Who is More "Relative"?

[Janus]

My point is that velocity is not the cause of the change in rate of the clock.

At constant speed the rate of the clock doesn't change. At v=.86 the rate of the clock is .5 and will always be .5 as long as v=.86

You are speaking of rate' date=' I am speaking of change of rate. Can you reread my post and I think you will understand what I want to tell

Thanks[/quote']

 

Actually, it isn't clear from your post.

 

But that aside, it still isn't correct to attribute even the "rate of rate" of the clock to acceleration.

 

To use your example of a clock in space compared to a clock on the Earth, then the difference in the clocks rates would be always changing. (the clock in space would not only run faster than the Earth clock but at an ever increasing rate. This is not the case, while the two clocks will run at a different rate, that rate diference wil remain constant.

 

Another example uses a centrifuge. If you put a clock on the arm of a spinning centrifuge it will will both be traveling at a constant speed and constantly accelerating. If acceleration had the effect of changing the rate between clocks as you suggest, then the rate of the clock would be constantly changing. Again, this is not the case.

 

This experiment has been actually done with radioactive isotopes. By changing the speed of the centifruge and the length of its arms, you can get all kinds of combinations of accelerations and velocities.

All the experiments show that the difference in time experienced by the samples are related to the magnitude of the velocity of the sample and the that the acceleration had no effect.

[Jacques]

Thanks for taking the time to answer me.

it still isn't correct to attribute even the "rate of rate" of the clock to acceleration.

Then, what is the cause of change in clock rate when we change reference frame ?

You resolve the twin paradox by answering the question "Is it A or B clock who run slow ?" by "the clock who run slow is the clock who accelerated".

 

I have a question:

At a space staion far far away where the gravity field is neglictable (around 0)

a space ship have is clock sychronized with the clock of the station. The 2 clock run at the same rate. On January 1st 3000 the spaceship leave the space station and accelerate to .86 C and take 1 years to get to that speed.

What will the clock on the spaceship indicate ?

[Jacques]

Can I say that Einstein priciple of equivalence betwen gravity and and accelerated frame is false ?

Gravity is not equivalent to an accelerated frame.

If acceleration had the effect of changing the rate between clocks as you suggest, then the rate of the clock would be constantly changing. Again, this is not the case.

In the ascencor the acceleration is causing a rate of rate change in time.

AS the space ship speed up thee relativitic time dilatation is increasing.

In a gravitational acceleration the the change of rate is constant.

I am conscios that saying something like that will make me look like a freak but think about it.

Thanks

[5614]

I thought of a good analogy to answer the original post.

 

Imagine a black man that grew up among black people only and had never seen a white man. Then also imagine a white man that grew up among white people only and had never seen a black man.

 

One day they both meet each other. The white man looks and thinks "he looks weird" and the black man looks back and thinks "he looks weird".

 

They both think that the other looks weird. There is no real answer as to who is really weird.

 

Similarly in relativity I look at you and you are moving... then you look at me and I am moving. There is no real answer as to who is moving.

 

NB: No racism intented.

[kenshin]

Read the books called "The Elegant Universe" and "The fabic of the cosmos" by Brian Greene - he dose a good job of explaining it through mst of the book is on multiple dimensions' date=' M-theory and string theory

Ryan Jones[/quote']

 

agreed.I was thinking the same while going through the posts.When I first read this twin paradox,I also asked the same question.But Brian Green handles it very well.It's a must read for you,at least the chapter on relativity.

[YT2095]

I thought of a good analogy to answer the original post.

 

Similarly in relativity I look at you and you are moving... then you look at me and I am moving. There is no real answer as to who is moving.

 

rather than Answer it, it actualy re-asks the question in a different way.

If there`s no way to determine Who is Moving, then there`s no way either of them can be younger than the other when they eventualy meet up

[s pepperchin]

rather than Answer it' date=' it actualy re-asks the question in a different way.

If there`s no way to determine Who is Moving, then there`s no way either of them can be younger than the other when they eventualy meet up [/quote']

 

That is exactly why it is called the twin paradox. That statement sums up the paradox.

[timo]

If there`s no way to determine Who is Moving, then there`s no way either of them can be younger than the other when they eventualy meet up

EDIT: I misread your post first. I read "... except when they eventually meet up".

 

As I tried to show in my first post in here, you cannot objectively tell who ages faster (which line inceases faster). But you can compare age differences when they meet. Translating this to my line-example: You can tell which connection from A to B is the shorter one:

[s pepperchin]

Yes, that fits it quite well. As I tried to show in my first post in here, you cannot objectively tell who ages faster (which line inceases faster). But you can compare age differences when they meet. Translating this to my line-example: You can tell which connection from A to B is the shorter one:

 

From your diagram we can see which line is shorter, however if I would apply the right transformation to the lines I could make the other line shorter. My transformation could be the way the other person witnesses an event and this would lead us once again to a paradox.

[timo]

From your diagram we can see which line is shorter, however if I would apply the right transformation to the lines I could make the other line shorter.

Print it out on a piece of paper and then tell me which way to turn the piece of paper around such that the green line becomes shorter. There is none. Using scissors or streching parts of the paper is not valid, btw. That´s equivalent to modifying spacetime (the piece of paper).

 

EDIT: To be a bit more helpful: Within SR, transformations between inertial frames of reference are really only rotations in spacetime (plus an offset, perhaps - but feel free to move the piece of paper around your desk, too).

In fact, my statement that you can tell which line is longer is realized in an even stronger way in relativity. In relativity, the statement "lengths of lines remain unchanged under ANY coordinate transformations" holds true. It finds its mathematical realization in the transformation laws for covariant and contravariant indices and the transformation law for the metric. I´d even say that it´s a nessecary statement for relativity to be physically meaningfull but don´t pin me on this as I didn´t bother to formally check this.

[s pepperchin]

Print it out on a piece of paper and then tell me which way to turn the piece of paper around such that the green line becomes shorter. There is none. Using scissors or streching parts of the paper is not valid, btw. That´s equivalent to modifying spacetime (the piece of paper).

 

Turning the piece of paper is a simple rotational change in the coordinates of the system. However I could apply a transformation matrix to a system which changes the shapes of lines. If you look in a calculus or linear algebra book there will be an explanation of different types of transformation matrices.

[timo]

I don´t have any books on such advanced topics, sorry. So let´s give an example: R², cartesian coordiantes. Red curve is {(0,p) : 0<=p<=1}, green curve is {(p,p) : 0<=p<=5, (p, 0.5-p): 0.5<p<=1}. Which matrix to you apply that results in the green curve being shorter than the red one?

 

EDIT: ^^ I knew I shouldn´t have posted this but I´m afraid it´s too late now. As a matter of fact, above example doesn´t really matter. Relativity isn´t based on LA but on differential geometry. Lengths of curves simply ARE independent of coordinate systems - the whole formalism of tensor algebra is based upon that principle.

[Jacques]

From what I read here there is no solution to the twin paradox.

[swansont]

From what I read here there is no solution to the twin paradox.

 

 

The acceleration did it. (Sorry if I ruined then ending for anyone)

[Jacques]

Twins A and B in space. A accelerate to the left and B accelerate to the right.

???

1) A age faster than B

2) B age faster than A

3) A and B age at the same rate

4) 1) and 2)

[s pepperchin]

If you have the proof I would like to see it.

[Jacques]

It's a question

[Klaynos]

In special relativity you ignore the acceleration effects, if you take these into account, which is part of general relativity I belive then the paradox no longer exists as the acceleration deals with the apparant time difference. I unfortunatly am not familiar with the maths, my relativity and mechanics course is currently on the second part of three, and the thrid one is general relativity, so after my easter break + a few weeks I'll hopefully be able to solve this for you...

[swansont]

Twins A and B in space. A accelerate to the left and B accelerate to the right.

???

1) A age faster than B

2) B age faster than A

3) A and B age at the same rate

4) 1) and 2)

 

They should age at the same rate. What's the paradox? (And this is not "the" twin paradox)

[wormholeman]

this has been bugging me for ages' date=' this whole twins and one in a rocket at near c thing.

 

if I`m stationary in space (I`ll do it there as opposed to a train and station for reasons that`ll become clear later), and a spaceship with my twin passes me at near c BUT at a constant speed, time will go slower for him than it will for me, but WHY? I`m moving just as fast relative to him in the other direction, so Who is getting "Younger"?

Gravity is playing little part as is mass (that would occur on a train and station on a large Earth).

 

who is to say WHO is actualy moving, what dictates the one whos time goes slower:confused:[/quote']

 

To answer your question on the bases of my thinking. Why I think time would

go slower for your twin is because your twin is moving at near c, but you say

at a constant speed, but because he is at a constant speed. Your twin, I think would be on another level of time and because your twin is traveling at a speed, he had to have accellerated somehow, and because you are not moving and are stationary, time stays neutral for you.