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# Relativity/time

Question
We know now time is relative.It can change. Then what will be the rate of change of time? With what quantity we can measure the rate change of time? There must be a physical quantity which tells that time changing on a certain planet is faster or slower than time changing on any other planet.

It is not that time itself changes. It is that the time interval between the same two events is measured to be different for observers moving with different speeds.

An example is the Doppler Effect. You can hear it for sound; you can measure it for light. When a train goes by, its whistle sounds sharp if the train is approaching you or flat if it is moving away. On the train it doesn't sound anything but normal. This is not relativity (for sound). For light, the colour change is a little different because of relativity, because what changes we observe are not speeds of light but colors of light.

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.