# The relativity of time: time dilation

1. Jan 22, 2008

### Jbum

QUESTION #1:

1. suppose a race on earth was monitored by a spaceship traveling in space at 0.900c relative to the earth and the space travelers measured the time of the race to be 125.6s. What was the time recorded on earth?

2. t = gamma t' where gamma = 1/ sqrt(1-v squared/c squared)

3. v = 0.900c
t = 125.6s??
t' = ???

I stopped here because I am not sure if I have my ts right. I know how to do all the math, just figuring out which t is which is harder for me in this particular question.

QUESTION #2

1. spacecraft is passing through the solar system at speed of 0.850c relative to earth. what does the captain measure for the number of hours in an earth day if the spacecraft is moving a) towards earth and b) away from earth?

2. v = 0.850c
t =???
t' = ???

3. No idea. How does traveling towards or away from earth affect the number of earth hours that one measures? that, i do not understand.

thanks for the help in advance.

2. Jan 22, 2008

### stewartcs

Don't put two unrelated question under the same thread...i.e. start a new one for new questions.

3. Jan 23, 2008

### Jbum

yes, i am aware of that thanks. i just happened to accidentally post it in the same thread, but did not know how to remove it.

4. Jan 23, 2008

### blochwave

They're both time dilation questions, I'd rather not see two topics pertaining to the same concept myself >_>

Keep in mind that on the spaceship in both cases, events on earth would appear to be happening faster

Does the previous problem even mention if it's going away or towards, or just "relative to"? Did that make a difference?

5. Jan 23, 2008

### stewartcs

Orignially the post was inside another unrelated topic, hence my comment above. These two question are related but the thread has already be split out by a mentor.

6. Apr 17, 2009

### callena

They would observe time of Earth's rotations as 24 hours long from either direction because they would have compensated for the redshift/blueshift in their computations.