SR Simultaneous Lines Drawn in the Sand

[geistkiesel]

The Einstein Train Gedunken


The observer O’ in the moving frame at M’ arrives at M, the midpoint of A and B in the stationary frame, at t0’ when A and B emit photons.

Later a photon from B is detected when M’ is at t1’; the photon from A is detected when M’ is at t2’ in the moving frame. For convenience the velocity of the moving frame is v = 1 and dt = t2' – t1'.
t0'
--------------------------------------t0'|--------t1'-|----------|-t2'
||||||||||||---------------------------M’------------------------------------||||||||||||||| -> motion

-----A-----------------------------------M------------------------------------------B

There are added sections of photo-sensitive strips ||||| such that A and B afre guaranteed to be within a section length when the photons are emitted at A and B. The midpoint of the photo-sensitive strips was determined using the same techniques used to determine M the midpoint of A and B. The strips are numbered starting from the inside positions and then consecutively to the ends of the sections. Each equally numbered pair of photo-sensitive strips have a common midpoint at M’. The resolution of the strips is in the sub-micron range.

As photons are emitted at A and B the photo-sensitive strips located within one photon wave length of A and B, or less, are exposed.

The postulates of special relativity theory state that the laws of physics and the measure of the constancy of the speed of light are invariant in all inertial frames. From special relativity theory observers in the moving frame conclude the events of the emitted photons were not simultaneous in the moving frame.

Are the emitted photon events that are simultaneous in the stationary frame simultaneous in the moving frame?

1.Comments on experimental arrangements or conditions are gratefully accepted.

2.Comments on explicit or implicit stipulations and/or assumptions are gratefully accepted.

3. Other comments..

 

[Doc Al]

Einstein's argument

The Einstein Train Gedunken


The observer O’ in the moving frame at M’ arrives at M, the midpoint of A and B in the stationary frame, at t0’ when A and B emit photons.

I'll rephrase this a bit. In the stationary frame (O), M is the midpoint of two light sources A and B. Lights A and B are switched on at the exact moment that a moving observer O' passes M as observed in the stationary frame. All observations in the stationary frame confirm that the lights were turned on at the same time. For simplicity, let's call that time t = 0.

Since the entire issue is whether or not observers in the moving frame will agree with the stationary frame's assessment that the lights were turned on simultaneously, we must take care to make no assumptions about simultaneity in the moving frame.

Einstein's argument is simple. Rather than add things (like length measurements) which may only serve to confuse the issue, let's deal with Einstein's argument itself (as I recall it).

Einstein reasons thusly:

(1) If an observer is exactly between two lights when they emit pulses simultaneously (according to the observer), then
(2) the pulses from both sources will be detected (received) by the observer simultaneously.

Do you not agree then, that if statement (1) is true, that statement (2) must follow?

Let us also stipulate, per Einstein, that since the speed of light is an invariant in any frame, this argument applies regardless of the speed of the observer. It equally applies to the stationary observer or to the moving observer.

There is no question that for the stationary observer both statements are satisfied. But what can we conclude about the moving observer?

Einstein argues that, from the viewpoint of the stationary observers, O' is moving towards B and away from A. Thus light from B must reach O' before light from A. Do you agree with this? Do you agree that every observer (in any frame) must agree that the light from A and B reached O' at different times?

If you agree with this conclusion, which follows from the invariance of the speed of light, then you agree that statement (2) of Einstein's argument is denied.

Since Einstein's argument is of the form:

If A, then B.
not B,
thus not A.​

We are forced to conclude that statement (1) is not true! Thus O' must conclude that the lights were switched on at different times (according to his observations).

That's Einstein's gedanken experiment. Can you point out an error in that argument?

Later a photon from B is detected when M’ is at t1’; the photon from A is detected when M’ is at t2’ in the moving frame. For convenience the velocity of the moving frame is v = 1 and dt = t2' – t1'.
t0'
--------------------------------------t0'|--------t1'-|----------|-t2'
||||||||||||---------------------------M’------------------------------------||||||||||||||| -> motion

-----A-----------------------------------M------------------------------------------B

There are added sections of photo-sensitive strips ||||| such that A and B afre guaranteed to be within a section length when the photons are emitted at A and B. The midpoint of the photo-sensitive strips was determined using the same techniques used to determine M the midpoint of A and B. The strips are numbered starting from the inside positions and then consecutively to the ends of the sections. Each equally numbered pair of photo-sensitive strips have a common midpoint at M’. The resolution of the strips is in the sub-micron range.

As photons are emitted at A and B the photo-sensitive strips located within one photon wave length of A and B, or less, are exposed.

Not sure what you are measuring with these photo-sensitive strips.

The postulates of special relativity theory state that the laws of physics and the measure of the constancy of the speed of light are invariant in all inertial frames. From special relativity theory observers in the moving frame conclude the events of the emitted photons were not simultaneous in the moving frame.

Right!

Are the emitted photon events that are simultaneous in the stationary frame simultaneous in the moving frame?

No.

 

[ram2048]

uhh.

before a photon even hits the moving observer he's already moved to t'1 (b photon). then he's already moved to t'2 before the second one hits him (a photon)

all motion aside, put an observer at t'0 t'1 and t'2 and which observer does the photon from B hit first?

the one from t'2 of course.

it's quite rudimentary, i am not understanding the confusion behind all this

 

[ram2048]

Einstein reasons thusly:

(1) If an observer is exactly between two lights when they emit pulses simultaneously (according to the observer), then
(2) the pulses from both sources will be detected (received) by the observer simultaneously.

are you sure that's what he's reasoning? because he would have to assume light travels instantaneously in order for that to be true.

as another observation, if a person arrives AT the midpoint M at the exact time to be hit by photons from A and B, NO MATTER what direction speed acceleration, we can safely assume the photons were emitted from the sources simultaneously, even if they were not calibrated to do so.

but this is simply an observation of speeds and distance midpoints known by any elementary school student

 

[Doc Al]

are you sure that's what he's reasoning? because he would have to assume light travels instantaneously in order for that to be true.

Obviously the pulses are emitted and detected at different times.

as another observation, if a person arrives AT the midpoint M at the exact time to be hit by photons from A and B, NO MATTER what direction speed acceleration, we can safely assume the photons were emitted from the sources simultaneously, even if they were not calibrated to do so.

Not true. If you get hit by two bullets simultaneously, can you conclude that they were fired simultaneously? Of course not: it depends on where they were when they were fired.

but this is simply an observation of speeds and distance midpoints known by any elementary school student

Time to move to a better school district.

 

[ram2048]

Not true. If you get hit by two bullets simultaneously, can you conclude that they were fired simultaneously? Of course not: it depends on where they were when they were fired.

if the bullets ALWAYS traveled the same speed AND i was at the MIDPOINT distance between the shooters WHEN HIT.

yes, yes i could

 

[Doc Al]

if the bullets ALWAYS traveled the same speed AND i was at the MIDPOINT distance between the shooters WHEN HIT.

Nope. It doesn't matter where the shooters are when you are hit, it only matters where they were when they pulled the trigger.

Think about it. By the time the bullets reach you, the shooters have moved.

 

[ram2048]

the shooters don't move. they're stationary, the observer is the only thing moving in my example

sorry if you were confused by that

 

[Pergatory]

This is the same as the other two "SR questions of the century" that have been posted earlier on this forum. I'll admit I didn't read those all the way through because they were so long! But I'll take a shot at this one.

Using M as the point of origin (so that AM = MB = AB/2, and A = -B), at the point when observer O reaches t1, the photon from B will also be at t1 (by definition) but the photon from A will be at -t1. Given the same duration of local time, both photons will have traveled an equal distance regardless of the frame of reference. At the point when observer O and photon A reach t2, photon B will be at -t2 (the photons have both passed M).

(1) If an observer is exactly between two lights when they emit pulses simultaneously (according to the observer), then
(2) the pulses from both sources will be detected (received) by the observer simultaneously.

#2 is true only if the observer is exactly between the lights when the photons are DETECTED. It does not matter where the observer is when they are emitted. In fact, the observer does not even need to exist when they are emitted. Look at the stars tonight. Consider how long it has been since the light you are seeing has been emitted. Have you really been alive that long? The events you are seeing are not occurring, they have already occurred in the past.

Time is local, so simultaneity is a matter of your frame of reference.

 

[ram2048]

#2 is true only if the observer is exactly between the lights when the photons are DETECTED. It does not matter where the observer is when they are emitted

exactly, which was the point i was trying to make, but i left out that the emitters do not move <woops>

 

[baffledMatt]

Have you ever looked at the so-called 'pole-vaulter paradox'? That's an interesting one as it shows you explicitely how according to SR you must lose simultaneity or face paradox.

Matt

 

[Doc Al]

#2 is true only if the observer is exactly between the lights when the photons are DETECTED.

Incorrect. In fact, exactly the opposite is true. I don't care where the lights are when the photons are detected--they need not even exist by that time.

It does not matter where the observer is when they are emitted.

It matters if you wish to make a deduction about whether the pulses are detected simultaneously. Which is the entire point.

In fact, the observer does not even need to exist when they are emitted.

The thought experiment assumes that both observers have existed forever traveling at the same speed. The point is that statement (2) follows from statement (1). That's all.

Look at the stars tonight. Consider how long it has been since the light you are seeing has been emitted. Have you really been alive that long? The events you are seeing are not occurring, they have already occurred in the past.

True, but I don't see the relevance to Einstein's argument.

Time is local, so simultaneity is a matter of your frame of reference.

Now that I agree with!

 

[Pergatory]

Incorrect. In fact, exactly the opposite is true. I don't care where the lights are when the photons are detected--they need not even exist by that time.

It matters if you wish to make a deduction about whether the pulses are detected simultaneously. Which is the entire point.

My apologies for not being clear. What I meant by the light, is A and B. Not the physical light, you're right, it could be removed once the photons have been emitted, it does not matter.

My point is that in order for the photons to arrive at the observer at the same time, the observer must be equidistant from both originating locations at the point in time when both photons are observed. It does not matter where the observer is or is not when the photons are emitted. THAT was my point.

Please don't waste your time by further tearing apart minor details of my responses, and focus solely on the point I'm trying to prove in response to the point you've tried to make. If we lose focus, it will turn into another 4-page discussion and there will be another identical thread created in a few days discussing the same principal.

 

[Doc Al]

the shooters don't move. they're stationary, the observer is the only thing moving in my example

From the observer's point of view, the shooters are moving. Regardless, all that matters for the current argument (in analogy with Einstein's) is where the shooters were (with respect to the observer) at the moment the guns were fired. If the observer (victim?) was exactly between the shooters at the time they fired, then we can deduce that the bullets will arrive simultaneosly. (These are special photon bullets, of course, that always travel the same speed with respect to all observers. )

 

[Doc Al]

My point is that in order for the photons to arrive at the observer at the same time, the observer must be equidistant from both originating locations at the point in time when both photons are observed. It does not matter where the observer is or is not when the photons are emitted. THAT was my point.

I believe I understood your point the first time. You're still wrong. The position of the lights at the moment the photons are detected is irrelevant.

Please focus on the argument at hand: If statement (1) is true, then statement (2) is true.

Please don't waste your time by further tearing apart minor details of my responses, and focus solely on the point I'm trying to prove in response to the point you've tried to make. If we lose focus, it will turn into another 4-page discussion and there will be another identical thread created in a few days discussing the same principal.

I am completely focused. The point of yours that I am "tearing apart" is not a minor detail.

 

[jdavel]

Pergatory,

Doc Al is right.

If two lights flash simultaneously (in my frame) and the distance from me to each one is the same at the time of the flashes, then light from the two flashes reaches me at the same time. That's what it means for light speed to be a constant with respect to all observers.

Your bullet analogy let's you down because the bullets are traveling at constant speed with respect to the shooters, but if you are moving wrt the shooters, the bullets are moving at different speeds wrt you.

If you want to get to the point where constant light speed and all its consequences seem more intuitive, stop thinking about bullets!

 

[ram2048]

that makes NO sense.

A and B flash. observer M is in the middle WHEN they flash. He immediately accelerates to light speed in the direction of B.

Photon from A never reaches him.

Photon B is intercepted halfway to B

 

[jdavel]

ram2048,

Sounds like you have a real solid understanding of this theory!

 

[ram2048]

what part of photons traveling the speed of light is hard to understand?

if you travel AWAY from a clock AT LIGHT SPEED and look to see what time it says what do you see?

NOTHING. no new photons are hitting your eyes from that direction

 

[quantumdude]

what part of photons traveling the speed of light is hard to understand?

if you travel AWAY from a clock AT LIGHT SPEED and look to see what time it says what do you see?

NOTHING. no new photons are hitting your eyes from that direction

I think what jdavel is hinting at is that you can't accelerate to light speed.

 

[ram2048]

fine. i AM a photon

i'm looking behind me at a clock :P

 

[geistkiesel]

The line in the sand : remain where you are or step across.

I'll rephrase this a bit. In the stationary frame (O), M is the midpoint of two light sources A and B. Lights A and B are switched on at the exact moment that a moving observer O' passes M as observed in the stationary frame. All observations in the stationary frame confirm that the lights were turned on at the same time. For simplicity, let's call that time t = 0.

Sure, but also as to the moving observers their clocks are t' = 0. The two '0' are the same.

Since the entire issue is whether or not observers in the moving frame will agree with the stationary frame's assessment that the lights were turned on simultaneously, we must take care to make no assumptions about simultaneity in the moving frame.

Right. We only define simultaneity as "the photons emitted at the same time in the frame." This is the question, not the answer. OK?

Einstein's argument is simple. Rather than add things (like length measurements) which may only serve to confuse the issue, let's deal with Einstein's argument itself (as I recall it).

Einstein reasons thusly:

(1) If an observer is exactly between two lights when they emit pulses simultaneously (according to the observer), then
(2) the pulses from both sources will be detected (received) by the observer simultaneously.

Do you not agree then, that if statement (1) is true, that statement (2) must follow?

Your observer here is the stationary observer, right? No ambiguity here, right?

I agree. The sequence goes like this: 1.The stationary observer is at the midpoint of A and B 2. Photons are emitted from A and B simultaneously. 3. Later, thw photons from A and B arrive at M (the observer) at the same time, simultaneously. You logic is correct. At this point characteristics of the speed of light have no special significance as long as what we are calling photons move with the same speed to the mindpoint. The photons could be crawling ants.

Let us also stipulate, per Einstein, that since the speed of light is an invariant in any frame, this argument applies regardless of the speed of the observer. It equally applies to the stationary observer or to the moving observer.

No stipulation. I already stipulated that a moving observer using SR theory will conclude the photons were not emitted from A and B simultaneously in the moving frame. This is my stipulation. Can you agree to this?

There is no question that for the stationary observer both statements are satisfied. But what can we conclude about the moving observer?

Einstein argues that, from the viewpoint of the stationary observers, O' is moving towards B and away from A. Thus light from B must reach O' before light from A. Do you agree with this? Do you agree that every observer (in any frame) must agree that the light from A and B reached O' at different times?

This is effectively the same as stated above. The answer is yes, whether we are using crawling ants emitted from A and B, or light photons. Yes.

If you agree with this conclusion, which follows from the invariance of the speed of light, then you agree that statement (2) of Einstein's argument is denied.

Since Einstein's argument is of the form:

If A, then B.
not B,
thus not A.​

We are forced to conclude that statement (1) is not true! Thus O' must conclude that the lights were switched on at different times (according to his observations).

That's Einstein's gedanken experiment. Can you point out an error in that argument?

I didn't stipulate to Einstein's postulate regarding the speed of light. I stipulated that SR theory would predct the photons were not emitted at A and B in the movinng frame. Do you have a problem with this? I am not going to debate the truth or falsity of the 'speed of light' postulate. If you say that the SOL postulate is fundamental to the SR derivation of simultaneity, so be it.

I am scrutinizing the operation of the postulates. I am not testing the factual reality of that postulated. Do you see the difference?

The difference goes like this: simultaneity(SR) is placed in an enclosed logical box that cannot be entered and the contents modified, by cleverness, wit, dishonesty or mistake, or stipulation.

Not sure what you are measuring with these photo-sensitive strips.

Right!

No.

The photo-sensitive strips in the moving frame are arranged such that the photons emitted at A and B immediately expose the closest ps-strips in the sections, which are located within one wave length of the photon source when the moving frame passes by. Using the same laws of physics that determined M the midpoint of A and B, the moving frame scientists have determined the midpoint M' of all co-numbered ps-strips at each end of the measuring rod.

 

[russ_watters]

fine. i AM a photon

Fine. I am Elvis.

Saying it doesn't make it true and a thought experiment is only useful if it conforms to the theory it is used to describe.

 

[geistkiesel]

line in thwe sand

uhh.

before a photon even hits the moving observer he's already moved to t'1 (b photon). then he's already moved to t'2 before the second one hits him (a photon)

all motion aside, put an observer at t'0 t'1 and t'2 and which observer does the photon from B hit first?

the one from t'2 of course.

it's quite rudimentary, i am not understanding the confusion behind all this

The sequence of events: T0 the moving frame M' = M in the stationary frame at t0' = t0.
You cannot do as you say. The photon from B strikes the moving observer at t1', later the photon from A, behind, strikes the moving observer at t2'. You are mixing spatial location with timed points.

 

[geistkiesel]

line in the sand

are you sure that's what he's reasoning? because he would have to assume light travels instantaneously in order for that to be true.

as another observation, if a person arrives AT the midpoint M at the exact time to be hit by photons from A and B, NO MATTER what direction speed acceleration, we can safely assume the photons were emitted from the sources simultaneously, even if they were not calibrated to do so.

but this is simply an observation of speeds and distance midpoints known by any elementary school student

Doc Al is ambiguous. he is constantly observed to holding little factual tidbits so he can confuse the issue and distrct the flow of the thread. He isn't being honsest is what I am saying. He really is saying that an observer at M in the stationary frame will see the photons arrive at M simultaneously. I agree with your second paragraph. But some using SR theory calculate the photons that arrived at M simultaneously were NOT emitted simultaneously in the moving frame. In fact, before my exile, Doc Al and I discussed this issue in another thread.

 

[geistkiesel]

Obviously the pulses are emitted and detected at different times.

Not true. If you get hit by two bullets simultaneously, can you conclude that they were fired simultaneously? Of course not: it depends on where they were when they were fired.

Time to move to a better school district.

Not true. Bullets fired from 1 km to the midpoint at the instant bullets fired from fired from 2 kim to the midpoint reach a point 1 km to the midpoint, will arrive at the same time. The same holds for photons emitted at the same locations as those launching the bullets. The farthest emitted photon will arrive simultaneously with the nearest emitted photon.

This isn't trivial for everybody?

 

[geistkiesel]

Nope. It doesn't matter where the shooters are when you are hit, it only matters where they were when they pulled the trigger.

Think about it. By the time the bullets reach you, the shooters have moved.

This is what I mean abiout dishonesty. After the bullets are launched, or photons are launched the location of the point of emitted entities is still the same point.

ram2048 - you must see the Doc Al 'confuse and distract methodology'

read the first pot again. The issue under disussion is whether the photons that were emitted simultaNeously when M' of the moving frame was at M in the stationary frame, which is the instant the photons were emitted at A and B were also emitted simultaneously in the moving frame, THIS IS THE THE SAME TIME THEY WERE EMITTED IN THE STATIONARY FRAME. SR THEORY CALCULATES THE PHOTONS WERE NOT EMITTED SIMULTANEOUSLY IN THE MOVING FRAME.

Doc Al knows this, he is consciously throwing distractions and bull **** into the conversation. Doc Al is not being honest, do you get it everybody?

 

[geistkiesel]

line in the sand

This is the same as the other two "SR questions of the century" that have been posted earlier on this forum. I'll admit I didn't read those all the way through because they were so long! But I'll take a shot at this one.

Using M as the point of origin (so that AM = MB = AB/2, and A = -B), at the point when observer O reaches t1, the photon from B will also be at t1 (by definition) but the photon from A will be at -t1. Given the same duration of local time, both photons will have traveled an equal distance regardless of the frame of reference. At the point when observer O and photon A reach t2, photon B will be at -t2 (the photons have both passed M).



#2 is true only if the observer is exactly between the lights when the photons are DETECTED. It does not matter where the observer is when they are emitted. In fact, the observer does not even need to exist when they are emitted. Look at the stars tonight. Consider how long it has been since the light you are seeing has been emitted. Have you really been alive that long? The events you are seeing are not occurring, they have already occurred in the past.

Time is local, so simultaneity is a matter of your frame of reference.

Pergatory, you have just finished you probationary period. Step up to the big time. You have said it all perfectly. I would only add the observation that SR theory does not agree with your assesment of SR theory. SR theory says that the moving observer will detect the photons as not being emitted simultaneously in the moving frame.

Of course the photons do not arrive simultaneously, but this is not sufficient to prove they weren't emitted simultaneously.
http://frontiernet.net/~geistkiesel/index_files/

There is a simple method described in the link to determine if the phoons were emitted simultaneously in the moving frame.

 

[geistkiesel]

My apologies for not being clear. What I meant by the light, is A and B. Not the physical light, you're right, it could be removed once the photons have been emitted, it does not matter.

My point is that in order for the photons to arrive at the observer at the same time, the observer must be equidistant from both originating locations at the point in time when both photons are observed. It does not matter where the observer is or is not when the photons are emitted. THAT was my point.

Please don't waste your time by further tearing apart minor details of my responses, and focus solely on the point I'm trying to prove in response to the point you've tried to make. If we lose focus, it will turn into another 4-page discussion and there will be another identical thread created in a few days discussing the same principal.

What you say is true. The moving observer who was at the midpoint of the photons when they were emitted later observes the photons arriving at different times as he is moving towards one of the photons and away from the other.

SR theory says, that the different arrival times at the moving observer means the photons were emitted at differnt time in the moving frame. This is different than saying his mere preception is the photons were emitted at diifferent times. SR theory has the PHYSICAL EMISSION of the photons into the moving frame not being simultaneous. This is fundamental SR.

Doc Al is being dishonest.

 

[ram2048]

so. here's what I'm getting from everyone trying to confuse the issue...

if I'm in the middle of A and B, and they emit photons towards me, no matter WHAT i do, move left right up down side to side stand on my head, WHATEVER...

i will always get hit by photons A and B at the same time.

is THAT what they're saying?

 

[geistkiesel]

that makes NO sense.

A and B flash. observer M is in the middle WHEN they flash. He immediately accelerates to light speed in the direction of B.

Photon from A never reaches him.

Photon B is intercepted halfway to B

your statement is recognition of the stupidity of SR theory.

 

[geistkiesel]

Fine. I am Elvis.

Saying it doesn't make it true and a thought experiment is only useful if it conforms to the theory it is used to describe.

it is also useful if the thiought proes the theory wrong.

 

[geistkiesel]

so. here's what I'm getting from everyone trying to confuse the issue...

if I'm in the middle of A and B, and they emit photons towards me, no matter WHAT i do, move left right up down side to side stand on my head, WHATEVER...

i will always get hit by photons A and B at the same time.

is THAT what they're saying?

No. If you are the middle of he photons when they are emitted and you reamin there th ephiotons will arrive at the saem time. If you move like the experiment here, the photons will arrive at difeent times. Bullets, photons or craw;ing ants, the same is true. Keep everything in a straight line. It is the simplest of simple.

Doc Al is throwing useless bull **** around to distract.
Read the first post in this thread. As the moving frame passes the stationary frame when M' in the moving frame was at M in the stationary frame, the photons were emitted in the stationary frame simultaneously, and the photons were detected at this very instant simultaneously in the moving frame.

 

[geistkiesel]

Pergatory,

Doc Al is right.

If two lights flash simultaneously (in my frame) and the distance from me to each one is the same at the time of the flashes, then light from the two flashes reaches me at the same time. That's what it means for light speed to be a constant with respect to all observers.

Your bullet analogy let's you down because the bullets are traveling at constant speed with respect to the shooters, but if you are moving wrt the shooters, the bullets are moving at different speeds wrt you.

If you want to get to the point where constant light speed and all its consequences seem more intuitive, stop thinking about bullets!

Read the first post in this thread. As the moving frame passes the stationary frame when M' in the moving frame was at M in the stationary frame, the photons were emitted in the stationary frame simultaneously, and the photons were detected at this very instant simultaneously in the moving frame. Do you understand?

 

[ram2048]

No. If you are the middle of he photons when they are emitted and you reamin there th ephiotons will arrive at the saem time. If you move like the experiment here, the photons will arrive at difeent times. Bullets, photons or craw;ing ants, the same is true. Keep everything in a straight line. It is the simplest of simple

so they DON'T hit you at the same time if i move left or right.

which is what i thought, so why the arguments if everyone agrees?

 

[geistkiesel]

ram2048,

Sounds like you have a real solid understanding of this theory!

In the first post of this thread the moving observer at M' was at M the midpoint of sources of photons when the photons were emitted simultaneously. These photons were instantaneously detected in the moving frame as the were emitted in the stationary frame. The moving frame detected the simultaeous emission of the photons in the moving frame. .

Using the detected arrival times of the photons in the moving frame, SR theory calculates that the photons were not emitted simultaneouslly in the moving frame. THE PHOTONS WERE DETECTED SIMULTANEOUSLY IN THE MOVING FRAME AT THE INSTANT THE PHOTONS WERE EMITTED IN THE STATIONARY FRAME.

All you theorists can argue all you want about SR theory, speed of light, Einstein, laws of physics, constancy of the speed of light foreever. The fact of the observation the photons were emitted simultaneously in the moving frame remains invariant under any theoretical perturbation.

Your problem is one of embarrassment when you ponder: "How could I ever have accepted special relativity in the first place?" Like I said, it is your problem, you solve it.

 

[geistkiesel]

Not sure what you are measuring with these photo-sensitive strips.

quote geistkiesel: "Were the photons emitted simultaneously in the stationary frame also emitted simultaneously in the moving frame?"

No.

In the first post of this thread the moving observer at M' was at M the midpoint of sources of photons in the stationary frame when the photons were emitted simultaneously. These photons were instantaneously detected in the moving frame as they were emitted in the stationary frame. The moving frame detected the simultaeous emission of the photons in the moving frame.

This is an experimental observation.

And you say no they were not emmitted in the moving frame simultaneously.

 

[geistkiesel]

Pergatory,

Doc Al is right.

If two lights flash simultaneously (in my frame) and the distance from me to each one is the same at the time of the flashes, then light from the two flashes reaches me at the same time. That's what it means for light speed to be a constant with respect to all observers.

Your bullet analogy let's you down because the bullets are traveling at constant speed with respect to the shooters, but if you are moving wrt the shooters, the bullets are moving at different speeds wrt you.

If you want to get to the point where constant light speed and all its consequences seem more intuitive, stop thinking about bullets!

In the first post of this thread the moving observer at M' was at M the midpoint of sources of photons in the stationary frame when the photons were emitted simultaneously. These photons were instantaneously detected in the moving frame as they were emitted in the stationary frame. The moving frame detected the simultaeous emission of the photons in the moving frame.

What are you talking about " ...seeming more intuitve . . ?.Aren't observations intuitive enough for you?

 

[ram2048]

why must you use a moving frame and a stationary frame?

i think that's what is throwing me off

do one experiment where he's stationary and THEN do the exact same thing when it's moving

combining the two creates unnecessary confusion :P

1) A -> ________________M________________ <- B
1) A ____ ->____________M____________<- ____ B
1) A __________ ->______M______<- __________ B
1) A _________________ xMx _________________ B

2) A -> ________________M________________ <- B
2) A ____ ->______________M__________<- ____ B
2) A __________ ->__________M__<- __________ B
2) A ________________ ->______Mx ___________ B
2) A ______________________ ->__Mx _________ B
2) A ____________________________xMx _______ B

so I'm still not seeing the contradiction. everyone AGREES that the photons don't hit him at the same time in the moving frame. How hard would it be to do the calculations in reverse for the moving frame setup and acquire that the beams WERE emitted simultaneously BECAUSE of the frame shift, extrapolate it using M's velocity towards B.

 

[geistkiesel]

why must you use a moving frame and a stationary frame?

i think that's what is throwing me off

do one experiment where he's stationary and THEN do the exact same thing when it's moving

combining the two creates unnecessary confusion :P

1) A -> ________________M________________ <- B
1) A ____ ->____________M____________<- ____ B
1) A __________ ->______M______<- __________ B
1) A _________________ xMx _________________ B

2) A -> ________________M________________ <- B
2) A ____ ->______________M__________<- ____ B
2) A __________ ->__________M__<- __________ B
2) A ________________ ->______Mx ___________ B
2) A ______________________ ->__Mx _________ B
2) A ____________________________xMx _______ B

so I'm still not seeing the contradiction. everyone AGREES that the photons don't hit him at the same time in the moving frame. How hard would it be to do the calculations in reverse for the moving frame setup and acquire that the beams WERE emitted simultaneously BECAUSE of the frame shift, extrapolate it using M's velocity towards B.

Why do we need two frames?
Because SR theory says that events that are simultaneous in the stationary frame are not simultaneous in the moving frame. We are talking about the same physical event. We must do the experiment with two frames, one stationary and one moving to test the theory. Hence we have the photo-sensitive strips to measuee the emission of the photons.
Here is the contradiciton that everyone is having such a difficult time with.

"Were the photons that were emitted simultaneously in the stationary frame also emitted simultaneously in the moving frame?"[/b ]

There was the record of the phosensitive strips attached to the moving frame that were exposed just when the photons were emitted in the stationary frame. These photo-sensitve strips were within a photon wave length of the emitted photons at A and B in the stationary frame when they wee exposed.

SR theory says, the photons were not emitted simultaneously in the moving frame. SR Theory gets to work backwards in time and redo the physical events that occurred there.

 

[Hurkyl]

why must you use a moving frame and a stationary frame?

Because we're disagreeing about what SR says when we analyze the exact same events from different frames.

Specifically, Geistkiesel is asserting that both of these diagrams are representing the exact same sequence of events:

A        M        B
A\       M       /B
A \      M      / B
A  \    M      /  B
A   \   M     /   B
A    \  M    /    B
A     \M    /     B
A      M   /      B
A      M  /       B
A     M  /        B
A     M /         B
A     M/          B


A       M       B
A\      M      /B
A \     M     / B
 A \    M    /   B
 A  \   M   /    B
 A   \  M  /     B
  A   \ M /       B
  A    \M/        B

We have two relatively stationary light sources (A and B), and an observer who starts in the middle and moves towards A.

The first diagram depicts how things look in the rest frame of the lights, if the lights are activated simultaneously.

The second diagram depicts how things look in the rest frame of the observer, if the lights are activated simultaneously.

However, there is a very important difference between the two diagrams; in the first diagram the photons do not meet M at the same event, however in the second diagram the photons do meet M at the same event.

The conclusion is that these diagrams cannot possibly represent the same events. Among the possible assumptions we can abandon, abanding that of absolute simultaneity is by far the most reasonable; the emission of photons is simply simultaneous in one frame but not the other.

 

[Doc Al]

Sure, but also as to the moving observers their clocks are t' = 0. The two '0' are the same.

You cannot arbitrarily set all clocks in O' to read t'=0. Doing so requires assuming that simultaneity is independent of the reference frames. Since that's what we're trying to discover, we can't just assume it.

No stipulation. I already stipulated that a moving observer using SR theory will conclude the photons were not emitted from A and B simultaneously in the moving frame. This is my stipulation. Can you agree to this?

Absolutely not! I don't want anyone making assumptions or stipulations about simultaneity. The entire point of Einstein's simple argument is to deduce the nature of simultaneity, not make assumptions about it.

I didn't stipulate to Einstein's postulate regarding the speed of light. I stipulated that SR theory would predct the photons were not emitted at A and B in the movinng frame. Do you have a problem with this? I am not going to debate the truth or falsity of the 'speed of light' postulate. If you say that the SOL postulate is fundamental to the SR derivation of simultaneity, so be it.

Once again, the point of Einstein's argument is to deduce the relativity of simultaneity, not assume it. The invariant speed of light is fundamental to any gedanken experiment concerning light. Without that, there is nothing to discuss.

The difference goes like this: simultaneity(SR) is placed in an enclosed logical box that cannot be entered and the contents modified, by cleverness, wit, dishonesty or mistake, or stipulation.

Don't be cute. Re-read my post and tell me exactly where you think Einstein's argument fails. If you can't accept the starting point--the invariant speed of light--then there is no point in continuing.

 

[Doc Al]

Doc Al is ambiguous. he is constantly observed to holding little factual tidbits so he can confuse the issue and distrct the flow of the thread. He isn't being honsest is what I am saying.

Please tell me exactly where I am being ambiguous. Refer to my post #2 in this thread. And dishonest? Come now, geistkiesel, have you run out of intellectual ammunition this early in the game?

He really is saying that an observer at M in the stationary frame will see the photons arrive at M simultaneously.

Anyone curious as to what I actually said, can read my own words in post #2.

I agree with your second paragraph. But some using SR theory calculate the photons that arrived at M simultaneously were NOT emitted simultaneously in the moving frame. In fact, before my exile, Doc Al and I discussed this issue in another thread.

We have "discussed" this many times. I am giving geistkiesel a golden opportunity to clearly and unambiguously point out the flaws in Einstein's argument. Is he up to the challenge?

 

[Doc Al]

Doc Al is throwing useless bull **** around to distract.
Read the first post in this thread.

Re-read my response in post #2.

As the moving frame passes the stationary frame when M' in the moving frame was at M in the stationary frame, the photons were emitted in the stationary frame simultaneously,

Right!

and the photons were detected at this very instant simultaneously in the moving frame.

Now what possibly can you mean by this garbled statement? Are you talking about photons being detected by O'? Or O' deducing that they were emitted simultaneously? Speak clearly and stop wasting people's time.

 

[Doc Al]

Read the first post in this thread. As the moving frame passes the stationary frame when M' in the moving frame was at M in the stationary frame, the photons were emitted in the stationary frame simultaneously, and the photons were detected at this very instant simultaneously in the moving frame. Do you understand?

I defy anyone to understand your point. See my last post. Talk sense, man!

 

[Doc Al]

how geistkiesel sneaks in an assumption of simultaneity

In the first post of this thread the moving observer at M' was at M the midpoint of sources of photons when the photons were emitted simultaneously. These photons were instantaneously detected in the moving frame as the were emitted in the stationary frame. The moving frame detected the simultaeous emission of the photons in the moving frame.

Assuming observers in the moving frame were posted at the right positions, then they WILL detect the photon emissions. But what makes you think that they will detect them SIMULTANEOUSLY? Since that is the point we are arguing, please give us your argument. (Note how Einstein's simple argument does not involve multiple moving observers. Why not deal with that argument directly?)

Using the detected arrival times of the photons in the moving frame, SR theory calculates that the photons were not emitted simultaneouslly in the moving frame.

We all agree that the moving observer detects the photons as arriving at different times. Using that fact, plus simple assumptions of the invariance of light speed, Einstein deduces that the moving observer must conclude that the photons were emitted at different times. Every observation made in the moving frame--including the direct observation of the photon emissions by the moving observers--must agree with this conclusion!

THE PHOTONS WERE DETECTED SIMULTANEOUSLY IN THE MOVING FRAME AT THE INSTANT THE PHOTONS WERE EMITTED IN THE STATIONARY FRAME.

Again, you merely ASSume, where Einstein argues.

All you theorists can argue all you want about SR theory, speed of light, Einstein, laws of physics, constancy of the speed of light foreever. The fact of the observation the photons were emitted simultaneously in the moving frame remains invariant under any theoretical perturbation.

I truly believe that you believe this. But you are still wrong. Rather than add questionable assumptions to Einstein's gedanken experiment, please deal directly with Einstein's simple argument.

Your problem is one of embarrassment when you ponder: "How could I ever have accepted special relativity in the first place?" Like I said, it is your problem, you solve it.

Geistkeisel, I am making a special effort in this thread to be nice. Why don't you do the same?

 

[geistkiesel]

A Simultaneous Line in the Sand for Doc Al

I defy anyone to understand your point. See my last post. Talk sense, man!

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..

Is this enough "sense talk, man"?

I title this: A Simultaneous Line in the Sand for Doc Al.

If you were from Texas, or had spent any time in Texas, maybe, just maybe you would be able to understand. And this even though it is common knowledge that Texans have half their brains tied behind their back, leaving one loose piece of gray matter to rattle around inside their skull cavities.

You defied anyone to understand the point. OK, someone from Texas, splain it to Doc Al.

 

[geistkiesel]

Doc Al's special effort fails the nice simultaneity test, again..

Again, you merely ASSume, where Einstein argues.

I truly believe that you believe this. But you are still wrong. Rather than add questionable assumptions to Einstein's gedanken experiment, please deal directly with Einstein's simple argument.

Geistkeisel, I am making a special effort in this thread to be nice. Why don't you do the same?

You don't know how to be nice. There were no added assumptions that corupted Einstein's gedunken. You just haven't realized that you've lost this game.

As from me to you, this is as nice as it gets.

 

[russ_watters]

it is also useful if the thiought proes the theory wrong.

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.

 

[Doc Al]

geistkiesel's assumptions

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.

Can observers in the moving frame detect the emission of the photons? Yes.
Are the marks on the photo-sensitive strips (caused by the photon emissions) in the moving frame equally spaced from the point M' (which passed M at the exact moment that the clock at M read t=0): YES!
Do the moving observers detect the photon emissions as happening simultaneously: NO!

By building incorrect assumptions into your "thought" experiment, you have left the realm of real physics. (As we know it today.)

Note that Einstein makes no such assumptions--and is able to simply deduce the relativity of simultaneity. Why not address Einstein's actual argument?