Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Trying to understand Special Relativity

  1. Apr 10, 2010 #1

    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, travelling 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?
  2. jcsd
  3. Apr 10, 2010 #2
    There is no contradiction, all three statements are correct.
  4. Apr 10, 2010 #3
    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?
  5. Apr 11, 2010 #4


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    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: Apr 11, 2010
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook