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# Most Difficult Relativity Puzzle contradicting observations

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Ok here is one of the most difficult puzzles about relativity. It regards those phenomena known as time dilation and lorentz contraction. We will use a relative velocity of 99.5% of the speed of light for which we know from previous posts give a lorentz contraction factor of gamma = 10.So the idea is that if you (in a ship with clocks) are passing a planet (which we will assume has both observers and clocks on it) with a relative velocity of 99.5% of the speed of light, that object will be shorter in the direction of relative motion by a factor of 10 and the clocks on that planet will be going 10 times slower than the clocks on you ship. This is not an optical illusion or anything like that because we are assuming that you have some way (which defies explantion like ESP) of knowing instantly what time is on the clocks of the planet and of knowing the length of the planet.Ok, now here is the crazy part. Motion is relative, so the situation for the observer on the planet you pass is the same as your own. This means that, for the observer on the planet, your ship is shorter by a factor of 10 in the direction of motion and the clocks on your ship are going 10 times slower than the clocks on his planet. So who is really shorter in length and whose time is really going slower?Now remember from our previous discussion that lorentz contraction and time dilation are not illusions. These are real and they have a concrete effect on the space traveler making his journey shorter for him than for the people he left behind. So how do you reconcile the contradictions between the observations of you on the ship and the observer on the planet?I will explain this later, but I would like to give people time to respond first. I will give everyone a hint though. The solution lies in fully understanding the relativity of simultaneity and understanding what is really meant by time dilation and how it is derived.

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So who is really shorter in length and whose time is really going slower?

Relative to what ?

relative to the ship, the plannel is shorter, relative to the plannet, the ship is shorter.

And in reality, the ship isnt realy changing shape, just the space that ship lives in.

if you reduce the length of a glass window by a factor of 10, the glass would shatter.

but the lorentz contraction effect would not damage the glass, right ?

i dont think i understand the question.

all of my "How it works" boots are in the loft at the monent.
they have a cool article about syncronisity beeing relative, and not absolute.

and a kick *bottom* explanation of the thought experiment that shows it.

it involes clocks ocupying all off space, and trying to synchronise them by beaming nformation as light, and timing the lights trip and thus canculating distances to use while synchronising clocks.

clock1 sends clock 2 a lazer beam and starts counting.
when it gets a responce it stop counting, get the current time, adds half the trip time to it, and beams the info off, clokc 2 recivs the time, corrects itself. its a great experiment, hurts your brain, if i w#find a link, ill post it.

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Relative to what ?relative to the ship, the plannel is shorter, relative to the plannet, the ship is shorter.
And in reality, the ship isnt realy changing shape, just the space that ship lives in.

Of course you are quite right. And yet when the ship is aiming at a destination the distance is shorter for him. Why isn't the distance that the ship travels shorter for the observer on the planet?

i dont think i understand the question.

The question is trying to apply common sense. There is only reality right? How can both have slower time. We know that when he arrives at a destination it is the guy on the ship who has less time passed. Lorentz contraction and time dilation looks so symmetrical between the ship observer and planet observer, but the result after reaching a destination is not symmetrical. Why is that?

all of my "How it works" boots are in the loft at the monent.they have a cool article about syncronisity beeing relative, and not absolute.

and a kick *bottom* explanation of the thought experiment that shows it.

it involes clocks ocupying all off space, and trying to synchronise them by beaming nformation as light, and timing the lights trip and thus canculating distances to use while synchronising clocks.

clock1 sends clock 2 a lazer beam and starts counting.
when it gets a responce it stop counting, get the current time, adds half the trip time to it, and beams the info off, clokc 2 recivs the time, corrects itself. its a great experiment, hurts your brain, if i w#find a link, ill post it.

Sounds really good. I'll look forward to your post of it.

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Sounds like to me this is a physics question you cant answer and youre hoping to find somebody who is a physics genius to answer it for you... hahahaProve me wrong by answering it yourself since we already read the puzzle...chin chin

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Well I would wait longer but frankly I am ready to start a new topic in a different area.When working out the solution I found that gamma = 2 or 86.6% of the speed of light was a more convenient choice of relative speeds for the problem. The diagram was easier to do in MS Word, so that document is attached. But here is the basic explaination.The point is that since velocity is relative, you cannot say who is moving and who is not. So when two observers are moving away from each other there situation is completely symmetrical and both see the same time dilation and lorentz contraction in the other. This seems to contradict the fact that when one is making a journey to a destination at a distance from the other that it is the traveler who traveled a contracted distance and experience time dilation, since for him the journey took less time, than for the other person watching.One of the basic tools for understanding this are two rows of regularly spaced synchronized clocks stretching out in the direction of motion, in front and behind both observers. One of these rows of clocks follows (keeping the same speed as) each of the two observers. The relativity of simultaneity means that when one observer looks at the row of clocks following the other observer traveling at a relative velocity close to the speed of light, those clocks do not give all the same time.The key question is then, how is the symmetry between the two broken in the travelers case and the answer is two-fold. First, the destination chosen for the traveler is basically at rest with respect to the other observer. Once you start thinking in terms of such a destination the symmetry is already broken and the distance is shorter for the traveler. This is breaking of symmetry is only in how we look at the problem. It is only when the traveler arrives and slows down and stops is the symmetry really broken. When he slows down two things change. First the distance to the destination stretches back out to what is measured by the "stationary" observer. The second is that the time on all the clocks following the other observer change to match the the one at the postition where he comes to a stop.

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When making the previous post I realized that many people might object that the result of the actions described for A and B, that is A slowing down and B speeding up to follow one year behind A, would not make sense. And I think the main objection by common sense is what if they both do these actions at the same time?Well, think about that question again while looking at the two rows of clocks and tell me what you mean when you say "at the same time." Our intuitive grasp of what we mean by this phrase does not apply to this situation at all. What is at the same time for observer A is not what observer B thinks of as being at the same time, and if either one stops or accelerates. what "at the same time" means to the observer doing this becomes uncertain (since all the clocks are changing). This makes it impossible to talk about both stopping or accelerating at the same time in any meaningful way.

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to me it seems as if you are making a simple concept difficult. to ask who is slower or who is shorter reveals that u dont understand relativity. when we ask who is slower we cannot answer that without asking 'relative to' because as Einstein showed time itself gets curved when a body is in motion. life for the people on the planet will go as normal even if it seems slower to us.....life of the people in the spaceship will go normal too but it will seem slower to the ppl on the planet, that is wat is meant by time dilation. of course they are not illusions, they are products of the einsteinian discovery of relativity, when 2 bodies are moving relative to each other there is time dilation, no matter how fast or slow one is travelling.even if im running and u are stationary our clocks will move at different speeds, we dont notice this only because the difference is very miniscule at the speed im running at.

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I'm a fan of quantummechanics. The relativitytheory only applies to large things (the evolution of the universe and so on). And because I got the question and the answer so well, I'll remember Stephen Hawking: nobody can really understand the relativitytheory. Thank you, mr Hawking.

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life for the people on the planet will go as normal even if it seems slower to us.....life of the people in the spaceship will go normal too but it will seem slower to the ppl on the planet, that is wat is meant by time dilation.  of course they are not illusions, they are products of the einsteinian discovery of relativity, when 2 bodies are moving relative to each other there is time dilation, no matter how fast or slow one is travelling.

even if im running and u are stationary our clocks will move at different speeds, we dont notice this only because the difference is very miniscule at the speed im running at.

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This is a good and accurate description. Perhaps this will clear up a few things for anyone who did not get what I was saying.

to me it seems as if you are making a simple concept difficult.  to ask who is slower or who is shorter reveals that u dont understand relativity.

I am glad it all makes simple sense to you. Other people have a harder time. I am an educator as well as a physicist and it is my job to unravel the difficulties and not just say how simple it really is. My question was posed in the language of common sense, because that is the way most people think. You cannot educate by simply speaking your own special (physics) language and expect all people to understand it.

I would be careful about starting a fight here by questioning how well other people understand something just because they don't understand it the same way you do. If you want to talk about real understanding, well then the only language suitable for relativity is mathematics. Real understanding of relativity is being able to do the math. Show me a solution to a problem to show me your credentials and point out the errors in my math to make a valid criticism. Otherwise your just talking some philosophy of relativity (some meta-physics), and in that case your only authority can come from how well you argue your case, not how well you can put down your opponent.

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I'm a fan of quantummechanics. The relativitytheory only applies to large things (the evolution of the universe and so on). And because I got the question and the answer so well, I'll remember Stephen Hawking: nobody can really understand the relativitytheory. Thank you, mr Hawking.

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Very interesting quote. I am very much want to know where you got it. I like to see the context of such quotes. I have seen many of Einstein's quotes misused terribly.

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