So you are postulating luminiferous aether? There are multiple experiments against that, and we don't even need it anymore, because of Einstein. Go read about its history. Sure, there's a small small small group that wishes to believe it still exists, but the evidence isn't there. The newer results are all fairly conclusive; no luminiferous aether. And Michelson–Morley didn't behave as aether should have, and...not so much luck there. Granted, that experiment was inconclusive on its own, but after more refined experiments took place, luminiferous aether was growing insanely complex in weird attempts to save it, and when Einstein came around, the whole reason aether was postulated fell apart. By that time, luminiferous aether was pushing on untestability, because every single time an experiment was made, it went against it, so they built a more complex system to explain those results away.