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Relativity/Regarding relativity refutation

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Question
Hi,

I read the link written by a physicist that general/special relativity is not used in GPS positioning. Please see the link: http://www.alternativephysics.org/book/GPSmythology.htm

Is what has been stated in the link correct? The link appears to be logical for a non-physicist like me. I am a software professional but interested in physics. Can you pls clarify.

Answer
Thank you, Ameen, for the interesting question.

No, the claim is not correct.  Both Special and General Relativity are actually in use to keep the satellite clocks synchronized.  Without going into detail, you can take it from the National Institute of Standards and Technology of the US government as being a fact.

One way you can gain confidence in the NIST as opposed to the book you referred to is to look at other claims in that book.  The very first chapter purports to explain why time dilation is "impossible."  

But time dilation is used every day in analyzing the behavior of particles in atom smashers (better known as particle accelerators) and even in ordinary laboratory experiments with cosmic rays. Pi mesons created in collisions in the high atmosphere travel to earth laboratories in spite of their lifetimes in the laboratory being so short that they would all decay long before getting to earth, except for the fact that at their speeds, their lifetimes are much, much longer. That is the simplest example of time dilation being true, supporting the common understanding of relativity nowadays and contrary to the "alternative science" book that you found.

Relativity has always attracted skeptical attention from amateur physicists, who are the smartest people on their street and certain that they have found errors in Einstein's papers. Every physics department in the world gets letters from these people begging for attention to their "obvious" corrections to Einstein.  They routinely wind up in the waste basket.

Uncle Ben

Relativity

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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.

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