Post by: Yahya on 31/03/2017 17:42:58
Post by: Demolitiondaley on 31/03/2017 19:21:16
is the twin paradox real ? is there any experiment of two twins one traveling at high speed and one on earth at rest aging differently ?
This has never been experimented in real life, we don't have the technology to put a person in a craft that would reach the near to speed of light necessary to observe a difference in ageing of the twins.
Post by: geordief on 31/03/2017 19:33:22
[quote author=Yahya A. SharifHow would one verify quantitatively that one twin had indeed aged more than the other?
This has never been experimented in real life, we don't have the technology to put a person in a craft that would reach the near to speed of light necessary to observe a difference in ageing of the twins.
Would it not be enough to simply stipulate that each twin carry a clock?
Comparing clocks would show that one had aged more than the other?
I think this has been done routinely with astronauts in the Space Station.
One of the astronauts might have a twin on the ground if that made the experiment seem more convincing
Post by: Colin2B on 31/03/2017 23:20:46
Post by: evan_au on 01/04/2017 00:43:50
However, there is another twin paradox that comes about through general relativity, where one twin climbs farther out of a gravitational well, and then returns. This experiment has been done with very accurate aluminium-ion clocks at NIST.
See: https://www.nist.gov/news-events/news/2010/09/nist-pair-aluminum-atomic-clocks-reveal-einsteins-relativity-personal-scale
Post by: PhysBang on 01/04/2017 14:05:19
Post by: hamdani yusuf on 01/04/2017 14:58:24
An astronaut actually has a twin stay on earth.[quote author=Yahya A. SharifHow would one verify quantitatively that one twin had indeed aged more than the other?
This has never been experimented in real life, we don't have the technology to put a person in a craft that would reach the near to speed of light necessary to observe a difference in ageing of the twins.
Would it not be enough to simply stipulate that each twin carry a clock?
Comparing clocks would show that one had aged more than the other?
I think this has been done routinely with astronauts in the Space Station.
One of the astronauts might have a twin on the ground if that made the experiment seem more convincing
https://en.wikipedia.org/wiki/Scott_Kelly_(astronaut)
https://en.wikipedia.org/wiki/Mark_Kelly
Post by: geordief on 01/04/2017 16:31:54
Very good :)An astronaut actually has a twin stay on earth.[quote author=Yahya A. SharifHow would one verify quantitatively that one twin had indeed aged more than the other?
This has never been experimented in real life, we don't have the technology to put a person in a craft that would reach the near to speed of light necessary to observe a difference in ageing of the twins.
Would it not be enough to simply stipulate that each twin carry a clock?
Comparing clocks would show that one had aged more than the other?
I think this has been done routinely with astronauts in the Space Station.
One of the astronauts might have a twin on the ground if that made the experiment seem more convincing
https://en.wikipedia.org/wiki/Scott_Kelly_(astronaut)
https://en.wikipedia.org/wiki/Mark_Kelly
Post by: CPT ArkAngel on 01/04/2017 22:10:15
Post by: evan_au on 01/04/2017 23:00:31
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The twin paradox is like going to the gym. You can slow down aging, but you have to work really hard - accelerate quickly and move at high speeds. Your twin who just stays at home and sits on the lounge ages faster.
http://7thavenueproject.com/post/110697301080/general-relativity-introduction-pt1
I've downloaded part 2 to listen later...
Post by: Yahya on 02/04/2017 05:15:56
I was listening to a podcast Introduction to Relativity with Anthony Aguirre. He had an interesting analogy on the twin paradox, that went something like this:I do not think it's useful . if my body is capable to age a certain degree each year ,and I spend 10 years it will age this certain degree everywhere when these ten years elapse , if the other twin spent 40 years it just means he spent most of his lifetime! and does not mean you slow down aging , the traveling twin will come to find his on -earth twin had his grandchildren while he only just got married! and enjoyed 40 years while he only enjoyed 10 years supposing he had everything he needed in his spaceship.
The twin paradox is like going to the gym. You can slow down aging, but you have to work really hard - accelerate quickly and move at high speeds. Your twin who just stays at home and sits on the lounge ages faster.
Post by: PhysBang on 02/04/2017 16:18:45
Within special relativity, it is a paradox.No. Anyone who says this merely fails to understand special relativity.
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All explanations within the frame of SR alone are wrong because there is no key to differentiate the twins.Except that there is: one twin remains at rest in a single system of coordinates that is an inertial reference frame that covers all events and another twin can only be described using a series of at least two systems of coordinates that are inertial reference frame and this series either does not cover all events or covers events in multiple ways that are inconsistent with the final system of coordinates. This is explained very well in most introductory textbooks on contemporary relativity theory. For example, see Bernard Schutz's textbook.
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The change is associated to the twin in the rocket by a purely arbitrary a priori choice. There are no explanations concerning acceleration and inertia in SR.Except that there are: the frame of reference of SR is an inertial frame of reference, i.e. a frame of reference in which Newtonian Mechanics holds to a first approximation.
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With GR, the twin feeling the acceleration of its inertial frame is linked to the increase in gravity potential and gives a first confirmation beyond the basic postulate of SR with the Equivalence principle.You are welcome to calculate the amount of this that effects the twin, it will not match that found from purely SR effects.
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In Special Relativity, the acceleration is entirely reciprocal for both twins. Any explanation stating it is a matter of coordinates just differentiates artificially the twins from the beginning...The twins are differentiated from the beginning because of what is given in the scenario: one turns around. In order to describe this in SR, one has to use momentarily co-moving reference frames to describe reference frames that co-move with that twin, just like one would do for any object that changes course in elementary SR.
Post by: CPT ArkAngel on 02/04/2017 19:57:42
Einstein could have chosen the twin in the rocket to age faster than the other twin and it would have made perfect mathematical sense in the context of the speed limit of C. But evidently, he chose the non accelerating twin to have a constant time rate because it was intuitively right.
Post by: PhysBang on 03/04/2017 04:31:20
You fell in the trap.Yes, the trap of reading textbooks on this subject that go into this in great detail. If you want to call that a "trap" then I recommend that you avoid all reading.
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SR is not just an add on to Newtonian mechanics, it is the start of a new theory.At this point I will point readers who do not worry about falling into a "trap" to take a look at the actual theory of SR. Einstein wrote as the very first step of SR: "Let us take a system of co-ordinates in which the equations of Newtonian mechanics hold good." (Note the footnote, too.)
http://www.fourmilab.ch/etexts/einstein/specrel/www/
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The choice is arbitrary because there is no explanation, it is just an a priori convention. With SR alone, you cannot really explain why the accelerating frame will have a slower time. This is a mathematical artefact due to the choice of coordinates based on a postulate. It is not because it is a right guess that it is not a guess, even though it made sense... Without an explanation of inertia (which is leading to gravity), you are stuck with a postulate... This is why Einstein worked so hard on GR after SR.While this may have been a motivation for EInstein (citation?) it doesn't change the fact that there is a reason for the difference in SR: there is no one inertial reference frame in which one of the twins can be described as being at rest.
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Einstein could have chosen the twin in the rocket to age faster than the other twin and it would have made perfect mathematical sense in the context of the speed limit of C. But evidently, he chose the non accelerating twin to have a constant time rate because it was intuitively right.No, there is no choice here because the mathematics are quite strict. Only if one ignores the mathematics of SR can one imagine that there is some sort of choice.
Post by: hamdani yusuf on 03/04/2017 10:57:42
Post by: PhysBang on 03/04/2017 16:27:13
Post by: CPT ArkAngel on 03/04/2017 21:53:25
I`ve been reading about this for more than 30 years... The proof offered is a circular reasoning, they just forget to look for their tail, even though they are chasing it. The only thing separating the twins is the acceleration, not the coordinates. The coordinates are chosen in regards of the acceleration, nothing else. Thus, the key is in the acceleration as Einstein pointed out! There is nothing preventing you to switch your choice of coordinates on the accelerating frame and making total abstraction of who is feeling the acceleration. This is my point. (unless you can explain how the acceleration produces a variable relative time rate!)
Post by: yor_on on 04/04/2017 13:31:49
Post by: yor_on on 04/04/2017 13:44:43
Post by: guest4091 on 04/04/2017 18:09:19
You totally missed my point. SR is born out of two new paradigms: there is no ether and an there is an absolute speed limit. All this in regards to principles of relativity. This breaks Newtonian mechanics.Here is an example with both twins changing course. Acceleration does not determine who is younger. Notice the gamma factor is a function of speed, v/c!
I`ve been reading about this for more than 30 years... The proof offered is a circular reasoning, they just forget to look for their tail, even though they are chasing it. The only thing separating the twins is the acceleration, not the coordinates. The coordinates are chosen in regards of the acceleration, nothing else. Thus, the key is in the acceleration as Einstein pointed out! There is nothing preventing you to switch your choice of coordinates on the accelerating frame and making total abstraction of who is feeling the acceleration. This is my point. (unless you can explain how the acceleration produces a variable relative time rate!)
https://app.box.com/s/c8yshj90l3c2eixu13cpkge8w53304cm
Post by: CPT ArkAngel on 04/04/2017 19:41:58
I understand that you can have an acceleration without a change in speed but it is an artefact of the choice of the observer (coordinates). Another observer won't necessarily agree on how each part of the paths affect the time rate. In the end, with SR, speed rules but it is incomplete because acceleration is obviously the key...
A non accelerating frame is chosen as the observer. But why? This is the key to understand the problem. The problem is swept under the carpet from the beginning. This is a reduction to Lorentz equations.
Post by: PhysBang on 04/04/2017 21:35:50
The difference of time rate is due to different relative speeds. The different relative speeds are due to different inertial accelerations... Accelerations are hidden in the Maths, they are implied... C'mon, this is obvious!Why do you ignore the part of the scenario where everyone agrees that one twin changes direction? Because of this, we have to use different kinds of reference frames for one than the other, without any trickery.
I understand that you can have an acceleration without a change in speed but it is an artefact of the choice of the observer (coordinates). Another observer won't necessarily agree on how each part of the paths affect the time rate. In the end, with SR, speed rules but it is incomplete because acceleration is obviously the key...
A non accelerating frame is chosen as the observer. But why? This is the key to understand the problem. The problem is swept under the carpet from the beginning. This is a reduction to Lorentz equations.
Post by: CPT ArkAngel on 04/04/2017 21:43:48
The difference of time rate is due to different relative speeds. The different relative speeds are due to different inertial accelerations... Accelerations are hidden in the Maths, they are implied... C'mon, this is obvious!Why do you ignore the part of the scenario where everyone agrees that one twin changes direction? Because of this, we have to use different kinds of reference frames for one than the other, without any trickery.
I understand that you can have an acceleration without a change in speed but it is an artefact of the choice of the observer (coordinates). Another observer won't necessarily agree on how each part of the paths affect the time rate. In the end, with SR, speed rules but it is incomplete because acceleration is obviously the key...
A non accelerating frame is chosen as the observer. But why? This is the key to understand the problem. The problem is swept under the carpet from the beginning. This is a reduction to Lorentz equations.
I don't!
Post by: PhysBang on 04/04/2017 23:44:41
Post by: geordief on 05/04/2017 00:54:23
It is easy to make a twin "paradox" scenario without acceleration. One merely needs to imagine the scenario with clocks that have constant velocity that merely pass each other at the relevant points and happen to be synchronized when they pass each other
I don't understand. How can two clocks moving at constant velocity wrt each other meet at two separate points in space-time?
Or are you perhaps referring to two clocks orbiting the same body in opposite directions? (both clocks are accelerating wrt to the body around which they are both orbiting but their respective accelerations "cancel out" in a sense)
Post by: guest4091 on 05/04/2017 18:42:27
twins-3 seg.gif (2.66 kB . 203x416 - viewed 9599 times)Using the notation (x, t) and fig.2,
A records B leaving (0, 0) a .6c, and returning (0, 10).
B records A leaving (0, 0) at .6c, and returning (0,t= 8).
Does the accumulated time differ?
A experienced 10 flashes, all observed by B.
B experienced 8 flashes, all observed by A.
B is younger than A.
Within the closed course, there are no missing events.
The reversal data is irrelevant.
The perceived doppler shifts for the diverging vs converging segments is irrelevant.
The instantaneous reversal by B is irrelevant, since it's duration is zero time, i.e. equivalent to "it never happened", thus not having any catastrophic results. The discontinuity is equivalent to two B frames participating in the experiment.
There is no acceleration/*deceleration involved, just inertial motion.
* Yes, there is such a word, for those too lazy to use a dictionary.
Post by: CPT ArkAngel on 05/04/2017 20:22:28
Post by: PhysBang on 05/04/2017 20:39:10
They just have to pass by each other. This happens every day when people pass each other in the street.It is easy to make a twin "paradox" scenario without acceleration. One merely needs to imagine the scenario with clocks that have constant velocity that merely pass each other at the relevant points and happen to be synchronized when they pass each other
I don't understand. How can two clocks moving at constant velocity wrt each other meet at two separate points in space-time?
In the no acceleration twin scenario, one clock, A, sits in space and another clock, B, passes very closely by. When A and B are very close to each other, they read the same. Then B goes out and at some point, another clock, C, going the opposite direction passes by B. At the point where B and C are very close to each other, they read the same. Then, at some point, A and C pass very close to each other.
We can work out all the details for these clocks and get the same twin scenario without any object undergoing acceleration.
Post by: PhysBang on 05/04/2017 20:41:07
All clocks must be synchronized in the same "rest" frame before the start for any SR experiment to be validate...This isn't an experiment, though similar experiments have been done. In this case, it is enough to imagine that all clocks are the same type of physical system that, if they were at rest next to each other, would remain synchronized. There is nothing in SR that demands that all clocks must be actually synchronized at some point for comparisons to be appropriate.
Post by: CPT ArkAngel on 05/04/2017 21:06:35
Post by: PhysBang on 05/04/2017 21:52:33
Even if you use relative time instead of proper time, acceleration (and deceleration) is still the key. Imagine A and B having a relative speed of V1 and being synchronized. At a later time V1 change to V2. How do you know which clock, A or B, had its time rate changed? The one that was subjected to acceleration.Trivially, any change in velocity is an acceleration. But it's the velocity that plays a role in the equations, not acceleration. And one can always reproduce any scenario with acceleration with one involving multiple clocks that pass each other, so no acceleration involved at all.
Post by: geordief on 05/04/2017 22:40:18
If the maths are not too complicated (actually even simple maths can defeat me) would you have a (link to a ) mathematical description of your scenario?
They just have to pass by each other. This happens every day when people pass each other in the street.
In the no acceleration twin scenario, one clock, A, sits in space and another clock, B, passes very closely by. When A and B are very close to each other, they read the same. Then B goes out and at some point, another clock, C, going the opposite direction passes by B. At the point where B and C are very close to each other, they read the same. Then, at some point, A and C pass very close to each other.
We can work out all the details for these clocks and get the same twin scenario without any object undergoing acceleration.
Is it not difficult to asses when B and C are "very close to each other," ? Would distance(from A) and velocity wrt A make that very difficult to assess physically?
Post by: PhysBang on 05/04/2017 22:54:25
Post by: CPT ArkAngel on 05/04/2017 22:59:38
We don't agree on semantic or so it seems.
My point is there is no explanation of how the time rate changes beyond the application to Lorentz equations of a constant communication speed and no preferred frame. There is no explanation on how the proper time may change. SR is more about E=MC2. If you want to give an explanation, you must express all the constraints in which it is valid. The limits form a closed circle and the only exit points to "acceleration".
Post by: yor_on on 06/04/2017 08:52:48
But if one think of it solely in terms of accelerations I think it becomes even weirder :)
=
Hmm, maybe not the best of arguments thinking of the equivalence principle in which gravity is 'indistinguishable' from a acceleration, ah well :) that means that they are 'constantly uniformly accelerating' in terms of GR. Then again, a 'frame of reference' does not only involve accelerations but also uniform motions, aka speeds. And different speeds are different frames of reference.
( A frame of reference is a set of coordinates that can be used to determine positions and velocities of objects in that frame; different frames of reference move relative to one another. ) or this Special relativity (http://physics.bu.edu/py106/notes/Relativity.html)
Post by: yor_on on 06/04/2017 10:26:49
Post by: PhysBang on 06/04/2017 20:11:56
There is accelerations involved in any cases. The Maths doesn't need it because the choice of postulate is right in the SR circumstances, though it is just an approximation in reality. The acceleration is hidden by the choice you make. This is willful blindness.If you would bother reading any of the links here or a decent introductory textbook on the subject, you would see that the accelerations play no role. If you still think otherwise, please go through the scenario and show, with some numbers, exactly where the accelerations are.
I'm sorry that you are wrong about this, but you really should let it go.
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We don't agree on semantic or so it seems.Sure, you keep saying things that are demonstrably false about SR, someone shows that your statements are false, then you say another demonstrably false thing or even the same thing again. You don't seem to want to agree on basic definitions of truth or falsity as they relate to the text of On the Electrodynamics of Moving Bodies, so there is not much hope that you can come to an agreement with anyone about SR.
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My point is there is no explanation of how the time rate changes beyond the application to Lorentz equations of a constant communication speed and no preferred frame.That's pretty much all of SR. You also go on to add that there is some paradox that is not resolved and this is false.
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There is no explanation on how the proper time may change. SR is more about E=MC2.The energy equivalence equation is derived from SR. Again, you seem to disagree with the basic definitions of truth and false with regards to the actual text of the relevant works.
Post by: CPT ArkAngel on 06/04/2017 21:04:50
An astronaut from planet A encounters an astronaut from planet B. They lost track of their planets and trajectories. When they met, they had an initial constant velocity. How can they know what is the difference in their proper time? They can't... To know this, they must meet in the same frame and synchronize their clocks, and only from then on they can know about their proper times. This is clear that acceleration has a key role, even though you can use the different speeds along each path to calculate a late disagreement in time. I disagree on what you define as a proof! I understand what you say but I think you don't fully understand the larger implications of SR. Einstein himself said that it is the acceleration which is important and the key to understand SR further. He said that acceleration explains the twin paradox!!! I will let you find this by yourself...
in your example without acceleration: http://www.phys.vt.edu/~jhs/faq/twins.html
Notes "According to Unprime, Prime is moving along (and always has been) at the speed v" and "Doubleprime has always been moving this way"
This proves my point!
Post by: PhysBang on 06/04/2017 21:43:58
You are wrong! I understand very well everything you pointed out. But you don't understand my point of view. I know that the SR equations doesn't need acceleration to be right! But SR is incomplete.Dude, we can read what you wrote.
You wrote, "Within special relativity, it is a paradox. All explanations within the frame of SR alone are wrong because there is no key to differentiate the twins."
Now, you are wrong. That's OK. Just don't double down on it.
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An astronaut from planet A encounters an astronaut from planet B. They lost track of their planets and trajectories. When they met, they had an initial constant velocity. How can they know what is the difference in their proper time? They can't... To know this, they must meet in the same frame and synchronize their clocks, and only from then on they can know about their proper times.That's ridiculous. Each one knows their own "proper time", since that is the time of a clock co-moving with them. If each one is carrying some system that the other knows the rate of (i.e., a clock), then they can each use their view of that that to establish time dilation. The thing about SR is that is gives an objective standard that anyone in any frame can use.
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I disagree on what you define as a proof!Of course, if you are going to freely disregard truth and falsity, then you are going to disregard proof.
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I understand what you say but I think you don't fully understand the larger implications of SR.I agree that I don't understand the implication of what you consider SR.
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Einstein himself said that it is the acceleration which is important and the key to understand SR further. He said that acceleration explains the twin paradox!!!"Citation missing"
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in your example without acceleration: http://www.phys.vt.edu/~jhs/faq/twins.htmlAgain, you are using "prove" in a way that doesn't match the usage that I expect. In that example, all the differing results of the twin "paradox" are there, but no acceleration has been used. Yet the same SR resolution is available.
Notes "According to Unprime, Prime is moving along (and always has been]) at the speed v" and "Doubleprime has always been moving this way"
This proves my point!
Post by: CPT ArkAngel on 06/04/2017 21:53:13
Post by: PhysBang on 06/04/2017 22:13:41
I proved my point. I think you can understand but you just don't want to admit it... If not, think again and look for "Einstein and the twin paradox". There are many good articles...Yes, and like the one linked to above and like the YouTube video, the good articles establish that there is no paradox and that SR handles the scenario quite well. I'm not sure what you imagine your point is, but given that you have abandoned the English language, I'm betting that it doesn't really matter.
Post by: CPT ArkAngel on 06/04/2017 22:52:15
"Prime is moving along (and always has been) at the speed v" is a statement of unknown, unreality and incompleteness.
The fact that you can compare proper time and calculate it involve a necessary acceleration. The subjects must be in the same frame at some point and at least one must have an acceleration... The fact that they are twins implies acceleration... ;)
Post by: yor_on on 07/04/2017 14:50:29
Post by: PhysBang on 07/04/2017 15:52:41
You just proved another of my points again!Since your points center on the idea that the twin "paradox" is a real paradox and that there is no way in SR to habdle the paradox, your points have been thoroughly refuted.
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And English is not my first language by the way.My apologies.
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You are accusing me of not reading your links but you didn't read carefully my arguments. You just rely on alleged experts.Well, no, since in the past I've actually worked through the twin scenario.
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Read about Einstein point of view of the twin paradox after 1914. Before that he never truly expressed himself on the subject other than saying he didn't see any problem with it. But he changed his mind.Einstein later developed a theory that treated the geometry of spacetime with more precision, of course he would update his approach. Still, please show the citation for your claim.
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There is a very important distinction between proper time and relative time. Relative time is a communication time while proper time is the actual time in a specific frame.The lesson of relativity is that one can always determine proper time from a determination of relative time and other factors and one can always tell from relative speed what proper time will be.
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"Prime is moving along (and always has been) at the speed v" is a statement of unknown, unreality and incompleteness.Says you. The scenario is an idealized one and, since we are using SR, giving relative speed gives proper time.
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The fact that you can compare proper time and calculate it involve a necessary acceleration.That's a wonderful theory you have, but it isn't SR.
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The subjects must be in the same frame at some point and at least one must have an acceleration... The fact that they are twins implies acceleration... ;)OK, so you are just ignoring the scenario where there were no twins, just clocks, and the numbers work out anyway.
Post by: guest4091 on 07/04/2017 17:39:41
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A non accelerating frame is chosen as the observer. But why? This is the key to understand the problem. The problem is swept under the carpet from the beginning. This is a reduction to Lorentz equations.SR was developed within the range of constant linear (inertial/free from accelerations/unchanging) motion, because it's free from the complexities of gravity.
I looked under the carpet and there's nothing there! It's unfortunate you spent 30 yrs with the misguided role of acceleration. Acceleration is a means to an end. Once you reach target speed, clocks continue to lose time. If you use a ladder to climb a tree and break a leg falling to the ground, the ladder didn't cause the injury.
Experimental evidence.
The clock hypothesis states that the tick rate of a clock when measured in an inertial frame depends only upon its velocity (speed) relative to that frame, and is independent of its acceleration or higher derivatives.
Bailey et al., “Measurements of relativistic time dilation for positive and negative muons in a circular orbit,” Nature 268 (July 28, 1977) pg 301. Bailey et al., Nuclear Physics B 150 pg 1–79 (1979).
They stored muons in a storage ring and measured their lifetime. When combined with measurements of the muon lifetime at rest this becomes a highly relativistic twin scenario (v ~0.9994 c), for which the stored muons are the traveling twin and return to a given point in the lab every few microseconds. While being stored in the ring they were subject to a proper acceleration of approximately 10^18 g (1 g = 9.8 m/s2). The observed agreement between the lifetime of the stored muons with that of muons with the same energy moving inertially confirms the clock hypothesis for accelerations of that magnitude.
1. Why do moving clocks run slow?
Fig.1 is a light clock moving to the right along the popular x axis at some fraction of light speed. It consists of an emitter/detector on the bottom with a mirror m at the top 1 unit distance. A second is defined as k cycles of a photon moving to m and returning. The light paths (blue) are shown for three speeds .3, .6, and .8. Since light speed is constant and independent of the source (it does not acquire the speed of the source), the photon direction can only rotate to maintain its position relative to the mirror. Geometrically the light vector is resolved into an x component which compensates for the clock motion and a p (perpendicular) component which becomes the working part of the clock, i.e. light speed is <c inside the moving clock. Compared to R the clock at rest, the cycle time is .95 sec at .3c, .8 second at .6c, and .6 sec at .8c. This motion induced phenomenon is not restricted to clocks, but any process involving energy transfer via em forms. Observer biology is chemistry, therefore they are not aware of the slow running clock. There is no mystery with relative speed. You have to aim ahead of a moving target in order to hit it. In terms of energy, at increasing speeds, light spends more energy chasing the moving clock and less in the clock function.
Fig.2 is a 'hermann' aka 'Minkowski spacetime diagram', but I don't care for verboseness. The vertical axis is 'time' in terms of light speed, light (seconds, years, ...). Einstein originally formulated his theory using spatial dimensions and time. Minkowski generalized these variables into a 4D theory. Despite the abstraction, his ct notation is beneficial since the graph now plots object motion vt to light motion ct, a speed profile. It's also necessary scaling for a usable graph since the distance unit ls is 30 million times the time unit sec. If vt/ct = 1, then light speed profile is a 45 deg line. The selected speeds A and B are straight lines, and thus constant. Our interest now is the lost time (red) for each clock when compared to the R clock.
Fig.3 shows a 3rd clock B2 moving at 0, getting a clock reading while passing B1 and passing A at 1.33 R-time. Rotating the graph 180 deg, the lost time for the rejoining portion is noted. Lost time for A is .27 sec vs .40 sec for B. B is younger than A.
If the B1 speed profile increases more time is lost. If the B1 speed profile is less than A, less time is lost compared to A but the B2 profile will lose more. Rotate the graph 180 deg. and interchange B1 and B2 to verify that the order of short path-long path makes no difference.
The least amount of lost time occurs for the A profile, and any profile that differs loses more time. The blue rectangle represents light speed constraints, i.e. a stopped clock.
time dilation 170406-3.gif (5.09 kB . 372x432 - viewed 4906 times) time dilation 170406-3.gif (5.09 kB . 372x432 - viewed 4906 times) time dilation 170406-3.gif (5.09 kB . 372x432 - viewed 4906 times)Post by: CPT ArkAngel on 07/04/2017 21:21:08
Case 1.
There are only the two twins in the universe and one is going away and come back, the only difference is acceleration and deceleration. The twin subjected to accelerations is now younger.
Case 2.
Astronaut A encounters astronaut B and they have a relative speed V. Each of them has the same relative time rate for the other, it is reciprocal within SR. But in reality, it cannot be true. There is something missing because it contradicts case 1. You need external frames to explain otherwise but there is none in case 1, so you limit your cases to non accelerating frames.
After GR, we understand that SR is never true because as soon as one moves, the gravitational potential changes. So SR is not a perfect solution but just an approximation of reality. As certainly GR is...
Post by: CPT ArkAngel on 07/04/2017 21:40:13
Post by: PhysBang on 07/04/2017 21:49:46
If you understand my arguments, you should understand there is not a single of your arguments disproving mines, even though the mechanics you explained is right. Within SR it is true, but when you scrutinize the implications, you find it is impossible.As far as I can tell, you do not have an argument.
You wrote, "All explanations within the frame of SR alone are wrong because there is no key to differentiate the twins." That's simply false, as many citations above have established.
You wrote, "The change is associated to the twin in the rocket by a purely arbitrary a priori choice." That is also false, because even the twin in the rocket knows that she changed direction.
You wrote, "There are no explanations concerning acceleration and inertia in SR." This is also false, because every textbook that deals with SR covers acceleration.
You wrote, "In Special Relativity, the acceleration is entirely reciprocal for both twins." That is false because, again, if we are to include acceleration, the acceleration for one twin is different because she changes direction according to her own initial trajectory.
You wrote, "SR is not just an add on to Newtonian mechanics, it is the start of a new theory." And while it is true that SR is in some sense a new theory, it begins with the assumption of Newtonian mechanics.
You wrote, "With SR alone, you cannot really explain why the accelerating frame will have a slower time." And there are various demonstrations that this claim is false.
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Case 1.Sure, and this will be the case using SR alone. Which was the point of developing the "paradox" in the first place.
There are only the two twins in the universe and one is going away and come back, the only difference is acceleration and deceleration. The twin subjected to accelerations is now younger.
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Case 2.What is "in reality"? Are you just another run-of-the-mill crank SR denier? If we accept SR, then, "in reality" requires us to describe motion relative to some system of coordinates. So A is time dilated relative to B in a reference frame co-moving with B and B is time dilated relative to A in a reference frame co-moving with A. There is no perspective outside of a reference frame.
Astronaut A encounters astronaut B and they have a relative speed V. Each of them has the same relative time rate for the other, it is reciprocal within SR. But in reality, it cannot be true.
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There is something missing because it contradicts case 1. You need external frames to explain otherwise but there is none in case 1, so you limit your cases to non accelerating frames.Only your idea of relativity, not SR, has any contradiction here. This is why we should continue to use SR and reject your idea of relativity.
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After GR, we understand that SR is never true because as soon as one moves, the gravitational potential changes. So SR is not a perfect solution but just an approximation of reality. As certainly GR is...GR is entirely irrelevant to the question of what SR actually says.
Post by: PhysBang on 07/04/2017 21:50:28
The key to that is in case 1, the twin going away must push the other twin to move! So no one will age slower than the other... If you don't consider any net energy transferred or lost by pushing, which is in fact the key...That's a nice fantasy physics, but it's not SR. Or GR.
Post by: CPT ArkAngel on 07/04/2017 22:58:46
There is no such a thing as a uniform motion in the real universe and no two elements can be in the same frame.
You are quick to judge without any proof. You constantly use unfounded attack trying to discredit others. Though, I usually agree with you, you have a narrow mind. And this is not unfounded.
You are making extensions by fantasy, not me, by interpreting and wrongly adding things to what I've said.
I don't play to "King of the Hill"...
Post by: PmbPhy on 08/04/2017 05:08:08
is the twin paradox real ? is there any experiment of two twins one traveling at high speed and one on earth at rest aging differently ?Yes. Its real. While some people may imply that it hasn't actually been observed in real life we know from the theory of relativity and the confirmation of that theory, especially concerning time dilation, that it is indeed real.
Never take seriously statements by those who imply a particular thing has never been observed to mean its not "real". That's like assuming that because nobody has ever observed a hippopotamus walk around Boston's city hall to meant that one can't theoretically do so.
In the present case its an observed fact that time dilation is real, i.e. a fact of life. That fact quite literally means that the win paradox is real. Those who claim otherwise don't know what they're talking about in that their philosophical grounding is totally false and without any merit. Since its pretty much a fact of life that others will post some nonsense claiming otherwise I refuse to respond to such ignorant responses.
BTW - that's not meant as an insult but as a scientific fact of life.
Post by: PhysBang on 08/04/2017 14:03:36
Yes, time dilation is real, but that doesn't mean that there is some sort of paradox in existence! The term "paradox" is used to indicate that this twin scenario means that there is some sort of problem with SR. There is not.is the twin paradox real ? is there any experiment of two twins one traveling at high speed and one on earth at rest aging differently ?Yes. Its real. While some people may imply that it hasn't actually been observed in real life we know from the theory of relativity and the confirmation of that theory, especially concerning time dilation, that it is indeed real.
Never take seriously statements by those who imply a particular thing has never been observed to mean its not "real". That's like assuming that because nobody has ever observed a hippopotamus walk around Boston's city hall to meant that one can't theoretically do so.
In the present case its an observed fact that time dilation is real, i.e. a fact of life. That fact quite literally means that the win paradox is real. Those who claim otherwise don't know what they're talking about in that their philosophical grounding is totally false and without any merit. Since its pretty much a fact of life that others will post some nonsense claiming otherwise I refuse to respond to such ignorant responses.
BTW - that's not meant as an insult but as a scientific fact of life.
Post by: PhysBang on 08/04/2017 14:06:08
There is no such a thing as a uniform motion in the real universe and no two elements can be in the same frame.A frame of reference is, by definition, an idealization. And by that idealization, all objects are in every well-formed frame of reference.
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You are quick to judge without any proof. You constantly use unfounded attack trying to discredit others. Though, I usually agree with you, you have a narrow mind. And this is not unfounded.I try to narrow my mind to what is justified by the evidence and, in the case of where a text is involved, the actual text. I'm sorry that you don't think that quoting what you actually wrote is good evidence about your actual positions and I'm sorry that you don't think that Einstein's paper on SR is good evidence about the content of SR.
Post by: guest4091 on 08/04/2017 16:47:56
From the 1905 paper, par 4:
“From this there ensues the following peculiar consequence. If at the points A and B of K there are stationary clocks which, viewed in the stationary system, are synchronous; and if the clock at A is moved with the velocity v along the line AB to B, then on its arrival at B the two clocks no longer synchronize, but the clock moved from A to B lags behind the other which has remained at B by (up to magnitudes of fourth and higher order), t being the time occupied in the journey from A to B.
It is at once apparent that this result still holds good if the clock moves from A to B in any polygonal line, and also when the points A and B coincide.
If we assume that the result proved for a polygonal line is also valid for a continuously curved line, we arrive at this result: If one of two synchronous clocks at A is moved in a closed curve with constant velocity until it returns to A, the journey lasting t seconds, then by the clock which has remained at rest the travelled clock on its arrival at A will be second slow.”
The author A.E. has previously described clock synchronization, and now demonstrates that it only applies to that frame at its current speed. If one of the clocks moves relative to that frame, its rate changes and synchronization is lost.
Note he doesn’t concern himself with the means of acceleration to v, since it is not a relevant factor, and acceleration can be approximated with a polygonal line.
It seems your chain of causality is faulty,
Post by: yor_on on 08/04/2017 18:13:08
Astronaut A encounters astronaut B and they have a relative speed V. Each of them has the same relative time rate for the other, it is reciprocal within SR. But in reality, it cannot be true. There is something missing "
I know, that one hurt me too until I realized that all 'time dilation's' are the same. The 'twin experiment' is just a time dilation taking into the extreme. It's a proof of a concept CPT, and as such you will need a mathematical proof to refute it.
Post by: CPT ArkAngel on 09/04/2017 00:25:34
Read Einstein on the twin paradox... Later conclusions are very different after he looked at it in a deeper way. Before that, he thought about it as a measuring experiment, not as a real explanation of proper time dilation.
Post by: PhysBang on 09/04/2017 00:37:42
Time dilation is real, I've never expressed the contrary. But the SR explanation of the twin paradox is ultimately wrong or at least flawed due to incompleteness, even though in reality the twin accelerating will be truly younger if you make abstraction of gravity.Sure. You believe this despite all the demonstrations that the situation is explained exactly in SR. You have this belief about gravity even though you haven't actually worked through the effect that gravity supposedly has on this scenario.
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Read Einstein on the twin paradox... Later conclusions are very different after he looked at it in a deeper way. Before that, he thought about it as a measuring experiment, not as a real explanation of proper time dilation.You keep saying this, but you have no citation. Even if your citation is not purely a fabrication, Einstein often got some of the implications of relativity incorrect. So we need to see his actual statement and his reasoning to compare it to the actual mathematical reasoning of SR presented in the multiple citations above.
Post by: CPT ArkAngel on 09/04/2017 00:54:46
You can search by yourself, there are many references. What I am saying is not new. It is understood by the best theorists.
Post by: guest4091 on 09/04/2017 19:52:09
I have read later publications by Einstein, Max Borne, and others, and NEVER saw the math formulas include acceleration as a factor. Maybe you had a vision.
Post by: PmbPhy on 10/04/2017 09:26:18
If you understand my arguments, you should understand there is not a single of your arguments disproving mines, even though the mechanics you explained is right. Within SR it is true, but when you scrutinize the implications, you find it is impossible.Your analysis is incorrect, i.e.
Case 1.This part is correct.
There are only the two twins in the universe and one is going away and come back, the only difference is acceleration and deceleration. The twin subjected to accelerations is now younger.
Case 2.This part is incorrect. In fact it tells me that your understanding of the twin paradox is quite flawed. When the twins have the same acceleration relative to an inertial frame is not a twin paradox. Its only a twin paradox, as the term is defined in the literature, when one twin is at rest and the other accelerates away from a point in space and later returns to the same event, i.e. when one of the worldlines is a straight line in spacetime and he other worldline is curved and both start and end at the same place in space. Therefore what you describe here is not a twin paradox.
Astronaut A encounters astronaut B and they have a relative speed V. Each of them has the same relative time rate for the other, it is reciprocal within SR. But in reality, it cannot be true.
After GR, we understand that SR is never true because as soon as one moves, the gravitational potential changes.This is incorrect as well. In fact this part of your response is a common mistake, i.e. that SR doesn't apply to accelerating objects in an inertial frame.
GR doesnot apply to accelerating body's in an inertial frames but only when one is analyzing events from a frame at rest in an accelerating frame. SR only applies to inertial frames.
So SR is not a perfect solution but just an approximation of reality. As certainly GR is...Incorrect as well for reasons stated above and does provide a perfect solution.
Post by: CPT ArkAngel on 10/04/2017 21:42:07
My end point is that there is a more complete explanation to find for time dilation. The quest for a unified theory passes by a single explanation for time dilation. People tend to stick too much within SR and forget that it is only true within strong limitations. Some of them are limitations that the real universe doesn't have. If you disagree with that, this is where my point of view is irreconcilable with yours. If you understand this point of view, you can understand all my statements, if not, you just can't! The other thing to understand is that the choice of validation of SR with "inertial frame" only is an apriori choice. This choice produces the asymmetry of the twin paradox. This is consistent with Pete explanations and it is what I meant by emphasizing on the symmetry of astronaut A meeting astronaut B having a constant relative speed. Nothing more.
Post by: PhysBang on 11/04/2017 00:21:42
SR is a consistent theory according to its limitations and postulates. I agree. There is no reason for me to argue beyond that in this discussion. I am sure some readers understood what I meant. There is no point of arguing when someone continuously misinterpret your arguments by making imaginary extensions to them.Dude, why write things that are so obviously untrue.
I'll repeat...
You wrote, "All explanations within the frame of SR alone are wrong because there is no key to differentiate the twins." That's simply false, as many citations above have established.
You wrote, "The change is associated to the twin in the rocket by a purely arbitrary a priori choice." That is also false, because even the twin in the rocket knows that she changed direction.
You wrote, "There are no explanations concerning acceleration and inertia in SR." This is also false, because every textbook that deals with SR covers acceleration.
You wrote, "In Special Relativity, the acceleration is entirely reciprocal for both twins." That is false because, again, if we are to include acceleration, the acceleration for one twin is different because she changes direction according to her own initial trajectory.
You wrote, "SR is not just an add on to Newtonian mechanics, it is the start of a new theory." And while it is true that SR is in some sense a new theory, it begins with the assumption of Newtonian mechanics.
You wrote, "With SR alone, you cannot really explain why the accelerating frame will have a slower time." And there are various demonstrations that this claim is false.
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My end point is that there is a more complete explanation to find for time dilation. The quest for a unified theory passes by a single explanation for time dilation. People tend to stick too much within SR and forget that it is only true within strong limitations.But the point of trying to claim that there is a twin "paradox" is that there is some problem when we consider SR only. This is essential to understanding the scenario.You not only refuse to consider SR alone, you refuse to actually consider SR.
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The other thing to understand is that the choice of validation of SR with "inertial frame" only is an apriori choice. This choice produces the asymmetry of the twin paradox.But the choice isn't arbitrary: we are not free to consider either twin to be not moving, one is moving by definition and SR has an exact way to represent this.
Post by: hamdani yusuf on 17/04/2017 04:26:58
The 'twins' explanation #14 using the axis of simultaneity is extraneous fluff. That convention only assigns times to events observed locally, since a system of clocks would be logistically impossible for astronomical distances. The distant events result from the behavior of the remote clock and aren't altered by the simultaneity convention.Your diagram shows that A and B send and receive the same number of signal, which would mean that in the end they have the same age.
Using the notation (x, t) and fig.2,
A records B leaving (0, 0) a .6c, and returning (0, 10).
B records A leaving (0, 0) at .6c, and returning (0,t= 8).
Does the accumulated time differ?
A experienced 10 flashes, all observed by B.
B experienced 8 flashes, all observed by A.
B is younger than A.
Within the closed course, there are no missing events.
The reversal data is irrelevant.
The perceived doppler shifts for the diverging vs converging segments is irrelevant.
The instantaneous reversal by B is irrelevant, since it's duration is zero time, i.e. equivalent to "it never happened", thus not having any catastrophic results. The discontinuity is equivalent to two B frames participating in the experiment.
There is no acceleration/*deceleration involved, just inertial motion.
* Yes, there is such a word, for those too lazy to use a dictionary.
Post by: hamdani yusuf on 17/04/2017 04:45:27
What do you think about this explanation?Imagine if along rocket trajectory we install synchronized clock at every 1 light second. The rocket also bring a clock which is already synchronized before the journey.
When the twin in rocket is passing each clock on the way, what time do they read, and what time shown by his own clock for each passing?
Post by: yor_on on 17/04/2017 13:50:03
Post by: hamdani yusuf on 17/04/2017 14:21:54
as a pure byside Yusuf (presuming this your forename, correct me if I'm wrong:) synchronizing 'clocks' is a possibility, but it won't tell us a 'universal time'. Just that those two clocks share a same 'frame of reference' at some original point of place. To define clocks at for example different elevation as 'synchronized' is a no no the way I think about it. Even though one could set them to a same time, they would start to deviate after a while. And so it is with relative speeds too. No way to find a absolute time for anything, just correlations in time and space.You can call me Dani. Just Dani Okay?
I meant six clocks in the same frame of reference, i.e. clock on earth, clock at 1, 2, 3, 4, and 5 light seconds away from earth. They are stationary relative to each other, so after synchronized, they should tick at the same rate.
- When the rocket twin start moving, his clock should show the same value as the earth clock, which is 0 second.
- What would his clock show when he is passing the clock at 1 light second location?
- What would his clock show when he is passing the clock at 2 light second location?
- What would his clock show when he is passing the clock at 3 light second location?
- What would his clock show when he is passing the clock at 4 light second location?
- What would his clock show when he is passing the clock at 5 light second location?
The rocket then turn around. Is there something interesting happens to his clock?
- What would his clock show when he is passing the clock at 4 light second location?
- What would his clock show when he is passing the clock at 3 light second location?
- What would his clock show when he is passing the clock at 2 light second location?
- What would his clock show when he is passing the clock at 1 light second location?
- What would his clock show when he is coming back to earth?
Post by: yor_on on 17/04/2017 16:26:07
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Eh Dani, using 'velocity' as I'm thinking of you using both a speed and a direction for passing those other clocks :) Otherwise 'speed' should be the correct expression for it, furthermore I'm assuming acceleration, but maybe you're thinking of it in form of the acceleration already done so that the ship just 'coast' (uniform motion) past those clocks? If you want to prove your thoughts not using a acceleration you should eliminate Earth and just use the clocks,, a rockets uniform motion and 'space', eliminating gravity as far as possible. The way that is done normally is using 'test particles' as I understands it.
Post by: hamdani yusuf on 17/04/2017 16:34:36
To make it simpler, we can replace earth with a free floating space ship.
Post by: yor_on on 17/04/2017 16:38:28
Post by: bandtank on 17/04/2017 19:02:29
CPT - if you can provide a reference, you should do so. Multiple links have been posted with credible information to refute your position, but you've only expressed your opinions without any factual support. I tried looking for the statements you suggested I would easily find all over the internet and I found exactly zero that adopted or supported your position. As my man big willy said, put up or shut up.
Post by: yor_on on 17/04/2017 19:06:33
The best example I know of, and the simplest, is 'light clocks' moving at different uniform motions. The explanation given to why we then see them 'tick' differently depending on relative motion is due to the geometry for the light bouncing between the mirrors. the 'distance' it has to travel between those mirrors from the far away observers point of view. You sitting on one shouldn't experience this as you ideally/theoretically then would belong to the same 'frame of reference'. And that follows from the fact that all uniform motions, locally described, are the same. You can't differ between them locally, only when comparing your 'frame of reference' to someone else are uniform motions existent.
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I better add that even though it is the simplest it's just a analogy. It's not totally satisfactorily to me as if it was the geometry alone that defined it those mirrors rotated another direction would present us with a red shift. But geometrically I think it would hold then too as the distance traveled by this '[ bouncing light ] /clock' should be the same, as defined from the far away observers observation. for the local observer there is no 'motion' existent, unless he defines some stellar object as being 'still', which requires him to prove that it is. In a black box which is a crucial thought evidence/experiment relative motion doesn't exist, unless you mix in gravity tidal forces etc, which then becomes about GR, not SR.
What that means is that if you according to the far away observer was seen 'moving uniformly' at some speed, relative that observer, it still wouldn't red respectively blue shift any light due to a speed, locally. And you can use Earth to prove that relative speeds (uniform motions) don't blue respectively red shifts the suns light, or any light you use inside your room. In this case we then define the solarsystem as being in a approximately same frame of reference relative each other.
But I have to admit that I don't find it perfect, especially if you rotate that lightclock.
Post by: Yahya on 17/04/2017 19:20:04
if there is time dilation traveling in space with 0.6c m/s and I have a digital watch , what will happen exactly (to my watch) that will make it delay when compared to an on-earth watch? does that mean it ticks slower? if they both reads 4 pm on earth and they differs when I return , what happened exactly ? what is the actual physical process ? I see time as something that is controlled and not something can control the "watch" and make it move slower. if the watch moves slower does that mean other things on the spaceship move slower as well? then it is a matter of speed and not time.
Post by: yor_on on 17/04/2017 19:40:58
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The twin experiment is a setup to define whether time dilation's are 'for real' or just a illusion. And they are real, but you need that twin experiment to prove it. And locally defined time never change as long as we can define you to represent a same frame of reference. That's also why the wrist watch is a popular definition for it.
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Let me put it this way. People may not realize it but we all, well most of us, instinctively feel that the universe is 'one thing'. That's why we needed that twin experiment, and also why some of us can't accept it. We have a presumption coming from what we experience and in that presumption clocks either tick the same, or they don't. And so we miss that what we go out from is this instinctive response to reality, So the idea of a 'absolute time' builds on a presumption of what a universe is. Einstein really introduced a paradigm change, and even himself couldn't accept some conclusions from it, as 'spooky action at a distance/entanglements'. He too shared this instinctive response of a unified universe, even though he defined time as an 'illusion'. Myself I don't see it that way. To me ones life span is the same and ones wrist watch never lies. The real enigma, to me, is how to join it all into one 'universe'.
That is to say, from my point of view local time is a 'absolute time'. It's your 'proper time' and the one you use from birth to death.
One more thing. Local time is what builds a repeatable experiment. And a repeatable experiment is what physics rests on, and the real test is if it works. It does, otherwise I wouldn't be able to write this.
Post by: Yahya on 17/04/2017 19:49:54
I have a watch classical or digital, the tick of the classical moves by speed one revolution per minute , what would make it reads with delay if its speed did not change? for the digital one the same question.
Post by: yor_on on 17/04/2017 20:05:22
Post by: hamdani yusuf on 26/04/2017 07:15:09
I'll try to answer those question based on explanation in the video.as a pure byside Yusuf (presuming this your forename, correct me if I'm wrong:) synchronizing 'clocks' is a possibility, but it won't tell us a 'universal time'. Just that those two clocks share a same 'frame of reference' at some original point of place. To define clocks at for example different elevation as 'synchronized' is a no no the way I think about it. Even though one could set them to a same time, they would start to deviate after a while. And so it is with relative speeds too. No way to find a absolute time for anything, just correlations in time and space.You can call me Dani. Just Dani Okay?
I meant six clocks in the same frame of reference, i.e. clock on earth, clock at 1, 2, 3, 4, and 5 light seconds away from earth. They are stationary relative to each other, so after synchronized, they should tick at the same rate.
- When the rocket twin start moving, his clock should show the same value as the earth clock, which is 0 second.
- What would his clock show when he is passing the clock at 1 light second location?
- What would his clock show when he is passing the clock at 2 light second location?
- What would his clock show when he is passing the clock at 3 light second location?
- What would his clock show when he is passing the clock at 4 light second location?
- What would his clock show when he is passing the clock at 5 light second location?
The rocket then turn around. Is there something interesting happens to his clock?
- What would his clock show when he is passing the clock at 4 light second location?
- What would his clock show when he is passing the clock at 3 light second location?
- What would his clock show when he is passing the clock at 2 light second location?
- What would his clock show when he is passing the clock at 1 light second location?
- What would his clock show when he is coming back to earth?
According to earth's (and stationary clocks) reference frame:
when the journey start, clock on earth as well as in the rocket show 0 sec.
when the rocket is passing the first clock, it shows 1 sec, while rocket clock shows 0.8 sec.
when the rocket is passing the 2nd clock, it shows 2 sec, while rocket clock shows 1.6 sec.
when the rocket is passing the 3rd clock, it shows 3 sec, while rocket clock shows 2.4 sec.
when the rocket is passing the 4th clock, it shows 4 sec, while rocket clock shows 3.2 sec.
when the rocket is passing the 5th clock, it shows 5 sec, while rocket clock shows 4 sec.
when the rocket is passing the 4th clock, it shows 6 sec, while rocket clock shows 4.8 sec.
when the rocket is passing the 3rd clock, it shows 7 sec, while rocket clock shows 5.6 sec.
when the rocket is passing the 2nd clock, it shows 8 sec, while rocket clock shows 6.4 sec.
when the rocket is passing the first clock, it shows 9 sec, while rocket clock shows 7.2 sec.
when the rocket arrives on earth, earth clock shows 10 sec, while rocket clock shows 8 sec.
According to rocket's reference frame:
when the journey start, clock on earth as well as in the rocket show 0 sec.
when the rocket is passing the first clock, it shows 0.64 sec, while rocket clock shows 0.8 sec.
when the rocket is passing the 2nd clock, it shows 1.28 sec, while rocket clock shows 1.6 sec.
when the rocket is passing the 3rd clock, it shows 1.92 sec, while rocket clock shows 2.4 sec.
when the rocket is passing the 4th clock, it shows 2.56 sec, while rocket clock shows 3.2 sec.
when the rocket is passing the 5th clock, it shows 3.2 sec, while rocket clock shows 4 sec.
when the rocket is turning around 5th clock, it shows a jump to 6.8 sec, while rocket clock still shows 4 sec.
when the rocket is passing the 4th clock, it shows 7.44 sec, while rocket clock shows 4.8 sec.
when the rocket is passing the 3rd clock, it shows 8.08 sec, while rocket clock shows 5.6 sec.
when the rocket is passing the 2nd clock, it shows 8.72 sec, while rocket clock shows 6.4 sec.
when the rocket is passing the first clock, it shows 9.36 sec, while rocket clock shows 7.2 sec.
when the rocket arrives on earth, earth clock shows 10 sec, while rocket clock shows 8 sec.
Hence at the end of the journey both twins agree that earth twin is older then rocket twin.
Is my understanding above correct?
Post by: hamdani yusuf on 29/04/2017 05:45:25
I'll try to analyze it below.
According to earth's (and stationary clocks) reference frame:
when the journey restart, clock on earth shows 10 sec, while rocket clock shows 8 sec.
when the rocket is passing the first clock, it shows 11 sec, while rocket clock shows 8.8 sec.
when the rocket is passing the 2nd clock, it shows 12 sec, while rocket clock shows 9.6 sec.
when the rocket is passing the 3rd clock, it shows 13 sec, while rocket clock shows 10.4 sec.
when the rocket is passing the 4th clock, it shows 14 sec, while rocket clock shows 11.2 sec.
when the rocket is passing the 5th clock, it shows 15 sec, while rocket clock shows 12 sec.
when the rocket is passing the 4th clock, it shows 16 sec, while rocket clock shows 12.8 sec.
when the rocket is passing the 3rd clock, it shows 17 sec, while rocket clock shows 13.6 sec.
when the rocket is passing the 2nd clock, it shows 18 sec, while rocket clock shows 14.4 sec.
when the rocket is passing the first clock, it shows 19 sec, while rocket clock shows 15.2 sec.
when the rocket arrives on earth, earth clock shows 20 sec, while rocket clock shows 16 sec.
According to rocket's reference frame:
when the journey restart, clock on earth shows 10 sec, while rocket clock shows 8 sec.
when the rocket is passing the first clock, it shows 10.64 sec, while rocket clock shows 8.8 sec.
when the rocket is passing the 2nd clock, it shows 11.28 sec, while rocket clock shows 9.6 sec.
when the rocket is passing the 3rd clock, it shows 11.92 sec, while rocket clock shows 10.4 sec.
when the rocket is passing the 4th clock, it shows 12.56 sec, while rocket clock shows 11.2 sec.
when the rocket is passing the 5th clock, it shows 13.2 sec, while rocket clock shows 12 sec.
when the rocket is turning around 5th clock, it shows a jump to 16.8 sec, while rocket clock still shows 12 sec.
when the rocket is passing the 4th clock, it shows 17.44 sec, while rocket clock shows 12.8 sec.
when the rocket is passing the 3rd clock, it shows 18.08 sec, while rocket clock shows 13.6 sec.
when the rocket is passing the 2nd clock, it shows 18.72 sec, while rocket clock shows 14.4 sec.
when the rocket is passing the first clock, it shows 19.36 sec, while rocket clock shows 15.2 sec.
when the rocket arrives on earth, earth clock shows 20 sec, while rocket clock shows 16 sec.
Post by: hamdani yusuf on 29/04/2017 05:57:14
That's until we realize that to restart the journey, the rocket has to perform acceleration, which in turn should produce time jump.
In the other hand, if the second journey is done in the opposite direction, there would be no acceleration at restarting moment, hence no time jump.
Post by: hamdani yusuf on 06/05/2017 05:12:16
I need to make a correction to the scenario above. In order to make the rocket twin ages at 80% rate, he has to go at 0.6c, hence the time dilation factor would be 0.8.as a pure byside Yusuf (presuming this your forename, correct me if I'm wrong:) synchronizing 'clocks' is a possibility, but it won't tell us a 'universal time'. Just that those two clocks share a same 'frame of reference' at some original point of place. To define clocks at for example different elevation as 'synchronized' is a no no the way I think about it. Even though one could set them to a same time, they would start to deviate after a while. And so it is with relative speeds too. No way to find a absolute time for anything, just correlations in time and space.You can call me Dani. Just Dani Okay?
I meant six clocks in the same frame of reference, i.e. clock on earth, clock at 1, 2, 3, 4, and 5 light seconds away from earth. They are stationary relative to each other, so after synchronized, they should tick at the same rate.
- When the rocket twin start moving, his clock should show the same value as the earth clock, which is 0 second.
- What would his clock show when he is passing the clock at 1 light second location?
- What would his clock show when he is passing the clock at 2 light second location?
- What would his clock show when he is passing the clock at 3 light second location?
- What would his clock show when he is passing the clock at 4 light second location?
- What would his clock show when he is passing the clock at 5 light second location?
The rocket then turn around. Is there something interesting happens to his clock?
- What would his clock show when he is passing the clock at 4 light second location?
- What would his clock show when he is passing the clock at 3 light second location?
- What would his clock show when he is passing the clock at 2 light second location?
- What would his clock show when he is passing the clock at 1 light second location?
- What would his clock show when he is coming back to earth?
So to make the rocket pass the first clock at 1 second, the distance between adjacent clocks should only be 0.6 light seconds. But the argument is still intact.
Post by: Janus on 06/05/2017 06:00:31
What if right after the rocket twin get back to earth, he repeat his journey?Okay
I'll try to analyze it below.
According to earth's (and stationary clocks) reference frame:
when the journey restart, clock on earth shows 10 sec, while rocket clock shows 8 sec.
when the rocket is passing the first clock, it shows 11 sec, while rocket clock shows 8.8 sec.
when the rocket is passing the 2nd clock, it shows 12 sec, while rocket clock shows 9.6 sec.
when the rocket is passing the 3rd clock, it shows 13 sec, while rocket clock shows 10.4 sec.
when the rocket is passing the 4th clock, it shows 14 sec, while rocket clock shows 11.2 sec.
when the rocket is passing the 5th clock, it shows 15 sec, while rocket clock shows 12 sec.
when the rocket is passing the 4th clock, it shows 16 sec, while rocket clock shows 12.8 sec.
when the rocket is passing the 3rd clock, it shows 17 sec, while rocket clock shows 13.6 sec.
when the rocket is passing the 2nd clock, it shows 18 sec, while rocket clock shows 14.4 sec.
when the rocket is passing the first clock, it shows 19 sec, while rocket clock shows 15.2 sec.
when the rocket arrives on earth, earth clock shows 20 sec, while rocket clock shows 16 sec.
According to rocket's reference frame:
when the journey restart, clock on earth shows 10 sec, while rocket clock shows 8 sec.
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when the rocket is passing the first clock, it shows 10.64 sec, while rocket clock shows 8.8 sec.No. it will show 11 sec (just like it does in the Earth frame) . When the rocket leaves Earth at 0.6c this clock, in the rocket frame already reads 10.36 sec (relativity of simultaneity). It will then advance 0.64 sec between in the time it take for it and the rocket to become adjacent.
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when the rocket is passing the 2nd clock, it shows 11.28 sec, while rocket clock shows 9.6 sec.Again no. This clock will read 12 sec when the rocket passes it, it read 10.72 sec when the rocket left Earth.
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when the rocket is passing the 3rd clock, it shows 11.92 sec, while rocket clock shows 10.4 sec.each of these clocks, like the other two will read the same as what the Earth frame reads. According to the rocket each clock, from 1 to 5 were offset in their readings by 0.36 sec from each other with clock 5 the most advanced.
when the rocket is passing the 4th clock, it shows 12.56 sec, while rocket clock shows 11.2 sec.
when the rocket is passing the 5th clock, it shows 13.2 sec, while rocket clock shows 12 sec.
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when the rocket is turning around 5th clock, it shows a jump to 16.8 sec, while rocket clock still shows 12 sec.As long as the rocket performs this turn around while in the immediate vicinity of Clock 5, it will measure no change in clock 5 and this clock will continue to read 15 min. The other clocks will advance with the furthest one doing so the most. Clock 4 will jump to 15.36 sec, clock 3 will advance to 15.72 sec, clock 2 will advance to 16.08 sec, clock 1 will advance to 16.44 sec. and the Earth clock will advance to 16.8 sec.
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when the rocket is passing the 4th clock, it shows 17.44 sec, while rocket clock shows 12.8 sec.4th clock 16 sec, rocket 12.8 sec
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when the rocket is passing the 3rd clock, it shows 18.08 sec, while rocket clock shows 13.6 sec.3rd clock 17 sec rocket 13.6 sec
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when the rocket is passing the 2nd clock, it shows 18.72 sec, while rocket clock shows 14.4 sec.2nd clock 18 sec rocket 14.4 sec
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when the rocket is passing the first clock, it shows 19.36 sec, while rocket clock shows 15.2 sec.1st clock 179 sec rocket 15.2 sec
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when the rocket arrives on earth, earth clock shows 20 sec, while rocket clock shows 16 sec.Correct.
You will never have a situation where the rocket and any clock that it is passing will disagree as to what their respective clocks read as they passed each other.
Post by: hamdani yusuf on 06/05/2017 08:25:11
...Let me summarize your analysis to make it easier to read.
You will never have a situation where the rocket and any clock that it is passing will disagree as to what their respective clocks read as they passed each other.
According to earth's (and stationary clocks) reference frame:
when the journey restart, clock on earth shows 10 sec, while rocket clock shows 8 sec.
when the rocket is passing the first clock, it shows 11 sec, while rocket clock shows 8.8 sec.
when the rocket is passing the 2nd clock, it shows 12 sec, while rocket clock shows 9.6 sec.
when the rocket is passing the 3rd clock, it shows 13 sec, while rocket clock shows 10.4 sec.
when the rocket is passing the 4th clock, it shows 14 sec, while rocket clock shows 11.2 sec.
when the rocket is passing the 5th clock, it shows 15 sec, while rocket clock shows 12 sec.
the rocket then turn around
when the rocket is passing the 4th clock, it shows 16 sec, while rocket clock shows 12.8 sec.
when the rocket is passing the 3rd clock, it shows 17 sec, while rocket clock shows 13.6 sec.
when the rocket is passing the 2nd clock, it shows 18 sec, while rocket clock shows 14.4 sec.
when the rocket is passing the first clock, it shows 19 sec, while rocket clock shows 15.2 sec.
when the rocket arrives on earth, earth clock shows 20 sec, while rocket clock shows 16 sec.
According to rocket's reference frame:
when the journey restart, clock on earth shows 10 sec, while rocket clock shows 8 sec.
when the rocket is passing the first clock, it shows 11 sec, while rocket clock shows 8.8 sec.
when the rocket is passing the 2nd clock, it shows 12 sec, while rocket clock shows 9.6 sec.
when the rocket is passing the 3rd clock, it shows 13 sec, while rocket clock shows 10.4 sec.
when the rocket is passing the 4th clock, it shows 14 sec, while rocket clock shows 11.2 sec.
when the rocket is passing the 5th clock, it shows 15 sec, while rocket clock shows 12 sec.
the earth then turn around
when the rocket is passing the 4th clock, it shows 16 sec, while rocket clock shows 12.8 sec.
when the rocket is passing the 3rd clock, it shows 17 sec, while rocket clock shows 13.6 sec.
when the rocket is passing the 2nd clock, it shows 18 sec, while rocket clock shows 14.4 sec.
when the rocket is passing the first clock, it shows 19 sec, while rocket clock shows 15.2 sec.
when the rocket arrives on earth, earth clock shows 20 sec, while rocket clock shows 16 sec.
Post by: xersanozgen on 07/05/2017 14:35:27
In accordance with reciprocity principle (ın space condition) we may choice any one of twins for the role of relative actor or reference frame. If you confirm the theory SR, If person A has a high speed according to person B, when we suppoze that person A is rest (inertial/reference frame), at this time the person B has same speed according to person A. Both them are exposed to time dilation and their ages will become the same.
Post by: Janus on 07/05/2017 15:58:56
Twins must have same age ABSOLUTELY.Neither is ever "exposed" to time dilation. Time dilation is not an effect that "acts on" objects. Time dilation is the relative comparison of lock rates as measured from frames with relative motion. To use an analogy it is the equivalent of two men standing back to back and each saying that the other man is "behind him". There is no absolute method to determine who is really "behind" who, sine "behind" is a totally subjective direction. Each man is equally correct in his claim that the other man is behind him.
In accordance with reciprocity principle (ın space condition) we may choice any one of twins for the role of relative actor or reference frame. If you confirm the theory SR, If person A has a high speed according to person B, when we suppoze that person A is rest (inertial/reference frame), at this time the person B has same speed according to person A. Both them are exposed to time dilation and their ages will become the same.
Time dilation is also just one of three aspects of SR that needs to be taken into account when analyzing any relativity scenario, the other two being length contraction and the relativity of simultaneity. If you try to analyze any situation by just using time dilation alone you will uncover what appears to be contradictions. This isn't due to any problem in SR but due to an misapplication of it.
The other problem come when acceleration's role in the scenario is neglected. This is not to say that acceleration has an effect on a clock, but acceleration does effect what the accelerating observer will measure. A non-accelerating observer will always measure clocks with a relative motion relative to himself as ticking slower. This is not the case for an accelerating one; He will measure different clocks, even if they have the same relative motion relative to himself to tick at different rates depending on their position from him relative to the acceleration. (He will even measure clocks at rest relative to him as ticking at different rates if they are separated from him along the direction of the acceleration.)
It is break in the reciprocity of the measurements of the observers when one undergoes an acceleration that produces the end result that both observers will agree that one of them aged more than the other if they are separated and then brought back together. To go back to the earlier analogy is is as if the two back to back men are walking apart. As they walk each sees the other as getting further and further behind him. But if now one of the men were to turn around and start walking in the opposite direction he would find that the other man has "moved" to be in front of him. They now both agree as to who is behind who and by how much. The one man turning around in this analogy is the equivalent of one of the twins undergoing an acceleration between the outbound and return legs in the twin paradox scenario.
The whole idea behind the theory of Relativity is that we don't live in Universe that consists of space and time as completely separate things, but in one the consists of space-time, where the "directions" of space vs time are not absolute but depend on the reference frame from which they are being measured. ( just like what is "in front" of you depends on the direction you are facing.)
Post by: xersanozgen on 07/05/2017 16:53:26
Post by: Janus on 07/05/2017 22:10:21
If you know and internalize the principle of reciprocity; you have not any chance.Nonsense statement.
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Whether or not the Earth is assumed as an inertial frame is irrelevant in this case.
To suppose that the Earth is an inertial frame is not scientific.
In those cases were it is relevant the effect can be easily accounted for.
In this case, the total difference between treating the Earth as an inertial frame and accounting for it non-inertial frame status results in a total difference of ~300 nanoseconds, This is insignificant to the 4 sec difference the scenario produces between the Earth and rocket clocks.
Some hand-waving argument that the Earth is not an inertial frame is not a rebuttal of Relativity. In those cases were it is relevant, Relativity can easily deal with it.
Post by: PhysBang on 08/05/2017 13:40:17
In accordance with reciprocity principle (ın space condition) we may choice any one of twins for the role of relative actor or reference frame.Sure, we can do this if we ignore the text of the scenario, where one twin turns around relative to themselves.