I Proof of Lorentz transformation

murshiddreamengineer
Messages
3
Reaction score
0
What are the supporting arguments for the assumption that space and time are homogeneous?

1730681915413.png
 
Physics news on Phys.org
murshiddreamengineer said:
What are the supporting arguments for the assumption that space and time are homogeneous?
It is the simplest assumption, and it is consistent with all observations in the absence of tidal gravity.
 
Reply
  • Like
Likes PhDeezNutz, topsquark and Vanadium 50
murshiddreamengineer said:
What are the supporting arguments for the assumption that space and time are homogeneous?
Two things:
First there's pretty much no evidence to the contrary. The laws of physics don't change even though the earth is in a completely different place in winter and summer, the spectral lines from distant astronomical objects show that time and space works the same there as here, no matter which direction I point my laser I will find that the round trip time from laser to a fixed mirror and back is the same.....
And second, there's no plausible theory that starts with an inhomogeneous spacetime yet predicts the same observations.

(As a digression, there are implausible theories that do exactly that. The homogeneity assumption is also the assertion that these theories are implausible).
 
Reply
  • Like
Likes Dale and Bosko
murshiddreamengineer said:
What are the supporting arguments for the assumption that space and time are homogeneous?
Things derived from that assumption match observation and experiment.
 
Reply
  • Like
Likes PhDeezNutz and Dale

Thread 'Parallel transport'

In this video I can see a person walking around lines of curvature on a sphere with an arrow strapped to his waist. His task is to keep the arrow pointed in the same direction How does he do this ? Does he use a reference point like the stars? (that only move very slowly) If that is how he keeps the arrow pointing in the same direction, is that equivalent to saying that he orients the arrow wrt the 3d space that the sphere is embedded in? So ,although one refers to intrinsic curvature...
View full post »

Thread 'Describing the Big Bang'

I started reading a National Geographic article related to the Big Bang. It starts these statements: Gazing up at the stars at night, it’s easy to imagine that space goes on forever. But cosmologists know that the universe actually has limits. First, their best models indicate that space and time had a beginning, a subatomic point called a singularity. This point of intense heat and density rapidly ballooned outward. My first reaction was that this is a layman's approximation to...
View full post »
Thread 'Dirac's integral for the energy-momentum of the gravitational field'

Thread 'Dirac's integral for the energy-momentum of the gravitational field'

See Dirac's brief treatment of the energy-momentum pseudo-tensor in the attached picture. Dirac is presumably integrating eq. (31.2) over the 4D "hypercylinder" defined by ##T_1 \le x^0 \le T_2## and ##\mathbf{|x|} \le R##, where ##R## is sufficiently large to include all the matter-energy fields in the system. Then \begin{align} 0 &= \int_V \left[ ({t_\mu}^\nu + T_\mu^\nu)\sqrt{-g}\, \right]_{,\nu} d^4 x = \int_{\partial V} ({t_\mu}^\nu + T_\mu^\nu)\sqrt{-g} \, dS_\nu \nonumber\\ &= \left(...
View full post »

Similar threads

I Assumption in the derivation of the Lorentz transformation
Replies
33
Views
3K
I Alternative Ways to Realize Invariance: Lorentz Transformation
Replies
20
Views
2K
A Show Lagrangian is invariant under a Lorentz transformation without using generators
Replies
3
Views
1K
I Are the Lorentz Transformations False?
2
Replies
54
Views
3K
I Lorentz transformation on mode functions
Replies
7
Views
1K
I Question about full Lorentz transformation
3
Replies
101
Views
6K
I Time and Lorentz transformations
Replies
22
Views
1K
A What assumptions underly the Lorentz transformation?
3
Replies
120
Views
8K
I Invariance of 4-velocity
Replies
11
Views
709
I Lorentz Transformation: Premises + Derivation
Replies
5
Views
2K

Hot Threads

Recent Insights

Back
Top