# Trying to understand Special Relativity

1. Apr 10, 2010

### simpleton

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, 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. Apr 10, 2010

### starthaus

There is no contradiction, all three statements are correct.

3. Apr 10, 2010

### simpleton

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?

4. Apr 11, 2010

### Fredrik

Staff Emeritus
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