> "When it comes to the flow of time on those satellites, there are two important aspects related to Einstein’s theories of relativity. Special relativity states that a fast moving object experiences time dilation – its clocks slow down relative to a stationary observer. The lower the altitude the faster the satellite’s velocity and the bigger the time slowdown due to this effect. On the flip side, general relativity states that clocks run faster in lower gravitational field, so the higher the altitude, the bigger the speedup is."
> "Those effects are not even and depending on altitude one or the other dominates. In the demonstration below you can witness how the altitude of a satellite affects the dilation of time relative to Earth..."
There's also a nice if complex explanation of why your GPS receiever needs four satellite emitters to calculate the time bias of its clock.
> Special relativity states that a fast moving object experiences time dilation – its clocks slow down relative to a stationary observer.
For more fun: A less known fact is that SR also states that from the POV of the satellite, the satellite is a stationary observer and the guy on earth is fast moving, therefore that observer's clock slows down relative to the satellite.
Yes, that's right: Each of them sees the other one's clock as slower.
IIRC It takes the fact that the satellite moves in an orbit, not in a straight line, to resolve which one is actually "slower" because up until then, the word "slower" isn't really meaningful at all.
https://ciechanow.ski/gps/#time
> "When it comes to the flow of time on those satellites, there are two important aspects related to Einstein’s theories of relativity. Special relativity states that a fast moving object experiences time dilation – its clocks slow down relative to a stationary observer. The lower the altitude the faster the satellite’s velocity and the bigger the time slowdown due to this effect. On the flip side, general relativity states that clocks run faster in lower gravitational field, so the higher the altitude, the bigger the speedup is."
> "Those effects are not even and depending on altitude one or the other dominates. In the demonstration below you can witness how the altitude of a satellite affects the dilation of time relative to Earth..."
There's also a nice if complex explanation of why your GPS receiever needs four satellite emitters to calculate the time bias of its clock.