TIME DILATION. WHY do clocks that are

[sisoev]

Similarly, atomic clocks depend on temperature, so a hot and a cold atomic clock are not identical clocks.

Make perfect sense.
Thanks DaleSpam :)

We can conclude now that clocks moving in gravitational field are not identical to clocks which are in rest in the same gravitational field (satellite clocks/ground clocks)
Also fast moving in gravitational field are not identical to the slow moving clocks in the same field.
Would that be correct to say?

About Denius1704 question:
What is he saying is that a stationary observer would see the ticking of a fast moving light clock as follows:
the tick starts closer to us and completes further far from our position.
The light from the clock needs time to travel to us in order to be observed from us, thus making the end of the tick to be observed as delayed because as a light signal it needs more time to travel to our position of observation.
In a simple math we can deduct the known speed of the moving object and we will get the correct timing which will be equal to the time in the clock frame of reference.

To make Denius point clearer I'd say that we will not only observe "longer" second, but the light which represents that second will be seen by us as red shifted.
This take us further to another conclusion: the different light frequency and wave length has something to do with the speed of the light for different observers, but just ignore this and let stay in the topic.

 

[Denius1704]

I just wanted to see what kind of answers someone with more knowledge in physics would give to certain questions i had. I expected more or less what i got. It's just that i don't understand how can scientists connect an abstract construct such as time together with a physical construct such as space and think that that is ok. When a theory has so many paradoxes then there should be something wrong with it. You have the twin paradox, you have the ladder-garage paradox, you even have a paradox as explained by one of your own members here where the resting space of a photon makes absolutely no sense. And yet, people still keep on insisting that there is nothing wrong.

Thanks for the answers again. I'm out of this conversation, i don't want to start meaningless argument where no one agrees with the other.

@Buckleymanor: Thanks for that example Buckley, it was a perfect one, even though DaleSpam did not fully understand your reasoning :)

 

[Dale]

the tick starts closer to us and completes further far from our position.
The light from the clock needs time to travel to us in order to be observed from us, thus making the end of the tick to be observed as delayed because as a light signal it needs more time to travel to our position of observation.
In a simple math we can deduct the known speed of the moving object and we will get the correct timing which will be equal to the time in the clock frame of reference.

The statement in bold is simply incorrect. All of the basic relativistic effects (time dilation, length contraction, relativity of simultaneity) are what remains after correctly accounting for the delay due to the finite speed of light.

 

[sisoev]

The statement in bold is simply incorrect. All of the basic relativistic effects (time dilation, length contraction, relativity of simultaneity) are what remains after correctly accounting for the delay due to the finite speed of light.

DaleSpam, I don't put in doubt your knowledge and authority as a Science Advisor in Physics Forums, but your answer is unsatisfactory.
Einsteins relativity comes from the assumption that the speed of light is finite and same for all observers.
From there comes the subject of this discussion with all the paradoxes we try to understand.

You should not use the finite speed of light as supporting argument if the result from this assumption is in argument.
Instead explain and make us understand why the delay due to the speed of the object is not taken in account?
Why no one mention and explain the red shift of the light clock in a moving object?
How is measured the speed of light and why is measured that way?
Is one photon considered as light or the frequency of the successive waves are what we call light?
If the different frequency means slower or faster approaching successive waves doesn't that mean that every next wave is slower or faster for the observer?
If YES why should we still insist that the speed of light is constant and finite for all observers in a vacuum?
Why you don't see the moon clock as identical with the one on the Earth, but in the same time you consider identical the clocks on the satellite with those on the ground?

Too many questions, but I think that all of them are of a big importance for this discussion.

Thank You, and please bear with those who are striving to understand the theory of relativity.

 

[Dale]

Einsteins relativity comes from the assumption that the speed of light is finite and same for all observers.

Yes, and all of the results are derived on the assumption of intelligent observers which can rationally account for the known finite speed of light. Time dilation remains even after doing so.

To confirm this, note that time dilation is independent of the direction of motion and depends only on the speed. In contrast, the time between receiving the signal from successive "ticks" of a clock does depend on whether the clock is getting closer or further. After you account for the clock getting closer or further and the changing delay time due to that then you find that the clock is time dilated.

Please narrow down your questions to the one or two you feel are most important. That is just way too many questions to pursue.

 

[Janus]

I just wanted to see what kind of answers someone with more knowledge in physics would give to certain questions i had. I expected more or less what i got. It's just that i don't understand how can scientists connect an abstract construct such as time together with a physical construct such as space and think that that is ok. When a theory has so many paradoxes then there should be something wrong with it. You have the twin paradox, you have the ladder-garage paradox, you even have a paradox as explained by one of your own members here where the resting space of a photon makes absolutely no sense. And yet, people still keep on insisting that there is nothing wrong.

None of the so called "paradoxes" are real paradoxes in that they represent any actual contradictions. They are all a result of using an incomplete treatment of Relativity.

In a way, they are the equivalent of the "round Earth paradox" in which people used to argue against the world being a sphere by saying that the people on the underside would fall off.

 

[Denius1704]

None of the so called "paradoxes" are real paradoxes in that they represent any actual contradictions. They are all a result of using an incomplete treatment of Relativity.

In a way, they are the equivalent of the "round Earth paradox" in which people used to argue against the world being a sphere by saying that the people on the underside would fall off.

And people supporting the round Earth theory kept on asking how come we never get to the end of the horizon or how come certain stars are doing funny movements in the night sky if the Earth was the center of the Universe. Paradoxes on both sides. The question is which side has more of them. Because i believe the rule of thumb would be, the more paradoxes a certain theory has, the less likely it is to be true.

 

[D H]

Because i believe the rule of thumb would be, the more paradoxes a certain theory has, the less likely it is to be true.

You are looking at relativity from the wrong perspective.

There are no true paradoxes in relativity. All of the so-called paradoxes result from trying to look at relativity with Newtonian expectations. Relativity is, as far as we know, an internally-consistent description of the universe. Newtonian mechanics is also a self-consistent description (as far as we know; underneath it all there is always the problem of Gödel's incompleteness theorems).

Science has to do something that philosophy and mathematics don't have to do: Science has to agree with reality. The ultimate paradox of science is when a scientific theory fails to agree with reality, and this is where Newtonian mechanics falls apart. It simply does not agree with reality in the realms of largish velocities (special relativity), largish masses (general relativity), and smallish distances (quantum mechanics). All experiments to date show that relativity does agree with reality.

 

[sisoev]

Yes, and all of the results are derived on the assumption of intelligent observers which can rationally account for the known finite speed of light. Time dilation remains even after doing so.

Ha-ha :)
I'll not be quite intelligent if agree with the assumption without questioning it.
I understand the idea of relativity, but it does not make sense to me in some of its points, which I already mentioned.

To confirm this, note that time dilation is independent of the direction of motion and depends only on the speed.

Sure.
I didn't say otherwise.

In contrast, the time between receiving the signal from successive "ticks" of a clock does depend on whether the clock is getting closer or further. After you account for the clock getting closer or further and the changing delay time due to that then you find that the clock is time dilated.

I already introduced my understanding that the "up-tick" of the clock will be seen with delay, because due to the speed of the clock it will by further far from us when riches the top of the clock.
The signal from the "up" tick will travel longer to us, because it is further away from the "bottom" tick.
The light, I said, will be red shifted.

If the clock travels toward us, we will see that the tick starts further away from us, and the "up-tick" will happen closer to us.
We can visualize it the same way like in the first case(moving away), except that the angle of the clock light will be opposite and we will see it as blue shifted.
(Who makes the animations here? Please show it to us ;) )
Hence the time is "delayed" in both moving objects.

Please narrow down your questions to the one or two you feel are most important. That is just way too many questions to pursue.

Thanks for giving me the chance to ask :)
For now, would you please clear out for me the above.
Is it correct that in both cases we will see respectively red and blue shifted light from the clock?
Do you agree that the "slow" second is a result from the difference in the distance from which we perceive the "down" and "up" tick (starting and ending points of the tick)?

 

[Dale]

Paradoxes on both sides.

SR has no genuine paradoxes, only things that students find confusing to learn. It is simply Minkowski geometry, which is entirely self-consistent.

 

[Dale]

Hence the time is "delayed" in both moving objects.

And that delay is accounted for in both moving objects. Even after accounting for that delay time dilation still remains.

Is it correct that in both cases we will see respectively red and blue shifted light from the clock?

Yes. The signal from a departing clock will be redshifted and the signal from an arriving clock will be blueshifted.

Do you agree that the "slow" second is a result from the difference in the distance from which we perceive the "down" and "up" tick (starting and ending points of the tick)?

No, it has nothing to do with perception. The perception delays are accounted for and the time dilation remains.

 

[sisoev]

And that delay is accounted for in both moving objects. Even after accounting for that delay time dilation still remains.

Yes. The signal from a departing clock will be redshifted and the signal from an arriving clock will be blueshifted.

No, it has nothing to do with perception. The perception delays are accounted for and the time dilation remains.

Well, for now I have the feeling that relativity leans too much on the way we set the things to be perceived.
The traveling clock for instance; it won't give time delay for the observer if it travels in circle around him and instead up-down it moves left-right.
I cannot imagine that left-right moving clock will stop showing time delay while making U-turn around the observer only because it went into a half circle.
It appears that the shape of the path is of a great importance for the time delay.

If your answer for the above is short and you have time, would you please explain, how it comes that the clock on the moon is not identical with the clock on Earth, but the clocks on the satellites are identical with those on the ground?

Thank You.

 

[Passionflower]

And that delay is accounted for in both moving objects. Even after accounting for that delay time dilation still remains.

Exactly true!

Yes. The signal from a departing clock will be redshifted and the signal from an arriving clock will be blueshifted.

In special relativity departing clocks will always be redshifted, approaching clocks are typically blueshifted but in some cases they may be redshifted!

It might be an interesting exercise to calculate the conditions for which an approaching clock will not show any red or blueshift at all. :)

 

[Dale]

approaching clocks are typically blueshifted but in some cases they may be redshifted!

Good point, and congrats on breaking 1k posts!

 

[Dale]

Well, for now I have the feeling that relativity leans too much on the way we set the things to be perceived.

Your feeling is incorrect. It is an unfortunate misconception that happens sometimes. I have noticed it more in students who are taught relativity via "thought experiments" rather than geometrically, but it can happen either way.

The traveling clock for instance; it won't give time delay for the observer if it travels in circle around him and instead up-down it moves left-right.
I cannot imagine that left-right moving clock will stop showing time delay while making U-turn around the observer only because it went into a half circle.
It appears that the shape of the path is of a great importance for the time delay.

The shape of the path is indeed of great importance for the time delay, but of no importance whatsoever for the time dilation. That is because, as I have stated multiple times, the time delay is accounted for.

If your answer for the above is short and you have time, would you please explain, how it comes that the clock on the moon is not identical with the clock on Earth, but the clocks on the satellites are identical with those on the ground?

I cannot explain that. AFAIK it is not correct. Could you describe why you believe this? Perhaps I can help explain.

 

[Buckleymanor]

The principle of relativity says that identically constructed clocks all time dilate, it does not say that differently constructed clocks run the same. The gravitational field is an essential part of a pendulum clock, so a Moon pendulum clock and an Earth pendulum clock are not identical clocks. Similarly, atomic clocks depend on temperature, so a hot and a cold atomic clock are not identical clocks. You can find many other such examples.

Makes sense though it is not quite perfect how do you distinguish between relatavistic influencies and gravitational ones.
A Moon, Earth, pendulem, mechanical, or atomic clock are all effected by gravity or acceleration how do you decide if the effect is due purely to time dilation.
How do you separate the two.

 

[sisoev]

Your feeling is incorrect. It is an unfortunate misconception that happens sometimes. I have noticed it more in students who are taught relativity via "thought experiments" rather than geometrically, but it can happen either way.

Ha-ha :)
I got your point here :)

The shape of the path is indeed of great importance for the time delay, but of no importance whatsoever for the time dilation. That is because, as I have stated multiple times, the time delay is accounted for.

Now, here I am a bit of confused and embarrassed.
My English semantics is not as good as I'd like it to be.
Do you mean that in the curve of the U-turn the time will not delay, but it will carry the dilation from the approach toward the observer?
If so, we will have to assume that a clock starting its path in the curve will be in sync with our clock until it gets out of it (the curve)
Extending that though, the moving clock will never differ from our clock if it stays in the circle.
In other words, the clock which is moving in a circle does not show and does not even give us the idea for a time delay.
(How would we conclude that time dilation happens.)
Yet, we accept the illusion of the departing clock and dismiss the firs.

My point with the U-turn was that in it we observe the other frame of reference without any difference in the distance for any part of that frame.
In that case we don't observe red or blue shift of the light and no time delay or dilation.
Once the red (or blue) shift appears we see time delay.
Do you take in account the shift of the light spectrum.
Because it appears like the light approaches us with different speed (seen in the different shift of the light) and therefore we "experience" time delay in the other frame.

I cannot explain that. AFAIK it is not correct. Could you describe why you believe this? Perhaps I can help explain.

I don believe anything. I try to follow the facts.
We don't say that the time on the Moon is moving slower because the pendulum moves slower there. We know that this is due to the gravity.
You said that "the pendulum on the Moon is not identical with the pendulum on Earth".
A clock which is moving is not identical to clock which is in rest and so on.
But relativistic physicist say that the time on the satellites is slower than on Earth because the satellite clocks move slower.
How do you explain that claim if the clocks on the satellites cannot be identical with the clocks on the surface of Earth?

 

[Dale]

Makes sense though it is not quite perfect how do you distinguish between relatavistic influencies and gravitational ones.
A Moon, Earth, pendulem, mechanical, or atomic clock are all effected by gravity or acceleration how do you decide if the effect is due purely to time dilation.
How do you separate the two.

The period of a pendulum is approximately 2\pi\sqrt{L/g} so the dependence is very explicit. The period of an atomic clock is proportional to (m/M)\alpha^4mc^2, so I am not aware of any dependence on gravity or acceleration. A mechanical clock could probably be constructed either way, but I don't know a general formula for mechanical clocks.

 

[Passionflower]

Good point, and congrats on breaking 1k posts!

Wow 1k.
Have not posted much lately, perhaps to the relief of some :) , perhaps I can find some more time to post more often.

 

[Dale]

Do you mean that in the curve of the U-turn the time will not delay, but it will carry the dilation from the approach toward the observer?

The delay is proportional to the distance (delay=dist/c). Assuming that the U-turn maintains a constant distance to the observer then there is a delay, but it is constant during the turn. Despite the fact that the delay is not changing, time dilation is observed. This is known as the transverse Doppler effect, and has been experimentally measured.

Extending that though, the moving clock will never differ from our clock if it stays in the circle.
In other words, the clock which is moving in a circle does not show and does not even give us the idea for a time delay.

This is not correct. As I said above, this has been experimentally measured. Both with the frequency of emitted radiation as well as with the lifetime of unstable particles. I.e. both clocks based on EM and clocks based on the strong and weak nuclear forces demonstrate time dilation.

My point with the U-turn was that in it we observe the other frame of reference without any difference in the distance for any part of that frame.
In that case we don't observe red or blue shift of the light and no time delay or dilation.

Again, incorrect. We do observe a redshift.

I don believe anything. I try to follow the facts.

Excellent, here are the facts:
http://www.edu-observatory.org/physics-faq/Relativity/SR/experiments.html

You will want to pay special attention to section 4.

How do you explain that claim if the clocks on the satellites cannot be identical with the clocks on the surface of Earth?

I recommend that you learn special relativity before trying to learn general relativity. For now, let's avoid situations with gravity.

 

[Denius1704]

In a last effort to try and understand your explanations of relativity i will put the "paradox" in an example and i would like to "hear" from you what the exact explanation from the point of view of relativity will be.

The one twin is sitting on Earth, the other one is moving away at certain speed (let's use the half the speed of light example). So from the point of view of the twin on Earth, the moving one is aging two times slower than him and when he comes back to Earth he will be much younger, but... From the point of view of the moving twin, the one sitting on Earth will also be aging two times slower, because well... according to him, it is his brother that is moving away not him. So when he comes back to Earth, his brother would be much younger. Now if we assume that the time dilation happened, then both brothers would have aged less, equally... which will put them at the same age when they meet up with each other. So from what point of view would have the time dilation actually happened? From the perspective of a third observer? How would they be able to distinguish that time actually slowed down for any of them?

Or... Does the time dilation happen only for the "moving" brother, but not for the one sitting on Earth? And if so then how come the moving brother experiences only an illusion of the one sitting on Earth aging slower than him, without the actual time dilation, but the one sitting on Earth doesn't?

I know you said that this "paradox" is a paradox only to the people not using Relativity properly so i am asking how would one use Relativity properly to explain it and rule it out as an actual paradox?

 

[Dale]

I know you said that this "paradox" is a paradox only to the people not using Relativity properly so i am asking how would one use Relativity properly to explain it and rule it out as an actual paradox?

There are many ways to explain the twin paradox: http://math.ucr.edu/home/baez/physics/Relativity/SR/TwinParadox/twin_paradox.html

My favorite way is the spacetime diagram approach, but you should read them all and pick the one you like the best.

 

[ghwellsjr]

In a last effort to try and understand your explanations of relativity i will put the "paradox" in an example and i would like to "hear" from you what the exact explanation from the point of view of relativity will be.

The one twin is sitting on Earth, the other one is moving away at certain speed (let's use the half the speed of light example). So from the point of view of the twin on Earth, the moving one is aging two times slower than him and when he comes back to Earth he will be much younger, but... From the point of view of the moving twin, the one sitting on Earth will also be aging two times slower, because well... according to him, it is his brother that is moving away not him. So when he comes back to Earth, his brother would be much younger. Now if we assume that the time dilation happened, then both brothers would have aged less, equally... which will put them at the same age when they meet up with each other. So from what point of view would have the time dilation actually happened? From the perspective of a third observer? How would they be able to distinguish that time actually slowed down for any of them?

Or... Does the time dilation happen only for the "moving" brother, but not for the one sitting on Earth? And if so then how come the moving brother experiences only an illusion of the one sitting on Earth aging slower than him, without the actual time dilation, but the one sitting on Earth doesn't?

I know you said that this "paradox" is a paradox only to the people not using Relativity properly so i am asking how would one use Relativity properly to explain it and rule it out as an actual paradox?

I can see you like round numbers. Unfortunately, your example is flawed. You would have to go to a speed of 0.866c to get each twin to age two times slower than his twin, so with your permission, I'd like to illustrate what happens at a different speed, 0.6c because it makes the arithmetic come out in nice easy numbers.

At a speed of 0.6c the time dilation factor is 0.8. So let's assume that both twins are going to watch the other one age during the trip. There are many ways we could do this but let's just say that each twin has a blinking light that flashes exactly once per second and they each count the other one's flashes during the trip. As soon as the traveler starts out at 0.6c, they will each observe the other one flashing at exactly one have the rate of their own. This is a combination of time dilation and the delay in the light travel time.

Let's say that after many days, the traveler turns around. He will immediately now see the flashes from his Earth bound twin come in at double his own rate. But what will the Earth bound twin see? Well, he won't see anything different until several days later because the sight of his twin turning around is subject to the delay in the light travel time. Eventually though, he will see the light flashes coming from his twin suddenly go from one half his rate to double his rate. But this will happen near the end of the trip. It is this imbalance in the ratio of the observed rates by each twin of the other twin's flashes that accounts for the difference in the total count that each one makes of his twin's flashes and thus the amount that each one has aged during the trip.

Look up Relative Doppler for more details.

 

[sisoev]

The delay is proportional to the distance (delay=dist/c). Assuming that the U-turn maintains a constant distance to the observer then there is a delay, but it is constant during the turn. Despite the fact that the delay is not changing, time dilation is observed. This is known as the transverse Doppler effect, and has been experimentally measured.

This is not correct. As I said above, this has been experimentally measured. Both with the frequency of emitted radiation as well as with the lifetime of unstable particles. I.e. both clocks based on EM and clocks based on the strong and weak nuclear forces demonstrate time dilation.

I cannot find any reason of why the delay will be proportional to the distance.
It makes more sense to say that it is proportional to the light shift, because the light shift represents the distance.

I cannot also imagine that the light from a moving in circle object will be red shifted.
It is probably an error.
Since we do the measurements, the light travels in our frame of reference and since there is no difference in the distance, it MUST not show shift to red or blue, otherwise we will observe a paradox.

The red shift claim for circular moving object is very much like the explanation of the http://en.wikipedia.org/wiki/Ladder_paradox" ; it says that although both doors open simultaneously the ladder will see that the closer door opens first.
That's wrong, because the ladder sees the doors as light reflection and since the back door opens simultaneously with the front door, there will not be door at the back, to reflect a ligh which will travel to the lader and show a presence of a door.
To imagine it in easy way, we can put light source on the inside of the back door, and the switch to turn the light on we place on the front door when it opens completely.
If they open simultaneously, the ladder will never see the light beam from the back door, because new paradox will emerge; we will have two light beams, one directed to the ladder and one perpendicular down from the opened back door.

What do you say about that, DaleSpam?

Same is with the red shift of the light from a moving in circle clock.
If we say that we observe red shift, the clock will still see its own reflection from a mirror on "our side" as not shifted in any direction light. I put "Our side" between quotation marks, because we are actually a mirror in the clock's frame of reference.
In that case we will end up with two different wave lengths for same light, measured on same distance in two frames of reference.

 

[Denius1704]

I can see you like round numbers. Unfortunately, your example is flawed. You would have to go to a speed of 0.866c to get each twin to age two times slower than his twin, so with your permission, I'd like to illustrate what happens at a different speed, 0.6c because it makes the arithmetic come out in nice easy numbers.

As i stated in my first post i am not a physicist and the last time i used higher math was 12 years ago, so my use of numbers was just abstract to illustrate my point.

Let's say that after many days, the traveler turns around. He will immediately now see the flashes from his Earth bound twin come in at double his own rate. But what will the Earth bound twin see? Well, he won't see anything different until several days later because the sight of his twin turning around is subject to the delay in the light travel time. Eventually though, he will see the light flashes coming from his twin suddenly go from one half his rate to double his rate. But this will happen near the end of the trip. It is this imbalance in the ratio of the observed rates by each twin of the other twin's flashes that accounts for the difference in the total count that each one makes of his twin's flashes and thus the amount that each one has aged during the trip.

Look up Relative Doppler for more details.

So from what i understand it is the turnaround that gives the difference. What i don't understand is how come only the Earth bound twin takes into account this turnaround? I mean, the moving brother might not see the Earth bound one turn around, but from his point of view he would have stopped moving away from him, so for that amount of time the flashes would come at the same rate as his own flashes going out. But the same should be said for the Earth bound brother. He should see a transition from the 1/2 rate to 1 rate to 2 (double rate). It was even said in a previous post that time delay would change during a half circle turnaround. So basically both brothers should still experience the same changes.

Or it would be even simpler if we take out the whole turnaround event. Since this is purely theoretical example we can put an event of instant turnaround where the moving brother goes through one portal and comes out another at exactly the same distance but moving in reverse direction (towards Earth). That way the Earth bound brother won't have the turnaround event to mess things up for him. What happens in that situation then?

DaleSpam i opened that page you linked, and i still find it difficult to agree with the explanations. I take into consideration the fact that i don't understand most of the math in there, but still... the example that you prefer with the graph still takes into account only the POV of the Earth bound and does its math only from there. I opened another explanation which thankfully didn't have any math in it and the way they used to explain it there was with the whole inertial frame missing from the one brother. But even there they write that a possibility of the moving brother not experiencing any acceleration and gravitational forces with an instant turnaround could be considered and the explanation of that was left to the "reader". I take that as a failure to explain the problem fully and explaining it only when certain conditions are met and others aren't.

 

[ghwellsjr]

As i stated in my first post i am not a physicist and the last time i used higher math was 12 years ago, so my use of numbers was just abstract to illustrate my point.

The math in Special Relativity is very simple. If you have a calculator with a square root function, that's all you need. General Relativity, which involves gravity, requires very complex math. So please be content to leave gravity out of the discussions until you have mastered SR.

So from what i understand it is the turnaround that gives the difference. What i don't understand is how come only the Earth bound twin takes into account this turnaround? I mean, the moving brother might not see the Earth bound one turn around, but from his point of view he would have stopped moving away from him, so for that amount of time the flashes would come at the same rate as his own flashes going out. But the same should be said for the Earth bound brother. He should see a transition from the 1/2 rate to 1 rate to 2 (double rate). It was even said in a previous post that time delay would change during a half circle turnaround. So basically both brothers should still experience the same changes.

If you want the traveler to stop first and then turn around and start his journey home, then yes, there would be the transitions from 1/2 rate to the 1 rate to the double rate, and you are correct that the traveler sees this as soon as he stops and turns around. And the Earth twin will see exactly the same thing but not at the moment it happens because he has to wait for the flashes in travel over a very great distance to reach him which will take a long time.

Or it would be even simpler if we take out the whole turnaround event. Since this is purely theoretical example we can put an event of instant turnaround where the moving brother goes through one portal and comes out another at exactly the same distance but moving in reverse direction (towards Earth). That way the Earth bound brother won't have the turnaround event to mess things up for him. What happens in that situation then?

If I'm understanding you correctly, this is essentially what I was describing originally, that is, I didn't worry about how the traveling twin actually got turned around, I just assumed that he instantly changed from going away from the Earth (seeing 1/2 flash rate) to going toward the Earth (double flash rate).

So the bottom line is that the traveler counts the half-rate flashes from the Earth twin for the same amount of time that he counts the double-rate flashes, but the Earth twin counts the low-rate flashes from the traveler for most of the trip and doesn't start counting the high-rate flashes until near the end so he ends up with a much smaller count than the traveler does. And remember, they are each counting the one-second flashes from the other twin.

 

[sisoev]

........
And the Earth twin will see exactly the same thing but not at the moment it happens because he has to wait for the flashes in travel over a very great distance to reach him which will take a long time.
.........
So the bottom line is that the traveler counts the half-rate flashes from the Earth twin for the same amount of time that he counts the double-rate flashes, but the Earth twin counts the low-rate flashes from the traveler for most of the trip and doesn't start counting the high-rate flashes until near the end so he ends up with a much smaller count than the traveler does. And remember, they are each counting the one-second flashes from the other twin.

ghwellsjr, both brothers will see absolutely the same in a mirror turned image and will count flashes in absolutely the same ratio, since they are at same distance with same velocity relative to each other.
You'll eventually need to include the acceleration of the flying brother, but I don't see how that would resolve the time difference, because the brother on Earth (or in a motionless space craft) also sees himself as accelerating away. If the G-force during the acceleration helps somehow, then you will be right :)

 

[Dale]

DaleSpam i opened that page you linked, and i still find it difficult to agree with the explanations.

Well, the question was how relativity would explain it. All of those explanations are valid under relativity. It sounds like you do not understand relativity. Unfortunately for you, the experimental evidence is overwhelming. There is no avoiding relativity.

the explanation of that was left to the "reader". I take that as a failure to explain the problem fully and explaining it only when certain conditions are met and others aren't.

I think this is a little unfair to call a "failure". It is not possible for any document to cover everything. So any document must make a choice about what to cover and what not to cover. Then everything else is left to the reader or to other documents.

 

[ghwellsjr]

ghwellsjr, both brothers will see absolutely the same in a mirror turned image and will count flashes in absolutely the same ratio, since they are at same distance with same velocity relative to each other.
You'll eventually need to include the acceleration of the flying brother, but I don't see how that would resolve the time difference, because the brother on Earth (or in a motionless space craft) also sees himself as accelerating away. If the G-force during the acceleration helps somehow, then you will be right :)

The ratios that I'm talking about are not the 1/2 and double rates but rather the length of time that each twin sees those rates coming from the other twin. I will be 50-50 for the traveler and 80-20 for the Earth twin.

Earlier in this thread you have been asking about the light travel time but now you seem to believe that it is non-existent. Are you saying that when the traveler is far away from the Earth twin, the Earth twin will still see him change direction half way through the trip and he won't have to wait for the light from that action to reach him? If you believe this, then you are believing in action-at-a-distance or an infinite speed for light. Are you sure you want to maintain this position?

 

[sisoev]

The ratios that I'm talking about are not the 1/2 and double rates but rather the length of time that each twin sees those rates coming from the other twin. I will be 50-50 for the traveler and 80-20 for the Earth twin.

Earlier in this thread you have been asking about the light travel time but now you seem to believe that it is non-existent. Are you saying that when the traveler is far away from the Earth twin, the Earth twin will still see him change direction half way through the trip and he won't have to wait for the light from that action to reach him? If you believe this, then you are believing in action-at-a-distance or an infinite speed for light. Are you sure you want to maintain this position?

ghwellsjr with the twin brothers example you better think of the speed as of velocity, because in absence of a third object the speed is irrelevant.

Now try to imagine what happens to both brothers and you'll see no difference for both of them. One of them will do the real traveling, but the other will see himself as traveling the same path with the same acceleration, speed, turning around and arriving back.

When the "brother in motion" turns back, he will keep seeing the flashes sent to him before he turned back, and some time latter he will start seeing the flashes sent after he turned around.
Same for the other brother; he will see himself as turning around some time later after the "real turn" was made from his brother.

I do not imply limitless light speed in this example, for there is no space for such suggestion.