Time Dilation Problem!

[anxmetal]

An athlete has learned enough physics to know that if he measures from the earth a time interval on a moving spacecraft, what he finds will be greater than what somebody on the spacecraft would measure. He therefore proposes to set a world record for the 100m dash by having his time taken by an observer on a moving spacecraft. Is this a good idea?

My Answer: No, because the observer in the spacecraft would measure a longer time interval not a shorter time interval. Can anyone explain it further???

[sambristol]

An athlete has learned enough physics to know that if he measures from the earth a time interval on a moving spacecraft, what he finds will be greater than what somebody on the spacecraft would measure. He therefore proposes to set a world record for the 100m dash by having his time taken by an observer on a moving spacecraft. Is this a good idea?

Not a good idea as the judge on the moving spacecraft would see the track as moving and therefore contracted in Length so the athlete would not have run the full 100 metres. How much contracted I hear you ask well exactly what is required to keep the speed of light constant. The time is reduced by a factor of sqrt (1-v^2/c^2) and the length of the track by the same factor (V being the velocity of the judge with respect to the track and c being the speed of light in vacuum)

[BruceW]

According to the person on earth, a clock on the spaceship ticks slowly and according to a person on the spaceship, a clock on the earth ticks slowly (not including the affects of gravity).