Trying to understand Special Relativity

simpleton
Messages
56
Reaction score
0
Hi,

I was reading on special relativity and was trying to understand it. However, I am still not very sure about the concepts. For example, I have this problem:

I have 2 spaceships, A and B, traveling towards each other. Both have rest length x and speed v, where v is near the speed of light. Both are getting bombarded by photons that travel perpendicular to the direction of the spaceships.

The person in A will think "Hmm, due to length contraction, the rate at which he gets hit by photons is smaller than mine"

Person B will think the same way.

Person C in the observer frame will think that both ships will get hit at the same rate.

How do you resolve this contradiction?
 
Physics news on Phys.org
simpleton said:
Hi,

I was reading on special relativity and was trying to understand it. However, I am still not very sure about the concepts. For example, I have this problem:

I have 2 spaceships, A and B, traveling towards each other. Both have rest length x and speed v, where v is near the speed of light. Both are getting bombarded by photons that travel perpendicular to the direction of the spaceships.

The person in A will think "Hmm, due to length contraction, the rate at which he gets hit by photons is smaller than mine"

Person B will think the same way.

Person C in the observer frame will think that both ships will get hit at the same rate.

How do you resolve this contradiction?

There is no contradiction, all three statements are correct.
 
What I mean is, say person A and person B note down the number of photons that hit them. When they compare their readings, will they differ? And if they do, who got hit more times?
 
You need to specify the times at which they should start counting and stop counting.

If A says "I got hit by n photons between 12:00 and 12:01 on my clock", then B would say exactly the same. What you seem to be overlooking is that the events where A's clock change to 12:00 and to 12:01 are not one minute apart in B's frame.
 
Last edited:
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