The Twin Paradox Made Simple

[sluggo]

#29

Needless to say, notwithstanding the incoherent claims of SR to the contrary, the H-K experiments empirically prove that each of two clocks do NOT record elapsed time which is less than is recorded by the other.  Time dilation is simply not "reciprocal," as SR claims.

 

Reciprocal effects are required in SR, but not in GR. In the original H-K experiment, one clock lost time and the other gained time relative to the surface clock.

 

#25

It is logically impossible for it to be simultaneously true that clock A is slower than clock B AND clock B is slower than clock A.  Both propositions cannot, as a matter of logic,  be "true" in any objective sense.

------

But it is, concerning perceptions, which is what SR describes.

The drawing is worth a page of text.

U observes/perceives/sees A moving at .3c and B moving at .6c, in the x direction.

Each (A and :cool: sends a signal to the other at t=.68. The signals trigger the other clock to emit the current time t=1.00, which returns to the sender at t=1.47. Their clocks are synched and will remain synched while they maintain the same velocity. Per the Einstein simultaneity convention, each divides the round trip time in half and assigns

t=1.08 to the reflection event. Each calculates the other clock rate is 1.00/1.08=.93 slow.

We have covered this already, perception is reality confined to the mind, and just as real as everything else we experience.

A clock is a frequency, so no surprise when each sees doppler shift from the other receding source. 

This too is perception, since the clock runs at a constant rate.

Are electrons 'really' tiny porcupines with quills radiating in all directions?

Sensory input for humans is approx. 99% visual. Remember that slogan, 'what you see is what you get'.

[Moronium]

 

But it is, concerning perceptions, which is what SR describes.

 

  

 

I don't disagree at all about this observation.  I have made a number of posts, in different threads, pertaining to SR, and none of them have denied what the premises, and the logical implications entailed, of SR say.

 

I simply disagree with anyone who claims that SR in any way reflects "objective reality."  

Edited May 2, 2018 by Moronium

[Moronium]

#29

Needless to say, notwithstanding the incoherent claims of SR to the contrary, the H-K experiments empirically prove that each of two clocks do NOT record elapsed time which is less than is recorded by the other.  Time dilation is simply not "reciprocal," as SR claims.

 

Reciprocal effects are required in SR, but not in GR. In the original H-K experiment, one clock lost time and the other gained time relative to the surface clock.

 

 

Yes, and in H-K all three clocks lost time compared to the hypothetical "master clock" located at the ECI (because they were ALL moving with respect to it, just at different rates of speed).  H-K accurately predicted the actual clock readings ONLY BY positing the ECI as the preferred frame.  A preferred frame is prohibited by SR, so SR was NOT, as many mistakenly claim, used to get the correct predictions.  SR would have given wrong predictions.

 

The model used, probably the RMS, I'm not sure, was one which posited absolute simultaneity and rejected the relative simultaneity of SR.

Edited May 2, 2018 by Moronium

[A-wal]

Stop bloody multi-posing and spamming my thread with your ignorant drivel please! I've already asked you to stop and you just carry on polluting it with your dumb BS, that's extremely rude. Knock it off!

 

Thank you.  We finally explicitly agree on something.  Now, if you could only grasp the simple proposition that epistemology is NOT ontology, and that logical validity does not prove a posteriori soundness, then maybe we could actually get somewhere.  It's too bad that you can't take the next logical step implied by the assertions you just made.  Instead, you just continue to make ontological claims based on epistemological premises.  Tacitly, you are asserting that "whatever you measure is what is."  This is a fallacious proposition, sorry.

The velocity of light is based on a measurement of the distance it covers over time. Measurements are how science is done, it doesn't make sense to say that the speed of light is measured to be constant in every frame but it isn't really.

 

I don't "disagree" with the proposition that SR is "internally consistent."  It is.  Given the unproven postulates, the logical implications it deduces from those postulates are indeed logically valid (but not sound). That doesn't mean the implications can't be profitably used in certain limited circumstances, because they can be, even if they are unsound.  They simply cannot be "true" in an objective sense.

SR's implications have to be true in an objective sense if the speed of light is the same in all inertial frames. There's simply no other possible self-consistent model that includes a constant speed of light.

 

My position is simply that the implications of the premises of SR generate conclusions that CANNOT correspond to "objective reality."

 

Example of perfectly valid logic:

 

1.  All elephants are pink.

2.  This animal is an elephant.

3.  Therefore, this animal is pink.

 

As I said, perfectly valid, logically, yet completely unacceptable from the standpoint of the "soundness" of the argument.

That's a bad example. If 1 is true (all elephants are pink) and 2 is also true (this animal is an elephant) then this animal is pink, be know that 1 is not true. If you're trying to claim that we know that one of the postulate of SR isn't true then this simply isn't the case. Your real position actually that if you're not capable of grasping the implications of SR then the model can't possibly be describing objective reality, this is bollocks. The model doesn't require your understanding, what it requires is to give a self-consistent description of objective reality that matches observations and that's exactly what it does. Your lack of understanding has absolutely no baring on the validity of the model, get over yourself.

 

Your first sentence tacitly makes the unwarranted assumption that I'm getting at.  It should say "The measuring instruments have to change in other frames of reference or the speed of light couldn't be BE MEASURED TO BE constant (in that frame)."

 

Then it would be accurate.  Instead you say that it IS constant.  I have already made a series of posts addressing the simple, universally acknowledged, fact that there can be a significant  difference between "what you measure a thing to be" and "what that thing actually is."  All you did was dispute (ridicule, actually) that simple claim.

Because the way you're attempting to use that claim to refute SR is truly absurd and deserves far more ridicule than I can be bothered to write.

 

No, it is not "true" in any objective sense.

 

It is true that SR posits this claim, but it is not "true" in fact.

It's entirely true in the real universe and any claim otherwise contradicts known reality.

 

Innumerable empirical observations show that time dilation is NOT reciprocal in actuality, even if it is "logically implied" by the premises of SR.

This is a lie! No such empirical observations have been made.

 

And again, the claim is logically impossible to begin with, so no empirical "test" is even required.

The fact that you can't get your head around true reality is not in any way an indication that the model is at fault.

 

It is logically impossible for it to be simultaneously true that clock A is slower than clock B AND clock B is slower than clock A.  Both propositions cannot, as a matter of logic,  be "true" in any objective sense.

Given that the speed of light is constant it's logically impossible that it isn't the case that clock A runs slower than clock B in some frames while clock A runs faster than clock B in others.

 

The resort to solipsistic assumptions in an absurd attempt to "justify" this claim can, as my thread title claims, only seem plausible to solpisists.

Solipsism has absolutely nothing to do with relativity. To think that it does shows that you don't have the slightest grasp of the model you're so keen to dig yourself a hole with. I think it's time you took a good long look at yourself. Either that or you could continue to make an utter fool of yourself and carry on pissing off people who actually do have some level of understanding if you prefer, your call.

 

There is an interesting video on youtube where Hafele and Keating repeat their classical experiment with even more modern, more accurate, atomic clocks.

 

At every stage of their journey they are (accurately) announcing the precise amount by which their (moving) clock differed, at that point,from the earth clock which it was synchronized with before they took off.

 

When they land, their final calculations do in fact agree with the observed difference in the clocks.

Yes, but while they were moving at a constant rate relative to the ground, from their perspective the clocks on the ground were running slower than their own.

 

What the video does not reveal is that, in order to make their precise calculations, they assumed at all times that their clock was the one moving, and that therefore the earth clock was running FASTER, not slower, than their airborne clock.  In other words, they refused to adopt "reciprocal dilation" assumption of SR and the concomitant  mandate that they "assume" that they are stationary.  That would have forced them to conclude  that the earth clock was running slower than theirs, not faster.

 

The narrator in the video says they are using "Einstein's equations."  But in fact they were using Lorentz's equations.

 

The narrator also says that the result was in accord with what "Einstein predicted."  This too is inaccurate.  Einstein would have told them to "predict" that the earth clock was running slower than theirs, not faster.

It was!

 

Another thing that this video doesn't reveal is that they were not using the "relative motion" of SR to reach their (accurate) conclusions.  They were using the "absolute" motion posited by Lorentz.  Their calculations were achieved by using the ECI as a preferred frame for calculating what the difference between the readings on the earth clock and their clock would be.  In this analysis, both the earth clock and the plane clock are moving, actually.  It is the one which is moving faster (with respect to the ECI, not each other), which will run slower

Any choice of frame is an arbitrary one.

[A-wal]

A-wal said:

 

"The frame in which the CMB is at rest is in no way a preferred frame of reference and nobody but you is claiming that it is. You're free to use any inertial frame in which the CMB is in motion and it changes nothing because all inertial frame are equivalent."

 

A-wal, just to reinforce just how mistaken this claim is, I will quote the physics factbook website, which says:

 

"In 1987, a group of seven astronomers uncovered this coordinated motion of the Milky Way and our several million nearest galactic neighbors -- Alan Dressler, Sandra Moore Faber, Donald Lynden-Bell, Roberto Terlevich, Roger Davies, Gary Wegner and David Burstein. Their results were so astounding they acquired the equally astounding nickname of "The Seven Samurai"(the name of a classic Japanese Samurai movie that spawned the classic American Western movie "The Magnificent Seven"). The place towards which we all appear headed was originally called the New Supergalactic Center or the Very Massive Object until one of the discoverers, Alan Dressler, decided they needed a catchier name and came up with "The Great Attractor".

 

The mass of the Great Attractor truly is great....it's attraction is so strong that we are being sucked into it at the rate of 600 km/s. In comparison, the earth moves around the sun at the relatively pokey rate of 30 km/s and rockets escaping the earth's gravitational pull barely move at 11 km/s."

This has absolutely nothing to do with SR. Seriously, what the hell is wrong with you?

 

As a point of fact, cosmologists have been using the CMB as a preferred frame from which to calculate absolute motion for decades.  This practice is almost universally accepted as is Smoot's claim that the CMB is a valid universal rest frame or purposes of calculating absolute motion.  Needless to say, the proposition that absolute motion "can" be detected is also assumed, notwithstanding your denials.  You seem to be just a tad bit behind the times as far as theories of motion go, eh?

:) Yes they prefer to use certain reference frames. Do you think that one of the postulates of SR is that no person or persons shall have a preference when choosing a frame of reference from which to compare motions? Or do you think maybe the term 'preferred' has different meaning when it's used in a scientific context?

 

Notice that, among other things, the accepted "fact" is that the earth revolves around the sun, not vice versa, and certainly not "both."  As a practical matter, nobody accepts the "no preferred frame" premise of SR for everyday useage and ultimate conclusions about absolute motion, no matter how much they may otherwise claim that it is "valid."

Sr doesn't include gravitational acceleration. The valid equivalent here is that moon moves relative to the Earth, the moon moves relative to the sun, the moon moves relative to the centre of the galaxy and the moon moves relative to the greater universe. It moves at an entirely different velocity in each reference frame and all frames are valid, because there is no such thing as absolute motion.

 

It is assumed that absolute motion can be detected, and this can only be done by positing some frame as preferred.  "Every" or just "any" inertial frame will not suffice for this purpose, because every one will give you a different answer.  You must posit one which makes sense to treat as a preferred frame, such as the relative motionless solar barycenter for solar system purposes, as I have already pointed out. It would be inappropriate, and lead to inaccurate reults, for example, to use the CMB as a preferred frame for the purposes of calculating relative motion of the planets within the solar system.

Then you should be able to see that motion is an arbitrary choice of whatever object the observer compares themselves to. If you work out a planets motion around the sun then you get a completely different answer to a planets motion relative to the CMB, so there is no such thing as absolute motion through space!

 

I can almost hear your response now, which will be to call them all "highly stupid" like you did with Smolin because he didn't agree with your naive claims.

Why would I call them highly stupid? Nothing they said even remotely refutes anything in SR. I could however call someone who was under the impression that impression highly stupid.

 

The accepted resolution to the twin paradox simply adopts the earth's frame of reference as the preferred (as between the two twins) inertial frame of reference.

No it doesn't. The Earth's frame is simply the one the end up in. It makes no difference at all because all frames are equally valid, there is no preferred frame.

 

The earth twin assumes that he is motionless, and calculates the time dilation experienced by his travelling twin accordingly.  As it turns out, his calculations are 100% correct, and his twin's calculations (which are premised on the incorrect supposition that HE is "at rest") are 100% wrong.

Both twins make the correct calculations from their inertial frame. Each twin is time dilated and length contracted from the the perspective of the other, they have to be for the speed of light to be the same for both of them despite they're motion relative to each other. Neither one is wrong, and they get the same results whatever their velocity relative to the Earth when the they start the experiment. The is no contradiction because they're in different frames of reference.

 

Many people who discuss this issue don't even know what the perceived "paradox" is.  Many claim the "paradox" consists of the fact that clocks on moving objects tick at a slower rate than stationary ones.  That is not a paradox at all, although the reasons for it might be mystifying.

The apparent paradox (not a genuine paradox) is that twin A ends up younger than twin B from B's perspective and twin B ends up younger than twin A from A's perspective. It's easily resolved simply by using the perspective of whatever frame of reference they end up in. It can be any frame. If the Earth twin accelerates out to meet up with the twin who's in motion relative to Earth then that twin (the one who left Earth last) will be younger.

 

The true paradox, which has never been resolved (by SR, anyway), lies in the inconsistencies generated by SR itself.  If, as SR claims, all inertial frames are "equally valid," then why is the earth's frame preferred in this case?  That inconsistency is what creates the paradox.

Earth's frame isn't in any way preferred, it's simply the frame they end up in. It works the exact same way if they start from a frame that's in motion relative to the Earth.

 

Put another way, how is it possible to get an absolute answer from a theory which posits that all motion is strictly relative?  An absolute answer should be impossible to arrive at if the premises are correct.

It's easy to get an absolute answer once you actually understand the model. It's very straight forward and gives definite and absolute results but definite and absolute results that use relative rather than absolute motion and a constant speed of light in all inertial reference frames. This is the only way to get the correct answer.

 

The term "paradox" has been defined and explained as follows:

 

"a statement or proposition that, despite sound (or apparently sound) reasoning from acceptable premises, leads to a conclusion that seems senseless, logically unacceptable, or self-contradictory."

Nothing in SR is senseless, logically unacceptable, or self-contradictory. It's counter-intuitive if you're not used to it and some people simply don't have the intelligence required to grasp it. Unfortunately some of those people would rather live in denial and insist that the model must be wrong because they find that easier to swallow.

 

The way to resolve a paradox is NOT to accept mutually exclusive claims as both being true. That is what creates the paradox, not what resolves it. The solution is to determine what aspect of a claim is, despite being "apparently sound," actually unsound, and then reject, rather than accept, that aspect.

Yes, but there is no paradox in SR.

 

The twin paradox is easily resolved by rejecting the self-contradictory claim that "all inertial frames of reference are equally valid."  Once that's done, all of the numerous "paradoxes" generated by SR disappear.

No, that actually creates a paradox where none exists because we know that the speed of light is the same in all inertial frames of reference and the only way that can be true is described by SR.

 

An apologist for SR is prone to say that the stay at home twin and the travelling twin are "both correct" in their calculations.  But this is logically impossible, and so, not surprisingly, the accepted resolution denies that they are "both correct."  The resolution says that only one (the earth twin) is correct in his calculations and that the other (the travelling twin) is incorrect in his calculations.

 

So then, SR "resolves" the paradox it creates in the only way it can--it denies the soundness of its own premises. In order to resolve the paradox, it must abandon the claim that all inertial frames are equally valid and that therefore absolute motion cannot be detected.

Utter BS! The Earth's frame is in no way a preferred frame in the twin paradox, it's simply the one they end up in when they compare their age at the end.

 

SR apologists are also prone to point out that the situations of the two twins are "not symmetrical."  This is absolutely true, of course, but does nothing to answer the question posed.  Of course they are not symmetrical--one is moving (relative to the other) and one is not.  What the SR apologist does not, and cannot, explain or reconcile, is the concomitant claim that absolute motion cannot be detected.

One is moving and one isn't? :) Moving relative to what? They are moving relative to each other. There's nothing to reconcile, that's the only type of motion that can be determined and that makes any sense.

 

Feynman said that the answer to the twin paradox is simple:  The one which has accelerated is the one who experiences time dilation, he says.  He's undeniably correct, because it is the one who has accelerated that is moving (relative to the one who has not).  And in SR (and every other theory which adopts the LT, for that matter) it is the moving clock which slows down.  Acceleration is universally admitted (even by SR) to be absolute motion, not relative motion.

It is the one who accelerates that experiences less proper time in the twin paradox but acceleration itself isn't the cause. If they repeat the test again and the twin who leaves Earth accelerates to the same velocity relative to Earth as before but waits twice as long before turning round and coming back then the difference in proper time that elapses for the two will be double what it was the first time, but the acceleration was the same.

 

To elaborate somewhat, the proposition that "all inertial frames are equally valid" is, in certain respects, true, (the laws of physics are the same, for example).  But one of the conclusions drawn from this "equality" by SR is unwarranted and fallacious.

 

The unwarranted conclusion is this:  Therefore you can never say which of two objects is moving relative to the other.  That by no means follows.  There are a great number of ways to determine which (of two) clocks is moving relative to the other.  SR itself (the LT, actually) provides the means to determine that, because it holds that the "moving" clock will run slow.   

 

Empirical experiments, such the one performed by Hafele and Keating, show that clocks do tick at different rates due to varying speeds.  So, when the experiment is complete, you only need see which clock(s) have slowed down.  Those are the ones that were "moving."

 

Needless to say, notwithstanding the incoherent claims of SR to the contrary, the H-K experiments empirically prove that each of two clocks do NOT record elapsed time which is less than is recorded by the other.  Time dilation is simply not "reciprocal," as SR claims.

 

http://www.sciencefo...e-2#entry355972

More complete BS. Objects that are in motion relative to the frame of reference of the observer will be length contracted and time dilated. This is true in all inertial frames, if object B is time dilated and length contracted in the reference frame of object A than object A is time dilated and length contracted in the reference frame of object B. This is the only way that the speed of light can be constant in all inertial frames. The one clock that shows less elapsed time is the one that was in motion relative to the frame of reference that they end up in.

[A-wal]

Some people mistake Galileo's "parable of the ship" as a argument that relative motion cannot be detected, but that's hardly the case.

Yet more BS. That's exactly what it designed to show.

 

He noted that in a windowless cabin below deck you would not be able to sensibly discern lack of motion from uniform motion, sure. Senses aside, he also pointed out that the laws of physics would not change.   But he was also quick to point out that once the sailor went up on deck, felt the wind blowing, saw the sails billowed, and saw points on the shoreline in motion relative to him, he would know that, as between the two, he was the one moving, not the shore.

All inertial motion is relative. Obviously the wind and shore were moving relative to the ship.

 

SR advocates routinely presume that if the laws of physics are the same, then relative motion cannot be detected.  They will ask what physical experiment could be conducted on a uniformly moving train which would reveal your motion, AS IF that were the only conceivable way to know.  Wrong.  Stop trying to determine motion by looking only "inside" the train and  by refusing to consider all other available information.  If you are unsure and want to know if you're moving, just look out the damn window.

:) Looking out of the window tells you the motion between the train relative to what you're looking at, obviously.

 

The real point of the "parable of the ship" was NOT to claim that motion is undetectable.  It was to demonstrate Galileo's novel insights involving inertia.  The whole discussion was designed to demonstrate how it can be that the earth does, IN FACT, move, even though we don't sense it's movement.   It certainly was not that motion can't be detected, as SR revisionists routinely claim.

It was to show that there's no distinction between at rest and inertial motion. Inertial motion is undetectable and untestable unless it's in relation to something else.

 

It is true, that like Newton and Einstein after him, Galileo concluded that "absolute" speed could not be detected, only relative speed.  But, unlike SR proponents, he never fallaciously concluded that this implied that, as between two objects, it would be impossible to say which was moving, relative to the other.

That's a complete contradiction. Absolute speed cannot be detected and therefore it's impossible for only one object to be moving relative to another object, they are in motion relative to each other.

 

Even in Galileo's closed cabin we would know that if we dropped a coin, it would hit the floor of the ship and that the floor of the ship wouldn't rise from the ocean to come up to meet the coin while it remained motionless in mid-air.  How, and why?  Well, precisely because the laws of physics are still the same, that's why.

That's GR! The coin gravitationally accelerates towards the floor.

 

It is true that if you're on a sailing ship, wind at your back, sails billowed, etc. and then compared yourself to the shoreline, then things would "look" the same under either of the following asumptions:

 

1.  You are absolutely motionless, but the shore is moving relative to you, and

2.  You are moving and, relative to you, the shore is stationary.

 

Of course the same is true if you're standing on earth looking out at all the stars you can see.  Neither assumption would be inconsistent with the "appearances."

 

But that does not mean that it is "completely arbitrary" to favor one assumption over the other.  The appearances do at least assure you that at least one (if not both) of the objects is moving.  In other words they cannot both be "motionless" (as SR claims).  Still, it is true that "appearances" can be deceiving, and furthermore, that appearances, standing alone, could never tell you which of the two is moving.  

 

Physics is not about treating every subjective assumption pertaining to appearances as being absolutely true.  Nor does it assume that differing subjective assumptions are incapable of being rationally analyzed.   It is about deciding, based on empirical observations and coherent rational deductions therefrom, which of two (or more)  possible explanations makes more sense.  This is not "arbitrary."

There is no test that can distinguish between object A moving relative to object B and object B moving relative to object A. The fact that the speed of light is constant for all inertial observers proves that objects that are in motion relative to any observer are time dilated and length contracted. Object B is time dilated and length contracted from the perspective of object A and object A is time dilated and length contracted from the perspective of object B.

 

It was a huge achievement , and a substantial advance for scientific thought, for the heliocentric view of planetary motion to prevail over a  geocentric one as it pertains to astronomy.   Aristarchus, an ancient greek astronomer and mathematician, had posited a heliocentric model way back around 300 B. C.  But, for apriori philosophical reasons (which later became religious reasons), his view was rejected in favor of Ptolemy's geocentric model.

 

It took almost two millenium for scientists to transcend and move beyond the "known truths" of geocentrism..

 

Why SR advocates are so ready, and in fact eager, to deny the validity of such advances is a complete mystery to me.

 

The post initiating this thread, in the first paragraph, said this:

 

"First it's important to understand basic Galilean relativity, all motion is relative. That just means that there's no distinction between object A moving away from object B and object B moving away from object B (sic, he means A, not B, here I'm sure), "

 

In subsequent posts, I have done my best to dispel that  commony held, yet erroneous, notion and explain why this claim is unacceptable.  There is a HUGE difference "between object A moving away from object B and object B moving away from object A," both theoretically and practically.  Granted, it won't make any difference for a few limited purposes, such as determining the difference in their speed with respect to each other, but it is a serious mistake to overgeneralize that limited case.

All you've managed to do is show again and again that you're not capable of grasping even the basics of SR yet are unwilling to face the fact that it's your failure, not the model's.

 

I don't disagree at all about this observation.  I have made a number of posts, in different threads, pertaining to SR, and none of them have denied what the premises, and the logical implications entailed, of SR say.

 

I simply disagree with anyone who claims that SR in any way reflects "objective reality."  

SR is the only logically self-consistent model that describes an objective reality in which the speed of light is constant.

 

Yes, and in H-K all three clocks lost time compared to the hypothetical "master clock" located at the ECI (because they were ALL moving with respect to it, just at different rates of speed).  H-K accurately predicted the actual clock readings ONLY BY positing the ECI as the preferred frame.  A preferred frame is prohibited by SR, so SR was NOT, as many mistakenly claim, used to get the correct predictions.  SR would have given wrong predictions.

 

The model used, probably the RMS, I'm not sure, was one which posited absolute simultaneity and rejected the relative simultaneity of SR.

You're full of it! The experiment in no way implied a preferred frame, and it would make absolutely no sense if it had. So you think the ECI just so happens to be the preferred universal frame despite it's motion around the galaxy and relative to other galaxies? Go away. Your only problem with SR that actually makes sense is that you're simply incapable of understanding it. Learn to live with it. Don't post in this thread again.

[A-wal]

This is a modified twin (non-)paradox to show that there's no room for a preferred frame.

Twin A and Twin B accelerate the same amount in opposite directions. It doesn't matter what their motion is relative to the Earth or any other object in the universe when they do this. They're now moving away from each other and have stopped accelerating so they're now inertial. Each twin is time dilated and length contracted from the perspective of the other twin, this is the only way that light can move at the same velocity in both frames.

Twin A accelerates towards Twin B then stops accelerating and now Twin B is moving towards them. They accelerate again in the opposite direction so that Twin B doesn't go flying past them, instead they become at rest relative to each other and compare watches. Less time has passed on Twin A's watch than on Twin B's.

Now they reset their watches and do the same experiment switching but switching roles. They now actually in motion relative to the original frame they started in but it makes no different because this works the exact same way in all inertial frames.

Twin A and Twin B accelerate the same amount in opposite directions. It doesn't matter what their motion is relative to the Earth or any other object in the universe when they do this. They're now moving away from each other and have stopped accelerating so they're now inertial. Each twin is time dilated and length contracted from the perspective of the other twin, this is the only way that light can move at the same velocity in both frames.

Twin B accelerates towards Twin A then stops accelerating and now Twin B is moving towards them. They accelerate again in the opposite direction so that Twin A doesn't go flying past them, instead they become at rest relative to each other and compare watches. Less time has passed on Twin B's watch than on Twin A's.

 

 

While they're in motion relative to each other each twin is length contracted and time dilated from the perspective of the other but when they meet back up only one twin is younger. If we go back to the first time they were moving away from each other, from Twin A's perspective Twin B is moving away from them at some fraction of the speed of light and is length contracted and time dilated. When Twin A starts to accelerate towards Twin B they see that Twin B's time dilation is lessening and at a certain point (even with a constant rate of acceleration) they see that Twin B is moving through time at a faster rate then themselves.

Twin B is still moving away from them at this point and at some point and before reaching the frame of Twin B (before being at rest relative to Twin B but still some distance away) Twin B will not only have caught up to them (in terms of the amount of time that has passed for Twin B from Twin A perspective), Twin B will have overtaken them so that when twin reaches the frame of Twin A so that Twin A is no longer moving away from them more time will have passed for Twin B then than for Twin A from Twin A's perspective.

Twin A continues to accelerate so that Twin B is now moving towards them at a steadily increasing rate (their acceleration has remained constant the whole time). Now they're accelerating away from Twin A's frame rather than towards it so now they see Twin B's watch start to slow down again. When the accelerate for second time so that Twin B doesn't go past them they again see Twin B's watch moving faster than they're own because they accelerating towards Twin B's frame. When they're in the same frame again more time has passed for Twin B and the difference is twice as much as it was when they were accelerating towards Twin B and reach Twin B's frame.

[Moronium]

Hehehehe.  My, my, A-wal.  Quite upset now, aren't you?

 

1.  Your "understanding" of the philosophy of science boils down to; SR HAS CONCLUSIVELY BEEN PROVEN TO BE OBJECTIVELY TRUE, BY GOD!!!!!!!  Nice try.  I didn't know anyone could get quite that naive.  Given your utter devotion to solipsism, I guess I shouldn't really be surprised, but still....

 

2.  You deny empirical facts, historical facts, stone-cold logic, all semblance of rationality, and everything else in your path to repeatedly scream this.  Sorry, but mere repeated assertion proves nothing.  You don't do anything to buttress the supposed "truth" of your claims, you merely presuppose it, then SCREAM it.

 

I have nothing to discuss with you.  You lack all intellectual integrity it seems.  You are a cheer-leader, not a player.

 

Rave on.

Edited May 2, 2018 by Moronium

[Moronium]

I'll repeat that I have no inclination, desire, or intention to respond to your ravings at any length.  Even so, I'll comment on this:  You ask:

 

 Do you think that one of the postulates of SR is that no person or persons shall have a preference when choosing a frame of reference from which to compare motions? 

 

 

 

I absolutely "think" that, and have demonstrated it to be the case on several occasions.  They MUST have a preference, but they have no freedom to "choose" it.  SR prohibits any observer from even remotely contemplating the notion that any frame of reference, other than his own (which he MUST treat as being ABSOLUTELY MOTIONLESS), is "at rest."

 

That's very basic, yet you don't know it.  Nor do you understand the nature or source of the paradox involving the twins, to mention one other (of many) fundamental misunderstandings which you harbor.  That doesn't stop you from pretending to "understand" SR, of course.

 

Rave on.

Edited May 2, 2018 by Moronium

[Moronium]

Einstein had unsuccessfully struggled to reconcile Gaileo's "principle of relativity" with Maxwell's equations for 8-10 years, and, by his own admission, was ready to give up entirely when he suddenly conceived of the solipsistic notion that simultaneity is relative.

 

Years before, Lorentz had created, developed, and published the concept of "local time."  For him, this was strictly a mathematical fiction which could be used as a convenient shortcut when making mathematical calculations.  It had no correspondence to "reality."

 

Years before, Poincare had noted that one could easily see a "subjective" principle of relativity, if only each observer would ignore his own motion.  Poincare never (to the end of his life) considered this to be any "real" principle of relativity (and rightfully so).  Out of desperation (he says) Einsteins took Lorentz's fictitious notion of local time, and proclaimed it to be "real time."  He latched onto Poincare's insight that a "subjective" sense of relativity could be achieved if all observers would simply deny their own motion.

 

Presto!  He had "relative simultaneity," and, he thought at the time anyway, a defensible "theory of relativity." I have a separate thread which addresses this highly dubious concept at some length.

 

It's a theory, not a fact.  Constant speed of light is a mere, inherently unprovable "postulate" not a fact (or even a hypothesis capable of being "proven").  It is, by NO means, the only possible theory of relative motion which explains all known empirical observations.  In fact, it has been discovered, relatively recently, that it's premises contradict some observable facts, while theories incorporating absolute simultaneity do not.

 

For many reasons, Einstein was never satisfied with (let alone happy with) SR as a theory of motion.  He immediately set out to devise a "general theory" of relative motion.  He did not achieve this ambition.  He did, however, finally devise a magnificent theory of gravity about 10 years later, which he called "general relativity."  As I have shown elsewhere, GR does NOT maintain that the speed of light is constant.

Edited May 2, 2018 by Moronium

[A-wal]

Hehehehe.  My, my, A-wal.  Quite upset now, aren't you?

 

1.  Your "understanding" of the philosophy of science boils down to; SR HAS CONCLUSIVELY BEEN PROVEN TO BE OBJECTIVELY TRUE, BY GOD!!!!!!!  Nice try.  I didn't know anyone could get quite that naive.  Given your utter devotion to solipsism, I guess I shouldn't really be surprised, but still....

 

2.  You deny empirical facts, historical facts, stone-cold logic, all semblance of rationality, and everything else in your path to repeatedly scream this.  Sorry, but mere repeated assertion proves nothing.  You don't do anything to buttress the supposed "truth" of your claims, you merely presuppose it, then SCREAM it.

 

I have nothing to discuss with you.  You lack all intellectual integrity it seems.  You are a cheer-leader, not a player.

 

Rave on.

I'll repeat that I have no inclination, desire, or intention to respond to your ravings at any length.  Even so, I'll comment on this:  You ask:

 

"Do you think that one of the postulates of SR is that no person or persons shall have a preference when choosing a frame of reference from which to compare motions?"

 

I absolutely "think" that, and have demonstrated it to be the case on several occasions.  They MUST have a preference, but they have no freedom to "choose" it.  SR prohibits any observer from even remotely contemplating the notion that any frame of reference, other than his own (which he MUST treat as being ABSOLUTELY MOTIONLESS), is "at rest."

 

That's very basic, yet you don't know it.  Nor do you understand the nature or source of the paradox involving the twins, to mention one other (of many) fundamental misunderstandings which you harbor.  That doesn't stop you from pretending to "understand" SR, of course.

 

Rave on.

I utterly dismantled every argument you attempted to make and showed them to be nothing more than misunderstandings and provably false claims. All you can do in response is throw stones. It's perfectly clear which one of us understands the model and which one of us is attempting to grasp what they are completely incapable of understanding.

 

You can find no valid refutation of SR, all you can do is say that it can't be true. I've clearly shown that it not only can be true but it must be true because it's the only self-consistent description of observed reality. Assuming that it holds that the speed of light is unaffected whenever an observer changes inertial frames, SR is the only model that works.

 

Einstein had unsuccessfully struggled to reconcile Gaileo's "principle of relativity" with Maxwell's equations for 8-10 years, and, by his own admission, was ready to give up entirely when he suddenly conceived of the solipsistic notion that simultaneity is relative.

 

Years before, Lorentz had created, developed, and published the concept of "local time."  For him, this was strictly a mathematical fiction which could be used as a convenient shortcut when making mathematical calculations.  It had no correspondence to "reality."

 

Years before, Poincare had noted that one could easily see a "subjective" principle of relativity, if only each observer would ignore his own motion.  Poincare never (to the end of his life) considered this to be any "real" principle of relativity (and rightfully so).  Out of desperation (he says) Einsteins took Lorentz's fictitious notion of local time, and proclaimed it to be "real time."  He latched onto Poincare's insight that a "subjective" sense of relativity could be achieved if all observers would simply deny their own motion.

 

Presto!  He had "relative simultaneity," and, he thought at the time anyway, a defensible "theory of relativity." I have a separate thread which address this highly dubious concept at some length.

 

It's a theory, not a fact.  Constant speed of light is a mere, inherently unprovable "postulate" not a fact (or even a hypothesis capable of being "proven").  It is, by NO means, the only possible theory of relative motion which explains all known empirical observations.  In fact, it has been discovered, relatively recently, that it's premises contradict some observable facts, while theories incorporating absolute simultaneity do not.

 

For many reasons, Einstein was never satisfied with (let alone happy with) SR as a theory of motion.  He immediately set out to devise a "general theory" of relative motion.  He did not achieve this ambition.  He did, however, finally devise a magnificent theory of gravity about 10 years later, which he called "general relativity."  As I have shown elsewhere, GR does NOT maintain the the speed of light is constant.

GR has NOTHING to do with it! The consistency of the speed of light is across inertial reference frames and that's what SR deals with. The fact that the speed of light isn't constant in GR in no way invalidates SR. That level of misunderstanding is why you're nothing but a joke.

Edited May 3, 2018 by A-wal

[Moronium]

I've clearly shown that it not only can be true but it must be true because it's the only self-consistent description of observed reality.

 

 

 

It's nice that YOU have shown that because no one of any merit, not Einstein himself or any one else, before or since, has ever claimed to have shown that either:

 

1. SR must be true, or

 

2. That SR is  the only self-consistent description of observed reality.

 

On the contrary, every competent theoretical physicist (including Einstein) DENIES such claims.  Maybe, just maybe, it's time for you to update your "education," eh, A-wal?

 

Your "arguments," at best, come down to saying "If SR is true, then it's true."  But you pretend that there's no "if" about it.

Edited May 3, 2018 by Moronium

[A-wal]

It's nice that YOU have shown that because no one of any merit, not Einstein himself or any one else, before or since, has ever claimed to have shown that either:

 

1. SR must be true, or

 

2. That SR is  the only self-consistent description of observed reality.

 

Maybe, just maybe, it's time for you to update your "education," eh, A-wal?

 

Your "arguments," at best, come down to saying "If SR is true, then it's true."  But you pretend that there's no "if" about it.

It's been shown that if the postulates of SR are true then both 1 and 2 are also true, and it's never been shown that the postulates of SR aren't true.

 

I'll repeat that I have no inclination, desire, or intention to respond to your ravings at any length.  Even so, I'll comment on this:  You ask:

 

"Do you think that one of the postulates of SR is that no person or persons shall have a preference when choosing a frame of reference from which to compare motions?"

 

I absolutely "think" that, and have demonstrated it to be the case on several occasions.

You missed the point. Of course they can have a preference. The point is it doesn't make any difference what they decide, all frames are equally valid and the results are unaffected by their choice of frame.

 

You have not demonstrated that there's a preferred frame. You've demonstrated that you don't have the first clue what a preferred frame actually is or what it would entail if it were true.

 

That's very basic, yet you don't know it.  Nor do you understand the nature or source of the paradox involving the twins, to mention one other (of many) fundamental misunderstandings which you harbor.  That doesn't stop you from pretending to "understand" SR, of course.

There is no paradox in the twin paradox. It's named that because there's an apparent paradox if you only have a flimsy understanding of what SR actually describes. It's not a paradox for one object to be time dilated and length contracted from the perspective of an object in relative motion to it while the reverse is also true. It is in fact the only way to avoid a paradox. This is apparent to anyone who is capable of grasping the model, but not to you. You're dozyness is not evidence of some deeper truth, it's just evidence that you're particularly dozy.

Edited May 3, 2018 by A-wal

[Moronium]

It's not a paradox for one object to be time dilated and length contracted from the perspective of an object in relative motion to it while the reverse is also true.

 

 

 

Of course that's not a paradox at all.  And that's also not the reason it's called a paradox.

 

Two people can have totally opposite "perceptions"  Nothing paradoxical about that at all.  It happens every day.  People make mistakes.

 

The "paradox" comes when SR tries to simultaneously claim that:

 

1.  There is no mistake at all.  Both are correct, but that

2.  Only one of the two twins is correct.

 

That's the "paradox," which SR "resolves" only by repudiating the first claim and affirming the second--which gives an absolute (frame independent) answer, not a relative one.

Edited May 3, 2018 by Moronium

[Moronium]

 Of course they can have a preference. The point is it doesn't make any difference what they decide, all frames are equally valid and the results are unaffected by their choice of frame.

 

 

Try telling that to any knowledgeable theoretical physicist who has ever looked at the results of the H-K experiment.  Or, for that matter, anyone who has even a rudimentary familiarity with logic.

 

I have already explained in more detail why your assertion can't be true, as an objective matter, in another thread:

 

http://www.scienceforums.com/topic/31081-preferred-frame-geometry/?do=findComment&comment=355943  (post #3)

Edited May 3, 2018 by Moronium

[Moronium]

Cheerleaders will get out at half-court and loudly chant:  "From the east to the west, we're the BEST!!" even if their team is down by 50 points at halftime in a basketball game.

 

That's understood.  That's their job. They are used for their enthusiasm, not for keeping or understanding the score. They aint no player, and they aint got no game.  No reason to expect any game from them.

Edited May 3, 2018 by Moronium

[Moronium]

Here's more elaboration on this general topic, once again imported from a pre-existing  thread where this post was originally made:

 

 

1.  SR starts with the reasonable-sounding proposition that, because the laws of physics are the same in all inertial frames, all such frames are 'equally valid."  It goes on to assert that, because they are "equally valid," you can randomly and arbitrarily pick "any old" inertial frame of reference from which to assess relative motion, and it will make no difference.  There is no reason to "prefer" any inertial frame over another.  OK, kinda sounds fair enough.  What next?

 

2.  In truth, it's all a "bait and switch" tactic that's being employed. In practice SR does not allow me to freely choose a frame of reference to calculate my relative motion from.  I MUST, instead, treat my own frame of reference as being absolutely motionless (like Lorentz' ether).  If I'm on a train, I cannot adopt the viewpoint that I am moving relative to the earth's surface.  I must insist that IT is moving, relative to me.  I am therefore, by strict mandate of SR's protocols, in a preferred frame which is not "freely chosen," but which is dictated by SR.  SR likes to assert that "you can never tell who's moving,"  but ironically this is all while undertaking to "inform" you about who's moving in every instance where you employ SR formulas (again, it's always all other objects in the universe which are outside of your reference frame--never you).

 

3.  Apart from being intuitively false as an empirical matter, this forced choice of a preferred frame presents other serious problems.  Once you move beyond just two objects, you end up with a infinite number of mandatory "preferred frames," i.e., one for each possible inertial frame.  This ends up in  implying such logical absurdities as asserting that each of two clocks (or every clock, of many) runs slower than the other(s), for example.  Because this is a self-refuting proposition, the theory cannot make empirically accurate predictions with respect to actual tangible objects in the objective physical world.

 

-----

 

So the original claim, i.e., that you could freely choose any inertial frame in SR, and still get the same results, is quickly shown to be a false promise and an invalid claim.  Unfortunately shoddy sophistical tactics like these completely fool some people (like A-wal) who refuse to think critically about what they are being told.  Such people will then repeat the false claims, ad nauseum, and become more convinced that what they're saying is "true" with each repetition--at least so long as they are "preaching to choir," whose only response is to shout "Amen, Brother!"

Edited May 3, 2018 by Moronium