[Space] Ditching Relativity, with minimal collateral damage

[teviet]

Since relativity is the true depiction of what actually goes on in our Universe, a universe without relativity would need completely different fundamental physics (i.e. quantum field theory) tuned to give the same "classical" effects. But that's okay, since quantum field theory is pretty much offstage in any game (while relativistic effects can be quite important).

To get a self-consistent classical nonrelativistic world, you pretty much just need to add one thing: a luminiferous ether. For the points you mentioned:

Originally Posted by vicky_molokh

Gravitational time dilation. I suspect this may be stated to simply not occur in this universe, however see below.

Doesn't exist.

Originally Posted by vicky_molokh

Frequency shift. Blueshift/redshift. Can this be ditched too without consequences? Or can it be harmlessly attributed to light being slowed down/sped up slightly below/above its normal vacuum speed while under the effects of gravitational force? (I guess gravity is most likely a force in this universe, but not sure).

Doppler shift due to motion relative to the ether still exists; gravitational redshift would not exist.

Originally Posted by vicky_molokh

Light deflection and gravitational time delay. Can either the freefall universal rule be applied to photons, or a law of nature state that the freefall rule applies twice to photons/light, without any further consequences?

I don't think this will exist; light would be a wave propagating through the ether, not a particle subject to gravity.

Originally Posted by vicky_molokh

Gravitational Waves. Can they be applied to a non-relativistic universe by simply fixing their speed at either c or infinity? Are there better solutions?

Won't exist if you treat gravity as Newtonian: i.e. instantaneous action-at-a-distance.

Originally Posted by vicky_molokh

Orbital physics. Orbits no longer decay? Orbits decay as usual with slight change in explanation? Anything else?

No decay due to gravitational radiation, but that's unnoticeable in the Solar system. Very small corrections to planetary orbits, especially Mercury, but only noticeable with precision measurement.

Originally Posted by vicky_molokh

Black hole physics. Do these become simpler by simply stating that the 'horizon' is a de-facto case of everything simply being pulled in with enough acceleration to reverse the direction of a photon trying to come up from the black hole surface?

They no longer exist, since there is no gravitational redshift.

Originally Posted by vicky_molokh

Anything else?

Well, it means a complete rewrite of the laws of quantum mechanics as well. You're basically replacing the existing laws of nature with a completely different set that gives some of the same classical effects, and you have some freedom to choose which ones to mimic.

For instance: do nuclear reactions exist in your universe? Maybe, maybe not, or maybe there are completely different reactions in their place; the underlying mechanisms would be different. Without E=mc^2 they would not be associated with a change in the "rest mass" of the constituents. Antimatter and total conversion make no particular sense without relativity. Etc.

TeV