Determining Absolute Motion Between Inertial Frames of Reference

Determining absolute motion between inertial frames of reference.

In deep space two frames, A and B, are at rest with respect to each other and separated by some distance. B accelerates in the direction of A and after a period of time the two frames “pass” each other. With no other information and ignoring the fact that the observer on B knows of his frame’s acceleration, neither observer is able to determine which of the two frames is actually moving.

However, here each frame is equipped with golf balls that can be directed perpendicular to the relative motion of the two frames. Also, each frame has a flat strip of material along the 100 meter length of each frame identical to the mottled surface of the golf balls.

Here, we know that B is the frame that accelerated, while the A frame remained “at rest”. As the front ends of the two frames reach each other separated by, say 10 meters, each launch a series of golf balls at the mottled surface of the other frame of reference.

The balls from the A frame will strike the surface of the B frame and will be directed at some reflected angle in the same direction as the B frame motion. This is so as the A frame’s golf balls will have zero relative momentum in the direction of the relative A and B motion, until the A golf balls strike the B frame surface.

The B frame’s golf balls will strike the A frame’s mottled surface and will tend to bounce back along the same trajectory toward the spot where the B golf balls were launched. This occurs due to the momentum of the golf balls in the direction of the B frame motion. Frictional forces and imperfect surface to surface interfaces prevent perfect 180 degree reflection.

Observers on both frames will observe the same reflection trajectories and both must conclude that it is the B frame that is actually in actual motion and must be the frame that had accelerated. A check of accelerometers on both frames will verify the conclusions that the B frame is the only frame in actual motion.

Exact numbers are determined from results of a comprehensive testing program.
QED

Geistkiesel ​

 

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I am using the term as a frame of reference, a physical entity upon which devices are located. Except for short periods of acceleration by the B frame, both A and B are at rest. After the B frame acceleration B moves in the direction along the x axis toward the A frame.

Your assumption is correct.

We know it because we set up the problem. I said in the paragraph to which you refer, that “without more information” the A and B observers are ignorant of the B acceleration.

Remember, James R you said you would assume that the strips were in the x direction and that the golf balls were launched perpendicular to the direction of motion. Nice try.

The two frames are aligned parallel to the x-axis separated by ten metres. When B "reaches" A, both ends of the frames are located at x = 0, while A is located at +5y, B is located at -5y (dimensions in metres).

James R you are either confused or intentionally misquting my post, I assume the latter. First a you assume motion is along the x direction, the strips are along the x direction and the balls are launched in the y direction.

Now you are intentionally attempting to confuse the interested readers to this thread aren't you?
Why do you respond as you do? It appears to me that your sole intention here is to sabotage, to addle, to withdraw from a serious intended discussion that is soliciting serious scientific responses.

I said the following:

However, here each frame is equipped with golf balls that can be directed perpendicular to the relative motion of the two frames. Also, each frame has a flat strip of material along the 100 meter length of each frame identical to the mottled surface of the golf balls.

The strips run the length, the x direction of the frames. The golf balls are launched perpendicular to the direction of motion. You cannot be so in the dark as you claim James R.

Now, the balls launched from B have the inherited momentum of the accelerated B frame. The A frame’s launched golf balls have no inherited relative A/B momentum. Therefore, the B launched golf balls reflect back along the original B golf ball trajectory (with some friction corrections). The A launched golf balls, when striking the B frame strip, are “chipped” in the direction of the B frame motion.

Hence, both A and B frame observers determine that the B frame had accelerated, exclusively.

Geistkiesel ​

 

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Way back once upon a time and not too far away, I too believed that JamesR's frequent apparent confusion was the result of deliberate attempts to be intentionally dense and obfuscate the study of serious science. I have reached the conclusion that his display of confusion and ignorance is actually not a deliberate crafty ploy.

If I may paraphrase the thread starter's premise, to illustrate to all that it is not difficult to understand ( if I can understand it, what kind of a nutjob cannot? ); suppose that two observers are individually on two seperate platforms represented by their respective reference frames, and that these two platforms and therefore their reference frames have a relative constant velocity. The two platforms and their reference frames have parallel unit vectors. They are seperated laterally by a certain stated distance ( in the same manner that two cars on the highway are going parallel and side-by-side and seperated by some distance sideways because they are in seperate lanes . They are both traveling at constant but different velocities, and in fact one may be sitting still. So, there will be a moment when their front bumpers will be exactly in parallel alignment although they will be some distance apart sideways ).

Now comes the part of my post which must be partway but continued soon, because it is already past my effective time of day for even trying to do good work; Geist's scenario appears to me, on the basis of several runs through it, to hold good promise to be a functional way to discover absolute motion. My understanding of it at this moment is to add a small fillip to it as a result of his insight into the recognition of real momentum. When I have worked on it again I will post my fillip and my bottom line result whether I subsequently seemingly agree or disagree with his proposition.

At the best, his scenario will be a method to seriously prove absolute motion. At the worst, it will be another valuable insight into how Special Relativity is somehow immune to disproof.

 

If geistkiesel's experiment were carried out and had the predicted (by geistkiesel) result, then it would not only disprove Einstein's relativity, but also Galilean relativity.

It's not a difficult experiment to conduct, as high speeds are not required.
Propel a ball onto a rough surface. According to geistkiesel, the angle of incidence will precisely equal the angle of reflection in the surface's rest frame if and only if the surface is at absolute rest.

I guess that geistkiesel has never played snooker, or bounced a ball while riding on a train.

 

G's post is much more rich with nuance and possibility than I recognized 24 hours ago. It will take me more time to adequately and completely logically and mathematically analyze the scenario until I can post my personal conclusion. At this time it can certainly be said that G's proposition is an excellent vehicle to examine the legitimacy of Special Relativity on a purely mechanical basis.

 

And when is the exact date that Pete did these things ( in reality, not in only his imagination )?

 

I have gone through this scenario of where one platform and its associated frame is moving and the other is not a number of times. At first, I was cautious (and optimistic, as a relativity heretic) because I had never before explored Special Relativity on the basis of frictional transfer of momentum and kinetic energy. And at first I was optimistic that this might be another purely mechanical means of revealing the illegitimacy of Special Relativity.

I have been unable to find an asymetrity in the scenario. My results fail to show a difference in which platform and its frame is actually moving and which is not.

For some time now I have believed that the largest (but not the only ) flaw in the relativities is the proposition(s) based on the apparent activity of light. It is accepted that physical matter inherits momentum from its parent emitters, while it is accepted that photons do not (except that some fringe crackpots believe that light is "swept along in its frame.").

 

Accepted by whom? Internet crackpots?

 

A natural language like English is not well suited to describing experiments relating to relativity. It is tedious and often counter intuitive, but discusssion like this should discuss events and the intervals between them using (x y,z,t) to specify the where & when of each event. It is often convenient and correct to deal with preferred coordinates so that one or two of the space coordinates can be ignored.

In the absence of precise mathematical descriptions, our intuitive notions can mislead us. It seems like a waste of time to try to analyze these thought experiments. When I took a course in modern physics a long time ago, the mathematical logic convinced me that my intuition was lousy when applied to relativity and quantum theory.

Mathematical analysis and all sorts of experimental evidence support the counter intuitive notions of relativity. If somebody posts an argument against relativity using proper mathematics and the notion of the interval between events specified using (x,y,z,t) coordinates, I might find it interesting to at least try to understand the argument.

It seems like a waste of time to try to follow English language descriptions of such arguments. For all I know, the natural language argument might have merit, but is not convincing due to ambiguities introduced by imprecise semantics

 

Thi experiment is equivalent to dropping a ball from a moving train onto the statioaney embankment, or if you will, dropping a ball from a stationary train onto a moving embankment.
Your reference to dropping a ball lm the surgface rest frame is misplaced.

I am not dropping the ball onto the floor of one of the frames. The balls are launched towards other inertial frames. If the ball is launched from a stationary frame toward the surface of a moving frame the ball will assume the direction of the moving frame as ifd receiving a chip shot.

If the ball is launched from a moving frame onto the surface of a stationary frame the ball will reflect back along the tracjectory of travel with deviations induced by friction. This is so as the ball has a real momentum. When launched from a stationary frame onto a moving frame the ball will assume the momentum of the moving frame (the target).

Snooker is not my game - I prefer nine ball and I do not play for fun, money only.
Geistkiesel

 

Please, geistkiesel, learn what "reference frame" means. Your use of the terminology is embarrassing.
A reference frame is not a solid thing - it is a coordinate system of infinite extent in time and space.
Whether you understand it or not, you are predicting exactly what I said, ie that if a ball is propelled onto a rough surface, the angle of incidence will precisely equal the angle of reflection in the surface's rest frame if and only if the surface is at absolute rest.

If you were correct, then if a ball on a moving train were dropped vertically (according the the train observer), it would be kicked toward the front of the train.

Think about this:
If you drop a golf ball through a hole in the floor of your car, would you expect it to bounce straight back up through the hole?

Do the experiment, let us know what you find.

Then you'll know that a well struck ball that slides hard onto a rail will bounce back at a larger angle than it hit.

 

According to both. The A observer can see ther alm,opst perfect reflection using the B frame as reference, which is the same thiong the B observer sees.

According to both.

Geistkiesel: Remember, the B frame is the frame that accelerated in the AB inertial system. Therefore, only the B balls will have an imposed or inherited momentum determined by the velocity of the accelerated B frame.

Drop a ball from a moving train. The ball will tend to refclect back uo along the original downward trajectory with the attendent friction losses. The embankment observer will see this reflection using the train as a spatial reference marker. The observer on the train will be expecting the ball to be carried in the direction of the moving embankment and will be surprised to observed the difference in special relativity theopry and simple Newtonion physics.

Geistliesel ​

 

Start with Albert Einstein.

P.S. Pete is much, much more capable of asking questions in a quest to try to appear intelligent, than he is capable of really contributing to a serious science discussion.

P.P.S. Anyone who is fortunate enough to somehow find an extremely rare copy of the Serway physics textbook will be able to turn the pages to the Relativity section and see for themselves that an illustrated example of the activity of photons shows that, according to currently accepted and taught relativityt physics, photons do NOT inherit momentum from their emitter. In the same book one may also find examples too numerous too count of massive particles ( non-photons, Pete ) taking an inherited momentum.

 

I'm pretty sure that Einstein never implied that he accepted that photons do not inherit momentum from their emitters. Of course, without reading and re-reading all his works (difficult, considering that I don't read German), I can't be sure.

But please feel free to provide a citation and prove me wrong.

Modern Physics or College Physics?
Which edition do you have, out of interest?

 

Hi Cangas,
I'm guessing that you're confusing speed with momentum. Ie that because the speed of an emitted photon is independent of the motion of the source, that its momentum is as well.

Contrary to your opinion, however, it is well accepted that both the velocity and momentum of a photon is dependent on the velocity of the source at the instant of emission.
For example, see Serway's College Physics 6th edn (hardcover), p816, which illustrates a light pulse going straight up and down in one reference frame, and following a diagonal path in another. The speed of the pulse may be the same in both reference frames, but the velocity and momentum certainly isn't.

In a reference frame which (with respect to the emitter) is moving in the same direction as the light pulse, the velocity of the pulse will be the same in both frames. But the momentum will still be different. The frequency of the pulse in the two frames will be different (doppler shift), and so will its momentum (because the momentum of a photon depends on its frequency) .