the exact masses of heaver generation standard model particles (top quark, tau mass, W-to-Z mass ratio for example) and somewhat frustratingly Newton's gravitational constant, all of which have relative standard uncertainties worse than 10^-5.
(There's a quick explanation of standard uncertainty and relative standard uncertainty at <https://www.physics.nist.gov/cgi-bin/cuu/Info/Constants/defi...>)
However, assuming cosmic inflation, one might expect incredibly small scale fluctuations in physical constants to be stretched, just like incredibly small scale fluctuations in the densities of matter and radiation. This could lead to later-universe regions of arbitrary size with a significantly different value for one or more physical constants, just like we see regions relatively stuffed with galaxies (filaments) and regions that are relatively empty (supervoids). We'd expect that when we look at different parts of the sky we'd see differences in things like the Lyman-alpha forest, the population and/or spectra and/or light curves of quasars/supernovae/variables, and so on.
So, in order to have the apparently constant physical constants we observe, while keeping your idea that there are tiny fluctuations in them, you'd have to suppress high frequency fluctuations in the constants in the very early universe, because otherwise you'd have to suppress gross effects like different gas and dust chemistry when comparing one galaxy cluster to another.
And we are looking: https://cen.acs.org/physical-chemistry/astrochemistry/Scient...
(The cosmic inflation epoch predates the "freezing-out" of some of the physical constants, so my thinking is that during inflation there must be some precursor constant(s) that determine(s) the mass of the electron (for example) once there are electrons after the electroweak epoch. Even after inflation the ordinary expansion of the universe can stretch fluctuations enough that (assuming your idea) there is likely to be a directional dependence on precision extragalactic astronomy.)
If we detect a change then it's worth checking if this is also observable over shorter distances and timescales, and at that point we would look at our own galaxy.
I'm sure someone has proposed this is due to physical constants changing over time, rather than the expansion of space-time, and I'm sure someone else has explained why this is wrong.
Absorption lines of the elements in the stars whose starlight we observe. THey are the same after correction for redshift.
No one has proven that this is impossible, AFAIK.
Turns out that our gaze has no effect on anything and we’re uninteresting squishy bags of mostly water as far as physical processes are concerned.
Not specifically a "intelligent" observer per se.