Recent content by solveforX

Hey, in general relativity, essentially I am asking how any metric (I.e. schwarzschild metric) was found. are the metrics derived or are they extrapolated from the correct lagrange equations of motion? If there is a derivation available, please provide a link. thanks

thank you

hi, I understand that Tab,b=0 because the change in density equals the negative divergence, but why do the christoffel symbols vanish for Tab;b=0?

yeah I've seen the method for the contraction of bianchi identities to arrive at the einstein tensor but I was determined to use this method too. It's really tedious and i just can't find the expression. I guess I'm just forced to believe the equation but thanks so much for the help.

about 1:05:44 in

I've tried over and over again. If someone could post a solution I'd really appreciate it.

OK thank you. I saw in a youtube lecture though that Rab;a=1/2gabR,a. I cannot find the proof for this. can anyone help me with this problem?

what would Rabcd;e look like in terms of it's christoffels? or Rab;c

I'm reading gravitation and having trouble with one of the exercises. aRab+bRgab is the general tensor the exercise asks to show that the divergence of this tensor vanishes if and only if b=-1/2a how do I go about solving this problem?

I suppose I was using the word "practical" in an unusual fashion. I only wanted to make the point that the original problem to the thread could be solved with basics of SR, as you yourself have done, and I failed to do with a dumb error haha. And if one looks at my earlier reply, I said that...

You have dug into what I think is the most fruitful part of the special theory, and I encourage asking questions that challenge even such a well known theory. The answer is that the speed of light needs to be constant for both Ann and Bob. If, at a certain point a light beam is sent...

There is nothing practical about special relativity. I want to clarify this because it seems important to me at least. Basic special relativity ignores things like acceleration, gravity, and motion in 3 dimensions so that it CAN simply and elegantly illustrate time dilation, length contraction...

Assuming one could see the other end, and the gravitational field is on a flat surface for the seesaw, it would be an incredible experience. You would hit the ground and still see your friend rising. Good thought experiment

Oh wow whoops I made a lightyear a year on Bob's clock. That's embarassing. Don't be confused, sylas has the correct answer.

Sorry that no one has adequately answered your question, but I believe (and hope) that I am capable of answering. You say that you don't want a full explanation so I will perform estimate calculations, which are actually quite simple, and give you the results. Others, please don't scrutinize...