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Q & A: time, gravity and light

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Most recent answer: 05/11/2015
I am a complete layman who has been studying physics and relativity lately. I'm taking a break from my ancient history studies. I was particularly interested in the period in history where physicist believed that the aether was the media in which light waves travel starting in the 17th Century. The Michelson Morley experiment brilliantly disproved this. Eventually relativity also disproved the aether. I can't let go of the idea of a media for the wave though. I am sure that some physicist at some time already explored this, but I can't find a reference. My questions are these:1. Could time be the media in which light waves travel? Could this explain how the speed of light stayed constant within the Michelson Morley experiment?2. Could gravitational forces be the media in which light waves travel? We already know that gravity has an effect on light. Is that effect driven by the particles? The particles have no mass. Or maybe it's just that they have negligible mass. The effect shows that there is some sort of relationship. Do gravitational forces effect time? Maybe time is the media and gravity effects it. How would you even experiment to show this?Anyway thank you for your consideration. It's probably not the best question, but it's bugging me. I may be stuck in 19th Century Physics.
- Dan Brennan (age 48)
Smyrna, De

This old answer should help get you started on the relation between light and gravity: .

On the question of whether somehow there's an ether despite its failure to pick out one state of motion as a preferred reference frame. that's kind of a semantic question. Spacetime itself is more active (e.g. it can support gravity waves, as described by General Relativity) than it seemed when Einstein first came up with Special Relativity. Some other feature of "empty" space, such as the cosmological constant, also indicate a more active role, again with a sort of ether-ish smell.

There's a hope, not yet fulfilled, to make a theory in which both spacetime, with its gravity, and the other forces, including electromagnetism, emerge as part of the behavior. String theory is perhaps the most prominent such attempt. Perhaps if something like that succeeds, it will become more natural to speak of electromagnetism as a behavior of something else, some deeper field (beyond the electroweak field). Gravity would also be a mode of behavior of that deeper field. 

On your other question, gravity definitely affects time. A clock in a basement will run slower than one in an attic. This is an important effect for GPS satellites. It's been confirmed many times to good accuracy.

Mike W.


(published on 05/11/2015)

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