Viewing a single comment thread. View all comments

Quaytsar t1_iy3o2df wrote

Reply to comment by Rcomian in ELI5: What does it mean by time slowing down at event horizon? by [deleted]

> this effect is actually seen in our gps satellites. time goes slightly different for them

There's a specific orbital height where the slow down in time from traveling at orbital velocity and the speed up in time from leaving the local gravity well exactly cancel each other out so you experience time at the same rate as someone standing on the surface.

It's just above 3000 km for Earth. So GPS goes slower faster due to their speed height.

4

Bensemus t1_iy4liea wrote

They don't. GPS's go faster due to being farther from Earth.

> The combination of these two relativitic effects means that the clocks on-board each satellite should tick faster than identical clocks on the ground by about 38 microseconds per day (45-7=38)!

https://www.astronomy.ohio-state.edu/pogge.1/Ast162/Unit5/gps.html#:~:text=As%20such%2C%20when%20viewed%20from,by%2045%20microseconds%20per%20day.

2