Today’s postulate is that radiant energy transversing a vacuum does so at a singular speed, regardless of any consideration of the time/space it occupies.
Light in a vacuum goes exceedingly fast, and light moving through a media does so as a (slightly) lesser amount.
Since they couldn’t find the Aether after Newton, no matter what they tried, Einstein equated gravity with acceleration, matter with energy, and figured everything is Relative.
I misremember the facts, but there is also some discussion of the current understanding being suffused with dark matter and dark energy, and there are researchers who aren’t joking when they equate our existence to a VR running alongside others, or overlayed holograms running at different harmonics.
QM and its antecedent Quantum utilities can predict events with hard to grok but useful probability, which makes engineering electronics, molecular self assembly, and biology (as examples) more productive endeavors. This is unfortunate because it just can’t get the little ol’ “gravity is acceleration” part. Every time it has been tried, poof, the physicist blows up (in frustration; then they shuffle off muttering about paradox violations and arrows and probabilistic crap).
So, see, Relativity has to be wrong cause it doesn’t work on that miniscule speck of near non-existence called Plank-(Space &/or Time), where the Quanta worldview is supreme (and counter-Newtonian). Or QM is wrong because Relativity keeps getting the gravity thing.
I think it’s a OS/Firmware interface issue myself, and the Dark Mass is the Hardware. D Energy would be a few other VR’s, or dimensions, or maybe a Multiverse.
I may be uncertain about it all, sometimes, but it all is very persistent, and fairly resilient, I find.