Time dilation

Gravitational time dilation is a physics concept about changes in the passage of time, caused by general relativity. A clock in outer space moves quicker than a clock on Earth. Heavy things like planets create a gravitational field that slows down time nearby. An example of gravity causing time dilation is that if an object is near a black hole its time will slow relative to that of time on earth. This means that a clock on a spaceship far away from any planet would move faster than a clock near Earth.

This is different from time dilation explained by special relativity, which says fast objects move more slowly through time. Close satellites like the International Space Station move very quickly to orbit the Earth, so they are slowed down. Because the ISS is in low Earth orbit (LEO), time dilation due to gravity is not as strong as time dilation due to its speed, so a clock on it is slowed down more than it is sped up. An object in Geostationary orbit moves less quickly and is farther away from Earth, so gravitational time dilation is stronger, and clocks move quicker than in LEO. This means that engineers need to pick different clocks for different orbits. GPS satellites work because they know about both kinds of time dilation.^[1]

Case #1: In special relativity, clocks that are moving run slower, according to a stationary observer's clock. This effect does not come from workings of the clocks, but from the nature of spacetime.

Case #2: the observers may be in positions with different gravitational masses. In general relativity, clocks that are near a strong gravitational field run slower than clocks in a weaker gravitational field.

If you were to have a rotor, or motor, moving at a very fast speed (any measurement of speed will cause time dilation just in varying amounts) and have a beam of sorts with a capsule, the faster it spins the more time changes.

This could theoretically make a time machine although it could only go forward and would be very dangerous.

1. ↑ Ashby, Neil (2003). "Relativity in the Global Positioning System" (PDF). Living Reviews in Relativity. 6 (1): 16. Bibcode:2003LRR.....6....1A. doi:10.12942/lrr-2003-1. PMC 5253894. PMID 28163638. Archived from the original (PDF) on 2015-11-05. Retrieved 2019-07-08.{{cite journal}}: CS1 maint: unflagged free DOI (link)