what is a practical use for Einstein's theory of relativity?

Question

making nuclear weapons is NOT a practical use.

Brief history of time was a best seller long time ago. Almost everybody read that, including myself. The book did not go to in depth with einstein's work though.

I meant to say, the book a brief history of time, did not go too in depth into the theory of relativity. It was just a simple book of physics for laymen, that's how I saw it. Just wondering how is the theory of relativity used in every day life use, practical terms.

Answer 1

The "flow" or passage of time is slower for an object moving in a frame of reference than for a "stationary" object. This was predicted by Special Relativity and has been experimentally proved many times. One instance is where atomic clocks, accurate to the billionth of a second, were synchronized and then one was put onto [I think it was] the Concorde SST and flown across the Atlantic and back. When compared, the moving clock was behind in time compared to the clock that had not moved. Also, the farther away from the source of a gravity field you are, the slower time moves for you compared to an observer closer to the source. This has also been proved many times by same type of clocks being left to run with one at sea level and the other at top of a mountain or extremely tall structure. When brought back together, their times are off. The resulting discrepancies are exactly what Einstein's equations predict. One example of how this aspect of Relativity has to be taken into account is the GPS. The time of the handheld units will not pass at same rate as the time for the satellites--the moving, high up satellites' internal clocks run slower. Their calculations of how long it took signal to go from unit to satellite and back in order to triangulate your ground position will be different for everything involved and bad results would be returned if relativistic effects were not also calculated.
My statement before saying clocks run slower is not quite the right way to say it. Every atomic clock will always measure the passage of a second as taking a second to happen. It is simply that a second in one frame of reference does not equal a second in another frame of reference. All clocks "run", or thei internal parts move, at the same speed, just what they are running through and measuring--i.e. time--is different. So, their resulting measurments are different when brought back together into the same frame of reference.

Answer 2

When NASA's (and ESA's and Italy's) Cassini probe reached Saturn in 2004 (or was it 2005?), It turned on a radio beacon so that ground crews (on Earth) could listen to it's velocity. They knew how fast it was going as it approached Saturn. They knew how fast it needed to slow down to slip into Saturn orbit. So according to (IIRC) relativity ground crews could monitor the Doppler shift (change in frequency) in Cassini's radio beacon to monitor the change in it's velocity.

At least I think the theory of relativity predicted Doppler shifts... at least in electromagnetic radiation (radio).

Answer 3

Making nuclear weapons is a practical use. It may not be a wise use, from a survival standpoint, but nuclear weapons are certainly practical devices.

A wiser use would be to assist in the design of interstellar spacecraft, which could be nuclear-powered.

Answer 4

Read: a brief history of time by stephen hawkings.

Answer 5

the global positioning system (GPS) accounts for relativity (it would be far less accurate if it didn't). i hope this "counts"!

Answer 6

yes do what the top guy did