# Clock runs slower when speeding?

Discussion in 'Physics & Math' started by Saint, May 1, 2020.

1. ### SaintValued Senior Member

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I read that 2 same clocks, one on the Earth another in satellite orbiting the earth,
clock on satellite runs slower than clock on Earth?
My questuon is:
If one person on earth, one person on satellite, both measure the ticking of the clocks,
does 1 second duration appear the same relatively to each of them?
If same, why you say the clock on satellite is slower?

3. ### SeattleValued Senior Member

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General Relativity says that the clock on a satellite would run faster than one on Earth due to Earth's gravity. Special Relativity say says that the clock on a moving satellite would run slower than a stationary clock on Earth.

Both effects have to be worked out for GPS to be accurate.

In your example both people (Earth and satellite) would see their clock as being accurate. It's when you bring them back to the same reference frame that you would notice a different.

That's the example of the twins. One stays in one location on Earth and the other travels near light speed for some period of time and then comes back to Earth. The twin that did the traveling would have aged less than the twin who stayed on Earth.

Most of these examples, including the cat example in another post that I see you referenced seem "odd" because we are trying to think of them in terms of our normal daily lives. It's better to just accept that as the way the world works.

It's odd to think of a cat as being dead or alive but that's not what actually happens. There are no cats at the quantum level.

It's a matter of probably and wave functions.

It's odd to think of twins aging at different rates but that happens if they travel near the speed of light. That's not going to happen either.

Think of it more as taking different paths. With clocks, the two clocks are taking different paths though "spacetime". If you look at it that way it's not so unusual that clocks are different when taking different paths once you accept that time is relative and not fixed.

5. ### Write4UValued Senior Member

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Time emerges relative to the frame of reference?

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8. ### SaintValued Senior Member

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The astronaut in space station, their clock ticks slower than us?
But the astronaut and a person on earth look at their clocks, they still measure 1 second as 1 second, correct?
1 s is still 1 s relative to them.

9. ### HalcRegistered Senior Member

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I'm not sure how one would go about measuring the rate at which a second goes by, but yes, per the principle of relativity (dating back to Galileo), the laws of physics are the same in any frame of reference, which means the astronaut cannot tell the difference.

10. ### billvonValued Senior Member

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The net result is that clocks run slower, yes.
To both astronauts and people on the ground, clocks still keep accurate time from their perspective.

11. ### Write4UValued Senior Member

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I read this once and it kinda stuck. Now it seems appropriate to ask .
https://plato.stanford.edu/entries/spacetime-iframes/

12. ### originIn a democracy you deserve the leaders you elect.Valued Senior Member

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Time does not emerge. Time is a dimension. You intuitively know this, if you setup a meeting for instance, time is one of the 4 coordinates that must defined. Space does not bend in the presence of mass, spacetime bends. If only space bent, then a photon and a jet would follow the same geodesic. Time slows just like length contracts with velocity because both are dimensions.

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13. ### Write4UValued Senior Member

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Don't they? According to Einstein a photon does not recognize a temporal dimension at all (when riding a light beam time stands still ?) What happened to the time coordinates in a four dimensional spacetime?
Are you telling me that 60 miles is 50 miles when I go faster than 60 mph? Or is the duration of travel shorter when I go faster than 60 mph, which would suggest that time is an emergent variable depending on velocity, no ?

Last edited: May 1, 2020
14. ### exchemistValued Senior Member

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But I fear you put yourself at risk of getting sucked into the maelstrom of Write4U's chronic inability to apply terms correctly, or with any consistency. He's got no f***ing idea what "emergence" is or, if he has at one moment, it will be gone the next. Just like with function and potential.

Mind you, he's a perfect interlocutor for Kumar 5 on the "infection" thread.

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15. ### billvonValued Senior Member

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They go together like peas and carrots.

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16. ### Write4UValued Senior Member

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Instead of slinging mud again, why don't you specifically demonstrate where I display "no f***ing idea of what "emergence " is ?

What Are Emergent Properties? Definition And Examples
https://sciencetrends.com/what-are-...and-examples/#examples-of-emergent-properties

Perhaps your understanding of "emergent properties" is incomplete? Just as your understanding of the fundamental principle of "potential" seems limited.

I can demonstrate that time emerges as a result of duration. Can you prove that time exists independent from the three spatial dimensions?
I know what a tetrahedron looks like. But can you prove the existence of 4 minutes of time?

Last edited: May 1, 2020
17. ### originIn a democracy you deserve the leaders you elect.Valued Senior Member

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I have him on ignore. I took the thread off ignore to see something or other and saw his boneheaded comment and responded. I won't see his reply if he does reply, because it isn't worth my time, he detracts from the forum.

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18. ### SaintValued Senior Member

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The guy standing outside the train really measures longer time for the ball to bounce back to the hand of the guy inside the train?

19. ### SaintValued Senior Member

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My question is:
1) The train travel form position A--> B, the elapsed time is Δt, this is the time for the event of Ball-bouncing to occur, both persons in and outside train shall measure the same duration of
Δt, right?
2) To take the geometry of the ball traveled path, and say that the man outside train will measure longer time for the event of Ball-bouncing. This is not right, an illusion.

20. ### HalcRegistered Senior Member

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Wrong, but close most of the time.
Take a train going a nice fast 180 km/hr. If the guy in the train measures 1 second for the ball to bounce back, the guy outside will measure that same bounce to take 1.000000000000014 seconds. Not much different, but different none the less.

Your geometry diagram has nothing to do with this. The ball travels perhaps 50 times further in the latter frame, but it takes nowhere near 50 times as long.
The time difference between the two observers is real, not an illusion at all.

Really, you've shown no competence at even grade school subjects. You have dozens of prerequisites to take before trying to understand relativity.

21. ### Janus58Valued Senior Member

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If you add a light clock to this scenario, light bouncing back and forth between mirrors, the observer in the train measures that light as moving at c relative to the train, and measures the round trip time as 2d/c where d is the vertical separation between the Mirrors. The outside observer also has to measure the light moving at c relative to himself, and since he measures the round trip distance as being longer, he will measure a longer time than 2d/c for the round trip for the light.
Now we consider the bouncing ball. The ball moves slower than the light, and thus the light will make several bounces for every round trip the ball makes. The train observer and outside observer have to agree as to how many round trip the light makes per bounce of the ball. The ball does "bounce" slower according to the outside observer. So using Halc's speed for the train of 180 km/hr, let's also say that as measured from the train the ball is bouncing bask and forth at 180 km/hr.
Under Newtonian physics, the ball would be moving along a diagonal at ~254.5584412 km/sec, and the ball would take the same amount of time to bounce according to both train and outside observer. However, we don't live in a Newtonian universe, but a Relativistic one. In our real universe, the ball as measured by the outside observer would be moving at a tad less than that speed and take longer to complete a bounce as measured from outside* the train than it does as measured from in the train.
You can't use Newtonian physics assumptions to examine events in a Relativistic universe.

*and just to clear up any confusion by "outside" the train I simply mean someone for which the train has a relative motion. Someone physically outside of the train but having the same velocity as the train would measure the same as someone in the train.