Luigi Fortunati

2023-07-15 06:27:02 UTC

The Earth takes 24 hours of the Earth's twin time for one complete

rotation on its axis.

How much time does the traveling twin (v=0.866c, gamma=2) take for the

same rotation?

Does it take 12 hours (24/2) or 48 hours (24*2)?

[[Mod. note -- A couple of comments:

1. I presume that in the 2nd sentence, the author actually meant to ask

how much time the travelling time *measures* for the same rotation.

2. The Earth's rotation period with respect to an inertial reference frame

is actually about 23 hours and 56 minutes. Because the Earth is also

orbiting about the Sun in the same direction as its rotation

(counterclockwise when looking down from above the North pole), the

mean time from noon to noon is slightly longer, namely 24 hours.

The first image in

https://en.wikipedia.org/wiki/Sidereal_time

shows this nicely; in this context "the fixed stars" means an inertial

reference frame.

-- jt]]

rotation on its axis.

How much time does the traveling twin (v=0.866c, gamma=2) take for the

same rotation?

Does it take 12 hours (24/2) or 48 hours (24*2)?

[[Mod. note -- A couple of comments:

1. I presume that in the 2nd sentence, the author actually meant to ask

how much time the travelling time *measures* for the same rotation.

2. The Earth's rotation period with respect to an inertial reference frame

is actually about 23 hours and 56 minutes. Because the Earth is also

orbiting about the Sun in the same direction as its rotation

(counterclockwise when looking down from above the North pole), the

mean time from noon to noon is slightly longer, namely 24 hours.

The first image in

https://en.wikipedia.org/wiki/Sidereal_time

shows this nicely; in this context "the fixed stars" means an inertial

reference frame.

-- jt]]