B Does Time Dilation Occur in a Perfectly Circular Orbit at Near-Light Speed?

  • Thread starter Thread starter Steeve Leaf
  • Start date Start date
  • Tags Tags
    Speed Time
Click For Summary
In a perfectly circular orbit at near-light speed, time dilation occurs, affecting the perceived time between clocks on Earth and a spaceship. The spaceship, moving at 0.5c and 300,000 km away, broadcasts images of its clock, which will appear to lag behind Earth's clock due to both light propagation delay and time dilation effects. The time difference observed will not remain constant; it will increase over time as the speed and distance affect the measurements. Acceleration due to the ship's circular path does not contribute to the time difference as measured from Earth, but it does influence how the ship perceives Earth's clock. Experimental evidence, such as GPS satellite data and high-speed centrifuge studies, supports these conclusions regarding time dilation and gravitational effects.
  • #61
Ahaha , That is the big question. you got it , that is my problem Doctor !

The man on M will he see the tv clock moving at faster rate than his own because of time dilation on M , but because the signal doesn't delay at M at all this dilation don't appear on ISS TV.
Any delay on M will affect the tv on iss with dilation.
Am I correct ?
 
Last edited:
Physics news on Phys.org
  • #62
Steeve Leaf said:
Thanks,
ISS got a clock on it , it send a tv signal of this clock to M which broadcast it with no delay back to ISS monitor.
Now at ISS we can see the actual watch and the tv image after the round journey.
Why the difference between the actual clock and the monitor clock will change and not stay the same if
1. the distance stays the same.
2. The change in frequency don't change the time the signal travel.
3.This is ISS own clock.
4. No looking through telescope.
The difference is the time it takes to cover the unchanged distance.
Where the complication occur ?.☺

There won't be a difference between The ISS local clock and the TV image on the ISS monitor.
To illustrate why this is, we will consider a 10 second message again. The ISS send a message that is 10 seconds long. Remember from my last discussion, Marcella will receive this message over a period of 8.66 sec. If it immediately rebroadcasts this message just as it received it, it will transmit a 8.66 sec long message. You will also remember that the ISS would receive a signal from Marcela over a time period 1.155 times longer that of the length of the message sent by Marcela. Thus is Marcela sends a 8.66 sec message at its end, the ISS receives a 10 second message at its end.
The ISS sends out a 10 sec message and gets a 10 sec message echoed back.
 
  • #63
Steeve Leaf said:
Any delay on M will affect the tv on iss with dilation
A fixed delay on M will result in a corresponding, but longer fixed delay on ISS. If, for instance, the incoming signal were fed through a 10 second delay loop on M before being rebroadcast, the result would be an 11.55 second delay added to the round trip time measured at the ISS.

That's not dilation. That's an offset.
 
  • #64
Steeve Leaf said:
Yes, ISS speed is 27,576 - 28080 km/h.
I admit that I don't completely understand this, but let's leave it for now.
( I can't tell how fast M is moving if it is broadcasting tv signal of the clock and you don't know the original broadcast frequency ).

Acceleration and gravity affect on visualized clocks, that need now your appreciated explanation.

We can consider acceleration in the following way:

Consider a rocket ship, with a clock at the nose and one at the tail. It is undergoing a constant acceleration. Imagine signals traveling between the two clocks, each keeping the other appraised of the others tick rate.

The signal leaves the nose clock at some moment t0 and arrives at the nose clock at t1.
Since the rocket is accelerating, The velocity of both clocks changes between t0 and t2
This is important, because, in the Relativistic Doppler shift formula I gave in an earlier post, v stands for the difference in velocity of the transmitter at the moment of transmission and the velocity of the receiver at the moment of reception.

Since the tail clock has been accelerating for a duration of t1-t0, it will have a different velocity at reception than the nose clock had at transmission. This results in a positive non-zero value of v, and the tail clock will see a higher frequency coming from the Nose clock than that emitted by the nose clock. If the Nose clock sent a 100 hz signal, at 100 waves per one sec tick of the clock, the tail clock receives those 100 waves at a higher frequency in less than one second, and thus measures the nose clock at ticking fast.

Conversely, a signal sent from the tail clock to the nose clock also takes some non-zero time to cross between them, meaning that the nose clock will have a different velocity when it receives the signal than the tail clock and this results in a negative non-zero value for v (in the first example, the tail clock's direction of acceleration is towards the nose clock, But now we are considering the nose clock, and its direction of acceleration is away from the tail clock. The result is that the tail clock sees a lower frequency coming from the tail clock and measures it as ticking slower.

Again, like in the ISS-Marcela scenario, the actual distance between the two clocks does not change, and they can not attribute any of the frequency shift they measure as being due to changing propagation time, and can only be attributed to the two clocks actually keeping different time.

Also note that if we increase the distance between the tail and nose, while maintaining the same acceleration, we increase the length of time between t0 and t1. Thus the receiving clock have a longer time to accelerate between transmission and reception, and this results in a larger difference in velocities. Ergo, increasing the distance between the clocks increases the difference in tick rates even if the acceleration is the same.

Of course, it should go without saying that increasing the acceleration and maintaining the same distance will also cause a larger difference in tick rate.

Now consider the viewpoint of someone in the rocket. If you let's go of an object at the nose of the rocket, to them it will "fall" towards the tail. the speed at which it arrives at the tail relative to the rocket will be the same as if it were accelerated by a constant force for the distance it fell, much like it would in a gravity field.
It will also have gained kinetic energy relative to the rocket.

You can also treat the light traveling from nose to tail the same way, It can't gain speed relative to the rocket as measured by the rocket, but it will gain momentum/energy, and that will be measured as an increase in frequency. Conversely, light moving from tail to nose loses energy with respect to the the rocket and decreases frequency. The combination of the distance of the fall and the acceleration during the fall determines the frequency change.

The same happens with light in a gravity field, light traveling upwards against gravity loses energy/frequency as it does so, and light moving downwards gains energy/frequency. Again this occurs even if the distance between transmitter and receiver is constant and none of the frequency shift can be the result of changing distance. Thus a clock higher in a gravity field runs faster than than one lower. Note that really doesn't have anything to do with gravity being weaker at the higher clock. In fact, the drop off in gravity actually decreases the difference in time rates vs no difference in gravity.
 
  • #65
jbriggs444 said:
A fixed delay on M will result in a corresponding, but longer fixed delay on ISS. If, for instance, the incoming signal were fed through a 10 second delay loop on M before being rebroadcast, the result would be an 11.55 second delay added to the round trip time measured at the ISS.

That's not dilation. That's an offset.
10 sec delay cause 1.55 sec time dilation. that is 11.55 offset ?

Janus said:
There won't be a difference between The ISS local clock and the TV image on the ISS monitor.
To illustrate why this is, we will consider a 10 second message again. The ISS send a message that is 10 seconds long. Remember from my last discussion, Marcella will receive this message over a period of 8.66 sec. If it immediately rebroadcasts this message just as it received it, it will transmit a 8.66 sec long message. You will also remember that the ISS would receive a signal from Marcela over a time period 1.155 times longer that of the length of the message sent by Marcela. Thus is Marcela sends a 8.66 sec message at its end, the ISS receives a 10 second message at its end.
The ISS sends out a 10 sec message and gets a 10 sec message echoed back.

The first wave in the 10 sec broadcast will take the same time as the last wave to reach M.
Because M is moving toward ISS it receives the transmission in higher frequency and in less time but the clock on M ticks slower in a manner that even for it the time it took the first wave to reach it is equal to the time it takes the last wave to reach it ?
Janus said:
The same happens with light in a gravity field, light traveling upwards against gravity loses energy/frequency as it does so, and light moving downwards gains energy/frequency. Again this occurs even if the distance between transmitter and receiver is constant and none of the frequency shift can be the result of changing distance. Thus a clock higher in a gravity field runs faster than than one lower. Note that really doesn't have anything to do with gravity being weaker at the higher clock. In fact, the drop off in gravity actually decreases the difference in time rates vs no difference in gravity.
Gravity is measured in the same units as acceleration,but with gravity the distance and the speed are not changing it is a "potential acceleration" only still the same affect on the clocks, Can you detect the effect of small change in gravity such as on ISS on signal broadcast frequency from Earth surface ?
How gravity has the same affect as acceleration when the distance and speed stay constant , is it the force behind the two which make the affect ?
 
Last edited:
  • #66
Steeve Leaf said:
Gravity is measured in the same units as acceleration,but with gravity the distance is not changing it is a "potential acceleration" only still the same affect on the clocks, Can you detect the effect of small change in gravity such as on ISS on signal broadcast frequency from Earth surface ?
Neither is the distance changing with the accelerating rocket. The tail and nose clock maintain a constant distance, yet still measure each other as ticking at different rates from each other.

With the ISS, You have two factors effecting its time dilation: Its orbital altitude and its orbital velocity.

A far distant observer would see its clock time dilated by a factor of
\sqrt{1- \frac{3GM}{rc^2}}
Where M is the mass of the Earth and r is the radius of the ISS orbit.

The same observer would see a clock time dilated by a factor of
\sqrt{1- \frac{2GM}{r_ec^2}- v^2/c}
where re is the equatorial radius of the Earth and v is the tangential velocity of the Earth's surface at the Equator measured relative to the Earth centered inertial frame.
I'll leave it to you to work what difference this would result in between Earth surface and ISS.
 
  • #67
It is very small, still we can measure it.
Edit : ",but with gravity the distance and the speed are not changing "
Can we say that when light is blueshift at A the clock at A will run slower and when light redshift at B the clock at B will run faster than at the source?
What if M lost its visual connection with ISS would it be possible to stay synchronized only from Instrumental data monitoring the changes in frequency and time and delay and they have the same software ?
 
Last edited:
  • #68
I can't figure it out, if the clock on M running 86.6 % the rate of the one on ISS than wouldn't it measure the time a light beam travels from ISS to it 115% faster ?
The two observers they can't agree on time , distance etc, what they can agree on ?
 
Last edited:
  • #69
Steeve Leaf said:
I can't figure it out, if the clock on M running 86.6 % the rate of the one on ISS than wouldn't it measure the time a light beam travels from ISS to it 115% faster ?
The two observers they can't agree on time , distance etc, what they can agree on ?
Observers agree on:

(Square) Spacetime interval between events.
Speed of light.
 
  • #70
Can you give an example of faster than light signaling that will create reference frame in which the signal arrived before it was sent ?
 
  • #71
Steeve Leaf said:
Can you give an example of faster than light signaling that will create reference frame in which the signal arrived before it was sent ?
You are headin away from me at any speed. I send a signal that reaches you instantaneously in my frame. You reply with a signal that reaches me instantaneously in your frame, which arrives before I sent my signal.

You can do it with non-instantaneous communication too, but the circumstances where things go acausal are a bit more restrictive and I'd need to do some maths.

You could Google for "tachyonic anti-telephone".
 
  • #72
Ibix said:
You are headin away from me at any speed. I send a signal that reaches you instantaneously in my frame. You reply with a signal that reaches me instantaneously in your frame, which arrives before I sent my signal.

You can do it with non-instantaneous communication too, but the circumstances where things go acausal are a bit more restrictive and I'd need to do some maths.

You could Google for "tachyonic anti-telephone".
What is heading away from me at any speed, got to do with it, is it just appear to be because you know (assume in this case) that FTL is not possible ?.
 
  • Like
Likes nitsuj
  • #73
Steeve Leaf said:
Can you give an example of faster than light signaling that will create reference frame in which the signal arrived before it was sent ?

In a single reference frame, FTL signals do not do anything strange. They simply get from one place to the other faster than light.

To derive a problem with FTL signals, you need to consider the relationship between two reference frames moving with respect to each other. And, you need to assume as a postulate of relativity (or an experimentally proven fact) that the speed of a light signal is the same for both frames. It's when you put this together with a FTL signal between the two that you get a problem.
 
  • #74
Steeve Leaf said:
What is heading away from me at any speed, got to do with it, is it just appear to be because you know (assume in this case) that FTL is not possible ?.
As Ibix said... Google for "tachyonic anti-telephone".
 
  • #75
Steeve Leaf said:
What is heading away from me at any speed, got to do with it
Because that's the condition for the simultaneity conventions of your frame and mine to clash in a way that is paradoxical if faster than light communication is possible within relativity.
 
  • #76
What Einstein had to say about this ?
I don't see any observer that will say that the reply was received before the message was send.
Math must be interesting .
 
  • #77
Steeve Leaf said:
What Einstein had to say about this ?
I don't see any observer that will say that the reply was received before the message was send.
Math must be interesting .

You should read post #73. You need two frames of reference and a Lorentz Transformation between them. Otherwise, there isn't going to be a problem in anyone frame.
 
  • #78
2807 Ok.
It was mention as " any speed " , in order for Lorentz Transformation to play a role they have to move apart close to the speed of light, then time dilation might cause the reply to be received before... but I THINK it will work only with instantaneous info transfer .

Am I 'm even getting closer ?:)
 
Last edited:
  • #79
Steeve Leaf said:
2807 Ok.
In was mention as any speed , in order for Lorentz Transformation to play a role they have to move apart close to the speed of light,than time dilation will cause the reply to be received before... but I THINK it will work only with instantaneous info transfer .

Am I 'm even close ?:)

FTL causing a problem is not that easy to demonstrate since you first need to really understand how events (time and place) in one frame relate to another frame. It's a thing called the relativity of simultaneity (not time dilation) that is really the issue.

If you have an absolute notion of time (as in classical physics), then FTL is not a problem at all. But, time is not absolute, simultaneity is relative and when you have a FTL signal, that causes a problem.

Using an instantaneous signal is easier than using a signal at, say, twice the speed of light; but both can lead to a problem.

Did you find anything on line?
 
  • #80
To use the tachyonic antitelephone, the user must aim it at the position in space occupied by the Earth in 1930. The user then must dial the telephone number a2807a and the device will transmit a beam of modulated tachyons back into time. When the beam arrives in 1930 the telephone will ring at the University of Berlin and none other than Albert Einstein will answer to help the caller with his or her physics questions.
http://www.physics.buffalo.edu/ubexpo/posters/tachyonic.pdf
You see that you got the answer before the question.
You absolutely right the relativity of simultaneity was recommended by the Prof but I thought I can skip it, I guess I was wrong ( again ).
 
Last edited:
  • #81
PeroK said:
To derive a problem with FTL signals, you need to consider the relationship between two reference frames moving with respect to each other. And, you need to assume as a postulate of relativity (or an experimentally proven fact) that the speed of a light signal is the same for both frames. It's when you put this together with a FTL signal between the two that you get a problem.

Maybe oxymoron is a better term? One hand says you can do instantaneous physics and the other says you're limited to c.
 
  • #82
nitsuj said:
Maybe oxymoron is a better term? One hand says you can do instantaneous physics and the other says you're limited to c.
It's more a proof by contradiction, because the argument that causal effects cannot propagate faster than ##c## is that if you assume it is possible, contradictions appear.
 
  • #83
Steeve Leaf said:
http://www.physics.buffalo.edu/ubexpo/posters/tachyonic.pdf
You see that you got the answer before the question.
You would be better served by the wikipedia article: https://en.wikipedia.org/wiki/Tachyonic_antitelephone
You absolutely right the relativity of simultaneity was recommended by the Prof but I thought I can skip it, I guess I was wrong
There is indeed no way of making it through special relativity unless you have thoroughly understood the relativity of simultaneity.
 
  • Like
Likes Dale, Ibix and PeroK
  • #84
Steeve Leaf said:
It was mention as " any speed " , in order for Lorentz Transformation to play a role they have to move apart close to the speed of light
No. The only thing moving faster does is let you detect the effects more easily. For the case where you pass me at time zero and I send you a tachyon pulse at time Tlater, the "reply" arrives ##v^2T/c^2## seconds before the original signal. Either T needs to be really huge or v needs to be very close to c for this kind of gap to be detectable. But it's there for any speed.

Faster than light communication is impossible in relativity, but it is a general truth that relativistic effects are present at all speeds, just undetectably small for every day speeds.
 
  • #85
nitsuj said:
Maybe oxymoron is a better term? One hand says you can do instantaneous physics and the other says you're limited to c.
An oxymoron is a linguistic device, where you combine two words that ought not to go together. Perhaps "thought experiment" is a relevant example.
 
  • Like
Likes Dale
  • #86
PeroK said:
An oxymoron is a linguistic device, where you combine two words that ought not to go together. Perhaps "thought experiment" is a relevant example.

? in other words speed is limited and unlimited...an oxymoron.
 
  • #87
nitsuj said:
? in other words speed is limited and unlimited...an oxymoron.
A claim that speed is both limited and unlimited would be a contradiction, not an oxymoron. But no such claim has been advanced in this thread.
 
  • #88
Steeve Leaf said:
You absolutely right the relativity of simultaneity was recommended by the Prof but I thought I can skip it, I guess I was wrong ( again ).
The relativity of simultaneity is the single most difficult concept in relativity. Students struggle more with that than anything else.
 
  • #89
nitsuj said:
Maybe oxymoron is a better term? One hand says you can do instantaneous physics and the other says you're limited to c.
http://www.theculture.org/rich/sharpblue/archives/000089.html
If we need others point of view I recommend the above link.
I'm ready for the first lesson about relativity. ( I Think ).
 
Last edited:

Similar threads

B Time Dilation Effect: Corrections to Clocks on ISS
  • · Replies 5 ·
Replies
5
Views
3K
A 1-Way Speed of Light
  • · Replies 42 ·
2
Replies
42
Views
1K
I A matter of time dilation: how much time has actually passed?
  • · Replies 26 ·
Replies
26
Views
2K
I Effects of time dilation for near-speed-of-light travel
  • · Replies 65 ·
3
Replies
65
Views
11K
B Gravity and speed of information for orbiting planets
  • · Replies 22 ·
Replies
22
Views
801
B Let me ask a thing about the Speed of Light
  • · Replies 6 ·
Replies
6
Views
2K
B Theories about light and time near a black hole
  • · Replies 20 ·
Replies
20
Views
2K
B Time Dilation: Orbit Earth at Light Speed, What Happens?
  • · Replies 8 ·
Replies
8
Views
2K
B Time dilation in a planet-moon system
  • · Replies 58 ·
2
Replies
58
Views
6K
I Time dilation for the Earth's orbit around the Sun
  • · Replies 58 ·
2
Replies
58
Views
7K