Understanding the Validity of Relativity: Questioning and Learning

[Joanna Dark]

I have just read the "Read Before Posting" sticky thread and am wondering. Relativity is a difficult theory to understand. How is a person supposed to learn of its validity if they are to automatically assume it is correct.

How do I know it is absolutely correct? If people can't question it how can they learn? Also why would it matter if people argued for or against it? People who don't care about discussing its validity would just ignore such a thread. Or is it a subject that evokes personal insults and gets out of hand?

Curious.

 

[Tachyonie]

Mabye because there is very little to no evidence that Einstein is wrong and therefor, give it that this is internet we are talking about, people could write whatever they want and that never has a good end.

But main reason is probably that this forum is supposed to help people learn and solve problems. If every second thread was an attempt to disproove this theory, students wouldn't be amused would they?
Oh and that doesn't mean you cannnot ask why is it correct when according to [your piece of evidence] it should be incorrect. You are right that a lot of learning comes from questioning the theory, but people often overreact.

Tachyon.

 

[Ich]

Also why would it matter if people argued for or against it? People who don't care about discussing its validity would just ignore such a thread. Or is it a subject that evokes personal insults and gets out of hand?

This is your first time online?
There are hundreds of cranks out there who question the validity of relativity. They all share at least three characteristics:
1. Discussions with them get out of hand.
2. They have insufficient knowledge of relativity.
3. They don't want to learn about it.
That's why there are specific rules.

 

[Joanna Dark]

Ok thanks. So I can discuss the difficutly I'm having and not be dismissed. Hopefully.

I'm currently studying relativity and my teacher doesn't seem to grasp the problem I'm having and continuously gives me the same answers. As if that will help my confusion, if you catch my drift.

Einstein pointed out that events aren't observed simultaneously from all frames of reference. I see a lightning bolt 3 miles away at a different time to a person 6 miles away. In order to know this we might create an artificial absolute frame of reference, calculate the speed of light, time observed and distance. We can know when the event occurred and when each observer saw the event.

That is to say our single frame of reference is incomplete. We could create a model of the entire visible universe and understand each frame of reference, it's distance to one another, it's time dilation and when each frame observes every event taking place. This model in my mind would be a collective, yet limited, absolute reference point within its own context.

My teacher keeps telling me that there is no absolute reference point. But within reason we can create one. Is this right?

The reason this is confusing to me is why Einstein makes the claim that if I am moving it appears as if the whole universe is moving. On the one hand you could state this is true. But on the otherhand we can know by calculating time dilation which body is traveling at which speed comparatively to another. You could suggest that both references were correct but I'm more inclined to accept the artificial absolute as acceptable and my single point of view is an illusion, or in appearance only.

Why is this a problem for me? I seem to gather from Einstein that he understood that according to the experiments in water that light the speed of light was constant. He then extrapolated it to mean that the speed of light was constant for all frames of reference. This is a big leapof faith. If you remember the mental experiment of the passenger on the train observing the speed of light compared to the observer on the station, he uses an artificial absolute reference point to suggest that time dilation occurs for the passenger so the speed of light is constant. That makes sense.

He then eliminates this absolute reference point to suggest that for the passenger on the train it appears that time dilates also for the observer standing at the station. If that were true then the theory is definitely counter-intuitive. But we can calculate the time dilation of the observer on the train. So the reciprocation that Einstein suggests, based on the hypothetical absolute frame of reference, is true for only one observer and an illusion for the other.

But this is the reason, I believe, that Einstein makes the claim that the speed of light is the same for all observers. Seems to be half true and half in appearance only.

See if I can make this clearer. The observer sees the man at the station apparently moving and the man at the station sees the train apparently moving. Both believe the other to be experiencing time dilation but when they meet up only one observer did.

The only reason we know of time dilation occurs is because of Einstein's artificial absolute point and experimentation to prove it. When I reverse the experiment and use the same artificial absolute I get reprimanded and told there is no absolute, that I don't understand reciprocation and that I can't understand it logically. Not just by my teacher either. I've taken this issue to others aswell. It seems that I can understand what others are saying but they can't quite grasp the actual reason I'm confused and explain it back to me. Seems more like dogma, in reference to anyone I've ever spoken to about it, than actual understanding.

On one hand you can create an artificial absolute and on the other it doesn't exist, seemingly depending on what works for the theory that the speed of light is constant fot all observers to be true.

That is my current understanding and have not yet received adequate explanation. Thanks

 

[Joanna Dark]

I'll dumb it down a bit.

An observer on a moving train sees a light traveling between the floor and the ceiling. An observer on the train station sees the same light travel a different distance yet they perceive the light to be traveling at the same speed. How is that possible? Time slows down for the observer on the train. Right? Basic relativity example used by Einstein based on an artificial absolute frame of reference.

Now try reverse the experiment. Pretend the light is still on the train, the train is stationary. The train station, with the observer still standing there, is actually moving. How is it possible that both observers see the same speed of light now? This is where my teacher throws the artificial absolute frame of reference out the window and the theory sticks.

Seems like a contradiction to me.

 

[Joanna Dark]

Huh I figured it out.

So it's a simple answer because in the first eg. the moving observer sees the light traveling a shorter distance than it really is and in the second example the moving observer sees the light traveling at a longer distance (and the light is moving between two moving points in the first eg. [add time dilation] and two stationary points in the second eg. [negative time dilation]) then both observers will see it traveling at the speed of light. Double negative equals positive.

So this is neither counter-intuitive nor has it got anything to do with reciprocation. Duh! Why don't people explain this properly? Make me go nuts with this illogical frigging reciprocation.

 

[peter0302]

I have just read the "Read Before Posting" sticky thread and am wondering. Relativity is a difficult theory to understand. How is a person supposed to learn of its validity if they are to automatically assume it is correct.

How do I know it is absolutely correct? If people can't question it how can they learn? Also why would it matter if people argued for or against it? People who don't care about discussing its validity would just ignore such a thread. Or is it a subject that evokes personal insults and gets out of hand?

Curious.

Go to sci.physics.relativity on usenet if you want to see what happens when people are allowed to post whatever they want with no evidence.

 

[pervect]

Ok thanks. So I can discuss the difficutly I'm having and not be dismissed. Hopefully.

I'm currently studying relativity and my teacher doesn't seem to grasp the problem I'm having and continuously gives me the same answers. As if that will help my confusion, if you catch my drift.

From my POV, what needs to happen is that you need to listen more to your teacher. I'm sensing a certain hostility here between you and him or her, which is unfortunate.

My teacher keeps telling me that there is no absolute reference point. But within reason we can create one. Is this right?

No, you can't create an absolute reference point.

You are making some false assumptions about the way time acts, apparently they are so deeply ingrained into your worldview that you don't realize that they _are_ assumptions (incorrect assumptions, to boot) rather than facts.

A litmus test for how time acts is the twin paradox. If you have two twins, each with their own clock, a twin following an accelerated trajectory will have a lower elapsed time on their clock than a twin following an unaccelerated trajectory.

Assumptions: the twins are in the flat space-time of SR, and the twins start out at the same location in space-time and eventually re-unite.

see for instance.
http://math.ucr.edu/home/baez/physics/Relativity/SR/TwinParadox/twin_paradox .

The twin "paradox" is fundamentally incompatible with any notion of "absolute" time.

 

[Joanna Dark]

I thought the speed of light was the problem.

This idea that if I'm moving faster than another that I will observer their clocks going slower is silly.

To explain it properly let's just say that observer one is stationary and observer two is moving. Let's compare them side by side. Observer one sees his own clock traveling normally and observer two is in slow motion and so is his clock. Observer two's clock is traveling normally however he sees observer one in fast forward and so is his clock. Then the speed of light is equal for all observers and the Theory of Special Relativity makes perfect LOGICAL sense.

Reverse the lorentz transformation to understand a slower moving bodies actual time and velocity. No wonder people don't understand it.

It may seem perfectly acceptable that if I am moving it appears as if I'm stationary. But I won't see slower time dilation in others. It's a simple optical illusion like escher drawing that is physically impossible, not some freak of nature phenomena. Had me going for months.

 

[Tachyonie]

Huh I figured it out.

So it's a simple answer because in the first eg. the moving observer sees the light traveling a shorter distance than it really is and in the second example the moving observer sees the light traveling at a longer distance (and the light is moving between two moving points in the first eg. [add time dilation] and two stationary points in the second eg. [negative time dilation]) then both observers will see it traveling at the speed of light. Double negative equals positive.

So this is neither counter-intuitive nor has it got anything to do with reciprocation. Duh! Why don't people explain this properly? Make me go nuts with this illogical frigging reciprocation.

I see you figured it out yourself, but just incase I posted this very useful link containing 24 lectures mainly about special/general relativity.
Check them out, I remember this exact problem being discussed in there, I believe it could have been lecture 5 or something near that number.

Tachyon.

 

[Joanna Dark]

No, you can't create an absolute reference point.

You are making some false assumptions about the way time acts, apparently they are so deeply ingrained into your worldview that you don't realize that they _are_ assumptions (incorrect assumptions, to boot) rather than facts.

The twin "paradox" is fundamentally incompatible with any notion of "absolute" time.

No your misunderstanding the problem like my teacher.

There is an ARTIFICIAL absolute frame of reference. That is not the same thing. By calculating all reference points you do get an absolute of sorts. Whereby we can tell who's time is moving faster of slower or who's velocity is faster. If there was no artificial absolute then we'd still be in the dark ages.

Between you and me who is traveling faster hypothetically? How would you know? Without some reference to make an accurate judgement then we both are! Illogical explanations. Einstein's theory could have been so much easier to learn.

 

[Doc Al]

I thought the speed of light was the problem.

This idea that if I'm moving faster than another that I will observer their clocks going slower is silly.

Open your mind, grasshopper.

To explain it properly let's just say that observer one is stationary and observer two is moving. Let's compare them side by side. Observer one sees his own clock traveling normally and observer two is in slow motion and so is his clock.

OK. Observer one certainly observes his own clocks running normally, and he measures Observer two's clock and concludes that it operates more slowly than his own.

Observer two's clock is traveling normally however he sees observer one in fast forward and so is his clock.

Half right. Observer two sees his own clock running normally. But he also measures Observer one's clock as running slow--according to his clocks. The relativistic effects are completely symmetric.

Then the speed of light is equal for all observers and the Theory of Special Relativity makes perfect LOGICAL sense.

If what you said were true it would contradict the fact that the speed of light is the same for all observers.

Reverse the lorentz transformation to understand a slower moving bodies actual time and velocity. No wonder people don't understand it.

Huh?

It may seem perfectly acceptable that if I am moving it appears as if I'm stationary.

You will appear stationary to yourself.

But I won't see slower time dilation in others.

Sure you would, if they were moving fast enough with respect to you.

It's a simple optical illusion like escher drawing that is physically impossible, not some freak of nature phenomena. Had me going for months.

Not quite. You haven't seen the light yet.

 

[Doc Al]

There is an ARTIFICIAL absolute frame of reference. That is not the same thing. By calculating all reference points you do get an absolute of sorts. Whereby we can tell who's time is moving faster of slower or who's velocity is faster.

To use your terminology, the idea of telling who's velocity is actually faster is silly. Forget Einstein for the while, you need to study Galileo.

If there was no artificial absolute then we'd still be in the dark ages.

Oh?

Between you and me who is traveling faster hypothetically? How would you know? Without some reference to make an accurate judgement then we both are!

The answer is that it's a meaningless question to say who's traveling faster unless you specify with respect to what. And the "what" is completely arbitrary.

Illogical explanations. Einstein's theory could have been so much easier to learn.

Perhaps because you missed the point?

 

[Joanna Dark]

What I believe happened was that Einstein developed an accurate theory that is rather complicated and after he explained time dilation he couldn't quite figure out how to reverse the situation. So instead he went off on a long tangent of reciprocation (or symmetry as you put it) which has no basis in logic.

Therefore for the next hundred years this theory got repeated by a whole bunch of people whose specialty is mathematics as opposed to mental visualisation, which is the process by which Einstein's brain worked.

Now you honestly try to tell me that if my time is going faster than yours (based on a previous experiment whereby only your clock experienced time dilation, if you will) that you could possibly see my clocks running slower.

I'm now not so sure that the "cranks" as they were so endearingly termed are necessarily nuts. They are just trying to get their heads around a concept that Einstein fans admit can't be logically understood.

I have just offered my theory of the situation based on the best of my knowledge, so please anyone, give me one good reason for the validity of reciprocation, when it makes no sense and Einstein's theory functions perfectly without it?

Just one good reason and i'll accept it without question.

 

[chroot]

You have demonstrated here in this very thread that you haven't the faintest grasp of the theory, yet you're completely confident in dismissing it, and even putting words in Einstein's mouth! Don't you see the irony in your position?

Special relativity is incredibly simple; all you need is a decent explanation and high-school algebra. The fact that you do not yet understand it means nothing about its veracity. You're simply ignorant. If you wish to remain ignorant, it's a personal decision -- you can fault no one but yourself.

- Warren

 

[Joanna Dark]

Hey I said his theory functions perfectly. I offered an opinion on a possible mistake in his theory no words were put in anyone's mouth. But if you would like to put words in my mouth and make personal insults then that is a choice too.

 

[chroot]

I haven't read a single coherent explanation of any "mistake," Joanna. All I've read are misconceptions that indicate you don't know what you're talking about.

- Warren

 

[Joanna Dark]

I am giving you the solution.

Offer me one good explanation for reciprocation and I'll accept it without question.

If einstein was right on this point, then I'm wrong. If not the Theory of Special Relativity makes complete sense to me.

It's your call.

 

[chroot]

Please define "reciprocation."

- Warren

 

[Doc Al]

What I believe happened was that Einstein developed an accurate theory that is rather complicated and after he explained time dilation he couldn't quite figure out how to reverse the situation. So instead he went off on a long tangent of reciprocation (or symmetry as you put it) which has no basis in logic.

You seem to think that because something makes no sense to you, that that is somehow an argument against it. (It's actually a famous fallacy of informal logic: The argument from personal incredulity.)

Therefore for the next hundred years this theory got repeated by a whole bunch of people whose specialty is mathematics as opposed to mental visualisation, which is the process by which Einstein's brain worked.

Now you honestly try to tell me that if my time is going faster than yours (based on a previous experiment whereby only your clock experienced time dilation, if you will) that you could possibly see my clocks running slower.

Have you even lifted a finger to actually learn something about relativity and why both observers must see the other's clocks run slow?

I'm now not so sure that the "cranks" as they were so endearingly termed are necessarily nuts. They are just trying to get their heads around a concept that Einstein fans admit can't be logically understood.

Nothing wrong with not understanding something. It's the ranting and railing that gets tedious fast.

I have just offered my theory of the situation based on the best of my knowledge, so please anyone, give me one good reason for the validity of reciprocation, when it makes no sense and Einstein's theory functions perfectly without it?

You are sadly mistaken if you think Einstein's theory "functions perfectly" without the "reciprocity" of time dilation (and other relativistic effects). In fact, one of the premises underlying relativity states that the laws of physics are the same in all inertial frames. So if it's true that a moving clock "runs slow" in one frame, that same principle had better apply in every frame.

In order to properly understand how it could possibly be true that both observers see the other's clocks run slow, you first have to understand what it means to measure the rate of a moving clock. You'll see that a full appreciation of time dilation requires understanding length contraction and the concept of simultaneity, as well as just "time dilation". It's tricky, but not that hard. And it's perfectly logical.

Just one good reason and i'll accept it without question.

It's never a good idea to accept anything "without question".

There are many books out there that do a great job of teaching the basics of relativity from the ground up. (If you are interested, just ask.)

Here's a link to one in a series of lectures covering the basics: http://galileo.phys.virginia.edu/classes/252/time_dil.html" . This particular lecture explains by example how the symmetry of relativity is consistent and perfectly logical. (To understand it, you'll have to go back and read the earlier lectures in the series.)

If you're interested in learning, by all means stick around. But if all you want to do is rant against your professors or against relativity--take it elsewhere.

 

[Joanna Dark]

Let's just say you're seeing me off at the station (which you might well wish to do right now ) and I'm on the train and my clock is running slow. Why would I also observe your clock to be running slow? That has had me up for nights on end over the past few months. I just figured out this morning that if I didn't see your clock running slow, rather the opposite it was fast, then everything falls into place and alleviates all the confusion I had experienced.

Give me one good reason as why my understanding is misguided and I'll graciously accept it. Otherwise I think I'll get a few good nights sleep.

 

[chroot]

If you see a traveler's clock as running slowly (because he is moving quickly with respect to you), then he must see your clock as running slowly, too (because you are moving quickly with respect to him).

- Warren

 

[Doc Al]

Let's just say you're seeing me off at the station (which you might well wish to do right now ) and I'm on the train and my clock is running slow.

Why is your clock running slow?

Why would I also observe your clock to be running slow? That has had me up for nights on end over the past few months.

Why don't you crack the books or the link I gave and find out? If you expect a one sentence answer that explains relativity using "common sense", stop wasting time.

I just figured out this morning that if I didn't see your clock running slow, rather the opposite it was fast, then everything falls into place and alleviates all the confusion I had experienced.

It eliminates confusion by ignoring the complications of relativity. Not a good deal.

Give me one good reason as why my understanding is misguided and I'll graciously accept it. Otherwise I think I'll get a few good nights sleep.

Summarizing your logic: If I think X, then I conclude Y and Y makes sense. Sadly, Y has nothing to do with relativity (and doesn't really make sense).

I think you should just relax and get some sleep.

 

[Mentz114]

I'm on the train and my clock is running slow. Why would I also observe your clock to be running slow?

Your clock is not running any differently than it would if you were not on the train. You would not be aware of any effect of your motion. Only when your clock is measured by an observer in motion wrt your frame will it appear to be slower than the observers clock.

Also you seem to be confusing the situation where two inertial observers measure each others clock rate, and the round trip situation where clocks are synchronised, and one of them takes a round trip. This is not a symmetrical situation.

[simultaneous with Doc Al's post]

 

[Joanna Dark]

Well good explanation meaning that I agree with it. Just to clarify.

You are sadly mistaken if you think Einstein's theory "functions perfectly" without the "reciprocity" of time dilation (and other relativistic effects). In fact, one of the premises underlying relativity states that the laws of physics are the same in all inertial frames. So if it's true that a moving clock "runs slow" in one frame, that same principle had better apply in every frame.

That's an answer. So you are saying that if you were at a stationary or inertial train station and I was traveling at ANY constant velocity in any straight line (towards you or away from you or even parallel to you) my clock would run at the same rate as yours? I was led to believe that in this case time dilation would still occur for me and my clock would still be behind yours. So if my speed being non-inertial and you are stationary or inertial might I see your clocks running fast?

 

[chroot]

If you're moving with respect to me -- in any fashion whatsoever so that your distance from me is changing -- your clock will appear to me to be running slowly, as compared to my own. Similarly, my clock will appear to you to be running more slowly than your own.

If we are at rest with respect to each other, we would both observe each others' clocks running at the same rate as our own.

- Warren

 

[MikeLizzi]

Here we go again

Well, yes, I guess things do get out of hand when the admin starts insulting people. Maybe its time chroot got it. Special Relativity is incredibly difficult. All you can do with high school algebra is plug numbers into equations. If that’s chroot's criteria for understanding then I would add him to the list of the ignorant. Maybe if people were told that SR was difficult they would stop assuming they could understand it after only a few hours and stop posting premature conclusions.

 

[chroot]

Well, yes, I guess things do get out of hand when the admin starts insulting people. Maybe its time chroot got it. Special Relativity is incredibly difficult. All you can do with high school algebra is plug numbers into equations. If that’s chroot's criteria for understanding then I would add him to the list of the ignorant. Maybe if people were told that SR was difficult they would stop assuming they could understand it after only a few hours and stop posting premature conclusions.

Go get a copy of Feynman's lectures. Look at the chapter on special relativity. It's perhaps 20 pages long, and as complete and thorough as anyone could hope. Any high schooler could understand it, given the desire to understand it. It's not hard.

I didn't insult Joanna personally -- I simply called her ignorant, which is a factual statement. I want her to understand that her opinions about the theory are irrelevant when she is demonstrably unaware of what the theory even says. You know, the old adage about books and covers...

- Warren

 

[matheinste]

Hello chroot.

-------If you're moving with respect to me -- in any fashion whatsoever so that your distance from me is increasing -- your clock will appear to me to be running slowly, as compared to my own. Similarly, my clock will appear to you to be running more slowly than your own.---------

Would it not be best to use changeing instead of increasing here. It could lead to misunderstanding in this particular case.

Matheinste.

 

[chroot]

Would it not be best to use changeing instead of increasing here. It could lead to misunderstanding in this particular case.

Correct.

- Warren

 

[Doc Al]

That's an answer. So you are saying that if you were at a stationary or inertial train station and I was traveling at ANY constant velocity in any straight line (towards you or away from you or even parallel to you) my clock would run at the same rate as yours? I was led to believe that in this case time dilation would still occur for me and my clock would still be behind yours.

As has been stated several times: If you and I are in inertial frames moving with respect to each other, then we both see each other's clocks run slow. We both see our own clocks running just fine.

Further: Just because my clocks run slow according to your measurements, does not mean that something has physically changed in my clocks. (And vice versa.) Time dilation (and other relativistic effects) are best viewed as due to the (admittedly strange at first) nature of time and space itself. It would be quite bizarre indeed if just by moving with respect to someone that you could somehow physically affect their clocks in their own frame. Relativity is strange, but not that strange.

To really understand this, and not just parrot the conclusions, you must study the details. It doesn't take any more than a bit of algebra to derive time dilation and other effects from the premises of relativity. Of course that doesn't prove relativity true--just that it is internally consistent and makes sense. What gives us confidence that relativity is "true" is the mountain of experimental evidence that has been accumulated over the last 100 years. Much of modern physics would make no sense without relativity.

 

[Joanna Dark]

Well if I'm traveling in a straight line at a constant speed away from a stationary individual and my clock is still traveling slower than the stationary clock. All appearances suggests that we are traveling at the same speed but with different clock speeds I can't see how I observe your clock at the same speed as you observe mine. Who cares about synchronising the clocks. We bought them at the same manufacturer mine says 4am yours says 10pm and yours will reach 11pm before mine hits 5.

If I was orbiting a person at half the speed of light same thing. Your clock is traveling way faster than mine. Mines traveling way slower than yours.

If I'm increasing velocity away from you, and you are stationary, it appears we are traveling at the same rate away from each other symtrically. My clock is slower and yours is faster.

On the other hand:

You travel at 50 mph and I travel at 50 mph in opposite direction our clock is traveling at the same rate and should appear to be equal. But this example I never used.

Inertial frames or not I cannot see how I am wrong. No good answers yet.

 

[Doc Al]

Well if I'm traveling in a straight line at a constant speed away from a stationary individual and my clock is still traveling slower than the stationary clock.

What are you talking about with your clock "travelling" slower than the "stationary" clock? What happens is that the "stationary" observer sees your clock as running slow according to his clocks.

All appearances suggests that we are traveling at the same speed but with different clock speeds

Huh? How could you be traveling at the same speed? Compared to what? What matters is your relative speed.

I can't see how I observe your clock at the same speed as you observe mine. Who cares about synchronising the clocks. We bought them at the same manufacturer mine says 4am yours says 10pm and yours will reach 11pm before mine hits 5.

You still want an answer that doesn't require you to actually learn something about relativity. Good luck!

If I was orbiting a person at half the speed of light same thing. Your clock is traveling way faster than mine. Mines traveling way slower than yours.

Wrong again.

If I'm increasing velocity away from you, and you are stationary, it appears we are traveling at the same rate away from each other symtrically. My clock is slower and yours is faster.

Wrong again.

On the other hand:

You travel at 50 mph and I travel at 50 mph in opposite direction our clock is traveling at the same rate and should appear to be equal. But this example I never used.

Wrong again.

Inertial frames or not I cannot see how I am wrong. No good answers yet.

Done playing yet?

 

[chroot]

Well if I'm traveling in a straight line at a constant speed away from a stationary individual and my clock is still traveling slower than the stationary clock.

What?

All appearances suggests that we are traveling at the same speed but with different clock speeds I can't see how I observe your clock at the same speed as you observe mine.

What?

Who cares about synchronising the clocks. We bought them at the same manufacturer mine says 4am yours says 10pm and yours will reach 11pm before mine hits 5.

What? You keep changing your scenarios so quickly that I can't even keep track of what you're asking anymore.

If I was orbiting a person at half the speed of light same thing. Your clock is traveling way faster than mine. Mines traveling way slower than yours.

Orbits involve only tangential velocity, not radial velocity.

If I'm increasing velocity away from you, and you are stationary, it appears we are traveling at the same rate away from each other symtrically. My clock is slower and yours is faster.

Suppose two people are moving away from one another. Neither is able to say the other is at rest; in fact, both assert themselves as being at rest, and that it is the other who is moving. Since both people are free to consider themselves at rest, the situation is identical for each. They each see the others' clock running slowly.

Since this is at least the fifth or sixth time this has been repeated in this thread, you either:

a) have poor reading comprehension
b) do not wish to let go of your glaring misconception
c) are purposefully wasting our time

You travel at 50 mph and I travel at 50 mph in opposite direction our clock is traveling at the same rate and should appear to be equal. But this example I never used.

What is "our clock?" Where is "our clock?" Who is holding "our clock?" If you actually have any desire to understand what relativity actually predicts, you need to stop changing your scenarios so quickly. It would be nice if you could thoroughly analyze and understand one scenario before bringing up another.

Inertial frames or not I cannot see how I am wrong. No good answers yet.

At this point, I'm pretty sure you're just wasting our time for your own enjoyment.

- Warren

 

[Doc Al]

How about this: Explain to us how you would measure the rate of a moving clock.

Then we can continue.

 

[Joanna Dark]

OK

If you were sitting at the station and I was on a train traveling along a perfectly flat track, it appears to me that it is you who is moving. Remember that?

So I'm moving away from you in a straight line and you are stationary, regardles of velocity it appears we are traveling at the same velocity. You are moving at a 1000 mps and to you I am moving at 1000mps. If I were to slow down and reverse the train back to you it would still appear that for me it is you who are reversing back to me. So this situation is completely symmetrical. Now If I traveled to Pluto and back at a 1000 mps when I got back my clock would have traveled slower for the entire journey evidenced by the fact our clocks don't match.

So on a single journey to Pluto (with no return fare) regardless of velocity didn't my clock travel slower than yours? So how is it possible in this symetrical situation that we see each others clocks traveling at the same speed?

I'm not sure I could make my point of view any clearer than that, regardless of whether I am right or wrong?

 

[Doc Al]

If you were sitting at the station and I was on a train traveling along a perfectly flat track, it appears to me that it is you who is moving. Remember that?

Got it! You say you are at rest (speed = 0) and you say I am moving at some speed (speed = v). And vice versa.

So I'm moving away from you in a straight line and you are stationary, regardles of velocity it appears we are traveling at the same velocity. You are moving at a 1000 mps and to you I am moving at 1000mps.

OK. Our relative speed is the same.

If I were to slow down and reverse the train back to you it would still appear that for me it is you who are reversing back to me. So this situation is completely symmetrical.

It would be symmetrical if you swapped coordinates. But some things change: In one case I'm moving towards you; in the other I'm moving away from you. The big change is that you have moved from one inertial frame to another.

Now If I traveled to Pluto and back at a 1000 mps when I got back my clock would have traveled slower for the entire journey evidenced by the fact our clocks don't match.

That happens to be true. But the analysis of that situation is more complicated. Since you change directions, the situation is not symmetric. I, on earth, stayed in a single inertial frame throughout your trip; you did not. Relativistic effects between inertial frames are symmetric; acceleration breaks the symmetry.

So on a single journey to Pluto (with no return fare) regardless of velocity didn't my clock travel slower than yours? So how is it possible in this symetrical situation that we see each others clocks traveling at the same speed?

Edit: On a single journey in which both observers stay in a single inertial frame, we both see each other's clock run slow.

I'm not sure I could make my point of view any clearer than that, regardless of whether I am right or wrong?

I recommend that you first understand why relativistic effects (time dilation, length contraction, clock desynchronization) are symmetric as long as both sets of observers remain in single inertial frames.

 

[chroot]

So on a single journey to Pluto (with no return fare) regardless of velocity didn't my clock travel slower than yours?

Another grand misconception. It is meaningless to compare the time on two clocks unless you are able to bring them back together at the same place and time. The reason? Such a comparison would require some standard of absolute time. How could you tell travelers exactly when to report the reading on their clocks? You can't. That conclusion isn't a failing of technology or imagination, it's an unusual consequence of the real nature of time.

The classical view of time is that time marches on at the same rate, lockstep, everywhere in the universe. It's as if you could snap your fingers, say "now!" and take a snapshot photograph of the entire universe, showing exactly where everything is and what every clock reads. This is a naive concept of time, though one which is very adequate for use on Earth, where velocities are so small compared to c.

A more accurate view is that time is experienced locally. Every clock moves on a different path through spacetime, and objects moving along one path experience a different duration of time than do objects moving on other paths. It's impossible to synchronize two clocks unless they are at the same spot in spacetime because the very concept of simultaneity is relative.

If you attempt to synchronize two distant clocks in one frame of reference, they will not be synchronized in any other frame of reference. Even if you build an apparatus using light signals or what not to synchronize the clocks from one observer's perspective, every other observer in the universe will claim that you failed. The entire concept of comparing elapsed time on clocks is flawed, unless you can bring those clocks back together. If they are brought back to (effectively) the same point in spacetime, every observer in the universe will agree that they have been synchronized, and the times elapsed on each will then have universal validity.

That's the resolution of the twin paradox: clocks moving on unique paths through spacetime experience unique durations of time. The only way to universally compare their readings is to bring them back together. When you do so, you are actually comparing the proper times elapsed over their unique paths through spacetime, and they need not be the same.

- Warren

 

[Joanna Dark]

So we are almost there.

The similarities as I see it are that if we are stationary to one another our clocks match. Naturally. Or say we were traveling at the same speed in the same direction or opposite directions our clocks would match. I believe we have full agreement on that. Both our clocks slow down at the same rate.

You agree that if I am moving and you are stationary, it appears that you are moving. So in all appearances neither one of us believes we moved. Hence the reason it would be easy to believe the sun revolves around the Earth without knowing any better. My point was to show our perspective is exactly the same. Only difference being clock speed. So it would be impossible for us both to see the exact same clock speed. You appear to understand.

If I were to accelerate or decelerate my way to pluto, and you were stationary, we would observe each others clocks traveling at different times. Perhaps when I arrived my clock is a year to 10 years behind yours. Agreed.

We don't seem to agree that if I traveled to pluto at a constant speed, and you were stationary, that there would be any time difference in our clocks.

That is confusing to me because if we go back to the original Einstein eg. I used of the moving train observer and the train station observer (who are timing the same light traveling between the ceiling and the floor of the train) they observe the light traveling at the speed of light despite the light having traveled at two different distances. Even if the train was at a constant speed this would require time dilation. i.e. their clocks couldn't possibly match. So we have a problem. What I am getting from you does not match my basic understanding in this case.

If you mean you actually do agree on this then we have agreed on everything so far and I lost as to what the actual problem is.

If by the same inertial frame you mean traveling at the same constant speed in a straight line, then I'm lost aswell, as that is like saying if I paint a white wall white it will still be white. I am getting a sense that we are close to the crux of the problem but not quite there.

 

[Joanna Dark]

Wait I think I have it. So you are saying that If we are traveling at the same speed then our clock times match. So therefore reciprocation does occur. Is that it?

 

[RandallB]

Joanna your still presenting a confusing description that is not allowing you yourself to maintain a constant reference to understanding what is being seen by anyone observer: example:

If you were sitting at the station and I was on a train traveling along a perfectly flat track, it appears to me that it is you who is moving. Remember that?

A good start especial the part about remembering the perspective your taking; that while on the train you are not in fact moving but Dr Al is (presumably back on earth) But in the very next sentence you say;

So I'm moving away from you in a straight line and you are stationary, regardles of velocity it appears we are traveling at the same velocity.

What you forgot already?
You’re not moving, Dr Al is! If you were both moving at the same velocity the two of you would be stationary with respect to each other.

You are moving at a 1000 mps and to you I am moving at 1000mps.

Same problem pick a perspective and complete all your measurements before taking on the other view.

If I were to slow down and reverse the train back to you it would still appear that for me it is you who are reversing back to me. ….. … Now If I traveled to Pluto and back at a 1000 mps when I got back my clock would have traveled slower for the entire journey evidenced by the fact our clocks don't match.

NO remember you said you were not moving!
Pluto is coming toward you! at the same speed that Dr Al in moving away from you. Use a speed of 0.5c for both of them putting them in the same reference frame. (just two frames here yours & Dr Al’s ok). That means YOU DO NOT SLOW DOWN! No reverse the train and go back to AL! You take off from your stationary position at a new speed (and reference frame) designed to chase down Dr Al who has been getting away from you. I’d suggest twice his original separation speed (0.5c + 0.5c = 0.8c, for now you have to trust the addition used here) from your starting stationary position on the train. That way he will see you coming at a speed of 0.5c. [assume you instantly jump off the ‘stationary train’ and onto one following Dr Al to overtake him at a speed of 0.5c]

So this situation is completely symmetrical.

Well not yet,
Only now are you ready to just begin to look at the other view of Dr Al (and Pluto) being stationary watching you go towards Pluto at 0.5c and then turn around and come back at 0.5c. Now it is “completely symmetrical” IF you starting in a stationary position on the train and completely working out the problem should get the same answer as Dr Al does when he assumes he remains stationary.
PS. If you crunch these numbers and do not get the same result – trust me check for an error.

But do not say:

So on a single journey to Pluto (with no return fare) regardless of velocity didn't my clock travel slower than yours? So how is it possible in this symetrical situation that we see each others clocks traveling at the same speed?

I'm not sure I could make my point of view any clearer than that, regardless of whether I am right or wrong?

Frankly there was no point of view there to get a fix on. The way to make your view clearer is work through a problem completely for just one reference view before debating how it must look to someone else.
Then work out the other reference frame view – completely.

Only then can Dr Al or others help you out in how you are evaluating the results in each frame of view.

 

[chroot]

The similarities as I see it are that if we are stationary to one another our clocks match. Naturally. Or say we were traveling at the same speed in the same direction or opposite directions our clocks would match. I believe we have full agreement on that. Both our clocks slow down at the same rate.

You need to be careful with your language, as it's the cause of many of your misconceptions. "Both our clocks slow down at the same rate" should be expressed as "both clocks appear to the other observer to be running slowly." You cannot ever make a statement about a measurement without expressing who is making that measurement.

My point was to show our perspective is exactly the same. Only difference being clock speed. So it would be impossible for us both to see the exact same clock speed. You appear to understand.

Again, this is the same problem. "Clock speed" means nothing. You must specify who is measuring which clock for this statement to have any meaning. It sounds like you're still unwilling or unable to grasp that if two people are in relative motion then they will each measure the others' clock as running slow. If that's true, I give up, and I will lock this thread. You can take your questions elsewhere, as they have been thoroughly answered here, several times over.

If I were to accelerate or decelerate my way to pluto, and you were stationary, we would observe each others clocks traveling at different times. Perhaps when I arrived my clock is a year to 10 years behind yours. Agreed.

This statement contains more gross misunderstandings:

1) You cannot compare distant clocks.
2) Once you involve acceleration you're not really dealing with special relativity anymore.

We don't seem to agree that if I traveled to pluto at a constant speed, and you were stationary, that there would be any time difference in our clocks.

Again, this is a meaningless statement. You can't compare the clocks until you bring them back together.

That is confusing to me because if we go back to the original Einstein eg. I used of the moving train observer and the train station observer (who are timing the same light traveling between the ceiling and the floor of the train) they observe the light traveling at the speed of light despite the light having traveled at two different distances. Even if the train was at a constant speed this would require time dilation. i.e. their clocks couldn't possibly match. So we have a problem. What I am getting from you does not match my basic understanding in this case.

Time dilation occurs for objects in relative motion. Constant relative motion included.

- Warren

 

[Doc Al]

So we are almost there.

The similarities as I see it are that if we are stationary to one another our clocks match. Naturally. Or say we were traveling at the same speed in the same direction or opposite directions our clocks would match. I believe we have full agreement on that. Both our clocks slow down at the same rate.

There's no need to drag a third reference frame in. If we both move together, our relative speed is zero--we are in the same frame. That's all that counts. Our clocks run at the same rate.

When you say we are both moving together, you mean with respect to some third party. Don't think in terms our clocks running slow in that third frame. (It's true, but irrelevant for determining how we see each other.) Because there could be a fourth frame in which we are moving together at some different speed--do our clocks slow down twice?

You agree that if I am moving and you are stationary, it appears that you are moving. So in all appearances neither one of us believes we moved. Hence the reason it would be easy to believe the sun revolves around the Earth without knowing any better. My point was to show our perspective is exactly the same. Only difference being clock speed. So it would be impossible for us both to see the exact same clock speed. You appear to understand.

Bad example of Earth about the sun--the Earth is accelerating. Yet again, if we travel in two different inertial frame, we would measure each other's clock as running slow. (Key: How do you measure the rate of a moving clock?)

If I were to accelerate or decelerate my way to pluto, and you were stationary, we would observe each others clocks traveling at different times. Perhaps when I arrived my clock is a year to 10 years behind yours. Agreed.

If our clocks read the same time on earth, then you went to pluto and back, our clocks will no longer read the same time when we compare them side by side after your trip. Your clock (and you) will show less elapsed time.

We don't seem to agree that if I traveled to pluto at a constant speed, and you were stationary, that there would be any time difference in our clocks.

I don't like the term "time difference in our clocks". Again, we would each measure the other's clock as running slowly. As far as whether the times on our clocks match--that brings in the question of how do you define simultaneity. If we happen to pass by each other (only once, since we agree not to change frames), we can just look at each other's clock as we passed each other. But other than that, we'd have to agree on how to compare clocks--and that involves the question of simultaneity. As Warren stated, there's no universal definition of simultaneity--that too depends on relative motion. (Again I suggest you learn how one would go about measuring the rate of a moving clock.)

That is confusing to me because if we go back to the original Einstein eg. I used of the moving train observer and the train station observer (who are timing the same light traveling between the ceiling and the floor of the train) they observe the light traveling at the speed of light despite the light having traveled at two different distances. Even if the train was at a constant speed this would require time dilation. i.e. their clocks couldn't possibly match. So we have a problem. What I am getting from you does not match my basic understanding in this case.

Again, all we've talked about is the observed rate at which moving clocks run. We both observe "time dilation": moving clocks run slow.

If you mean you actually do agree on this then we have agreed on everything so far and I lost as to what the actual problem is.

If by the same inertial frame you mean traveling at the same constant speed in a straight line, then I'm lost aswell, as that is like saying if I paint a white wall white it will still be white. I am getting a sense that we are close to the crux of the problem but not quite there.

Not sure what you're saying here.

Wait I think I have it. So you are saying that If we are traveling at the same speed then our clock times match. So therefore reciprocation does occur. Is that it?

I don't know what you mean by "our clock times match". At what instant? According to who? What I am saying (yet again) is that I see your clock run slow by the exact factor that you see my clock run slow--that's what I mean by saying that time dilation is symmetric.

The only time you can have agreement about what time is showing on two different clocks is if they are at the same place at the same time. In that case EVERYONE, regardless of their motion, will agree as to what each clock read at the moment they intersected. But if the clocks are moving with respect to each other and they are not at the same spot, then what they read when depends on who's definition of "when" is being used.

I strongly suggest that you answer my question: How can you measure the rate of a moving clock?

 

[Joanna Dark]

Right I got the problem. I can understand what you are saying theoretically, but I can't grasp an understanding of how your explanation works in any practical application.

My understanding is that If *I* (v=?) were moving away from a *stationary* observer (v=0) that my clock speed while seeming normal to me will be in a slower time frame than the stationary observers.

Why do I think that? Because if that were true then logically the speed of light would be equal for both observers. It is the whole basis for this theory.

If the stationary observer sees my clock as experiencing time-dilation and I calculate his clock as experiencing time-dilation then it would appear both of our clocks are running slower simultaneously and at the same time they are running faster than each others. That appears grossly absurd to me and completely contradictory. What do I logically do with that? Not meaning to be offensive, but it is honestly useless to me. If I don't imagine the two clocks to be simutaneously running in two different time frames then they can't possibly observe the same ray of light simultaneously traveling two separate distances and still maintain the speed of light on both clocks.

This is basis for my third reference frame, which allows me to know the simultaneous events taking place. Noone wants to let me offer me that luxury as there is no way I can know what each clock is doing at the same time.

Let's give this a tangible quality. Say I am recreating this event in a 3d computer environment (I'll call it "I Am God-a-vision"), which is practically how my mind is observing the experiment. Why couldn't I set it up so I can observe the speed of each clock simultaneously for example? I'll put four timers on my screen. Two timers represent the speed of the stationary and moving clocks and the other two represent their observation of each other's clock. Now according to you, the first two clocks would be traveling at normal speed in their own frame of reference and the second two would be experiencing equal time dilation. Effectively this cancels one another out and both clocks are actually traveling at the same speed. Err, um, yah?

My version appears accurate in that the two clocks are not running the same speed and their observations of each other's clock are not equal. This way I can put a light traveling between two points (moving or stationary) anywhere in the 3d environment and both observers will see the light beam travel at c. I can place ten observers traveling at ten different velocities and directions and they will all see the same thing... c.

But if I base my model on your explanation no one sees light travel at c, except for any observer traveling at the same velocity as the the two points my light is traveling between. Why is that? My understanding is based on visually understanding what is happening at each frame of reference simultaneously so it makes intuitive sense. It seems to work fine. Add reciprocation and it doesn't.

This is the same problem I have with my teacher and no one seems to understand the difficulty I have in accepting reciprocation.

 

[chroot]

If the stationary observer sees my clock as experiencing time-dilation and I calculate his clock as experiencing time-dilation then it would appear both of our clocks are running slower simultaneously and at the same time they are running faster than each others. That appears grossly absurd to me and completely contradictory.

Stop thinking about what the clocks are "actually" doing. You seem to have this idea that if one observer sees your clock running normally, yet another sees your clock running slow, then there is some kind of contradiction.

Stop thinking that your clock has some "correct" speed. It doesn't. One observer can see it running at one speed, and another observer can see it running at a different speed. There's nothing wrong with this. Similarly, one observer can look at a nearby tree and have it appear very large, while a distant observer sees the same tree as being quite small. It's the same tree, but each observer has a different view of it. There's nothing wrong or contradictory about this.

Repeat this to yourself five times: Every unique observer has a unique view of every clock.

This is basis for my third reference frame, which allows me to know the simultaneous events taking place. Noone wants to let me offer me that luxury as there is no way I can know what each clock is doing at the same time.

This is exactly the mistake you keep making. You keep wanting to move from a physically realistic frame of some real, human observer into some kind of mystical omniscient "God frame" in which you know what's really simultaneous and what's really on the face of the clocks. There is no God frame. The only information an observer has is that which he sees.

Why couldn't I set it up so I can observe the speed of each clock simultaneously for example?

You're welcome to make such a model, but it is not a model of special relativity. It is some kind of bastardization of relativity which will predict results which are incompatible with experiment, and thus provably wrong.

You cannot simply pick and choose which bits of relativity theory you want to examine and then toss out the rest. Doing so necessarily destroys the consistency of the theory.

the first two clocks would be traveling at normal speed in their own frame of reference and the second two would be experiencing equal time dilation.

CLOCKS DO NOT EXPERIENCE TIME DILATION. Time dilation is an effect that occurs when an observer in one reference frame views a clock in another reference frame. No matter how you move or where you go, you personally will never "experience" time dilation. You may look back at your buddies on Earth and see their clocks running slowly, though.

But if I base my model on your explanation no one sees light travel at c, except for any observer traveling at the same velocity as the the two points my light is traveling between.

The only things you need to accept ab initio are these postulates:

1) All observers measure the speed of light to be the same.
2) The laws of physics are identical in every inertial reference frame.

The entirety of special relativity (time dilation, length contraction, relativity of simultaneity, etc.) are all derived directly from these two postulates. You need not suppose or assume anything else.

Why is that? My understanding is based on visually understanding what is happening at each frame of reference simultaneously so it makes intuitive sense. It seems to work fine. Add reciprocation and it doesn't.

Your intuition is WRONG. The theory you're describing (and attacking!) is a strawman theory which is not special relativity.

This is the same problem I have with my teacher and no one seems to understand the difficulty I have in accepting reciprocation.

It's as if you were claiming the Earth were a cube, and then complaining that no one seems to understand the difficulty you have in accepting that the Earth has no corners.

- Warren

 

[Joanna Dark]

I don't actually think any of these things you are suggesting.

I like God vision? All I am doing is thinking that the only absolutely necessary element for Special Relativity to work is that the speed of light is the same for all observers. Each observer's time can be calculated relative to their velocity and direction based on an "absolute" constant speed of light.

If I know my velocity and direction and yours then I can work out both our time frames an punch that into my model. I could observe them simultaneously.

At v=0 then time is, let's say, "normal speed". At v=c time freezes. Time works on a sliding scale for anyone traveling at any velocity between the two. Speed of light is thus equal to c for all observers.

I know it is not as simple as this, but it's a rough explanation for how my model would work. The only thing I can't grasp is why two people traveling at different velocities would observe each others clocks traveling slow. And still no one has given me a reason for this. That's all I asked. The only difference really as far as I can gather is that in my version one observer would see the other's clock slow and one would see the other's clock traveling fast.

Otherwise it sounds really simple to me actually. I don't see where the confusion arises, between what I have trouble with and what others think I have trouble with. It's only one point. The best any of you have given me is that it is a fact. Not why.

 

[chroot]

So... you're really looking for someone to give you a reason to believe your own personal theory, which is not self-consistent and is demonstrably wrong? You're not actually trying to learn relativity at all, eh?

If you express your "theory" mathematically, you'll discover it contains absurdities. If you try to test it empirically, you'll predict incorrect results. It's wrong. Enough said.

- Warren