According to relativity, is time dilated only during periods of acceleration?

In other words, if two rockets, A and B, were to undergo the same acceleration during two separate journeys, but Rocket B “drifted” for much longer than Rocket A, would the time dilation be the same for both of them? I.e. According to an observer on Earth, would the time difference between the rockets be equal to the drift time of rocket B?

If for instance, rocket A came to a stop after having traveled 1 lght yr, and rocket B came to a stop after having traveled 10 lght yrs, At the rocket B will have aged less than rocket A at the tme that rocket B stops. As far as the Earth is concerned, it is only the Rockets relative velocity to Earth during the period that effects time dilation.

I think you'll need to be more specific about your example, dav57.

OK, Two rockets A and B launch from the earth and accelerate to a point C at the same rate.

They both stop accelerating at point C.

Rocket A then instantly stops (well almost instantly), turns around and accelerates back to Earth where it stops. It has experienced an acceleration over a given amount of time relative to itself.

However, Rocket B continues drifting after reaching point C and continues to drift for 1 year until it reached point D. It then instantly stops (well almost instantly), turns around and accelerates back to Earth for the same amount of time that Rocket A accelerated for. It then drifts back to Earth where it stops.

Question:

Are the clocks on Rocket A and B different by exactly 1 year?

Thanks

Hmm... tricky. I'm not sure. You'd need to integrate to find the proper time experienced by each rocket.

If for instance, rocket A came to a stop after having traveled 1 lght yr, and rocket B came to a stop after having traveled 10 lght yrs, At the rocket B will have aged less than rocket A at the tme that rocket B stops. As far as the Earth is concerned, it is only the Rockets relative velocity to Earth during the period that effects time dilation.

But wouldn't the instantaneous time of the A clock and earth clock be different due to the time the A clock was in a dilated mode when Va > 0? Or are you talking about clock rates?

I am assuming it is possible to have a special clock in the accelerated ships that can maintain an earth-frame correction for dilation during the acceleration and elevated velocity period? If this can be done then all communication between ship-frames can be tagged with the local-frame-time of emission and if the receiving frame sends an immediate time-tagged reply cannot all clock dilation differences ultimately be resolved into a universal and agreed now-time?

OK, let me put this one a different way.....

Rocket A and B synchronise their clocks with an Earth clock and launch with exactly the same amount of fuel.

When Rocket A has used 1/2 its fuel it turns around and returns. By the time it returns to earth it has experienced time dilation and compares clocks with Earth to prove this.

Rocket B, however, switches off its engines after using 1/2 the fuel and drifts for 1 year (relative to itself). It then turns around and accelerates back to earth. It soon uses all its fuel and drifts the rest of the way back to Earth where it compares its clock with rocket B.

Question: The rockets have experienced the same amount of acceleration and I'm trying to determine if this is the only period where time is dilated????? If so, then Rocket A and B's clocks will be different by exactly 1 year.

If this is tricky for James R then am I not going to get a correct answer here?

If acceleration happens to be the only period in which time dilates then I have something profound to say! If not, I'll just shut up here and now!

If acceleration happens to be the only period in which time dilates then I have something profound to say! If not, I'll just shut up here and now!

Starting with earth clocks both space stations do not evelop a relative motion into deep space without accelerating with respect to the earth frame, which may be considered 0. Why? Ve has some motion as we all know including turning (as little felt are these motions are) have, before accelrating into space, all shared the Ve motions, all of them. So when we write the expression for the relative motions of the Ve and Vn frames we include the cms or 'common motions' whch, when Ve = Vn each share the identical cms.
Now expressing the relative motion of Vn and Ve we see after, before, or during acceleration,

Ve + cms -(Ve +cms) = Vn - Ve > 0.

1st law: No observed relative motion of Vn and Ve without accelerations of Vn, only. In other words no corresponding acceleration of Ve wrt Vn as measured by accelerometers on each frame during acceleration of Vn are observed. Rocket induced vibrations are not corresponding Vn motions.

Some will tell you that acceleration is nothing, or can be neglected and that the extended constant velocity is what really matters. To indicate how this is used some will say: with an acceleration as "fast as possible", then dilation time due to the instaneous dilations during accelration can be set to zero, if the accelration is rapid [violent] enough.

Consider yourself on an acceleration sled that can accelerate your body from as low as 1g/s up to 10 kg/s (we are talking muzzle velocity using ultra high explosive accelerating medium) , or higher. In the first instance no problemo, in the second scraping your flattened body off the rear of he accelerator would be no problemo either, with use of a water high pressure water hose (hpwh).

I can see matter taking drastically varying forms of vibrations when violently accelerated. In your case there is some level of accleration that you would not want to even get close to before someone would open the door to the hpwh cabinet.

I say, everything is acceleration and that any Vn velocity observation is merely an accounting of the current, or last, acceleration of the systems under scrutiny.

Caveat Emptor: What buying into SR can get you: They apply the massive (or any) accelerations inferentially, ignore the inferred physical affect of these accelerations, then focus your attention only on their make believe world where velocity only is of scientific value, only velocity[and accelerations are nothing]. In other words the real physical affects on Vn matter are not open to scrutiny, an analog form of modern day quantum mechanical theory.

Thanks geistkiesel but I'm still confused. Is the time difference between the Rockets 1 year exactly, or not?

Thanks geistkiesel but I'm still confused. Is the time difference between the Rockets 1 year exactly, or not?
I am saying there is no time dilation, period, and that so-called mass increases measured by the instantaneous velocity is really a form of a measure of the unmodulated (crude) acceleration history, which is totally ignored by SR theory.

I am saying there is no time dilation, period, and that so-called mass increases measured by the instantaneous velocity is really a form of a measure of the unmodulated (crude) acceleration history, which is totally ignored by SR theory.

Time dilation has been measured and proved to be accurate to many millionths of a part of a second.

If you send a clock into space it comes back with a time reading slower than that of its earthly counterpart. That's a fact.

Based on this, I just want to know if the apparent time dilation occurs during periods of acceleration only, and this could be proved via my double rocket experiment.

Doesn't anybody know the answer to my question? :confused:

Alright, if nobody wants to answer this question reliably, I'd at least like to know WHY nobody can answer the question?

Time dilation has been measured and proved to be accurate to many millionths of a part of a second.

If you send a clock into space it comes back with a time reading slower than that of its earthly counterpart. That's a fact.

Based on this, I just want to know if the apparent time dilation occurs during periods of acceleration only, and this could be proved via my double rocket experiment.

Doesn't anybody know the answer to my question? :confused:

I already answered your question. The difference is that I assumed that you meant for ship A's clock to continue keeping time until B returned. In which case B would return showing less time than A.

To cut to the chase, no, time dilation does not only occur during periods of acceleration. To solve the time difference you have to take into consideration time dilation during both the acceleration and coasting phases.

I already answered your question. The difference is that I assumed that you meant for ship A's clock to continue keeping time until B returned. In which case B would return showing less time than A.

To cut to the chase, no, time dilation does not only occur during periods of acceleration. To solve the time difference you have to take into consideration time dilation during both the acceleration and coasting phases.

OK, thanks, but a couple more things:

Is there more dilation during periods of acceleration than periods of constant velocity. In other words, if two rockets launched and they both spent the same amount of time in space (according to their own clocks), but one was accelerating all over the place and one was just drifting around at constant velocity, am I right in assuming the accelerating rocket experiences the greatest time dilation?

My next question is closely linked to this thread:

Say that two rockets take off from the earth and speed off in straight lines with a trajectory difference of 30 degrees. Many millions of miles later they both stop. One rocket, however, accelerates back and forth along an arc (the arc having its centre at the earth). What happens here is that the relative distance to earth doesn't change as far as both rockets are concerned. But when both rockets return to earth, do they show similar time dilation?

The simplest way to answer this is with different example. Place a rocket some distance from the Earth and place it on a circular path around the Earth at a constant speed. Here will have a situation where the rocket is both accelerating and maintaining a constant speed.

Here, the time dilation for the rocket is due to its speed relative to the Earth alone. There is no additional time dilation due to its acceleration.

The simplest way to answer this is with different example. Place a rocket some distance from the Earth and place it on a circular path around the Earth at a constant speed. Here will have a situation where the rocket is both accelerating and maintaining a constant speed.

Here, the time dilation for the rocket is due to its speed relative to the Earth alone. There is no additional time dilation due to its acceleration.

Yes, I know things that travel in a circular path are accelerating but this is slightly different to the scenario I presented.

I posed the question regarding a possible difference in the clocks of one rocket being stationary and the other accelerating, not only in terms of centripital acceleration but linear (albeit on an arc).

So my question still stands: Does either of the rockets experience greater time dilation when returning to Earth?

Yes, I know things that travel in a circular path are accelerating but this is slightly different to the scenario I presented.

I posed the question regarding a possible difference in the clocks of one rocket being stationary and the other accelerating, not only in terms of centripital acceleration but linear (albeit on an arc).

So my question still stands: Does either of the rockets experience greater time dilation when returning to Earth?

Actually it makes no difference if the acceleration is circular or linear, the only thing that counts towards time dilation (as seen from the frame that they are accelerating in respect to) is the relative speed. Of course, if an object is accelerating linearly then it will be changing relative speed from instant to instant.

It is another ball of wax from the perspective of the observer who is in the accelerated frame, he will see additional effects in the time rate of the unaccelerated frame.