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Space Exploration/Einstein's theory of Relativity

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Question
Hello
I read an answer on Yahoo questions where a guy said that if you got on a space ship, with a digital calendar saying 'January 1, 2020,' flew straight out into space for 10 years, turned around for another 10 years BACK to earth; 20 years TOTAL, the date on the digital calendar would say "2040," but calendars on EARTH would say hundreds of years into the future. I asked him in an e-mail how that would be possible. I think; space, or Earth, there is still 24 hours in a day, 365 days in a year. He replied to look at 'Einstein's theory of Relativity.' That was difficult for me to understand.

Have you read any where how and why the calendar in space would not be the same calendar as on Earth. I mean, we sent a probe out years ago - one-way, and we are still getting information from it.

Answer
Hi, William, thanks for writing.  According to Einstein's Theory of Relativity (and it has been proved true with atom clocks on jets), the faster one travels, the slower time goes, until, at the speed of light (about 186,272 miles per second), time stands still.  This time chsnge is extremely small until large speeds are attained.  Write anytime!

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Kenneth Renshaw

Expertise

Answer basic space flight questions, research info on specific space flights. Answer questions on astronomy

Experience

Amateur astronomer and avid astronomy/space flight fan for 31 years.

Organizations
Official NASA/JPL Solar System Ambassador for Arkansas and Missouri (one of about 300 nationwide). (http://www2.jpl.nasa.gov/ambassador/profiles/Kenneth_Renshaw.htm)

Publications
Numerous local and area newspapers.

Education/Credentials
AA/BME/MME

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