This discussion centers on the nature of light and gravity, specifically addressing the misconception of aether as a medium for light travel. The Michelson–Morley experiment definitively disproved the existence of aether, establishing that light does not require a medium to propagate. The conversation also explores the concept of spacetime, emphasizing that gravity results from the curvature of spacetime rather than a physical medium. Observations of light behavior and gravitational lensing provide strong evidence for these theories, reinforcing the understanding of light's consistency across vast distances.
PREREQUISITESPhysicists, astronomy enthusiasts, students of general relativity, and anyone interested in the fundamental principles of light and gravity.
I'm not sure what that comment is in reference to, but our observations impacting Relativity span the entire observable universe.john-of-the-divine said:
The post that @bahamagreen edited used to have reference to the experiments using the retroreflectors on the moon.russ_watters said:
I'm saying that compared to the size of the universe, the distance to the moon is like an inch compared to 100 miles. I don't know the actual scale, but I'm saying we can't know the true effects on light until we can go a light year away, shoot a laser back to earth, and study that light.russ_watters said:
We've basically done that. We can look at the light from certain light sources (different kinds of stars and related bodies) at very different distances and compare them. What do you think the main difference is in the light coming from a nearby star and one a few billion light years (LY) away?john-of-the-divine said:
It may not give quite the same information, but studying light that has traversed much of or all of the universe is plenty helpful.john-of-the-divine said:
ah, but all that is based on the belief that in space, the light takes x amount of time to travel x amount of miles, when we really don't know what the "fabric" of space time is made out of? I don't know, maybe I'm thinking too high for my tiny mindberkeman said:We've basically done that. We can look at the light from certain light sources (different kinds of stars and related bodies) at very different distances and compare them. What do you think the main difference is in the light coming from a nearby star and one a few billion light years (LY) away?
If you're really asking what the "fabric" of spacetime is, I think I'll move this thread to the Relativity forum, where you can get more knowledgeable replies. I'll mark it with a "B" prefix to let others know that you'd like responses on a Basic level.john-of-the-divine said:
lol. thanks guys.berkeman said:If you're really asking what the "fabric" of spacetime is, I think I'll move this thread to the Relativity forum, where you can get more knowledgeable replies. I'll mark it with a "B" prefix to let others know that you'd like responses on a Basic level.
No they don't.john-of-the-divine said:
hence the reason why I said "or so it seems"rootone said:
There is no fabric in GR. That is a very misleading pop-sci trope and is utterly useless for actually doing GR.john-of-the-divine said:
There's some serious good news here: Thanks to the internet you don't have to go to a ridiculously expensive top-flight school to learn this stuff. Textbooks and lecturers' notes from very strong academic programs are available online; for example, Sean Carroll and Gerard t'Hooft have both placed first-rate general relativity textbooks on the web, and there are many more good online resources.john-of-the-divine said:
Yes, tautologically. X really is just X for any X.john-of-the-divine said:
The Michelson Morley experiment ruled out a rigid aether and ring interferometer experiments ruled out a dragged aether. The only aether that remains compatible with experiments is experimentally indistinguishable from no aether.john-of-the-divine said:
I've gotten most of my knowledge from science, discovery, ext. can see and I understand the theories, until I asked the great "what if" question. now I want to know what "it" is that mass effects to make gravity. guess I need to understand the mathNugatory said:
if that were true then you wouldn't be asking about fabric and aether. Pop sci sources are entertainment, not education. They make you feel good, but they don't teach you the theory.john-of-the-divine said:
"It" is the geometry of physicsjohn-of-the-divine said:
As @berkeman says, wikipedia is generally OK for well-understood stuff that's not near the cutting edge. A pretty good rule of thumb is that wikipedia coverage at the undergraduate level in math and science (but emphatically not the social sciences!) is probably reasonably good. Anything beyond that... Not so much. It is prudent to read the "Talk" section of any wikipedia article before you decide how trustworthy it is.john-of-the-divine said:
that's why i put it in quotations.Dale said:
that's why I'm here. and I ment I might not know the math, but I can invision it. beyond what their cg shows usDale said:
Excellent!john-of-the-divine said:
see, that's my biggest problem, I've never been able to make myself do math. I've always had a great imagionation, and that's good, till it takes me away from what I'm trying to consentrait on.Dale said:
Then realistically I think that you have to pick a different goal. At least I don't know of a way to learn physics without doing math.john-of-the-divine said: