Is Time Slowing or Are Processes Slowing Near High Gravity and Speeds?

[1977ub]

the resolution of the 'twins' is not at all clear to me.
JM

A somewhat more straightforward scenario is if the traveling twin moves in a circle. Every time he passes his origin point, he finds that his clock has ticked fewer times than the origin clock. Since he is traveling in a circle - not in an inertial frame - we won't be tempted to create any "paradoxical" inertial frame for him in which clocks in the original frame are measured to be moving more slowly.

 

[ghwellsjr]

The discussion is on page 76 of their book 'Spacetime Physics.
JM

The issue being discussed in Box 3-4 on page 76&77 of T&W is the meanings of the words "real", "really", and "reality". They present two arguments, one that agrees that there are differences in clock rates and one that denies that a clocks tick at different rates. Note how they conclude each argument with: If that is what you mean by real (or reality) then that is "what really happens" or then "there are really no such changes".

They are not taking sides--they are merely pointing out the futility of discussing ill-defined words.

 

[Dale]

The issue being discussed in Box 3-4 on page 76&77 of T&W is the meanings of the words "real", "really", and "reality". They present two arguments, one that agrees that there are differences in clock rates and one that denies that a clocks tick at different rates. Note how they conclude each argument with: If that is what you mean by real (or reality) then that is "what really happens" or then "there are really no such changes".

They are not taking sides--they are merely pointing out the futility of discussing ill-defined words.

Thanks. I can agree heartily with that.

 

[nitsuj]

Can you give references for the others that have denied the motion effects? I would like to see what they have to say.
JM

What references? It's a postulate. It hasn't yet been shown to be wrong. It's not remarkable because it's intuitive.

Inertial motion doesn't effect mechanical physics (Laws).

 

[JM]

The issue being discussed in Box 3-4 on page 76&77 of T&W is the meanings of the words "real", "really", and "reality". They present two arguments, one that agrees that there are differences in clock rates and one that denies that a clocks tick at different rates. Note how they conclude each argument with: If that is what you mean by real (or reality) then that is "what really happens" or then "there are really no such changes".

They are not taking sides--they are merely pointing out the futility of discussing ill-defined words.

I don't agree. The operative sentence in the first topic is " Different values of the time between two events as observed in different frames?" This addresses a relation such as the 'slow clock formula' t' = t √( 1 - v²/c² ). Acceptance of this formula does not imply agreement that the clocks themselves are changing their rates.
The second topic asks "Does something about a clock really change when it moves...?" This is a separate question from the first, it is asking whether the clocks are responsible for the time differences. Their denial makes sense and fits with other considerations.
Remember when Einstein said ' ...all the clocks of the two systems , be in all respects alike." Doesn't that mean that the clocks rates are the same?
JM

 

[nitsuj]

Remember when Einstein said ' ...all the clocks of the two systems , be in all respects alike." Doesn't that mean that the clocks rates are the same?
JM

I can't remember when Einstein said anything, but if the clocks are "in all respects alike" I'd take that to mean they've been synchronized to measure the same size time interval, like seconds or something.

The spacetime interval of the rate will always be the same no matter the comparative motion between the two clocks. In all respects (physical laws) are alike.

Specifically it means the clock rates are the same interval,

 

[nitsuj]

...time and space are equivalent in a dimensional sense; they cannot be separated. I just don't agree with your interpretation of relativity.

Must have missed this, I have the same view of spacial/temporal dimensions that you stated. (as of now, view spacetime as a "Unity of Opposites")

If you were saying in that specific sense Length is Time dependent I'd agree; the two are "dependent" on each other. However the two are also mutually exclusive. A black 'n white thing.

I never stated an interpretation of relativity, so am unsure what you disagree with.

 

[ghwellsjr]

The issue being discussed in Box 3-4 on page 76&77 of T&W is the meanings of the words "real", "really", and "reality". They present two arguments, one that agrees that there are differences in clock rates and one that denies that a clocks tick at different rates. Note how they conclude each argument with: If that is what you mean by real (or reality) then that is "what really happens" or then "there are really no such changes".

They are not taking sides--they are merely pointing out the futility of discussing ill-defined words.

I don't agree. The operative sentence in the first topic is " Different values of the time between two events as observed in different frames?" This addresses a relation such as the 'slow clock formula' t' = t √( 1 - v²/c² ). Acceptance of this formula does not imply agreement that the clocks themselves are changing their rates.
The second topic asks "Does something about a clock really change when it moves...?" This is a separate question from the first, it is asking whether the clocks are responsible for the time differences. Their denial makes sense and fits with other considerations.

There aren't two topics. The topic is expressed in the heading in large bold black type:

DOES A MOVING CLOCK REALLY "RUN SLOWLY"?

Notice the italicized word, "REALLY", above and several times below.

First comes the questioner depicted as an icon thinker:

You keep saying, "The time between clock-ticks is shorter as MEASURED in the rest frame of the clock than as MEASURED in a frame in which the clock is moving." I am interested in reality, not someone's measurements. Tell me what really happens!

Next comes the commentator depicted as a talking bird:

What is reality? You will have your own opinion and speculations. Here we pose two related scientific questions whose answers may help you in forming your opinion.

Now we have the affirmative argument:

Are differences in clock rates really verified by experiment?
Different values of the time between two events as observed in different frames? Absolutely! Energetic particles slam into solid targets in accelerators all over the world, spraying forward newly created particles, some of which decay in very short times as measured in their rest frames. But these "short-lived" particles survive much longer in the laboratory frame as they streak from target to detector. In consequence, the detector receives a much larger fraction of the undecayed fast-moving particles than would be predicted from their decay times measured at rest. This result has been tested thousands of times with many different kinds of particles. Such experiments carried out over decades lead to dependable, consistent, repeatable results. As far as we can tell, they are correct, true, and reliable and cannot effectively be denied. If that is what you personally mean by "real," then these results are "what really happens."

And the negative argument:

Does something about a clock really change when it moves, resulting in the observed change in tick rate?
Absolutely not! Here is why: Whether a free-float clock is at rest or in motion in the frame of the observer is controlled by the observer. You want the clock to be at rest? Move along with it! Now do you want the clock to move? Simply change your own velocity! This is true even when you and the clock are separated by the diameter of the solar system. The magnitude of the clock's steady velocity is entirely under your control. Therefore the time between its ticks as measured in your frame is determined by your actions. How can your change of motion affect the inner mechanism of a distant clock? It cannot and does not.

Every time you change your motion on Earth — and even when you sit down, letting the direction of your velocity change as Earth rotates — you change the rate at which the planets revolve around Sun, as measured in your frame. (You also change the shape of planetary orbits, contracting them along the direction of your motion relative to Sun.) Do you think this change on your velocity really affects the workings of the "clock" we call the solar system? If so, what about a person who sits down on the other side of Earth? That person moves in the opposite direction around the center of Earth, so the results are different from yours. Are each of you having a different effect on the solar system? And are there still different effects — different solar-system clocks — for observers who could in principle be scattered on other planets?

We conclude that free-float motion does not affect the structure or operation of clocks (or rods). If this is what you mean by reality, then there are really no such changes due to uniform motion.


And a final commentary:

Is there some unity behind these conflicting measurements of time and space? Yes! The interval: the proper time (wristwatch time) between ticks of a clock as measured in a frame in which ticks occur at the same place, in which the clock is at rest. Proper time can also be calculated by all free-float observers, whatever their state of motion, and all agree on its value. Behind the confusing clutter of conflicting measurements stands the simple, consistent, powerful view provided by spacetime.

Now everyone can have their own opinion about what T&W are presenting.

Remember when Einstein said ' ...all the clocks of the two systems , be in all respects alike." Doesn't that mean that the clocks rates are the same?
JM

Einstein makes that remark at the beginning of section 3 of his 1905 paper introducing Special Relativity. He answers your question in the middle of section 4:

it follows that the time marked by the clock (viewed in the stationary system) is slow by

seconds per second...

 

[dayalanand roy]

Dear ghwellsir, and all the other learned participants
Many thanks for participating in the discussion. The quote from T and W is specially helpful in understanding what is reality. However, it still throws liitle light on two clocks-one placed on Earth and one on a water tank, or one stationary and the other in a moving plane, ticking off differently, because these two are not that far apart. One more thing. They say that how can change in your velocity on Earth can alter the mechanism of distant clock in space- the solar system. But a change in our velocity can at least make a change in our clock, and this can in turn create the difference between the two.
Anyhow, things are now becoming much clearer. Thanks to all.

 

[D English]

Howdy Folks, I'm brand new, and really glad I found this place. I hope I'm not out of line by jumping in.

As a layman, can't I say: Nothing "slows down" as a result of being somewhere else, or as a funtion of being at a different speed, it is just that the perception of the slowing down is dependent on the point of view?

 

[1977ub]

Person A stays at home. They find that clock ticks away normally. Person B travels in a circle and comes back. B also finds their clock ticked normally. However they find that A's clock made more ticks than B's. You can pick your definition of "really" to decide if B's clock "really" slowed or didn't.

 

[russ_watters]

Welcome to PF!

As a layman, can't I say: Nothing "slows down" as a result of being somewhere else, or as a funtion of being at a different speed, it is just that the perception of the slowing down is dependent on the point of view?

Well, what would you say if you have two clocks sitting next to each other, synchronized, then you send one on a trip around the world, bring it back together with the other clock and find that they are no longer synchronized?

 

[bobc2]

Person A stays at home. They find that clock ticks away normally. Person B travels in a circle and comes back. B also finds their clock ticked normally. However they find that A's clock made more ticks than B's. You can pick your definition of "really" to decide if B's clock "really" slowed or didn't.

Both clocks continued to tick at the same rates as each proceeded at the speed of light along their respective worldlines (tick marks along the respective worldlines marked off equal proper time increments). However, B took a shorter path through the 4-dimensional space-time, so there were not as many tick marks along B's worldline from start event to reunite event.

 

[1977ub]

Both clocks continued to tick at the same rates as each proceeded at the speed of light along their respective worldlines (tick marks along the respective worldlines marked off equal proper time increments). However, B took a shorter path through the 4-dimensional space-time, so there were not as many tick marks along B's worldline from start event to reunite event.

Sure. In this case we don't need to bother to set each observer up with an inertial frame, so we don't have to answer questions such as how fast each observer find's the other observer's clock to be ticking "at a particular time."

 

[D English]

Welcome to PF! Well, what would you say if you have two clocks sitting next to each other, synchronized, then you send one on a trip around the world, bring it back together with the other clock and find that they are no longer synchronized?

First, I would say..."I knew I would have been better off being a lurker in these forums" :)

Intuitively, I would say that there must have been some physical change in one of the clocks as a result of motion or lack thereof.

However, this is possibility is removed by 1977's statement that both clocks are operating normally.

So, I would say that from the perspective of each person, their clocks continue to operate at the same rate, but due to the motion of one, their points of perception have changed significantly enough to show a difference between the two.

The problem with that is when the moving clock comes back to its original position, it is not synched anymore, indicating either a physical or dimensional change during the movement.

Ok, you can kick me out now. :)

 

[bobc2]

First, I would say..."I knew I would have been better off being a lurker in these forums" :)

Intuitively, I would say that there must have been some physical change in one of the clocks as a result of motion or lack thereof.

However, this is possibility is removed by 1977's statement that both clocks are operating normally.

So, I would say that from the perspective of each person, their clocks continue to operate at the same rate, but due to the motion of one, their points of perception have changed significantly enough to show a difference between the two.

The problem with that is when the moving clock comes back to its original position, it is not synched anymore, indicating either a physical or dimensional change during the movement.

Ok, you can kick me out now. :)

Not necessary. You can still find redemption if you will look into the Minkowski space-time diagram topic. Then you will see what I meant in the previous post about B taking a shorter path through space-time. The clock rates are not affected at all. B just simply took a shorter path that had fewer tick marks along his worldline in 4-dimensional space-time.

 

[petm1]

The clock rates are not affected at all. B just simply took a shorter path that had fewer tick marks along his worldline in 4-dimensional space-time.

Why a shorter path? I would think a longer duration between the changes counted by B's clock or the longer path of B's world line accounts for fewer tick marks when reunited with A's clock that keeps a steady duration or the shorter world line.

 

[barbacamanitu]

Does that mean time slowed down? Yes it does, does it mean the processes merely slowed down? No, they haven't the spacetime interval is the same. The geometry is comparatively "different".

How can you say that the processes didn't just slow down? The spacetime interval could be viewed the same because every conceivable time measuring device would slow down too. This really makes "processes" and "time" seem like the same thing.

 

[bobc2]

How can you say that the processes didn't just slow down? The spacetime interval could be viewed the same because every conceivable time measuring device would slow down too. This really makes "processes" and "time" seem like the same thing.

Here is why I think the slowing of the clock cannot be caused by some mechanism that affects the physical operation of the clock. That might be the case if it was just one of the clocks that is seen to be ticking more slowly. But, actually each observer sees the other’s clock as ticking more slowly. If red was at rest in aether, for example, and it was just the mechanism of the blue clock being affected (due to blue's absolute velocity in reference to aether), then both observers would always agree that it was the blue clock ticking more slowly. However, you can see in the sketch below that each observer sees the other’s clock displaying an earlier time (each sees the other’s clock ticking more slowly). This could not be the case if some mechanism of just the blue clock was affected. And if you wish to claim that both clocks were affected, then they would see no discrepancy, since both clocks would be affected the same way (assuming both moved with the same absolute speed with respect to the aether).

I personally have not been able to find in the literature a full account of any mechanism that predicts the results of Einstein's special relativity. It is recognized that there is disagreement with my position, so I don't want to claim expertise that establishes this view with some kind of finality--I would not want to deny others their views on this. I may be wrong here and would be very open to enlightenment on this point.

At one of the famous Solvay conferences, it is said that Poincare’ asked Einstein, “What is the mechanism accounting for time dilation and length contraction?” Einstein’s reply was simply, “There is no mechanism.”

petm1 quote: "Why a shorter path? I would think a longer duration between the changes counted by B's clock or the longer path
of B's world line accounts for fewer tick marks when reunited with A's clock that keeps a steady duration or the shorter world line."

The sketch below might be a little more difficult to interpret. Ask a question if it is not clear. This goes to the point that it is the path through space-time that accounts for differences in clock readings for two observers who have been separated for a while, then reunite (it has nothing to do with clock mechanisms). What may look like the longer path on the computer screen is actually the shorter path through the 4-dimensional space-time. The hyperbolic calibration curves are used to determine proper time spans from the origin of the black orthogonal coordinates (consistent with the Minkowski metric).

 

[1977ub]

It strikes me that the simplest and most paradoxical case in SR is the two-ships-passing-in-the-night version where A measures B's clock as slower and B measures A's clock as slower. This could easily be chalked up the relativity of simultaneity - an artifact of deciding to measure the world through the mechanism of an inertial reference frame. This is not simple "seeing" in the sense of A & B "seeing" the other's clock to run slower. In all cases where A & B are brought back together and their clocks differ, it is the one which experienced acceleration which had some "objective" slowing which both observers can agree upon and take to the bank. And so the non-paradoxical 'mechanism' needs to apply to the accelerated observer only, and that 'mechanism' would appear to be an interaction with the mysterious "Source of Inertia."

 

[Fredrik]

It strikes me that the simplest and most paradoxical case in SR is the two-ships-passing-in-the-night version where A measures B's clock as slower and B measures A's clock as slower.

It seems a lot less paradoxial when you realize that statements about A's experience of B's clock are actually statements about coordinate assignments to points on B's world line made by a coordinate system that a standard procedure associates with A's world line.

The SR result that I find the most counterintuitive is that if you see something like a dot from a laser pointer move faster than c, and you start running after it, its speed relative to you will be larger when you're running, not smaller. (This is also a consequence of the definition of your experience using the comoving inertial coordinate system).

...and that 'mechanism' would appear to be an interaction with the mysterious "Source of Inertia."

This I disagree with. No mechanism is needed.

 

[1977ub]

This I disagree with. No mechanism is needed.

Something - mechanism or something else - is required to explain why one person experiences acceleration when another does not. This same something appears to be involved in cases where A & B bring their clocks together and one of them has run slower somehow.

 

[Fredrik]

Here is why I think the slowing of the clock cannot be caused by some mechanism that affects the physical operation of the clock. That might be the case if it was just one of the clocks that is seen to be ticking more slowly. But, actually each observer sees the other’s clock as ticking more slowly. If red was at rest in aether, for example, and it was just the mechanism of the blue clock being affected (due to blue's absolute velocity in reference to aether), then both observers would always agree that it was the blue clock ticking more slowly. However, you can see in the sketch below that each observer sees the other’s clock displaying an earlier time (each sees the other’s clock ticking more slowly). This could not be the case if some mechanism of just the blue clock was affected. And if you wish to claim that both clocks were affected, then they would see no discrepancy, since both clocks would be affected the same way (assuming both moved with the same absolute speed with respect to the aether).

I personally have not been able to find in the literature a full account of any mechanism that predicts the results of Einstein's special relativity. It is recognized that there is disagreement with my position, so I don't want to claim expertise that establishes this view with some kind of finality--I would not want to deny others their views on this. I may be wrong here and would be very open to enlightenment on this point.

At one of the famous Solvay conferences, it is said that Poincare’ asked Einstein, “What is the mechanism accounting for time dilation and length contraction?” Einstein’s reply was simply, “There is no mechanism.”

Good stuff. I agree with these statements. It seems to me that the only way to make sense of the view that motion changes the properties of clocks is to label an arbitrary inertial coordinate system "the ether system", and then say that rulers and clocks with velocity v in the ether system are contracted/slowed by a factor of $\gamma(v)$.

 

[Fredrik]

Something - mechanism or something else - is required to explain why one person experiences acceleration when another does not.

OK, that I can agree with.

 

[bobc2]

Good stuff. I agree with these statements. It seems to me that the only way to make sense of the view that motion changes the properties of clocks is to label an arbitrary inertial coordinate system "the ether system", and then say that rulers and clocks with velocity v in the ether system are contracted/slowed by a factor of $\gamma(v)$.

Thanks, Fredrik. And I think the possibility of the $\gamma(v)$ resulting from an aether related effect, as you suggest, was the primary thrust of Fitzgerald, Lorentz, Poincare', et. al. My problem has been that for the past few weeks (off and on for months) I've tried to run that concept to ground and just haven't been able to find references that explicitly show how an observer moving relative to the aether can "see" a clock at rest in the ether as ticking slower by the same rate as the observer at rest in aetherr "sees" the clock in motion relative to the aether.

If red is at rest in aether, then his clock would be unaffected. If blue's clock, is affected due to his own motion, I have not seen the analysis that would show that blue "sees" red's clock to be affected in exactly the same way that red would "see" blue's. Whereas, with SR, each sees the other's clock tick slower by the same amount.

I probably just haven't found the right references and maybe someone here can provide an account of this mechanism that produces the same symmetric results as special relativity.

[edit] Just to add another note: It seems that the moving observer (his clock having a mechanistic slowing of his clock in an absolute physical sense) would "see" the at-rest-in-aether's clock ticking faster than his own. SR predicts just the opposite, i.e., the moving observer would "see" the at-rest-in-aether's clock ticking slower.

 

[1977ub]

It seems a lot less paradoxial when you realize that statements about A's experience of B's clock are actually statements about coordinate assignments to points on B's world line made by a coordinate system that a standard procedure associates with A's world line.

Yes. It is a standard procedure, it is intuitive, it is practical. But it also, in a way, elaborate. It is certainly not the same thing as seeing or perceiving or knowing the other person's clock.

 

[bobc2]

Something - mechanism or something else - is required to explain why one person experiences acceleration when another does not. This same something appears to be involved in cases where A & B bring their clocks together and one of them has run slower somehow.

1977ub, you can set up the experiment for two observers in relative motion showing differences in tick rates without any acceleration being involved. So, the acceleration is not a factor in the difference in clock rates (at least for special relativity). We can show examples if you wish.

 

[1977ub]

1977ub, you can set up the experiment for two observers in relative motion showing differences in tick rates without any acceleration being involved. So, the acceleration is not a factor in the difference in clock rates (at least for special relativity). We can show examples if you wish.

It relies upon construction of inertial frames. It could be understood that the "differences in tick rates" are an artifact of setting up these inertial frames in the first place. Until somebody accelerates, we don't end up with a difference that can't be chalked up to being such an artifact.

 

[Mentz114]

... It could be understood that the "differences in tick rates" are an artifact of setting up these inertial frames in the first place.

That is true.

Until somebody accelerates, we don't end up with a difference that can't be chalked up to being such an artifact.

Another way to put this is "Until their relative velocity changes, we don't end up with a difference that can't be chalked up to being such an artifact."

Only relative velocity enters the equations, through the γ factor.

 

[bobc2]

It relies upon construction of inertial frames. It could be understood that the "differences in tick rates" are an artifact of setting up these inertial frames in the first place. Until somebody accelerates, we don't end up with a difference that can't be chalked up to being such an artifact.

The construction of the inertial frames does not produce artifacts. You seem to be familiar with the examples I referred to (difference in tick rates without acceleration), so could you show us one of those examples and explain how the artifacts were produced. I don't understand where the artifacts come from. Does the Minkowski metric produce artifacts? Please explain that.

 

[1977ub]

The construction of the inertial frames does not produce artifacts. You seem to be familiar with the examples I referred to (difference in tick rates without acceleration), so could you show us one of those examples and explain how the artifacts were produced. I don't understand where the artifacts come from. Does the Minkowski metric produce artifacts? Please explain that.

Which distant events are simultaneous with events at my location? The simplest and most direct answer is "I have no idea." There, done. If you were accelerating, you'd stop there. If you're not satisfied, you can send light pulses back and forth and time them. Seems reasonable enough, and it works well enough if the events of concern are in flat-enough space-time. But it is reasoning and not simple perception. And it breaks down if the space-time in the area of concern is not flat enough. But given all the caveats, you end up with this intuitive and practical creation: the inertial frame. And reality when filtered through this creation yields slower ticking of moving clocks etc.

Perhaps you could describe how a Minkowski metric of my environs is best experimentally constructed. Can it be done if I am accelerating?

 

[D English]

Not necessary. You can still find redemption if you will look into the Minkowski space-time diagram topic. Then you will see what I meant in the previous post about B taking a shorter path through space-time. The clock rates are not affected at all. B just simply took a shorter path that had fewer tick marks along his worldline in 4-dimensional space-time.

I only looked at the part about time dilation, and I accept it.

Probably off topic: How does one reconcile this? In the measure of time the two clocks will never synch again yet they recorded the same amount of time, yes?

If yes, then can one say that the re-united clocks are now in their own separate temporal dimensions forever even though subsequent observations shared from the same vantage point will be measured equally by both clocks?

 

[Dale]

Probably off topic: How does one reconcile this? In the measure of time the two clocks will never synch again yet they recorded the same amount of time, yes?

If yes, then can one say that the re-united clocks are now in their own separate temporal dimensions forever even though subsequent observations shared from the same vantage point will be measured equally by both clocks?

Huh? This is word salad.

 

[Dale]

Perhaps you could describe how a Minkowski metric of my environs is best experimentally constructed. Can it be done if I am accelerating?

Use a set of inertial rods and clocks where the clocks are synchronized using Einsteins convention. It can certainly be done if you are accelerating. You will not be at rest (other than momentarily) in such a frame, but there is no reason that you must use a coordinate system where you are at rest.

 

[D English]

Huh? This is word salad.

I think because the whole notion is paradoxical. Yet, I know its a true phenomena.

The clocks measured the same amount of time, yet due to the motion of one, each according to the other is de-synced. Despite the de-syncing, neither is "wrong". Yes?