Consequences of LT on Length and Photons

  • Thread starter Thread starter DougBTX2
  • Start date Start date
  • Tags Tags
    Length Photons
DougBTX2
Messages
6
Reaction score
0
Hi all,

If I have a length L_p of an object which is at rest in my frame of reference, it will have length L = L_p (1 - \frac {V^2}{c^2}) in an inertial reference frame moving with speed V relative to me. If this frame is following a photon at speed c, that makes L = 0.

If my object is the universe, it seems like my photon thinks it is everywhere at the same time, because the distance to anywhere in its IFR is zero. How does that work?

Douglas
 
Physics news on Phys.org
You cannot make a LT to the rest frame of a photon.
A photon does not have a rest frame.
You have given some reasons why.
 
"LT" = "Lorentz transformation", by the way.
 
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...
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(...
In Philippe G. Ciarlet's book 'An introduction to differential geometry', He gives the integrability conditions of the differential equations like this: $$ \partial_{i} F_{lj}=L^p_{ij} F_{lp},\,\,\,F_{ij}(x_0)=F^0_{ij}. $$ The integrability conditions for the existence of a global solution ##F_{lj}## is: $$ R^i_{jkl}\equiv\partial_k L^i_{jl}-\partial_l L^i_{jk}+L^h_{jl} L^i_{hk}-L^h_{jk} L^i_{hl}=0 $$ Then from the equation: $$\nabla_b e_a= \Gamma^c_{ab} e_c$$ Using cartesian basis ## e_I...
Back
Top