Viewing a single comment thread. View all comments

klausesbois t1_j26vo1u wrote

Reply to comment by Aseyhe in How fast does the Milky Way spin? How far does Earth move through space in a year? by Sabre-Tooth-Monkey

Since time slows down as you move faster, we are aging slower than a person would if they were at “rest frame” right? Could a person exist at “rest frame”? If they did how much faster would a year be for them than for us?

4

Aseyhe t1_j2859vs wrote

The CMB rest frame is the frame in which we calculate the age of the universe, so it's definitely an interesting idea to think about how our elapsed time might differ. However, for 370 km/s motion, the effect of relativistic time dilation is about one part in a million, and the gravitational time dilation (due to the Milky Way's gravitational potential) is of similar order.

3

nicuramar t1_j284xxf wrote

> Since time slows down as you move faster, we are aging slower than a person would if they were at “rest frame” right?

Not really. You could as well say that we are at rest and they are moving faster. There is nothing special about the CMB frame in that respect. But we can compare the time dilation between us, and I’m sure someone did the math. I have a feeling it will be small.

1

australianjalien t1_j28lyt5 wrote

Got to admit I've never had a good concept of ageing with respect to speed. I can imagine a change in ageing when there is a speed differential, but once any two objects become adjacent again, say two atomic clocks, everything about relativity suggests they should show the same time again. If that weren't true then somehow relativity would be asymmetric, not conserved and/or there would necessarily be an absolute reference against which time dilation occurs, like what you are suggesting.

1