SR Simultaneous Lines Drawn in the Sand

[Doc Al]

geistkiesel's incorrect assumptions

There were no added assumptions that corupted Einstein's gedunken. You just haven't realized that you've lost this game.

You ASSumed that:

(1) The marks on the photo-sensitive strips (caused by the photon emissions) in the moving frame are equally spaced from the point M' (which passed M at the exact moment that the clock at M read t=0): True!
(2) That the moving observers detect the photon emissions as happening simultaneously: Not true!

As long as you insist on adding these assumptions, there is no point in continuing the discussion.

However, if you would like to discuss Einstein's actual argument--which you refer to constantly but obviously fail to grasp--have at it. If you truly understand Einstein's point, this should be no problem--since he makes fewer assumptions than you do.

 

[baffledMatt]

The instant photons were simultaneously emitted from A and B in the stationary frame the photo-sensitve strips in the moving frame were exposed (|||) at both ends of the moving frame, at locations equally spaced from M'. This is the point, the only point. For your convenience we give another picture.

|||----M'----||| -->moving frame-->
-A-----M-----B-| XX stationary frame XX

This is the picture the instant photons were emitted from A and B in the stationary frame.

Said another way, the instant the photo-sensitive strips were exposed in the moving frame by photons emitted in the stationary frame..

But how did you determine the distance between the photosensitive strips? If you made it the same length as A->B whilst in the moving frame then you have a problem because in the stationary frame this distance will be observed to be shorter than A->B due to Lorentz contraction. Thus in the stationary frame it is impossible for them to fall over A and B at the same time.

Ok, so you determined the length when the moving frame was actually stationary. But this doesn't help you either because when they start moving the moving observer will observe the distance between A and B to contract. Hence, again the strips cannot both be over the lights at the same instant in this frame.

The only way out of this mess is to accept the loss of simultaneity. This is why I suggested looking up the 'pole vaulter paradox' earlier because it points this out quite beautifully.

Matt

 

[ram2048]

makes no sense for SR to resolve that the photons were NOT emitted simultaneously.

it's a "Given" part of the experiment that they WERE emitted simultaneously as outlined in Einstein's original set up

there's a billion ways we can PROVE that they were emitted simultaneously hooking them up to synchronized clocks, photosensitive strips, whatever. that's not part of the argument, though. It's not even a possibility.

i think you SR supporters are somehow taking what einstein said the wrong way.

 

[wespe]

makes no sense for SR to resolve that the photons were NOT emitted simultaneously.

it's a "Given" part of the experiment that they WERE emitted simultaneously as outlined in Einstein's original set up

it's a "Given" part of the experiment that they WERE emitted simultaneously as outlined in Einstein's original set up

No it's not given or automatically assumed. It is deduced, because the stationary midpoint observer received the lights at the same time. The midpoint observer just happens to receive the lights at the same time, that's the setup. Only because of this you can deduce that they were emitted simultaneously *in the stationary frame*, you can' assume anything else. You can't analyse this like you have a bird's eye view and like you can see everything at the same time. But if you want a graphical view according to SR, check this link:

http://casa.colorado.edu/~ajsh/sr/simultaneous.html

 

[ram2048]

yeah i saw that one from the other thread.

i still think the moving observer KNOWING he is moving towards B can extrapolate using his velocity/acceleration backwards to determine that they were emitted simultaneously.

i believe this is the proper way to come to the conclusion in the experiment, not calculate forward and find out that your perceptions are skewed, calculate backwards and find out where "reality" is.

 

[ram2048]

in any case this setup is different from cerulean and vermilion by virtue of being contained within 2 other bodies (the photon emitters) which have a known property of being "fixed" in the universe which provides excellent reference points to capture movement data to work backwards from.

you wouldn't have that luxury in the example in that link

 

[wespe]

yeah i saw that one from the other thread.

i still think the moving observer KNOWING he is moving towards B can extrapolate using his velocity/acceleration backwards to determine that they were emitted simultaneously.

Yes, but the moving observer in fact considers himself stationary, and considers the embankement moving. If he extrapolates the values of his own measurements (his own speed = zero), he finds the SR result. Why would he think his measurements are faulty and correct them according to stationary frame's measurements? It's mutual. You can't determine who is really really really moving. Even if you assume there's a preffered frame, you can't detect your speed relative to it by any experiments.

 

[wespe]

in any case this setup is different from cerulean and vermilion by virtue of being contained within 2 other bodies (the photon emitters) which have a known property of being "fixed" in the universe which provides excellent reference points to capture movement data to work backwards from.

You assume absolute space by saying they are fixed. Otherwise, you can't say that the photon emitters can be a reference. And the speed of light is independent of its source, so the movements of the photon emitters does not matter. (And as far as I know, there is no blue/red shift for a single photon) In short, there is no reference to detect your own movement in space, you always consider yourself at rest.

 

[ram2048]

you've got to be kidding!

that can't be the way it works. that's completely backwards thinking :D

are you telling me when they plan a mission to Mars they calculate that Mars is traveling closer, not the probe/lander/vehicle is traveling towards it? :|

 

[wespe]

you've got to be kidding!

that can't be the way it works. that's completely backwards thinking :D

are you telling me when they plan a mission to Mars they calculate that Mars is traveling closer, not the probe/lander/vehicle is traveling towards it? :|

That looks equally valid to me, results of the calculations would be the same. But I guess you would normally plan a mission from a third frame's perspective (the earth).

 

[geistkiesel]

No it's not given or automatically assumed. It is deduced, because the stationary midpoint observer received the lights at the same time. The midpoint observer just happens to receive the lights at the same time, that's the setup. Only because of this you can deduce that they were emitted simultaneously *in the stationary frame*, you can' assume anything else. You can't analyse this like you have a bird's eye view and like you can see everything at the same time. But if you want a graphical view according to SR, check this link:

http://casa.colorado.edu/~ajsh/sr/simultaneous.html[/QUOTEYour link is bogus, unproved crap. Did you gothrough the maths that justifies what the link says?
No
you are talking silly. The photons were emitted simultaneoulsy and exposed the photo-sensitive deectors in the moving iframe as they were emitted. The fact that the photons were emitted at the same time has nothing to do with the obsever at M seeing teh photons later. This is given in the problem ()"relativity" pages 25 -27). . In this therad SR is assumed to predict that the photons were not emitted similtaneously.

Wespe, why do you come barging in here not even half prepared? You're screwing up a decent thread. Where do you get all that "you can't assume anything" crap?" prove it. You come here with your stupid useless intervention totally ignorant of what is happening, but so full of answers. Go away.

 

[geistkiesel]

Yes, but the moving observer in fact considers himself stationary, and considers the embankement moving. If he extrapolates the values of his own measurements (his own speed = zero), he finds the SR result. Why would he think his measurements are faulty and correct them according to stationary frame's measurements? It's mutual. You can't determine who is really really really moving. Even if you assume there's a preffered frame, you can't detect your speed relative to it by any experiments.

BS. It is given he knows his velocity and can measure it as he crosses M when the hotons are emitted. You're just as ignorantly dishonest as Doc Al, your mentor.. Otherwise the propblem is nothing. Yes you can. Blue/red analyses. Also each frame can emit 1 second inteval pulses. The stationary (slower) frame will read the moving frame pulses as slower than his two seconds. Likewise, the moving frame will read the stationary frame pulse rate as faster than his own. You say no absolute time? prove it.

Why ae you making things up? Showing off your childish television learned physics? Just to sabatoge and get even for your embarrassing loss awhile back?

Answer the question of the photo-sensitive strips being exposed when the photons are emitted simutaneously. These strip are located equidistant from the midpoint M' in the moving frame. Get up tp speed Wespe or get off the bus. Asswer this one question posed here. can you do this or do you want to measure the SOL first?.

 

[baffledMatt]

Your link is bogus, unproved crap. Did you gothrough the maths that justifies what the link says?
No
you are talking silly.

and I was just about to say exactly the same thing about your link.

Answer the question of the photo-sensitive strips being exposed when the photons are emitted simutaneously. These strip are located equidistant from the midpoint M' in the moving frame.

Errrm, hello?

*pointing to the last post I made*

Matt

 

[geistkiesel]

wespe's windmills

in any case this setup is different from cerulean and vermilion by virtue of being contained within 2 other bodies (the photon emitters) which have a known property of being "fixed" in the universe which provides excellent reference points to capture movement data to work backwards from.

you wouldn't have that luxury in the example in that link

Ram2048 Beware wespe. This is theone that started the other SR ain't working thread until surrenduring to frustration. He taks a lot of you can't do this and that. The photons were emitted simultaneously when M' was at M, THis is a given , You don't ahve to prove it. The velocity of the moving frame is determined whjen passing through M. Cerulean, aslo, has no proof of anyhing. However, it shows the inanity of SR. A physical event occurred and by them ere fact that an observer was thrown in at some time later that observer can make a physical alteration of the sequence of the emitted photons just because he is an observer, never having any contact whith any of the mechanics of thephoton, their sources, the photons themselves. This is how inane SR really is.

Wespe pisses me off. he has a limited extent of thinking range which he is unwilling to extend. All thos things he said about the experiment of this thread is bogus. he hasn't read the thread and knows not what is happening. Your figure is correct. I would remind you that th ethread stipulates that SR will predict the photons weren'y emitted simultaneously,

Have your quiestioners answer, among other questions, how can the photons be detected simultaneously in the moving frame, simultaneousl and marked and identified as equidistant from the midpoint of those exposed strips? No clocks needed, AN instantaneous event. The midpoint of he moving frame was determined the same way as the midpoint in the stationary frame, by the laws of physics that are invariant in all inertial frames., by the photo-sensitive strip, yet later be calculated as having occurred nonsimultaneously?

Im going to be off line for a few hours. Myself, I am not equipped to the taking of prisoners. Shoot anybody who surrenders.

 

[wespe]

Your link is bogus, unproved crap. Did you gothrough the maths that justifies what the link says?

It just shows graphically that it is possible for two frames to have relative simultaneity, when you abandon the idea that time is absolute.

Noyou are talking silly. The photons were emitted simultaneoulsy and exposed the photo-sensitive deectors in the moving iframe as they were emitted.

You say "emitted simultaneously" but you don't say in which frames. You just assume it is in both frames. That is the argued point but you start by assuming it.

The fact that the photons were emitted at the same time has nothing to do with the obsever at M seeing teh photons later. This is given in the problem ()"relativity" pages 25 -27). . In this therad SR is assumed to predict that the photons were not emitted similtaneously.

The only facts in an experiment are the measurements. Don't assume "something is so and so in reality". You can not dictate what reality should be.

Wespe, why do you come barging in here not even half prepared? You're screwing up a decent thread. Where do you get all that "you can't assume anything" crap?" prove it. You come here with your stupid useless intervention totally ignorant of what is happening, but so full of answers. Go away.

I'm just saying "don't assume anything except the measurements". The measurement is not "they were emitted simultaneously in stationary frame", that is the conclusion. The measurements are "M received the photons simultaneously", "M is equadistant from A and B", "speed of light is constant".

You have no math and no answers. When you are disproven by calculations you say "maybe so" "calculations must be flawed" "reality is like in fact this". And you didn't stop posting in my thread even I asked you nicely, why should I go away?

 

[geistkiesel]

But how did you determine the distance between the photosensitive strips? If you made it the same length as A->B whilst in the moving frame then you have a problem because in the stationary frame this distance will be observed to be shorter than A->B due to Lorentz contraction. Thus in the stationary frame it is impossible for them to fall over A and B at the same time.

Ok, so you determined the length when the moving frame was actually stationary. But this doesn't help you either because when they start moving the moving observer will observe the distance between A and B to contract. Hence, again the strips cannot both be over the lights at the same instant in this frame.

The only way out of this mess is to accept the loss of simultaneity. This is why I suggested looking up the 'pole vaulter paradox' earlier because it points this out quite beautifully.

Matt

I don't like you Matt, you've been paying attention. They determined the midpoint using the same laws of physics as the stationary frame did. Also, the strips of photo-sensitive material is fractions of a micron wide, thousand of strips in a section. Each strip<< photon wave length.. The sections holding the strips are long enough so that shrinking in the moving frame is accounted for. Each pair of A', B' strips is equidistant fronm the midpoint M'. Assume the moving platform will shrink 100 units from velocity considerations. We make the sections at each end of A' and B' 200 units long er, totalling 400 units overkill. with the strips covering the whole 200 units. Overlap, overkill.

 

[geistkiesel]

and I was just about to say exactly the same thing about your link.



Errrm, hello?

*pointing to the last post I made*

Matt

matt, I answered another post of yours with the answer, bsically the midpoint of the strips was determio=ned by the same laws of physics thatadetermined M in the stationary frame. Each strip is ifractio s of a micron wide. Thousand in a section . The two section much longer 9calulated fro SR)to assure that the stips will overlap A and B whe the moving frame passes? OK uMMRRR?

 

[jdavel]

ram2048 said, "it's a "Given" part of the experiment that they WERE emitted simultaneously as outlined in Einstein's original set up"

Not quite! They were simultaneous in the stationary frame, but, as it turns out, they weren't simultaneous in the moving frame. That's not an assumption; it's a conclusion based on the assumption that c is the same in both frames.

Here's "Einstein's original set up":

IN THE STATIONARY FRAME THE FLASHES ARE SIMULTANEOUS and are equidistant from the moving observer at the time of the flashes. So, the stationary observer sees light from the two flashes reach the moving observer at different times.

The moving observer agrees, light from the two flashes reached him at different times. Then he looks at the marks that the flashes made on his train, sees they are at equidistant from his seat on the train. Since he knows that c was the same for the light of both flashes, he concludes that THE FLASHES WERE NOT SIMULTANEOUS IN THE MOVING FRAME.

 

[baffledMatt]

They determined the midpoint using the same laws of physics as the stationary frame did.

What do you mean by this? Did they determine the length whilst the moving frame was actually moving or not?

Also, the strips of photo-sensitive material is fractions of a micron wide, thousand of strips in a section. Each strip<< photon wave length.. The sections holding the strips are long enough so that shrinking in the moving frame is accounted for. Each pair of A', B' strips is equidistant fronm the midpoint M'. Assume the moving platform will shrink 100 units from velocity considerations. We make the sections at each end of A' and B' 200 units long er, totalling 400 units overkill. with the strips covering the whole 200 units. Overlap, overkill.

Hmm, if you like. But by this argument you are only able to determine the level of simultaneity to an accuracy set by the length of your strips. Do you see what I'm getting at? Say you do the experiment with strips of length 200 units and find that they do in fact both detect the emitted light. You say that this proves that the emission was simultaneous. However, if the emissions at A and B were in fact separated by a time interval t < 200 * v then you would still have detection on both strips even though the emission was not simultaneous. So to prove real simultaneity you MUST make your strips of vanishing length.

Matt

EDIT: changed some numbers to avoid possible confusion

 

[geistkiesel]

It just shows graphically that it is possible for two frames to have relative simultaneity, when you abandon the idea that time is absolute.

nothinmg was abanded. Th estrips were placed to coincide with A and B within a wave length of theemitted photons. The very instant the photons were emitted, what 10-6 of a second as an instant. You are the one that is asserting time is not absolue, prove it.

You say "emitted simultaneously" but you don't say in which frames. You just assume it is in both frames. That is the argued point but you start by assuming it.

emitted simultaneously in the moving frame. Detected as the photons were emitted the photo-sensitive strips attached to the moving frame.one wave length from the sources at A and B.

The only facts in an experiment are the measurements. Don't assume "something is so and so in reality". You can not dictate what reality should be.

The photons were exposed as the photons were enmitted. This means the photons were emitted simultaneously in the moving frame because that is when they were detected. I can dictate the truth when I see it. YOu know nothing. You have a childs view of SR and you are talking to me like they talked to you at one time. It sounds like you were beaten intio shape.

I'm just saying "don't assume anything except the measurements". The measurement is not "they were emitted simultaneously in stationary frame", that is the conclusion. The measurements are "M received the photons simultaneously", "M is equadistant from A and B", "speed of light is constant".

See there you go. You are either consciously lying or you haven't read the thread. The given is that the photons were emitted just as M' passed through M. Tere was no wait to determine this. The ones putting on the experiment did this. Do you have that yet after having it drilled in what you call a head a few dozen tuime? Why are you so carelss?" We all err. But with you its cronic. You have to make up crap to win don't you, just like Doc Al taught you. He is so proud.

You have no math and no answers. When you are disproven by calculations you say "maybe so" "calculations must be flawed" "reality is like in fact this". And you didn't stop posting in my thread even I asked you nicely, why should I go away?

Evry word out of your mouth is a lie. I stipulated at the beginning that SR would predict the phoytons were no emitted simultanoulsy. Go back to ANdorra or from wheever you originated. So whaT if i didn'tstop posting in "your" thread. So sue me. Actually i am cleaning up your unfinished business that you ran from like a frightend child. Why should you go away? because you bore me.

 

[geistkiesel]

If the thought process of the theory is wrong, then it can easily be shown to be wrong through experimentation. You you can't prove that a theory is wrong if you don't address what the theory says. You are stating (assuming, as Doc says) the theory is wrong and building a thought experiment around how you think the universe should work, then offering it up as a proof that the theory is wrong. Sorry, science doesn't work that way.

Depending on the theory you apply to the thought experiment, the outcome is different. Which is right and which is wrong? Well, that's a question answered by experimentation.

What's funny about this is you think you're making an argument against Relativity, but what you are actually doing is demonstrating you don't even understand the scientific method, much less Relativity. The other guys here aren't so much defending Relativity as trying to explain to you what it says.

read the opening thread.Istipulated SR would predict nonsimultaneity.

 

[ram2048]

non simultaneity is a stupid way to conclude that. there. i said it :D

a better way to conclude it is they WERE simultaneous (which IS reality) and extrapolate how much your perceptions were skewed (Time dialation) based on the distance covered

you wouldn't be able to do so in Vermillion and Ceruleon because there's no universal referance frame (my new postulate). but on a moving train "gedunken" you can. if you have the tools available to make conclusions that are correct, might as well use them.

ludicrous as it is they have every right to claim non-simultaneity because that's the way they want to conclude it. i highly doubt that line of thought will get very far though. It's not so much a paradox as the ignoring of pertinent data (fixed absolute locations) and drawing the wrong conclusions from there.

 

[baffledMatt]

a better way to conclude it is they WERE simultaneous (which IS reality) and extrapolate how much your perceptions were skewed (Time dialation) based on the distance covered

So are you saying that in this example the 'stationary' observer was the one who observed reality, yet the 'moving' observer saw a skewed reality?

How do we know who's reality is the 'correct' one?

Matt

 

[jdavel]

ram2048 said, "It's not so much a paradox as the ignoring of pertinent data (fixed absolute locations)..."

Fixed absolute locations? Even Newton didn't believe in that! No wonder your'e having trouble with 20th century phyiscs; you haven't learned 17th century physics yet!

 

[ram2048]

Fixed absolute locations? Even Newton didn't believe in that! No wonder your'e having trouble with 20th century phyiscs; you haven't learned 17th century physics yet!

so maybe you guys have been led astray since the 17th century? man that's wacky :D

So are you saying that in this example the 'stationary' observer was the one who observed reality, yet the 'moving' observer saw a skewed reality?

How do we know who's reality is the 'correct' one?

i haven't given my universal relativity postulate in this thread yet?

let's just say by majority rules ;D every other "thing" in the universe has the moving observer moving relative to itself, but every other "thing" has NOTHING else but the observer moving relative to it (for simplicity sake). The observer has the EVERYTHING else moving in relation to him.

on a scale of which is likely and which is no, the moving observer being stationary while the universe moves is "infinitely unlikely" whereas JUST the observer moving is "infinitely likely"

so now that we've determined which is moving it's simple to say which has the skewed perception ;D

 

[wespe]

Geistkiesel,

You are thinking simultaneity as something absolute, something you can measure. Then shouldn't everyone get the same mesurements of this absolute thing? Describe the method that measures simultaneity, and how everyone can get the same value. Einstein describes his method, and the observers get different measurements in the experiment according to that method, so they conclude simultaneity is relative. If your method of measurement is the formula in that infamous link, it has been invalidated mathematically in the other thread (which you responded "maybe so").

All the above also applies to time. Einstein says time is what a clock measures, and there is experimental support for time dilation, therefore the conclusion is that time is relative. If you claim that time is absolute, describe a method which measures time the same for all observers.

For this experiment, you won't get anywhere with blue/red shifts. Suppose, the light sources were co-moving with M'. There is no blue/red shift for M'. Still, the first pair of emitted photons get detected at the same time by M, which is the experiment setup. That's because speed of light does not depend on source speed, which is experimentally supported.

Geistkiesel, what is your alternative to relativity? Do you really have a theory, any math, any experimental support? I don't think so.

 

[baffledMatt]

let's just say by majority rules ;D every other "thing" in the universe has the moving observer moving relative to itself, but every other "thing" has NOTHING else but the observer moving relative to it (for simplicity sake). The observer has the EVERYTHING else moving in relation to him.

What makes you think reality would make this choice? Also, is there a way that I can (at least in principle) determine whether my reality is the correct one? i.e. how do i determine whether I am the 'moving' or 'stationary' observer?

on a scale of which is likely and which is no, the moving observer being stationary while the universe moves is "infinitely unlikely" whereas JUST the observer moving is "infinitely likely"

But everything in the rest of the universe is also moving, it's not just a case of here is the moving person and here is the static 'rest of the universe'.

Consider putting your thought experiment on its head. In other words, what if I called the observer who is receiving the light the 'stationary' one and the one who is emitting the pulses the 'moving' observer. By your reasoning the stationary observer has the correct reality so in fact the pulses really were not simultaneous and the fact that the moving observer saw them emitted simultaneously was just due to his 'skewed reality'. This allows me to change what reality is just by rewording the problem. Does this not bother you?

Matt

 

[jdavel]

ram2048

Evidently you don't want to understand this theory. The nice thing about physics is that if you don't want to understand it, you won't!

 

[ram2048]

Consider putting your thought experiment on its head. In other words, what if I called the observer who is receiving the light the 'stationary' one and the one who is emitting the pulses the 'moving' observer. By your reasoning the stationary observer has the correct reality so in fact the pulses really were not simultaneous and the fact that the moving observer saw them emitted simultaneously was just due to his 'skewed reality'. This allows me to change what reality is just by rewording the problem. Does this not bother you?

you can't call the moving observer "stationary" in my postulate. compared to the universal referance frame he IS moving it is "infinitely likely" that it is correct. you can't do the math on EVERYTHING in the universe, but if need be you CAN do the math on a lot of the things that would matter (anything local and Earth based) keep in mind that for every object you add to the "universal frame" you're also adding a slew of necessary calculations, as you would need to calculate not only that object's reference to the observer, but also that object's reference to every other thing you're allowing to be in that frame. it's this kind of "triangulation" that allows me to pinpoint who is perceiving reality as it conforms to the "majority" and determine who is the moving body with the perception shift and who is not.

the more objects you add to your universal reference frame in your calculations, the more "true" your results will become. in this case we only need relative reality calculated for maybe global scale. that way the results would be something everyone on Earth would agree upon. if you needed galaxy-wide, or universal-wide reality, calculations would be notably more complex and tedious :D

 

[geistkiesel]

wespe, god child of Doc Al speaks in hushed tones.

Geistkiesel,

You are thinking simultaneity as something absolute, something you can measure. Then shouldn't everyone get the same mesurements of this absolute thing? Describe the method that measures simultaneity, and how everyone can get the same value. Einstein describes his method, and the observers get different measurements in the experiment according to that method, so they conclude simultaneity is relative. If your method of measurement is the formula in that infamous link, it has been invalidated mathematically in the other thread (which you responded "maybe so").

All the above also applies to time. Einstein says time is what a clock measures, and there is experimental support for time dilation, therefore the conclusion is that time is relative. If you claim that time is absolute, describe a method which measures time the same for all observers.

For this experiment, you won't get anywhere with blue/red shifts. Suppose, the light sources were co-moving with M'. There is no blue/red shift for M'. Still, the first pair of emitted photons get detected at the same time by M, which is the experiment setup. That's because speed of light does not depend on source speed, which is experimentally supported.

Geistkiesel, what is your alternative to relativity? Do you really have a theory, any math, any experimental support? I don't think so.

what specific post invalidated the famous link?

supose instead of the light co-moving with the moving frame we finish the current experiment. Let the stationary and moving frame send sinals at one second intervals. The faster frame's signals will be slower, the slower frames signal faster, and each will know who is moving.

Your assumption that the stationry frame gets the signals the same as when the photons were emitted in the stationry frame may not be as you say. Inface the link you referred to in doctordicks thread about cerulean etc.? the moving frame here, according to SR and the link you referenced says your wrong. what thread and which specific post invalidated the famous link?

Are you submitting to the panel what Einstein said about "time is what a clock measures"? Check the literature there are tons of different ideas abot time and clocks, most disagreeing with AE. Again whicy post invalidated the famous link, which tyoy haven't read or understood, have you, and do you? Why are you so incompetent as to attempt to negate a mathematical formalism of which you are completely ignorant?

Now I know whay they were all laughing at you. I thought you had some balls there for a while, guess I was wrong, wasn't I?

 

[ram2048]

wow geist... harsh!

maybe not the best way to hold a discussion, but it's interesting in a JerrySpringer-esque kinda way :D

 

[baffledMatt]

you can't call the moving observer "stationary" in my postulate. compared to the universal referance frame he IS moving it is "infinitely likely" that it is correct.

So are you saying that in order for you to make any predictions for this thought experiment you need to know what the rest of the universe is doing so that you can determine which observer is 'stationary'? wow.

If there is any meaning to your universal reference frame then you should be able to determine which observer is in it simply from the results of the experiment. The results are: One observer sees simultaneous emission, the other doesn't. How do you determine from this which one is really 'moving' and therefore is not seeing true reality?

Imagine I described the thought experiment to you but just specified that one observer is moving relative to another. If there is anything to what you are saying there should be some observation they can make which will tell them who is in the universal frame. SR says that there is in fact no such observation so we have no choice but to treat each frame equally. What do you say?

Through all this you are also assuming that there is a whole load of universe 'out there' which is in the same inertial frame. Hubble told us many many years ago that this is far from the truth. Everything is moving with respect with each other so really you should conclude that every object in the universe is equally likely to be in the universal frame.

Matt

 

[baffledMatt]

Why are you so incompetent as to attempt to negate a mathematical formalism of which you are completely ignorant?

Now I know whay they were all laughing at you. I thought you had some balls there for a while, guess I was wrong, wasn't I?

Look now, let's try to keep this civil eh? If you want to have a discussion please have the courtesy to do it in a polite and mature manner.

Wespe is trying to do you a favour by sorting out your misunderstanding - he could quite easily let you rot in your own ignorance. This is something you should be grateful for!

Matt

 

[ram2048]

So are you saying that in order for you to make any predictions for this thought experiment you need to know what the rest of the universe is doing so that you can determine which observer is 'stationary'? wow.

not so, i said in order to do so with universally accepted accuracy you would have to poll the entire universe on its opinion and make a conclusion from there as the what the majority of objects would say. think of it in terms of triangulation it's a good way of looking at it.

If there is any meaning to your universal reference frame then you should be able to determine which observer is in it simply from the results of the experiment. The results are: One observer sees simultaneous emission, the other doesn't. How do you determine from this which one is really 'moving' and therefore is not seeing true reality?

if you allow me to include the rest of the universe i could determine to ridiculous and astounding accuracy which one is moving, but with just the two participants you can't. even adding a third you can't. or a fourth. but the more you add the closer you get to being able to describe exactly what is taking place. you get to the point where everything in the world is included in your reference frame (which is how we perceive the world) and it's as simple as instinct to determine which one is moving on a globally accepted scale.

Imagine I described the thought experiment to you but just specified that one observer is moving relative to another. If there is anything to what you are saying there should be some observation they can make which will tell them who is in the universal frame. SR says that there is in fact no such observation so we have no choice but to treat each frame equally. What do you say?

absolutely true. luckily we live within the universe and we will never EVER be forced into a situation where this is the case.

Through all this you are also assuming that there is a whole load of universe 'out there' which is in the same inertial frame. Hubble told us many many years ago that this is far from the truth. Everything is moving with respect with each other so really you should conclude that every object in the universe is equally likely to be in the universal frame.

and if you knew where everything was and had a huge computer you could accurately calculate how every universal object was moving within the whole and determine its perception and reality.

 

[baffledMatt]

not so, i said in order to do so with universally accepted accuracy you would have to poll the entire universe on its opinion and make a conclusion from there as the what the majority of objects would say. think of it in terms of triangulation it's a good way of looking at it.

When you ask each observer, how many of the answers do you think will be in exact agreement?

if you allow me to include the rest of the universe i could determine to ridiculous and astounding accuracy which one is moving, but with just the two participants you can't. even adding a third you can't. or a fourth. but the more you add the closer you get to being able to describe exactly what is taking place. you get to the point where everything in the world is included in your reference frame (which is how we perceive the world) and it's as simple as instinct to determine which one is moving on a globally accepted scale.

Then I suppose your answer to my question 'how do you determine this universal frame' will be 'I define it that way'. Ok, have it your way. If you want you can define the 'correct' frame which is this funny democratic average of all the frames in the universe. However, imagine I decide on a different definition, say that where I am sitting is the only stationary frame and everything else revolves around me. Will there be any way you can tell me which of our definitions is correct? will there be any observations which will differ between the universe with my definition and the one with yours?

absolutely true. luckily we live within the universe and we will never EVER be forced into a situation where this is the case.

Not so. I put you into space in a spaceship with no windows. Is there any experiment you can carry out (without looking outside of course) which will allow you to determine whether you are moving or not?

Matt

 

[geistkiesel]

What makes you think reality would make this choice? Also, is there a way that I can (at least in principle) determine whether my reality is the correct one? i.e. how do i determine whether I am the 'moving' or 'stationary' observer?



But everything in the rest of the universe is also moving, it's not just a case of here is the moving person and here is the static 'rest of the universe'.

Consider putting your thought experiment on its head. In other words, what if I called the observer who is receiving the light the 'stationary' one and the one who is emitting the pulses the 'moving' observer. By your reasoning the stationary observer has the correct reality so in fact the pulses really were not simultaneous and the fact that the moving observer saw them emitted simultaneously was just due to his 'skewed reality'. This allows me to change what reality is just by rewording the problem. Does this not bother you?

Matt

I don't know if I can satisfy the elevated level the conversation just went, but let me try. For the current experiment (we'll move to grander scales in a bit) you want to know if you can tell who is moving and who is stationary (or moving slower) right?

Both observers send out 1 second pulses from their respective clock timing circuits. The slower frame's pulse rate is less than the fastest frame's pulse rate and vice versa, right? This was off the top of my head a few days ago. I have used it and have had no reply,but is seems like it should work.

Assuming like I did in the opening post that when the photons were emitted in the stationary frame the moving frame's photo-sensitive strips (ps_strips) were exposed by a few extra photons at A and B in the stationary frame, while some of the ps-strips were going by within one photon wavelength from the sources. The photons exposed the ps-strips right then at both ends of the moving frame, in fractions of 10^-6 seconds. The strips are numbered and a #10 in the forward end is the same distance from M' as a #10 in th erear position. This was at the instant that M' was at the M when the photons were emitted. Some have suggetsed that no, the moving frame cannot guarantee I can find the midpoint of the ps_strip. My counter, which I havwen;'t seen challenged, is I used the same law of physics that allowed the stationry framwe to determine themisddle of he photon sources at A and B. at M. M is gien in the experimebnt. M is not measured by the photons in the experiment reaching M after the same travel time form the sources. This may have been the methos used, but this was stricly pre-current -experiment.

Can you see my position when I want to say that the photons were mesured in the moving frame equal distances from the midpoint of gthe moving frame when the pulses were emitted by A and B. Just can you see my reasonaning. I will not hold you to an adnmiission that I am right and you are adnmitting error. Only can yo see why I might say that?

If you do then hear this. I have stipulated that SR will predict that which I justs described differently. SR will predict the photons were not emitted simultaneously inthe moving frame. This is stipulated.

I am saying I do not have to argue time dilation, shrinking absolte space and time , noe of that. Why? I have agreed in the results of SR. Whi amI or you for that matter to be chosen as the obne who arbitrates what is physical law? Me saying SR will predict such and such doesn't make the poustulates true, the posstulates stand ot dall on their pwn merist.

Anyway, we have a comflict, I am sure you can envision. but if my observation by reading the ps-strips three weeks after the experiment does bring a nontrivial element into the discssion. You an get all the SR theorists on the planet and vote on the issue and I the anti-SR theorists al 5 of us, and I stipulate your vote would win, slam dunk win. But physical law isn't detemined by political means. Therefore, because the exposure of the ps-strips at the instant the photons were emitted appears contradictory, can you point to a physical experimental reality, fact or conditon that would unambiguously negate what I am calling a reasonable observation? Can you negate the observation with other than SR theory.

It is like the Ptolemy model of circles within cirlces of the solar system with the Earth at the center and all stellar matter revolving around the earth. If you were Galilleo and offered a contradicting observation to the Dr, Ptolemy who countered your observation that "the circles within circles model has worked for 2000 years, ergo your observation is void", you wouldn't accept that would you?

I can't force anyone to anything in this thread, except to look at the problem as I do and try to beat it on its own terms. If SR is so overwhelming "real" as some seem to think, it should be a "slam dunk" trivial exercise to defeat my observations model on its own merits. AT least you should try shouldn't you?

 

[baffledMatt]

Errm, slow down cowboy! - like really, I guess you're typing too fast which is causing you to make a lot of typos and they can make it difficult to understand you.

Matt

 

[ram2048]

When you ask each observer, how many of the answers do you think will be in exact agreement?

the majority :| the majority will always define reality for the minority.

next time you rear-end a parked car with no driver, i want you to argue with the cop that from a relativistic standpoint it's just as real that the parked car hit YOU so it should be equally to blame.

do that for me :D

Then I suppose your answer to my question 'how do you determine this universal frame' will be 'I define it that way'. Ok, have it your way. If you want you can define the 'correct' frame which is this funny democratic average of all the frames in the universe. However, imagine I decide on a different definition, say that where I am sitting is the only stationary frame and everything else revolves around me. Will there be any way you can tell me which of our definitions is correct? will there be any observations which will differ between the universe with my definition and the one with yours?

when 6 billion people come tell you that the world doesn't revolve around you, you have to at least be open to the possibility that they may be right...

Not so. I put you into space in a spaceship with no windows. Is there any experiment you can carry out (without looking outside of course) which will allow you to determine whether you are moving or not?

can i detect anything at all? gravity fluctuations, "radon waves", acceleration deceleration, centripetal inertia or whatever?

if not then this is a completely encapsulated universe, and whatever takes place here has no bearing on the grander universe, and vice-versa.

but within that spaceship, which is now "the universe" certain things will stand out as "fixed locations". bulkheads computer terminals, hatches whatever. using those locations in your "relativistic calculations" it's very easy to determine motion within the ship relative to the whole ship.

 

[wespe]

what specific post invalidated the famous link?

the famous link is the one you keep posting around
http://frontiernet.net/~geistkiesel/index_files/sim_fix_einstein/index.html

the invalidation I was referring to is in the "why relativity is wrong" thread.
https://www.physicsforums.com/showpost.php?p=227893&postcount=209

You give Hurkyl your formula to determine simultaneity, Hurkyl calculates and says "Since the observer is moving, this equation clearly cannot hold", then you say "maybe so""

supose instead of the light co-moving with the moving frame we finish the current experiment. Let the stationary and moving frame send sinals at one second intervals. The faster frame's signals will be slower, the slower frames signal faster, and each will know who is moving.

Huh? I don't see how this works, it's all mutual. You can't determine who is "really" moving. If you can prove you can do that, well, do so.

Your assumption that the stationry frame gets the signals the same as when the photons were emitted in the stationry frame may not be as you say. Inface the link you referred to in doctordicks thread about cerulean etc.? the moving frame here, according to SR and the link you referenced says your wrong. what thread and which specific post invalidated the famous link?

Are you submitting to the panel what Einstein said about "time is what a clock measures"? Check the literature there are tons of different ideas abot time and clocks, most disagreeing with AE. Again whicy post invalidated the famous link, which tyoy haven't read or understood, have you, and do you? Why are you so incompetent as to attempt to negate a mathematical formalism of which you are completely ignorant?

What is wrong with Einstein's definitions? Experiments agree with him. If you don't, please define your version of time, or define a method to measure time. Also please define simultaneity and how to measure simultaneity. Present math that predicts results of these measurements of all observers.

 

[baffledMatt]

I'll have to think a little about your last post (and if you could sort out the typos that would be a great help) but here is a little digression:

It is like the Ptolemy model of circles within cirlces of the solar system with the Earth at the center and all stellar matter revolving around the earth. If you were Galilleo and offered a contradicting observation to the Dr, Ptolemy who countered your observation that "the circles within circles model has worked for 2000 years, ergo your observation is void", you wouldn't accept that would you?

don't forget that 100 years ago it was Newtonian mechanics that was playing the role of Ptolemy (it had been working for almost 300 years!) and special relativity was the crazy new theory which all the stuffy old professors were trying to dismiss.

All that has happened is that the original sceptics of relativity have died and so many of their 'paradoxes' and 'simple demonstrations of the silliness of SR' died with them. Nobody records these ideas because in the day they were crushed by people like Einstein, so of course when people like you come up with similar arguments it feels all new and original. The only thing which will kill relativity now is something really wild and new, like trying to apply it with QM in the middle of a black hole.

I'm not saying that healthy scepticism of SR is a bad thing, indeed, accepting it blindly would mean the end of your days as a scientist! However, do you really think that there is any simple argument against it which you can come up with which probably hasn't allready been thought of? considering just how many great minds there were working on SR at the start of the 20th century I would think this very unlikely.

Anyway, back to our discussion...

Matt

 

[geistkiesel]

When you ask each observer, how many of the answers do you think will be in exact agreement?

Then I suppose your answer to my question 'how do you determine this universal frame' will be 'I define it that way'. Ok, have it your way. If you want you can define the 'correct' frame which is this funny democratic average of all the frames in the universe. However, imagine I decide on a different definition, say that where I am sitting is the only stationary frame and everything else revolves around me. Will there be any way you can tell me which of our definitions is correct? will there be any observations which will differ between the universe with my definition and the one with yours?

Just a slight interjection here. Aren't you both assuming you each know the direction to the "absolute frame"? Isn't there a way to solve this problem without being so universally esoteric? i don't want to deny any of you your say, but it seems slightly over the edge of relevence.
Before we get to your discussion points let us first dispose of the trivial.

1. Stipulation:SR theory predicts the photons emitted in the stationary frame in our experiment will predict the same photons were not emitted simultaneously in the moving frame.

2. PS-strips (photo-sensitive strips) located within 1 photon wave length of the sources of the photons emitted in the stationary frame are exposed (in the moving frame) as the photons are emitted. Super fast film, ps-strips << micorn wide, Each ps-strip locatable to the midpnt M' with mirror image ps-strip at other end within any mutuallly agreeable resolution.

Something's got to give.
Can SR defeat the observation ( that appears contradictory)?

Can the observation defeat SR.

If no observer in a moving frame then no problem, no discussion. Is the presence of the moving frame itself analyzable as a source of physical force that guarantees the photons will not be emitted simultaneously in the moving frame. As far as I can determine the alleged effect is purely one running directly from the postulates of SR exclusively.

Can you see my problem of understanding how a physical event, supported by my famous ps-strips can be modified, not by any real or imagined force, not even any quantum mechanical "nonlocal force channels" are implied or even speculated. The modification, as I call it, is brought into the reality of the universe by the mere presence of an observer. A million observers all moving at different angles all arrive at the same conclusion of nonsimultaneity, and all would have different calculated times for the emission of the photons.

If no moving platform we have a simple simultaneous event of photon emission. With observres, the only expeiemntal difference in the two situations, we have physical modification of an obsevable manifestly existent only by the presence of a moving platform.

If we look first only at the first postulate of SR that the laws of physics are invariant in all inetial frames, will someone please explain how in one frame an event is simultaneous but in another frame, inertial to be sure, that same physical event subject to the laws of physics being invariant in all inertial franes is an event that iss not simultaneous. ie the event in the moving frame is variant to the laws of physics in the moving frame? Maybe the rule is, there is just one exception to the invariance of physical law?

This is much lengthyer than your post and I wouldn't exoect an off the cuff answer. Pick and choose what you think is most important.

Not so. I put you into space in a spaceship with no windows. Is there any experiment you can carry out (without looking outside of course) which will allow you to determine whether you are moving or not?

Matt

what is wrong with looking outside?

 

[ram2048]

i'm going to sum up my arguments for the time being and take an interlude.

it is entirely valid for the moving observer to claim the photons were not simultaneous because that is his perception of reality.

it's entirely valid for any stationary observer to say the photons WERE simultaneous because that is their perception of reality.

when you get 5.99 billion people to say, "yeh dude, those were simultaneous" you must be open to the possibility that perhaps your perception of reality is wrong BECAUSE you were the one moving, NOT everyone else

possibly the reason you guys are complaining so much is because it is TOO trivial :D

-peace for now

 

[geistkiesel]

ram2048

Evidently you don't want to understand this theory. The nice thing about physics is that if you don't want to understand it, you won't!

jdavel please do us all one large favor, please.

Take two unambiguous subjects for analysis.

1.The opening thread stipulated that SR theory would predict the simultaneously emitted photons in the stationary frame would not be simultaneous in the moving frame. This given.

2. Photo-sensitve strips in the moviong frame were exposed by the subject photons when the photons were emitted. The locations of the exposed strips were efefctively exactly at A and B in the srationary frame an each srip, faction of a micron thick are sufficient in numbers on both ends of themoving platform such that the photons are guiarant3edd to be exposed whatever the shrinking of he moving platform. Finally, the ps-stips are identified in pairs where each pair is equal in distance from the midpoint M' of the moving frame, which was determined by the same physicallaws tha assured us that M was themidpoint of A and B in thre stationary frame. This is given,. We do not use the simultaneous arrival iof the photons as the source of the information taht M is the mispoint of the sources, nor in the calculations that SR used in the consklusion that were made, though theinforamtion couls be used. No reason to exclude it. But this was determined long before the experiment ran..

Refreshing your memory of the experiment, when M' was at M, the midpoint of the phioton sources at A and B, photons were emitted simulatneously in the stationary frame.

You can see the apparent copntradiction: Emitted photons simulatneously in the stationary platferom detected effectively instantaneously in the moving frame at the same instant the photons were emitted in the stationary frame.

Give us your veyr very best shot at analyzing the situation. Does SR defeat observation, pe se? IS there any physical law connecting the difference in simultaneity conclusion in the different frames? If physical laws arei invariant in inertial frames why is this exception allowed to continue in the language undiscussed?

 

[baffledMatt]

Both observers send out 1 second pulses from their respective clock timing circuits. The slower frame's pulse rate is less than the fastest frame's pulse rate and vice versa, right? This was off the top of my head a few days ago. I have used it and have had no reply,but is seems like it should work.

No, if they are sending the same 1 second pulses to each other they will each observe exactly the same thing - either a slowing down of the pulses (red shift) or a speeding up (blue shift) depending whether they are moving toward each other or away from each other.

Some have suggetsed that no, the moving frame cannot guarantee I can find the midpoint of the ps_strip. My counter, which I havwen;'t seen challenged, is I used the same law of physics that allowed the stationry framwe to determine themisddle of he photon sources at A and B.

I still don't see exactly what you mean by this. Could you perhaps give me the dumbed down version of how exactly this is done? It's no good you saying 'using the same physics' since we evidently don't agree on exactly what the physics is!

Can you see my position when I want to say that the photons were mesured in the moving frame equal distances from the midpoint of gthe moving frame when the pulses were emitted by A and B. Just can you see my reasonaning. I will not hold you to an adnmiission that I am right and you are adnmitting error. Only can yo see why I might say that?

I can see why you might think that - I remember having exactly these sorts of problems with SR. The way I would always go about solving these problems though was to sit down and just calculate the thing. To illustrate:
Let's make some definitions:
x : space coordinate in 'stationary' frame. x = 0 is the midpoint between A and B, which are located at x = -L and x = L respectively.

v : velocity of the moving observer relative to the stationary observer.

Ok, so now I will calculate what the 'stationary' observer sees. Note I am not going to use any SR as such. We first calculate the location of the point where the 'moving' observer and the light from A coincide. This happens at a time t_A after the light is emitted from A and the point where they meet we denote d_A. By equating the distance the light moves in this time to the distance the moving observer moves we have:

vt_A = d_A
ct_A = d_A + L
so
\frac{v}{c}(L + d_A) = d_A
and
d_A = \frac{\frac{v}{c}L}{(1-\frac{v}{c})}

Similarly, we can derive d_B which is the point where the moving observer meets the light from B
vt_B = d_B
ct_B = (L-d_B)
so
\frac{v}{c}(L-d_B) = d_B
and again
d_B = \frac{\frac{v}{c}L}{(1+\frac{v}{c})}

Evidently, d_A \neq d_B so the photons do not hit the moving observer at the same time/place.

I am saying I do not have to argue time dilation, shrinking absolte space and time , noe of that. Why? I have agreed in the results of SR. Whi amI or you for that matter to be chosen as the obne who arbitrates what is physical law? Me saying SR will predict such and such doesn't make the poustulates true, the posstulates stand ot dall on their pwn merist.

Ok, now repeat the calculation above, but for the moving observer. The only SR result I want you to use is that each observer must observe the same value for the speed of light. If you do this you should see that you need things like time dilation and lack of simultaneity to resolve the observations.

Matt

 

[Alkatran]

i'm going to sum up my arguments for the time being and take an interlude.

it is entirely valid for the moving observer to claim the photons were not simultaneous because that is his perception of reality.

it's entirely valid for any stationary observer to say the photons WERE simultaneous because that is their perception of reality.

when you get 5.99 billion people to say, "yeh dude, those were simultaneous" you must be open to the possibility that perhaps your perception of reality is wrong BECAUSE you were the one moving, NOT everyone else

possibly the reason you guys are complaining so much is because it is TOO trivial :D

-peace for now

But to you they really weren't simultaneous and those 5.99 billion people (who, understanding relativity,) admit that they're simultanity may not be your simultanity.

 

[geistkiesel]

i'm going to sum up my arguments for the time being and take an interlude.

it is entirely valid for the moving observer to claim the photons were not simultaneous because that is his perception of reality.

it's entirely valid for any stationary observer to say the photons WERE simultaneous because that is their perception of reality.

when you get 5.99 billion people to say, "yeh dude, those were simultaneous" you must be open to the possibility that perhaps your perception of reality is wrong BECAUSE you were the one moving, NOT everyone else

possibly the reason you guys are complaining so much is because it is TOO trivial :D

-peace for now

Amen, a moment of silence for ram2048 conclusions, if you please.

In my country, a free country, we have the freedom of thought to perceive as we do, nay as we will. One is allowed the freedom, yes just one person in a crowd of 70,000 say, is allowed the unconditional freedom to perceive pink elephants doing the moon walk, where all others, the 49,999 all perceive the running of the Kentucky Derby. Why do the people scream as they do when watching horse races, you might ask? Because tt makes the horses run faster.

ram2048, take a well deserved few days off. Perchance the bubbling thoughts in the myriad of vortexes in the mind will produce an moe enlightened way of describing what is so clear to others, namely this writer, and what is becoming clear to the host body of scientists.

Tis trivial is it? as a physics problem, I agree. However, the economics of the trivial physics problem poses a nontrivial barrier: Who will cover all the professional funeral expenses of the SR disenfrancised? I am not familiar with the insuance coverage in the theoretical physics industry, but surely these matters must have been discussed in the past, you know, a sudden demise of a preciously held physical theory, like when an observational guillotine suddenly falls foom on a high and . . . .?? Surely everybody is covered, aren't you?

 

[baffledMatt]

it is entirely valid for the moving observer to claim the photons were not simultaneous because that is his perception of reality.

it's entirely valid for any stationary observer to say the photons WERE simultaneous because that is their perception of reality.

Ok, I can safely say we agree here

when you get 5.99 billion people to say, "yeh dude, those were simultaneous" you must be open to the possibility that perhaps your perception of reality is wrong BECAUSE you were the one moving, NOT everyone else

The laws of nature are not a democracy! If you want to have one frame more 'correct' than another there must be a real physical difference so that you can determine which frame this is.

Why can't both perceptions be correct? You have the idea that there is some 'true' reality of whether or not these events were simultaneous. SR is trying to tell us to forget this notion, there is no way we can tell which frame is 'correct', so we shouldn't try to consider it.

Matt

 

[geistkiesel]

But to you they really weren't simultaneous and those 5.99 billion people (who, understanding relativity,) admit that they're simultanity may not be your simultanity.

Alkatran, pray tell man, is simultaneity a characteristic of humanity? Or, on the other hand, is simultaneity a righteous physical phenmomenon? Must one understand SR befoe simultaneity is physically real? In the same sense does my undersatnding of the laws of gravity the assurance I need in order not to drift over to Bakersfield California for instance? I have to know and understand the laws of gravity, you're suggesting in order to avoid Bakersfield, California? My god man, think of the consequences.

 

[baffledMatt]

2. PS-strips (photo-sensitive strips) located within 1 photon wave length of the sources of the photons emitted in the stationary frame are exposed (in the moving frame) as the photons are emitted. Super fast film, ps-strips << micorn wide, Each ps-strip locatable to the midpnt M' with mirror image ps-strip at other end within any mutuallly agreeable resolution.
Something's got to give.

Ok, so we have these film strips and after the experiment they will have two little dots on them corresponding to the points A and B when the photons were emitted. In the moving frame we measure the distance between these points using a metre ruler and come up with a length. We have (using my previous notation) that in the stationary frame the distance between A and B is 2L. However, due to Lorentz contraction the stationary observer will observe the moving observer to measure this distance to be 2L\gamma

NB
\gamma = \frac{1}{\sqrt(1-\frac{v^2}{c^2})} &gt; 1

This is because he sees the moving observer trying to measure a distance of 2L with a shorter (contracted) measuring stick. So he is observing the moving observer making a measurement larger than 2L.

The moving observer on the other hand sees the distance between A and B contracted. Hence, naively you might think he will measure a length of 2L/\gamma. This cannot be because what each observer sees must be the same (remember that we just had the stationary observer seeing the moving observer measure a longer length), so somehow the moving observer must also measure 2L\gamma. This happens because he does not observe the photon emissions to be simultaneous. Hence there is a little bit of time between the first and the second photon, which makes his measured length larger. This will ensure that his observation coincides exactly with that of the stationary observer.

Matt

 

[ram2048]

ok here we go.

suppose in the future we all live in space and drive spacecars around (whee fun)

suppose i get into an accident with another driver in a spacecar who happened to be stopped at a spacestopsign.

now on his UPS (universal position system) his data is telling him that by triangulating the positions of key points in the solar system he was "globally accepted" to be at rest in relation to the rest of the solar system.

MY UPS has the entire universe moving in relation to me.

when the cop comes by in his space cop car, do you think my defense of "relatively, he rammed me as well" is going to stand up in court?

what if spacecars were only built in such a way that they can only go FORWARDS, leaving absolutely NO DOUBT that i DID rear-end the other guy?