Twin paradox "resolution" article

makis
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21 years 5 months ago #6111 by makis

Replied by makis on topic Reply from

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>

...neither force nor acceleration can have any effect on clocks or time for any observer, apart from the known effect of velocity.

<hr height=1 noshade id=quote></BLOCKQUOTE id=quote>

Agree but I did not mention acceleration because of its effect or no effect on time. Just from the point of view of establishing which reference frame is affected by velocity changes in the twin's paradox. In other words, I proposed this as a test for braking down reciprocity and justifying the difference in aging. The travelling twin will experience a force when accelerating and the one back home will not. In the past this was presented as a resolution to the paradox. I propose it only as a means of establishing the fact that although the two reference frames may seems to have reciprocity in the context of the axioms of SR, there is an ultimate test of that and acceleration can provide it.

In other words: does reciprocity hold for non-inertial reference frames? If not, then this fact, although it doesn't not contrubute to time slippage, can be used to resolve the paradox. Because it is the frame of the travelling twin which has the property of changing to non-intertial and the earth bound twin cannot do that. But this change can only be interpeted in a consious way.

Do you see anything valuable in this chain of thought?

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tvanflandern
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21 years 5 months ago #5976 by tvanflandern

Replied by tvanflandern on topic Reply from Tom Van Flandern

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>[makis]: I proposed this as a test for braking down reciprocity and justifying the difference in aging. The travelling twin will experience a force when accelerating and the one back home will not. In the past this was presented as a resolution to the paradox. I propose it only as a means of establishing the fact that although the two reference frames may seems to have reciprocity in the context of the axioms of SR, there is an ultimate test of that and acceleration can provide it.<hr height=1 noshade id=quote></BLOCKQUOTE id=quote>

When the traveler turns around, time back on Earth jumps from the traveler's past to her future. Yet acceleration has no effect on time or clocks. Indeed, we can prove it wasn't the acceleration that did it. Another traveler coming from the opposite direction, who has never accelerated, will see the same thing as the traveler who went to AC and then turned around.

Acceleration is a red herring, and IMO interferes with understanding the correct explanation.

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>In other words: does reciprocity hold for non-inertial reference frames?<hr height=1 noshade id=quote></BLOCKQUOTE id=quote>

Yes, through the mechanism of Lorentz boosts -- a series of infinitesimal speed increments. -|Tom|-

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Jan
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21 years 5 months ago #5984 by Jan

Replied by Jan on topic Reply from Jan Vink

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>[TVF]: When the traveler turns around, time back on Earth jumps from the traveler's past to her future. Yet acceleration has no effect on time or clocks. Indeed, we can prove it wasn't the acceleration that did it. Another traveler coming from the opposite direction, who has never accelerated, will see the same thing as the traveler who went to AC and then turned around.

Acceleration is a red herring, and IMO interferes with understanding the correct explanation.<hr height=1 noshade id=quote></BLOCKQUOTE id=quote>

Isn't acceleration _the_ ingredient to the twin paradox? I don't understand why the traveler's paths jumps to the future. All I see is that traveling near light speed slows down _all_ processes. Once the twin returns to Earth, all processes come back to Earth-bound rates smoothly: no discontinuities are present. Hence when the leathered-up twin kisses her other twin goodby, she and her rocket _must_ accelerate to reach light speed. Of course, only the velocity determines the slow down of processes, but to reach particular velocities, one must accelerate.

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tvanflandern
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21 years 5 months ago #6365 by tvanflandern

Replied by tvanflandern on topic Reply from Tom Van Flandern

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>[Jan]: I don't understand why the traveler's paths jumps to the future.<hr height=1 noshade id=quote></BLOCKQUOTE id=quote>

That is normal behavior in special relativity. If all clocks are Einstein-synchronized in a moving frame, the laboratory frame will infer that receding clocks are in the past and approaching clocks are in the future. Plug some numbers into the Lorentz transformations and see for yourself.

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>All I see is that traveling near light speed slows down _all_ processes.<hr height=1 noshade id=quote></BLOCKQUOTE id=quote>

Then how do you explain this: If a laboratory observer watches a parade of successive clocks in a fast-moving frame go by, time on each successive clock will be advancing faster than time in the laboratory.

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>when the leathered-up twin kisses her other twin goodby, she and her rocket _must_ accelerate to reach light speed.<hr height=1 noshade id=quote></BLOCKQUOTE id=quote>

On the contrary. To emphasize that acceleration plays no role, the twin's paradox is often done with a traveling twin newborn as its spacecraft, arriving from infinity and never accelerated, passes Earth. The newborns synchronize clocks and ages as they pass one another.

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>Of course, only the velocity determines the slow down of processes, but to reach particular velocities, one must accelerate.<hr height=1 noshade id=quote></BLOCKQUOTE id=quote>

But special relativity claims that the spacecraft may legitimately regard itself as at rest and the Earth as traveling at high speed.

As I said in the above quote, acceleration is a red herring. If you want to understand SR, you must unlearn that incorrect "explanation" of the twin's paradox, and learn instead about "time slippage" in SR. The Lorentz time transformation has two terms, one of which represents clock-slowing, and the other of which represents time slippage into the future. I give a link to the paper discussing this in the other thread you started on this subject. -|Tom|-

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Jan
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21 years 5 months ago #5988 by Jan

Replied by Jan on topic Reply from Jan Vink

Having read the article "What GPS tells us about the twin paradox", I come to my following understanding with some added interpretations:

LR says that the difference in an objects speed and c matters only. Looking out the window of your rocket does not provide real information about "now" on earth, but just what "was", since that information can only reach us at c. Relative velocities are unimportant because Nature decides with objects approach the speed of light. Moreover, how does Nature decide when objects reach the light speed if there is no ambient background to relate to? Without background substance, Nature is simply not able to make up here mind about the speed of an object. Hence, the speed of light makes no sense without background substance: Relative velocities are pathological since there is only one and only one object traveling closer to c, A or B, and Nature decides which one, _not_ the traveler. Therefore, we know that the rocket travels near c, so clock slowing occurs, and we need to increase the ticking rate of the clock onboard if it is to match the ticking rate on Earth. The above is a first attempt I must add. Please comment.

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tvanflandern
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21 years 5 months ago #5990 by tvanflandern

Replied by tvanflandern on topic Reply from Tom Van Flandern

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>[Jan]: LR says that the difference in an objects speed and c matters only.<hr height=1 noshade id=quote></BLOCKQUOTE id=quote>

LR says that what matters is any object's speed relative to the local gravity field. All observers will agree about what that speed is for themselves and for all others.

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>Looking out the window of your rocket does not provide real information about "now" on earth, but just what "was", since that information can only reach us at c.<hr height=1 noshade id=quote></BLOCKQUOTE id=quote>

The effect of light's finite propagation speed can be removed by calculating the "real" time at the source. Any observer can measure the distance of the source, and knows the speed of light, so the time it took light to reach the observer can be calculated and removed from the visible clock readings.

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>Relative velocities are unimportant because Nature decides with objects approach the speed of light. Moreover, how does Nature decide when objects reach the light speed if there is no ambient background to relate to?<hr height=1 noshade id=quote></BLOCKQUOTE id=quote>

In SR, every object may regard itself as at rest. No matter how fast one travels, light will still have a relative speed of c.

In LR, observer motion changes the speed of light, just as it changes the speed of sound. No paradox arises.

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>the speed of light makes no sense without background substance<hr height=1 noshade id=quote></BLOCKQUOTE id=quote>

I agree.

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>Please comment.<hr height=1 noshade id=quote></BLOCKQUOTE id=quote>

A good initial effort. If you stick with LR, physics is classical and no special problems arise. But for those who want to understand SR (at least for historical reasons), your descriptions miss the mark by not accepting the two postulates of SR, especially the one that the speed of light is c for all observers. -|Tom|-

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