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# Relativity/Special relativity

Question
Assume that there is man A in a spacecraft moving at 1x10^8 m/s, about 1/3 the speed of light, and man B stationary on earth. In man B's frame of reference, time dilation occurs and for every 1 minute on earth, man B only see about 57 seconds tick on man A's watch. Thus in man A's frame of reference he travels 1x10^8 m in 1 second, while in man B's frame of reference he sees man A travel 1x10^8 m in only 57 seconds. If that is the case, doesnt it mean that man A is actually travelling faster than 1.1x10^8 m/s in man B's frame of reference? And if man A is actually travelling at 1.1x10^8 m/s, time dilation effects would increase even more and man A's speed would increase even more and this cycle continues until man A reaches a speed of infinity. How does this not happen? Since time dilation is real and not an apparent thing in man B's frame of reference, this does not violate the law of causality as it is not due to what man B sees that affects man A's speed. Man A's speed is really increasing

Raphael, you say that with respect to frame B, B sees A travel c/3 on A's clock in only 57 seconds. But the speed of anything with respect to frame B  has to be measured with a clock at rest in frame B. What A's clock reads is the time of travel with respect to frame A.

It may help you to keep this straight if you refer, as I do, not to what anybody sees but what the time IS with  respect to each given frame.

Clocks keep different times with respect to different frames. It makes no sense to talk of what the time ""really"" or ""actually"" is. A clock shows its time with respect to itself. What time it keeps is less with respect to a frame in which it is moving, but both times are real and actual.

Ben

Relativity

Volunteer

#### Uncle Ben

##### Expertise

I can answer questions regarding Einstein's Theory of Relativity, particularly in Special Relativity. I will not answer homework questions or mathematical problems that require special symbols.

##### Experience

I have taught physics at the college level, undergraduate and graduate, for many years including Special Relativity. I have taught at Johns Hopkins, Case-Western, and MIT. I have also served as a staff member of the Commission on College Physics, which was supported by the National Science Foundation to recommend improvements in the curriculum of college physics departments in the US. I am also the author of a textbook titled Vector Calculus, which was used at MIT in the teaching of electromagnetic theory and relativity. My research interests were mainly in solid state physics, especially the properties of metals at low temperatures. I am listed in the publication known as American Men of Science.

Publications
I have dozens of papers published in the Physical Review and in the American Journal of Physics.

Education/Credentials
I hold a Ph.D. degree in physics from the Johns Hopkins University.

Past/Present Clients
Johns Hopkins University, Case-Western Reserve University, Massachusetts Institute of Technology, Empire State College, Georgetown University, Commission on College Physics, and UNESCO.