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Feb2313 08:40 AM
ZapperZ

1 
42,756 
The section of the Usenet Physics FAQ titled "Experimental Basis of Special Relativity" has been cited here many...

Dec3107 02:06 AM
jtbell

0 
42,395 
I am trying to expand $$\varepsilon^{{abcd}} R_{{abcd}}$$ by using four identities of the Riemann curvature tensor:
...

T 06:08 AM
Emil

2 
140 
It is my understanding (perhaps I am wrong) that relativity implies that all frames of reference are equal. For...

T 06:06 AM
wittgenstein

5 
142 
Consider the following case:
First frame S, which is earth.
Second frame S', which is rest relative to rocket....

T 05:49 AM
jartsa

8 
300 
a metric is also used to raise/lower indices.
g_{\nu \mu } x^{\mu} = x_{\nu}
g^{ \nu \mu} x_{\mu} = x^{\mu}
...

T 05:07 AM
ChrisVer

0 
26 
Hi all, this is a followup variant to an earlier post
...

T 05:03 AM
ghwellsjr

6 
263 
I am attempting to read my first book in QFT, and got stuck.
A Lorentz transformation that preserves the Minkowski...

T 04:32 AM
ChrisVer

12 
491 
I have always been confused about time dilation in General Relativity.
In the twins paradox, it is the traveling...

Y 08:05 PM
pervect

3 
154 
The Friedmann equation states that
$$(\frac{\dot a}{a}) = \frac{8\pi G}{3} \dot \rho + \frac{1}3 \Lambda ...

Y 04:18 PM
PeterDonis

5 
127 
Is it possible to find the parametric representation X= x(y^{a}) of a surface given the components of the metric...

Y 03:24 PM
ChrisVer

0 
89 
SR directly addresses only inertial frames. Can SR be applied to analyze accelerated frames?
For example, consider...

Y 12:30 PM
jbriggs444

12 
285 
A simple experiment can be build to demonstrate a possible contradiction between thinking theory and reality.
Use...

Y 11:56 AM
nitsuj

53 
1,463 
According to SR, there is no measurement that can determine whether an object is stationary or under motion. So if two...

Y 11:19 AM
ghwellsjr

4 
136 
Can anyone answer this question?
What you would see while watching a stationary clock that you are moving directly...

Sep1514 11:52 PM
TumblingDice

12 
380 
Alright, I'm rather new to General Relativity, and I'm getting confused with four momentum. Back in SR, p^α=mU^α, but,...

Sep1514 08:55 PM
Dirac271

2 
177 
I recently watched a video in Einstein's train though experiment.
www.youtube.com/watch?v=wteiuxyqtoM
From what...

Sep1514 02:51 PM
Nugatory

31 
1,216 
Hi, I have been reading about gravitational waves for the last few days. I saw any cylindrically or spherically...

Sep1514 12:42 PM
WannabeNewton

1 
202 
A person in the earth (stationery frame) observes the clock in the spaceship (which almost moving at the speed of...

Sep1514 08:56 AM
sweet springs

4 
225 
On the surface of a unit sphere two cars are on the equator moving north with velocity v. Their initial separation on...

Sep1514 08:50 AM
peter46464

11 
446 
I just recently derived the metric tensor of the 4sphere by embedding the coordinate system within 5D spherical...

Sep1514 03:30 AM
ChrisVer

5 
162 
As you may know, the metric tensor for 3D spherical coordinates is as follows:
g11= 1
g22= r2
g33= r2sin2(θ)
...

Sep1514 01:49 AM
haushofer

2 
210 
Rephrase from another thread I posted a while back;
If you believe as masses increase in distance gravitational...

Sep1414 11:08 PM
Simon Bridge

1 
229 
I've been starting to look at the Hilbert action derivation of Einstein's equations, and have an introductory...

Sep1414 12:34 PM
Orodruin

1 
154 
A train (source) approaching a stationery observer, wavelength of the sound is equal to the distance between source...

Sep1414 12:24 PM
jtbell

2 
132 
While reading Special Theory of Relativity from Feynman Lectures, I fell into the confusion about invariant speed of...

Sep1414 09:31 AM
jtbell

7 
300 
If I understand everything correctly, space near (but outside) a mass is curved negatively, so that if I create a...

Sep1414 07:06 AM
Sonderval

5 
235 
This has come up in enough threads now that I feel the need to give my take on it in a convenient central location, so...

Sep1414 04:41 AM
martinbn

21 
1,088 
Why does light bend due to gravity? I thought hard, read a lot and I found 3 reasons I can give as the answer. But...

Sep1314 09:26 PM
DaleSpam

73 
1,591 
Pardon my elementary questions, but:
Why is it that photons can only travel at the speed of light?
I know because...

Sep1314 05:33 PM
Nugatory

7 
238 
I am not sure whether this is a 'relativity' query as it may not be concerned with the order of events nor...

Sep1314 11:37 AM
DaleSpam

32 
617 
I thought others might be interested in an old educational paper and fim demonstrating that you can't accelerate...

Sep1314 02:32 AM
bahamagreen

4 
295 
I wanna prove the invariance of the KleinGordon Lagrangian \mathcal{L}=\frac 1 2 \partial^\mu \phi \partial_\mu...

Sep1214 06:43 PM
samalkhaiat

7 
284 
http://i57.tinypic.com/2j5n9s4.jpg
We’ve all seen this little fellas up there. Two brothers, twins, in their 60’s....

Sep1214 02:22 PM
stevenhaid

4 
477 
I’ve just read Schutz: “Gravitation from ground up”. He says that there are 4 (not all independent) sources of...

Sep1214 08:09 AM
jedishrfu

1 
196 
For a long time I have studied and read about whether the photon has mass.
On this forum, I could find a link to a...

Sep1214 06:39 AM
stevendaryl

36 
936 
After my recent studies of the curvature of the 2 sphere, I would like to move on to Minkowski space. However, I can...

Sep1214 06:27 AM
stevendaryl

10 
412 
According to a quote from a past Physics Forums article, 4D spacetime can be embedded isometrically (preserving the...

Sep1114 10:08 PM
PAllen

4 
279 
Does anyone know why we are looking for dark mater  instead of say, modifying our laws of gravity to conform with...

Sep1114 06:08 PM
ohwilleke

6 
283 
Thought experiment: Alice, Bob, and the planet Zolan.
Alice is floating in space 10 light seconds from the planet...

Sep1114 02:44 AM
ghwellsjr

6 
516 
Objects in motion relative to an inertial frame S are measured to have contracted lengths in S in the direction of...

Sep1014 11:29 AM
CKH

18 
642 
Hi all. New to physics forum and glad to be here.
I have been referencing the site for a while now and have finally...

Sep1014 04:40 AM
pervect

17 
465 