Existence

If you wanted to hit an airplane painted on the wall of your open vehicle moving at constant speed, how would you aim your gun? Would you change your answer if the car were completely enclosed.If you want to say that photons are different from bullets, then why did you even bring up the anti-aircraft gun?ICANT, I completely understand what you are saying. It is simplicity itself. But what you are saying is just wrong. In addition, your vacuum antics dishonor you. You are better than that. The coordinate system in which the car is at rest is the same regardless of whether the car is open or enclosed. Further the reference frame extends infinitely beyond the confines of the car, while the extent of the car interior does not. And given that we are discussing light traveling in a vacuum, we don't even need to worry about air rushing past. If this is the best you can do, I'm completely happy with ending the discussion with you looking not unlike a moron.Edited by NoNukes, : Replace 'are' with 'or'

After reading some confused statements and questions about inertial reference frames, I thought it might be productive to say some correct things about them rather than to wait to refute incorrect statements about them.First, the definitionFrom Wikipedia,
Inertial frame of reference - Wikipedia

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Within the realm of Newtonian mechanics, an inertial frame of reference, or inertial reference frame, is one in which Newton's first law of motion is valid.

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http://www.physics.smu.edu/kehoe/1301S06/Ch4Relativity.pdf

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Given the concept of inertia, we find it useful to talk about 'inertial reference frames' which are three-dimensional coordinate systems which travel at constant velocity. In such a frame, an object is observed to have no acceleration when no forces are acting on it.

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Inertial Frame of Reference | Zona Land Education

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There are several ways to describe an inertial frame. Here are a few descriptions:

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An inertial frame of reference is a frame of reference with constant velocity.

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An inertial frame of reference is a non-accelerating frame of reference.

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An inertial frame of reference is a frame of reference in which the law of inertia holds.

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An inertial frame of reference is a frame of reference in which Newton's laws of motion hold.

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In an inertial frame of reference no fictitious forces arise.

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Given the above definitions, it should be quite easy to recognize that a coordinate system moving at constant speed and direction, whether enclosed or unenclosed is an inertial reference frame.Now let's see if some of the things said about inertial reference frames in this thread are correct. The car being discussed above is moving in a straight line at constant speed 0.5c along tracks. Thus the car, enclosed or open is an inertial reference frame.But what about the unbalanced forces acting on objects inside the car? Well in reality, there weren't any such forces. But if there were such forces, as long as the objects in the car obeyed the Newtons laws of motion, then the reference frame would still be an inertial reference frame. Since ICANT does not claiming that the objects do not obey Newton's laws, his rationale is simply wrong. First, ICANT provides no mechanism for a force to appear and disappear depending on whether the sides are taken down. Instead he insists that his prediction of where the photon will go is correct, and then insists that a force must exist or fail to exist so that his prediction can be correct. That is simply nonsense.But more importantly, the presence or absence of an unbalanced force on a photon does not qualify or disqualify a frame from being an inertial reference frame. The question to be answered is whether the photon responds to the presence or absence of an unbalanced force as required by Newton's laws of motion.

I've been trying to figure out a consistent framework for ICANTs thinking. I don't think your proposed idea is it. ICANT did express the belief that a force was required to maintain constant velocity at one time, but didn't we beat that fallacy out of him during the space cycle discussion? ICANT did finally admit that the space cycle did not need to operate a propulsion system to continue moving through space at 0.5c.Further, ICANT does not seem to have any problem understanding that an open system moving at 0.5c relative to the tracks is an inertial reference frame.ICANT does not have or pretend to have a coherent scientific understanding. He simply adopts whatever allows him to deny or oppose science he does not like. He does not want to admit that a photon can travel at a 26.5 degree angle in an inertial reference frame, because that is tantamount to admitting to time dilation. As a result, it is far easier to find inconsistencies in ICANTs post that it is to find any consistent ideas, correct or otherwise.Given that ICANT has admitted that photons cannot be accelerated beyond speed "c" in such situations, he's actually already admitted to far too much to avoid time dilation. For example in discussing the tube ICANT added to the light clock, ICANT and I had the following exchange in Message 855. ICANT here correctly describes acceleration as including changes in direction without a change in speed.So regardless of ICANT ever agrees that an enclosed car is an inertial frame, he's already taken the position that 1) The photon must travel at some angle other 90 to hit the blackboard and 2) that the photon travels at speed "c" while doing so. Those admissions are sufficient to establish time dilation. However, ICANTs admissions are not 100 per cent correct, so I'm uncomfortable with using this line of argument other than to illustrate the problems with arguing with ICANT.ICANT seems to have no problem with stating inconsistent things in order to avoid what appears to be immediately inevitable. For example, ICANT feels free to draw maps from an overhead perspective that include the paths of photons in the track frame of reference, but when Taq or I do the same thing for a different frame of reference, ICANT complains about observers in vacuums and events moving too fast to record without a high speed camera. See Message 1125.Here are a couple more of ICANT's greatest hitsExample #1.
Me in Message 846ICANT's response from Message 847Note ICANT quoting my question without any context so that he can pretend not to know what was asked.Example #2. Hello? Why isn't this discussion over? ICANT admits and denies the truth all in the space of a few sentences. It was actually necessary to introduce yet another thought admittedly identical in principle thought experiment (train/blackboard) without any opaque tubes just to make the tiniest of advances in the discussion.It is difficult to argue with someone who feels free to use the tactics illustrated above without expressing at least some frustration. I regret that I've allowed myself to slip a number of times during this thread. I'll try to do better.

Hi ICANT,There are answers to questions from more than one of your posts here. Easier, perhaps, but that's not how I roll. I want to understand the 'science' underlying your answers. I've already concluded that your explanations do not agree with reality as I understand it. But beyond that your explanations are not consistent. Yet this unbalanced force is without explanation. It appears and disappears as needed for the sole purpose of making your prediction of where the photon hits come true. This force inexplicably knows whether the car is open or enclosed and selectively applies or does not apply itself to the photon. You are badly misreading the correct statement above. Yes it is true that in an inertial reference frame, a particle not subject to forces moves in a straight line at constant speed (or remains at rest). But what happens in an inertial reference frame when a particle is subject to an unbalanced force? Well the above statement is silent about that.The answer is that the particle will obey Newton's laws. In particular, F=ma would apply. Wrong again, ICANT. You have again misunderstood the exact same physics. The sentence describes how a particle acts in an inertial reference frame WHEN no forces are acting on the particle. In such a case, the particle does not accelerate. The sentence says nothing about what happens when a force IS acting on the particle. But we do have other definitions/descriptions that do apply in that situation, don't we ICANT?Notice that the first part of the quote tells us that reference frames traveling at constant velocity (for example rail cars with their sides taken down) are inertial reference frames. Well isn't that awful inconvenient for you?The definitions/descriptions I provided in that prior post all apply to every inertial reference frame. A coordinate system moving at a constant velocity (like an open car) is an inertial reference frame. If a reference frame (the car) is not accelerating, then a particle not subject to a net force will either move at constant velocity or remain at rest. If a force is acting on the particle in an inertial reference frame, then a different one of Newton's law's applies, namely F=ma.Frankly, your attempts to lecture people who understand physics on inertial reference frames, when you don't understand how to use reference frames of any kind is pretty amusing. The sac involved in attempting to apply postulate 2 after admitting that you don't understand a substantial part of it ("As measured in any inertial reference frame") is even admirable in a way. But it would be the sheerest of coincidences if anything you said about an inertial coordinate system were correct. So far you are batting well below the Mendoza line. First, that statement has nothing to do with postulate #2, as you yourself have previously admitted. You indicated that the statement was based on the law of inertial and postulate #1. That's pretty much right. Let me know if you need a pointer to your previous message.Postulate #2 says that the speed of light in a vacuum having the value "c" as measured in any inertial reference frame. Postulate #2 would allow light to change direction by bouncing off a mirror without having a force applied.Second, I do not describe the photon changing direction after being emitted. Nobody here has done that.What I do say is that as measured in different frames, the angle between the tracks and the direction along which the photon travels (I will call this angle the photon's trajectory angle) will be different in different reference frames.As measured in the car frame of reference, the photon trajectory angle is 90. Since the blackboard and laser pen are stationary in the car reference frame, that 90 trajectory angle means that the photon hits the blackboard.On the other hand, the trajectory angle for the photon is different as measured in the track frame of reference. The reason for the difference is that the separation between the origin of the track reference frame and the origin of the car reference frame increases with time at a rate of 0.5c. If we ignore special relativity, we will calculate the trajectory angle as measured in the track frame of reference to be 26.5. If we apply postulate #2 of special relativity, we will calculate a trajectory angle of 30. These trajectory angles are consistent with the fact that the blackboard does indeed move away from the point at which the photon was emitted when measured in the track frame of reference.When we analyze the results one reference frame at a time, the results comply with postulate #1 for each frame. As measured in either one of the two frames under discussion, the photon travels at a constant speed, in a constant direction. That's all that's required to satisfy newton's laws of inertial, so no force is required to explain the results in either frame. There is no change in direction of travel. There are only different measurements in different reference frames. The photon trajectory angle, the light pen aiming angle, the velocity of the blackboard, and the velocity of the tracks are all parameters that have different values as measured in the two reference frames under discussion. If you can understand at least that, then you can see where your questions are not working. No ICANT. It would not be true in every inertial reference frame which is why everyone except you specifies the reference frame for the measurement whenever more than one reference frame is involved. Further, I have demonstrated that this statement is not correct using diagrams and mathematics. I also provided a link to a video in which a physicist discussed coordinate transforms between inertial reference frames to confirm my position. Yet you continue to insist on a wrong answer. It's well past time that you supported your belief with a reference.Trajectory angles for photons and other objects traveling at finite velocities are not consistent between different inertial reference frames when the origins of the coordinate systems are in relative motion. Neither postulate #1 not postulate #2 require any such thing either for massless photons or for objects with mass.Your position is that one of Einstein's postulates used to generate special relativity is actually inconsistent with SR. I'm open to having you demonstrate that, but you aren't going to make a successful argument without knowing even what an inertial reference frame is. And you don't.I think it is about summary time. Edited by NoNukes, : Grammar, and spell Mendoza with a Z.

The link below is to an animation of motion along a river. The simulation can show the motion of objects in different reference frames.Retired Service | The University of VermontYou can show the motion of the boats and a person in different reference frames. When your mouse is over an object (ground, river or boats) then the display shows things in the inertial reference frame in which that object is at rest.The most interesting display is the one with the person moving across the river. The directions to accomplish this are a little confusing, but you can give the person a vertical velocity to make her move across the river. Then you can select different reference frames to see that the persons angle across the river does change with the reference frame.Note that only regular old Newtonian mechanics is at work. Special relativity, not required.Maybe the simulation will help aid someone in understanding the math/geometry involved in making measurements in different reference frames. One can only hope...

It is summary time, at least for my participation, because I don't believe you are capable of understanding elementary physics and you have demonstrated to my satisfaction that you will never be capable. You aren't even trying.The fact that measured quantities (such as paths of particles, kinetic energies, momenta) and are different for different inertial observers was demonstrated 300 years ago. It is not a subject for debate. Yet that's exactly what we've been doing for hundreds of messages.I'm satisfied that you are the only one here that doesn't get it. I cannot tell whether your own failure to understand is out of ignorance or stubborness. It no longer matters.As for your OP, you don't have to end the thread, but your thread was essentially dead before I made my first post.I'll also note that this isn't your first thread on this subject and that you've gotten here essentially the same reaction that you got before.As for this photon thought experiment... That's not quite all of it. You believe that when the car is enclosed, a mysterious force appears so that the photon does what Einstein actually predicts, but that when the car is open, that force disappears so that Einstein is wrong.Your explanation for the force, is that enclosed frames are non-inertial frames of reference despite the fact that 1) calling a frame non-inertial does not make forces appear from nowhere and 2) enclosed frames moving at constant velocity, are by every definition either of us has produced, inertial frames of reference.I see your silly drawings. But remember that you predict a different result when the car is open than when it is enclosed. Your explanation for the difference is pure malarkey born out of desperation. ICANT, the above statement is just plain wrong. If the car is moving at 0.5c relative to the track, then the track is moving at 0.5c relative to the car. There is no other option. Do you understand what the word "relative" means?There is simply no point in discussing special relativity with someone who does not know, and cannot understand, how non-relativistic physics works. I like discussing physics, but I don't need conversation badly enough to discuss it on an idiot level.Edited by NoNukes, : Clean up

There is nothing wrong with using the word stationary. In fact, Einstein in his 1905 paper referred to inertial reference frames as stationary frames.Edited by NoNukes, : Remove stuff that Son already covered.

I agree that the point at which the photon is emitted does not move. The point representing the emission of the photon is an event in space time having fixed space and time coordinates. The emission event has fixed coordinates in both the car and the track frame of reference.But your question about the force is silly. Force does not make points in space time move. The above statement may or may not be true. If you want to be correct about whether something is at rest or moves, you need to communicate to which frame of reference is your observation applies.In a frame of reference in which the car is at rest, the laser pen, detector do not move relative to the point at which the laser was emitted.

There is no possible way to interpret this statement so that it can be accurate. The blackboard, which is fixed to the inside of the car, is at least four feet from the laser pen. So unless the board is moving towards the laser pen, and it does not do so in any frame of reference, then the photon must travel at least four feet to hit the blackboard.Possible correct answers (ignoring special relativity):The photon moves 4 feet towards the blackboard (and relative to the car, or in the car frame of reference)The photon moves 4 feet towards the blackboard while moving two feet in the direction along the tracks as measured in the track frame of reference.Do you understand yet why I say that discussing physics with you is pointless?Or if you insist on trying to use a photon frame of reference to do physics, you might say that no time passes within the photon frame and that the distance to the blackboard is length contracted to zero. But that would be fairly useless in analyzing the situation wouldn't it.Given all of the possible correct ways to describe the situation, you, ICANT manage to blow it. Just what manner of man are you?

All inertial reference frames are stationary frames. That should not be the least bit confusing. Choosing a reference frame determines which objects under discussion are stationary.Have you ever used the word stationary? What did you mean when you used the word, osmium-like one?

You have an unjustifiably high opinion of your posts here. You don't understand even the simplest points under discussion, yet you are hosting a classroom in physics? Your entire post is is replete with evidence that you don't even know what reference frame is. You cannot apply postulate #2 correctly, because doing so requires that you understand inertial reference frames.I disagree with you because you display little more than the physics knowledge we were all born with. I've taken the trouble to learn considerably more than that. No it does not. Every event in space-time exists in every reference frame, so merely identifying an event does not identify a
reference frame.Of course none of that has the least chance of get through your iridium skull? This is at least the dozenth time I've attempted to explain reference frames to you. We can discuss the coordinates of points in space that are located inside the car using any reference frame we choose. We can discuss the coordinates of points located outside of the car using a reference frame whose origin is inside the car. No it does not mean that, ICANT. The actual situation should be quite simple to visualize even for you.In the car frame of reference, the emission point is fixed in time and space, the car and blackboard are at rest, and the photon travels four feet between the emission point and the blackboard. Is that understandable? You don't have to agree, just accept that such is my position.In the track frame of reference, the emission point again is fixed in time and space, while the car and blackboard move along the tracks at 0.5c. Ignoring time dilation, the photon moves 4 feet in a direction perpendicular to the tracks while concurrently moving 2 feet parallel to the tracks (a total distance of 4.47 feet) before striking the blackboard.Yes the description of distances and times is different as measured in the two different reference frames. But so what? What is important is that the laws of physics including the speed of light be the same in both reference frames.There is absolutely nothing inconsistent with my position. In a given reference frame (inertial or not), the space-time coordinates of the photon emission point do not change. The values of the coordinates may be different in different inertial reference frames.Nothing particularly special about what I've said. The same thing is true for the coordinates in space-time of any event.Edited by NoNukes, : Add more about space-time events.

Big deal. If you can convince me I'm wrong, I'll change my mind.

Unless your program is capable of displaying reference frames that are in motion relative to each other, and I do not know why an Architect program would need such a capability, you are not using a tool capable of providing an accurate picture.Besides, none of us are describing light paths that are not straight lines. When you talk about straight lines, do you mean only lines that are at right angles to the tracks?And what sense does this make "I was beginning to believe you was right". I've never said anything to the contrary.

Yes, and we can identify any inertial reference frame as the stationary frame. Normally we pick a single reference frame based solely on convenience and consider objects at rest in that frame to be stationary. I don't understand why that creates some problem for you.There is no preferred rest frame. You can identify any inertial reference frame as the rest frame, because the laws of physics including the speed of light in a vacuum are the same in any inertial frame.You seem to be looking for a way to be right about the word "stationary" having no meaning. I don't think that is a worthwhile endeavor. Nonsense. I do understand your confusion, but you are wrong. I'll explain.Let's place the laser pen at the spatial origin of the car inertial reference frame, and let the time that the photon is emitted from the laser pen be t = 0 nanoseconds. The coordinates of the photon at time of emission are then 0, 0, 0, t=0 in the car frame of reference.In the car reference frame, emitting end of the laser pen never moves spatially. It remains exactly where it was (spatial coordinates 0,0,0 in the car frame of reference) when the photon was emitted. In fact, in our thought experiment, the only object within the car that moves in the car frame of reference is the photon.So (using the car inertial reference frame) every point on the car is always the same spacial distance from the emission point of the photon. Thus the photon emission point does not move in the car frame of reference. And stating the obvious the car does not move in the car frame of reference.In the track frame of reference, the laser emission point will always be over the same slat on the rails now and forever. So in that sense, the laser emission point does not move. However in this frame of reference the car does indeed move at 0.5c along the tracks. So in the track frame of reference the car does indeed move away from the emission point at 0.5c. As a matter of fact you are wrong. There is no frame of absolute rest, and we always assign velocities to objects (other than photons) based on an adopted stationary reference frame. It is our choice of stationary or rest frame that defines which objects are at rest, which objects are moving, and the rate of velocity of the moving objects.For example, we say that a parked car is moving at 0 mph despite the fact that the rotation of the earth can cause the ground to move at 1000 mph near the equator. We intuitively choose our reference frame to be the street when we are talking about cars.However it might be useful in some problems to acknowledge that the car is moving at 1000 mph due to the rotation of the earth. For example if I was launching a missile at the car from the north pole, I'd need to take into account that the 1000mph relative motion between me and the equator.Back to the emission point.The space-time coordinates of the point of emission have a fixed value in every reference frame (inertial or not), but the fixed value is different in every reference frame. But there is no point of absolute rest anywhere in the universe.Again most of this is basic stuff that has been understood since the time of Galileo. If you think it is fodder for debate, then you aren't up to discussion the physics of time.

You don't notice anything particularly irrelevant about your response?You have not described any capability for your program to show the path of moving objects from different inertial reference frames. So why should any of us be surprised when your tool does not verify what we are telling you about trajectory angles in inertial reference frames? Yes, and I agree that you've described things as measured in at least one reference frame.I don't care what prediction you make about which reference frame. If you say that the photon misses the detector, we can build on the assumption that your prediction is correct.In order to demonstrate the effect of special relativity, however, we need to demonstrate the ramifications of your prediction in two different inertial reference frames.It is at this point that you begin to flake out. You've use various tactics to avoid such an analysis. I'll list a few along with my impressions of them.1) ICANT denies that a driver in the car can see the chain of events.Me. But so what? We can still calculate the coordinates of the events in the observers reference frame, and the coordinates are what we use to do physics. What can be seen is irrelevant.2) ICANT denies that an enclosed frame moving at constant velocity is an inertial frame and then makes up some forces.Me. Nonsense. All frames in which Newton's laws hold true are inertial reference frames. Enclosed frames work the same as open frames.3) ICANT: L'il Architect program does not show different trajectory anglesBy your own admission L'il Architect is not capable of modeling the problem.4) ICANT I don't know what postulate #2 really means because I don't know what "As measured in any reference frame" means, but I'm sure that it proves Einstein is wrong.Me: Einstein's coordinate transform and velocity combination equations are derived from postulates #1 and #2 and thus must be consistent with the postulates. Accordingly, you cannot use the postulates to prove that length contraction and time dilation are not real. Let's discuss what postulate #2 really says.5) I don't care what the math says, what other physicist say. I'm right because...Me: Uh, I'm ready to summarize.Okay, back to your questions. As if we had not explained this dozens of times.As measured in any inertial reference frame. Let's not forget that supremely important part of postulate #2. Let's also note that the postulate only requires that the velocity of light be "c" as measured in any inertial reference frame and independent of the motion of the source. So the path of the light can change as long as the velocity is still "c" regardless of the motion of the source.Of course none of that explanation is anything new to you. I suspect that the I can now answer all of your questions using only references to my own prior messages.