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Physicists disagree


Getting back to our satellites—traveling around Earth at 17,000 miles per hour, a satellite’s time slows down, according to Einstein. Also according to Einstein, since gravity is weaker up where the satellites are, time moves a little faster. If that’s the case, wouldn’t a satellite’s GPS signal be inaccurate?

As I researched this question online, I got 2 answers to it: yes and no.

Yes. The satellites’ times slow down, but those amazing scientists who put the satellites up there in the first place cleverly adjusted their signals to compensate for it. Each satellite carries an atomic clock and sends a time & location signal at the speed of light, slightly adjusted (through programmed computer chips) for Einstein’s Special Theory. The clock takes into consideration both the slowing down because of speed and the speeding up because of weak gravity.


No. The satellites’ times slow down, but since they’re all zooming along at 17,000 miles per hour, all their times will be slowed down by the same ratio. So, it doesn’t matter. If all the satellites’ times agree with each other, the GPS system will be accurate. Or, the slowing down is cancelled out by the speeding up caused by weak gravity, so it’s what they call a ‘wash.’ Or, Einstein’s theories are a bunch of baloney so we shouldn’t pay any attention to them.
View at Medium.com

Um. I don’t know what to say here, gang. As you must be aware, I’m just some shmo who is learning as I write this. If you put me on the spot for which is the right answer, I’m going with the bloggers who have better proofreading/grammar skills and citations. If any of my loyal readers want to chime in, please do!

UPDATE: Regarding a satellite’s time difference because of relativity, our indefatigable physics consultant, Ms Physics, says:

Infinitesimal difference, yet a difference. You need to approach the speed of light 3.0 x 10^8 m/s (670,616,629 mph) to have a significant difference. Any way John you remember the precision of the Cesium clock, these differences would really become significant in GPSA calculation using General Relativity predicts that the clocks in each GPS satellite should get ahead of ground-based clocks by 45 microseconds per day.

A microsecond is one-millionth of a second. https://www.simetric.co.uk/si_time.htm

This is why I stick to drawing pictures and let others do the heavy brain-work.

I borrowed parts of this composition for my sketch. I removed the horses and put everybody in lab coats.

Back to the beginning of The Western Civ User’s Guide to Time & Space