City-Data Forum Is one second on earth same As elsewhere in the universe?
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01-22-2020, 03:57 AM
 Location: Redwood Shores, CA 428 posts, read 142,636 times Reputation: 343

I know day and year is different, but how about second?

Compare to, say,

>on the sun
>on Haleys commet when it is swinging fastest
>on a fastest traveling object in space

01-22-2020, 10:34 AM
 Location: Old Hippie Heaven 20,198 posts, read 9,050,237 times Reputation: 12109
Quote:
 Originally Posted by RobertFisher I know day and year is different, but how about second? Compare to, say, >on the sun >on Haleys commet when it is swinging fastest >on a fastest traveling object in space
There is a scientific definition of "second", which ties its duration to the radioactivity of cesium - https://en.wikipedia.org/wiki/Second

Using that definition, a second should be the same everywhere in the universe.

01-22-2020, 10:39 AM
 Location: Kentucky 669 posts, read 373,191 times Reputation: 2711
Time does slow done as speed of an object increases. It was a problem for early gps systems but math had a solution!

Rg

01-22-2020, 04:04 PM
 23,306 posts, read 17,534,899 times Reputation: 9912
Quote:
 Originally Posted by RobertFisher I know day and year is different, but how about second? Compare to, say, >on the sun >on Haleys commet when it is swinging fastest >on a fastest traveling object in space
Time is relative and is affected both by speed and gravity. The stronger the gravitational field, the more slowly time passes, and the faster an object moves, the more slowly time passes for that object relative to an outside observer who is stationary. But if a person was on that object ---a space ship, the passage of time for him would seem to be passing at the normal rate even though relative to the outside observer the traveler would be in a different time frame.

01-22-2020, 06:51 PM
 Location: Redwood Shores, CA 428 posts, read 142,636 times Reputation: 343
Quote:
 Originally Posted by Mike555 Time is relative and is affected both by speed and gravity. The stronger the gravitational field, the more slowly time passes, and the faster an object moves, the more slowly time passes for that object relative to an outside observer who is stationary. But if a person was on that object ---a space ship, the passage of time for him would seem to be passing at the normal rate even though relative to the outside observer the traveler would be in a different time frame.
if A is on a spaceship traveling at very high speed away from earth. B is on earth. relative speed for both of them is identical. whose time will slow down?

01-22-2020, 11:44 PM
 3,147 posts, read 1,199,706 times Reputation: 2198
Quote:
 Originally Posted by RobertFisher if A is on a spaceship traveling at very high speed away from earth. B is on earth. relative speed for both of them is identical. whose time will slow down?
The person on the ship will experience time slowing down as they approach the speed of light.

Yesterday, 12:21 AM
 23,306 posts, read 17,534,899 times Reputation: 9912
Quote:
 Originally Posted by RobertFisher if A is on a spaceship traveling at very high speed away from earth. B is on earth. relative speed for both of them is identical. whose time will slow down?
That's easy. Let's say that A and B start out on earth, and they are the same age. Then A gets into his spaceship and accelerates to a high speed. Depending on how fast he is going, and on how long he is gone, when he returns to earth, he will learn that B has aged and is now x amount older than he is. Time for A will have passed more slowly than time has passed for B.

This is going on right now. Time for the people aboard the International space station is passing more slowly than it is passing for us on earth.
With current technology severely limiting the velocity of space travel, however, the differences experienced in practice are minuscule: after 6 months on the International Space Station (ISS) (which orbits Earth at a speed of about 7,700 m/s[2]) an astronaut would have aged about 0.007 seconds less than those on Earth. The cosmonauts Sergei Krikalev and Sergei Avdeyev both experienced time dilation of about 20 milliseconds compared to time that passed on Earth.

https://en.wikipedia.org/wiki/Time_dilation
Time passes more slowly for a person who is walking than for a person who is standing still.

There's another aspect also. Since time passes more slowly in a stronger gravitational field than in a weaker gravitational field, time passes more quickly for a person living at a higher elevation than for a person living at a lower elevation. When you are standing up, time is passing more quickly for your head than it is for your feet. The difference is very slight, but it's real.

Last edited by Mike555; Yesterday at 12:35 AM..

Yesterday, 01:18 PM
 Location: The Driftless Area, WI 3,305 posts, read 1,285,783 times Reputation: 7290
Quote:
 Originally Posted by RobertFisher I know day and year is different, but how about second?

Good question!...and do they have the Fourth of July in China?

Check out "Simultaneity" vis-Ã -vis Special Theory of Relativity.

Yesterday, 02:07 PM
 Location: Redwood Shores, CA 428 posts, read 142,636 times Reputation: 343
If A is on a spaceship moving away from B on earth, the relative speed of A in reference to B, is same as speed of B in reference to A. In another world it can be viewed as B is moving away from A. In this view, could it be that B's time is slowing down as opposed to A?

Yesterday, 03:19 PM
 23,306 posts, read 17,534,899 times Reputation: 9912
Quote:
 Originally Posted by RobertFisher If A is on a spaceship moving away from B on earth, the relative speed of A in reference to B, is same as speed of B in reference to A. In another world it can be viewed as B is moving away from A. In this view, could it be that B's time is slowing down as opposed to A?
The issue is one of actual effect vs observational effect. As I said in post #7, if A gets on his spaceship and speeds away from earth and from observer B who is on the earth, and then returns to the earth, A will be younger than B.

This is because, even though it would appear to observer A on the spaceship moving directly away from the earth that time was moving slower for B who is on earth, but for B on earth, time would appear to be moving more slowly for A on the space craft, in reality, since it was A who was actually doing the accelerating he is the one for whom time dilated. He is the one for whom, in reality, time slowed relative to B on earth.

The video below explains it. At 6:16 into the video, the twin paradox is explained. That is what you will be interested in with regard to your question.

Special Relativity Part 2: Time Dilation and the Twin Paradox

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