Existence

Hi ICANT,Perhaps we are close to overcoming one source of error. Really? No exceptions? Must be tired to the motion of an observer?Wrong, the definition says "may".The origin of a frame of reference may well be tied to the motion of an observer if that is convenient for solving a problem. But the origin is only a single point represented by coordinates (0,0,0) of the infinite number of locations and events that have coordinates in a frame of reference. This definition is not helpful to you.Actually, we all know the reason why you want reference frames to be limited to an observer's vision. You want to be able to deny that events some observer did not see actually happened in a given reference frame. You've been using that lame "didn't see it" excuse every time it becomes clear that a particular reference frame provides an inconvenient fact.But physics is about applying known rules to describe the coordinates of events regardless of whether they are visible. If there is some definition of reference frame that is limited to what can be seen, that isn't the definition to which postulates #1 and #2 apply.Can we drop this line of argument from your bag o' tricks now?

Hi crash, The one I made on the mirror where the light met the mirror. Yes.If you had read and understood what I wrote you would realize the spot was directly in front of the laser pen. Well no it was not reflecting off the mirror and hitting the wall behind me.Since I had made sure the laser pen was level and pointed at the mirror so there was a 90 angle where the beam hit the mirror relative to the flat surface of the mirror the reflection from the mirror hit the head of the laser pen.In none of the experiments with the laser pen have they not been attached so as they don't move.The only movement the laser pen would have is the movement of the car.God Bless,

Hi NoNukes, Which experiment have we discussed that was not an observational reference frame?God Bless,

Hi CS, So why did you present a diagram that shows exactly what the bowling ball will do when thrown from the moving car?Oh I know you are using a light clock and the pulse is supposed to be traveling verticle between moving mirrors.So lets hold the bowling ball 4 foot from the ground and drop it from the car that is traveling at 0.5 c and the bowling ball will do exactly what you say the light pulse will do.The problem is they don't do the same things.The light pulse will go in a straight line at c from the point it is emitted regardless of the motion of the emitter.God Bless,

So the spot was on the pen, back where it started - not ahead of the pen in a straight line.So that answers your question about under what circumstances light won't travel in a straight line in the direction that the laser pen is pointed. In what reference frame? In the reference frame of the car, neither the laser pen nor the sensor have any motion at all. Do you see why? It's because of what motion is.What is motion, ICANT? It's a change in position over time. And the way that we measure position is relative to the position of something else that we refer to as the "origin", or sometimes "zero." That's the center of the coordinate system, the point (0,0,0). That point can be anywhere in space and have any intrinsic motion of its own that we decide.When we define an origin as being in motion, and having the same motion as another object (say, a moving car) then we describe that coordinate system as being the reference frame of the object. The reference frame extends in all directions to infinity, and it contains all objects in the universe as a result. Everything is in all reference frames at all time. When the reference frame has constant velocity, it is an inertial reference frame. When we say "observed reference frame" or "observers reference frame", that refers to the reference frame by which a certain observer is measuring the position of other objects in space. Practical concerns about how far observers can observe are irrelevant to that; an observer is defined as being able to observe the event in question.The same objects measured in different reference frames by different observers have different properties. Their speeds will differ. The direction of their velocity will differ. For reasons I've already explained, their masses and dimensions will differ as well, even though it seems like they shouldn't. This isn't any different from the fact that if you measure an angle from one side, it may be 30°, but if you measure it from the other side it may be 150°. Measuring always depends on what you're measuring from.The one exception to this is that any observer measuring the speed of light, in any reference frame, will measure the light to have speed c. This has been proven experimentally over and over again, and has been known for well over 100 years.

That is correct. As a result of its straight line motion it will hit the moving detector.

Hi ICANT, I'm not sure what "observational reference frame" means to you, but perhaps the following will answer the question.Whenever we apply physics to an inertial reference, which is mostly what we have discussed, we are not talking about a frame of reference that stops at the boundaries of what an observer can see. Obviously.When we you tell you that we don't care what that an event cannot be seen or when we ask you about an event that cannot be seen, we are clearly not talking about a point of view limited to some observers line of site. Obviously.When we tell you that objects do not leave a frame, what could that mean?When ICANT talks about a photon being in its own frame, ICANT cannot be talking about what can be seen, because no humans can even be in that frame. Obviously.Does that end this folly? Did you really think that only photons that some observer can see must travel at speed "c" in a vacuum? I doubt that you thought that.

Hi NoNukes, Only if you came up with the idea and created it. Talk about being dishonest what do you call this cherry picking you did? I sure hope it was not on purpose.This is what I said in the message you are replying too.

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I believe that according to postulate #1 which requires the pulse to travel in a straight line from the time emitted, the pulse will hit the blackboard.

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According to what you have been trying to convince me of the pulse will miss the blackboard as the pulse has to travel at an angle like it does in the stupid light clock with moving mirrors presented.

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Which would meant the pulse would reach the distance the blackboard is from the tracks after the laser pen has moved 12.5 feet from the point the pulse was emitted. That means the pulse would miss the blackboard by more than 4 feet.

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You should not be confused as to what I said.I said postulate #1 requires the pulse to hit the blackboard.I said according to what you have been trying to convince me of the pulse will miss the blackboard by 4 feet.If the pulse travels in a straight line at a 90 angle relative to the motion of the car the pulse will hit the blackboard 1.525055044801507 feet from the leading edge of the blackboard.The car travels 1.525055044801507 feet in the 3 nanoseconds it takes before the signal from the switch cause's the laser pen to emitt a pulse.It will take 25.41758408002512 nanosecond for the pulse to reach the blackboard from the time the pulse is emitted from the laser pen.During that time the car will travel 12.5 feet. You misquoting me again.I said according to what you have been trying to convince me of that the pulse will miss the blackboard by 4 feet. You have to read my posts is you want to make an intelligent reply to them.The laser pen is mounted in the side of the car.There is a switch mounted on the track that causes the laser pen to fire a pulse toward the blackboard. But the laser pen is mounted at a 90 angle to the motion of the car and does hit the blackboard 1.525055044801507 feet from the leading edge of the blackboard. The angle of what?If you are talking about the direction of the travel of the pulse relative to the track then, why not?The car is on the track so the track is directly under the car at the moment the pulse is emitted.Therefore the pulse has to travel at a 90 angle relative to the direction the track is laid.So how would it not travel at a 90 angle in the track frame?God Bless,

ICANT Not so, doubting one.It is not necessary to specify anything more than you've been told. When Einstein or I says that the speed of light in a vacuum is the same in any inertial reference frame, that means that all one needs to do find the distance covered and the time elapsed for the travel of light as measured in any one reference frame. Dividing the two gives the speed of light. If we do the same thing in a different coordinate system, we may get a different distance and a different elapsed time, but the ratio between the quantities (d/t) will still be "c".For example, a photon might travel 1 meter in 3.3356 nanoseconds as measured in one frame, and 1.1547 meters in 3.4617 nanoseconds as measured in the same frame, but in each frame the ratio of d/t gives "c".Viewed another way.If we know of any object at rest in a given inertial frame, we can say that light is moving at speed "c" relative to that object. We normally pick our reference frames so that we know of at least one object whose velocity is zero in that frame.In either case, you have all the info needed to apply ALL of postulate #2.

Hi NoNukes, When ICANT talks about a photon being in its own frame ICANT is talking about the photon having a position as shown in the following diagram.

e = position pulse emitted from the laser pen
c = car's position when pulse hits detector
D = detector on the track

e   c
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D      

Are you saying that does not constitute an inertial reference frame? Not yet.

Hi ICANT, So Einstein is stupid? Sure thing dude.I don't care whether you call me stupid. I accept the reputation for honesty and ability that my posts here establish for me. Besides, I'm rubber, you are glue Well then, you are wrong. I believe that the photon will hit the blackboard.If you also believe that the photon will hit the blackboard, then your answer is totally inconsistent with your pole/sensor answer. Or perhaps we are not discussing the same set up. As will the blackboard. I said that the blackboard was fixed to an interior side wall of the car. Did you change that setup to something different? If so, then that's not the set up I introduced. The angles under discussion are the angles between the photon's trajectory and the direction of motion of the car as measured in each of two reference frames? What other angles have we been talking about?If we are talking about two different scenarios, I accept the responsibility for not noticing that you had changed things. But I'd like to return to my original scenario. The blackboard is to be mounted inside the car. And I'm not trying to get you to accept any particular answer. The dimensions of the mirror are irrelevant.The rider on the car can use the rigid rod to determine a point on the blackboard directly across from light pen so that the rod is 1) right angles to the line of travel of the car and 2) the rod touches the blackboard dead center. If the rider points the light beam, along the rod, the rod identifies the ninety degree trajectory path. I predict that the leading photon will strike the board at the point indicated by the rod touch, no matter the speed of the car along the tracks as long as the speed is constant. Based on your previous answers, it would surprise me if you would agree with my prediction. But my surprise is irrelevant. No matter what you predict, there is a problem for you\[/i\].If the photon is off by any amount left or right of the rod touch point, as your previous posts would imply, then the angle of travel for the leading photon cannot be at right angles to the line of travel in the car reference frame, because the photon did not strike the point indicated by the rod. In other words, the rod is touching the blackboard at the point required by a right angle in the car frame, yet the photon missed the touch point left or right by some amount. You tell me the amount, and I'll calculate the angle.But suppose you go with the prediction that the photon does hit the 90 spot on the board as measured in the car frame.As you noted, the car is moving down the tracks in the track frame. So if the photon does strike the blackboard directly above the rod touch point, despite the fact that the blackboard has moved a dozen feet or so down the track since the photon was emitted, then the trajectory of the photon in the track frame of reference clearly cannot be 90 degrees. What angle would it take to hit a point a dozen feet down the track from the point at which the photon was emitted, ICANT?So, I don't really care what you predict. I'm not trying to convince you of either answer at this point. As I said before, either answer confirms that the photon trajectory path cannot be at right angles to the motion of the car as measured in both the car and track inertial frames. A right angle trajectory may result in one frame or the other, or neither, but not in both.And please drop the ridiculous observational frame nonsense. That is of no scientific interest.

ICANT,Apparently inane ideas die hard. In what sense is what you've shown the photon's own reference frame? I cannot tell if the photon is moving in your diagram, but if the photon is not moving in the so called "reference frame", then how can postulate #2 be satisfied for the frame. In other words, how can the photon be at rest in a frame, yet moving at speed "c" as measured in that frame. Hint. That last question is rhetorical.On the other hand, if the photon is moving at speed c using the coordinate system of that frame, then there is absolutely no reason to call said frame a photon frame. It is instead the track frame, the sensor frame, or some other frame identified by an object that actually does measure zero velocity in the frame.For that matter, who cares what you name the frame. The physics is what counts, not the name. Photons are never at rest as measured in any inertial frame. They always travel at speed c relative to every inertial observer.Is that clear yet? I'd really like to put this stuff out of our misery.

Hi NoNukes, You did not make that statement.You may have thought you did but in Message 1046 the following is what you said:

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Consider the following.

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One of the ramifications of postulate #1 is that it is impossible to design an experiment to measure absolute motion. Only relative motion can be detected. But if the laser pen works as you suggest, then every light source is an absolute motion detector. Based on your description, if you were in an enclosed car moving at 0.5c relative to the salt flats, and you aimed your laser pen at a point on the blackboard, photons would strike a point somewhere behind your aiming point on the blackboard simply because the car is moving. Your description actually violates the postulate that you insist is correct.

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You made no distinction of where the blackboard was located.In the car experiment with detector mounted on the pole attached to the roof and the laser pen mounted through the roof the pulse is released into the vacuum the car is traveling through.In the car experiment with the laser pen pointed at the ground on a frame on the rear of the car with detectors and sensors on the track the pulse is released into the vaccum the car is traveling through.If you want to put the blackboard in the car mounted to the side as you stated which I quoted above then the pulse is not released into the vacuum the car is traveling in. Therefore the pulse is not traveling in a vacuum.But putting that aside in Message 1056 I said:

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If the blackboard is in the car the laser pen would operate the same as it does in a classroom.

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I then laid out an experiment that would compare to the two car experiments we had been discussing.

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Lets set the stage for this experiment if the blackboard is on the Salt Lake Flats.

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The 4 x 8 blackboard is mounted at a 90 angle relative to the Salt Lake Flats parallel to the tracks, 25 feet from the tracks.

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There is a trip switch on the tracks the car is traveling on, mounted so it forms a 90 angle at the front end of the blackboard.

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The laser pen is mounted in the side of the car at a 90 angle to the travel of the car and a 90 angle relative to the Salt Lake Flats.

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When the car hits the switch a signal is sent which takes 3 nanoseconds to cause a short pulse to be emitted from the laser pen.

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I believe that according to postulate #1 which requires the pulse to travel in a straight line from the time emitted, the pulse will hit the blackboard.

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According to what you have been trying to convince me of the pulse will miss the blackboard as the pulse has to travel at an angle like it does in the stupid light clock with moving mirrors presented.

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Which would meant the pulse would reach the distance the blackboard is from the tracks after the laser pen has moved 12.5 feet from the point the pulse was emitted. That means the pulse would miss the blackboard by more than 4 feet.

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But yes I would not observe whether the pulse hit the blackboard or missed it as I would be 26+ feet past the point the pulse hits the blackboard when the image of the pulse reaches me. I would be traveling at 0.5 c, which would make a small pulse of light very hard to see.

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But if it were possible to see the pulse hit the blackboard I would observe the pulse to hit the blackboard after I had traveled 26+ feet from the point the pulse was emitted.

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So yes it would be behind me when it hit the blackboard.

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So we agree that if the blackboard is in the car the laser pen will act just like it does in the classroom.Now would you take time to read the setup for the experiment if the blackboard is on the Salt Lake Flats, and tell me whether the pulse will hit the blackboard or miss it.This compares with the pole detector and track detector and should give the exact same results. Will you also accept the responsibility that you did not state where the blackboard was located in your original scenario?What mirror are you talking about?There was no mirror mentioned in any discussion about the blackboard. Are you saying there is no such thing as an observational frame of reference as included in the definition of reference frame?God Bless,

Hi NoNukes, The same way the car can be at rest in a frame when it is traveling at 0.5 c.You just declare that the photon is at rest and everything else is moving relative to the photon. Call it whatever you want to call it.My point is that the photon is independent of the car and the motion of the car at the moment it is created and emitted from the laser pen. Where do you find "relative to every inertial observer" in this:

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2. Second postulate (invariance of c)
As measured in any inertial frame of reference, light is always propagated in empty space with a definite velocity c that is independent of the state of motion of the emitting body.

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SourceNope.I can't find in postulate #2 what you assert.I need a difference reference.You did explain how I could determine the speed of light in Message 1074 and told me I did not need anything to measure it relative too.But If I get what you are trying to convince me of is I think you are interpertating postulate #2 to say:'As measured in any inertial frame of reference, light is always propagated in empty space with a definite velocity c that is independent of the state of motion of the observing body.'The problem is it does not say that.God Bless,

Hi ICANT, Wrong, ICANT. I said that the car was enclosed. I then described using a rod to touch the blackboard from within the car before firing the lase. How can you touch the blackboard with a rod from inside an enclosed car unless the blackboard is also inside the car.I was about to apologize for being unclear until I re-read my proposal. I then noted this in your original response. So I definitely put the blackboard in the car, and you changed it. My error was failing to notice your change. I admit that I did not read your post carefully. But the answer to the question, where does the photon strike is unimportant. What is important is the path the photon takes, and the trajectory as measured in the car frame and the track frame.The problem with putting the blackboard on the salt flats is that we produce a thought experiment that operates in exactly the same way as the track sensor and detector thought experiment.To answer your question, yes, I believe that if the blackboard is in mounted on the ground, the photon will miss the blackboard. But I have no desire to convince you of that. None.Now that I've addressed your thought experiment, let's return to the experiment as I designed it. You say that the laser pen will operate "exactly as it does in the classroom". Well so do I. So let's analyze that result.In the car frame with the blackboard mounted inside the car, I say that the laser pen will strike the blackboard directly above the touch rod. That answer is the same whether or not the car is enclosed. In the car frame, the trajectory of the photon from emission to striking the blackboard is clearly at right angles to the direction of motion.However in the track frame, the blackboard moves up the tracks after the photon has been emitted as you yourself noted. Yet the photon must still hit the blackboard right above the touch rod. Quite obviously the photon trajectory cannot be at right angles to the direction of motion of the car in the track frame, or it could not hit the board in that spot. So, ICANT what is the angle between the motion of the car along the tracks and the trajectory of the photon?One simply question. Answer it correctly, and we can advance this discussion. I don't want to continue to discuss this without making some progress.I believe that you will refuse to address this scenario. You always become evasive whenever I request you to look at events as measured a two reference frames. Here is your chance to prove me wrong. Or tell me why the light pen in a moving car works "the same as it does in a classroom".