Recent content by marcosdb

Last part confusing me: wasn't the Michelson–Morley experiment using the rotation of the earth as a way to measure differences in the speed of light? Would it not amount to the fiberoptic example I gave above, but with opposite results?

So suppose we start with a fiberoptic cable that goes fully around earth, and a computer which has 2 ports so it can communicate with itself; when I send a signal out in the eastward direction, I measure the latency; then I send a signal out in the westward direction & also measure latency. The...

Does this mean, then, that if I have a fiberoptic cable running east-west from point A to B on the surface of Earth, that it actually takes longer for the signal to go from A -> B than B -> A?

So you can help un-confuse me, then? Why is the spinning disc (with an emitter & 2 detectors, all at rest with respect to each other) not the same as the train (with an emitter & 2 detectors, all at rest with respect to each other)? What is the difference?

Got it, that makes sense & confirms my understanding (apologies for not making clear that all references were to cart frame & not ground frame, and that the cart was moving at velocity v in relation to ground frame) Why is it, then, that when we put this in a circle (Sagnac effect), we don't...

Precisely, both clocks are on the cart, moving with the cart. Synchronized to each other (both clocks on the train, moving), so I guess the answer as to which frame is the cart's frame Given that, if we stop the clocks at the moment the light reaches them (i.e. take a reading on an LCD...

Detectors are attached to the cart & moving with the cart As for frame of reference, suppose we had an infinitely precise clock located at D1 & D2, synchronized; would it register the same value T2? (if I then walked over to them & looked at them?)

Is my understanding correct that if we have a moving vehicle moving to the right at speed v, as above, with a light source in center going in both directions, that (upon emitting the light at time T), a detector at D1 & D2 would both detect light reaching it at T2? (even though in the time it...

Thanks Ibix! The fact that "dark matter" is proportional to the visible mass is why I had an inkling that it seems highly likely that it's just a side-effect of matter we're not accounting for I am curious, though, why time dilation couldn't be one of these pieces (I agree, it may not be the...

Thanks so much Peter, much appreciated! I'll dig in to better understand, but first a quick question from the things I did understand: Wouldn't the change in gravitational potential be significantly different for a 3D sphere (where the mass is evenly distributed in 3-space and as we move in 3...

A lot of papers/studies are written/done about the effect of something being insignificant When considering a hypothesis (one like "dark matter is the likely cause of mass/velocity we can't account for"), I'd expect in that hypothesis a list of things which could explain but don't, with the...

I'm a big believer in: Being able to show receipts - even for a complex subject, there should be some rough estimate which can explain this to laymen (Einstein's explanation of relativity is a great example) That people who have been looking at something for a long time can miss something quite...

Won't me replying to it there cause it to be bumped up? The author has some really nice diagrams there which nicely demonstrate what I'm trying to say, and it seems that question went unanswered I'm happy to discuss here instead, whichever is preferred 👍

@ https://www.physicsforums.com/threads/time-dilation-in-a-galaxy-and-in-general.1007082/ Going to add my own +1 here as I'm also very interested in discussing this, and @sha1000 did a far better job at asking the question than me I would be really curious to know a rough estimate here of the...

Gotcha, that would make sense; do you know if there's research/thesis/paper/etc. on the subject, with numbers? i.e. where they calculated the time dilation delta between the center of the galaxy vs the outside of the galaxy, and the delta in time was negligible? It seems like, given the mass...