Alpha - use of time-of-flight of light in velocity measurements of moving objectse

Exclusive Use of Time-of-Flight of Light in Determining the Velocity of Moving Objects

Introduction
The system used here determines VA measured against (X0,t0) the point from where a test pulse of light was emitted. If the value t1 could be trusted (see Figure 1) the distance difference d1 – d2 is the distance the frame moved during t2 – t0 and the velocity calculation would be a trivial exercise.. Putting the value, or accuracy of t1 aside, the velocity VA = (d1 - d2)/(t2 – t0 ). This demonstrates the system is theoretically viable.

However, using Figure 1, we may ignore the t1 data (all B frame originating using odd subscripted times) and focus on, (d1 + d2) − (d3 + d4) the distance the frame moved during the time the pulse was in motion, hence we get, ΔX/Δt = VA, = {(t2 – t0 ) – (t4 – t2)}/(t4 – t0).
VA = {2t2 – (t4 + t0) }/( t4 – t0). (1)

For t0 = 0,
Then, or (2t2 – t4)/t4 = 2t2/ t4 - 1
V = k ─ 1, (2)
where k = 2t2/ t4.

Remember, this velocity was determined from manipulation of the distance the pulse travels as indicated by the dn , n = 1 – 4, and as determined by the recorded times, t0, t2 and t4.

So, the velocity VA is not measured from an absolute velocity, Vg = 0, nor is the velocity determined by any stop-watch and meter stick measurements. The clocks on A may be calibrated with respect to some earth centered frame (i.e. GPS), for instance, was in the same inertial frame as dn, at least as to calculating velocity and distances.

To emphasize, the velocity VA is not measured with respect to any inertial frame of reference confined to a physical entity, an object. The velocity is determined by the distances (and associated difference in distances) the pulse traveled during t4 – t0. The only measurement here is recording the three tn which can be automated as may the execution of the computer algorithm described in (1).

Various Alternative Velocity Measurements
Case 2.
A computer-slaved probe (C frame) is launched from A in the direction the B frame is moving {anti-parallel to the X frame}. Using time and acceleration data the speed of C relative to A at (X0,t0) is monitored (A considered initially at rest the instant the C probe was launched). Now, the instant the measured relative velocity VCB = 0, the accelerated speed of C with respect to A is delivered to the A observers ─ not by measuring VAC, the relative velocity, but from calculations using the C’s acceleration and time data. This velocity is measured with respect to (X0,t0), where the A frame was initially at rest the instant C launched. The VC, in this sense, is that velocity the A frame would have to decelerate to in order to achieve VAB = VA – VB = 0. Substituting VC for VB in the VAB = VA – VB expression all velocity contributions are determined, or if these expression are too reminiscent of restrictions against measuring the VA and VB in the VAB = VA – VB expression, both frames can determine their respective velocities with respect to their unique (X0,t0).
Case 3.
This is similar to Case 2 except a probe C is launched in the forward direction for an arbitrary distance, turned around and accelerated in an anti-parallel mode effectively simulating the B frame above.
Case 4.
The Conservation of Linear Momentum. By dropping a golf ball from a moving train onto a surface on the ground, consistent with the club face of a three wood strung along side the train, unambiguous information regarding the identification of the frame that had been accelerated with respect to the other is given away early in the search. If the embankment is moving and the train stationary the ground will add a ‘chip shot’ in the direction of the moving embankment ─ to the rear end of the train ─ or, if the train is actually moving, the golf ball will simply bounce back up the same ‘down trajectory’, with respect to the train, with some necessary friction losses; the golf ball maintains its momentum associated with the moving train. Angles of bounce can be correlated and calibrated to any relative velocity VA and VB as determined in laboratory measurements.

Is V Obtained Here Antithetical with any Theory of Motion?
I started to look at the problem from a slightly different perspective after receiving a plethora of objections centered on the concept of ‘absolute velocity’ and ‘wrt what’. In the first place I had never measured, or considered measuring a velocity using the technique shown schematically in Figure 1. I have never encountered any other agency utilizing the technique to arrive at (1). My answer to all objections is simple. The velocity is determined from the known distance, ΔX, light travels during a measured time, Δt. In this sense the velocity follows a strict definition of velocity,

V = [Xn+1 ─ Xn]/[tn+1 – tn] (3)

If this explanation of velocity insufficient as seen from the perspective of some interests, then so be it.
Discussion
Whatever the writer’s original intent here regarding the significance of the measurements with respect to relativity theory is purely irrelevant to the laws of physics. I am not blind to the postulate of relativity theory that stated in the form1,
“It is impossible to measure or detect unaccelerated translatory motion of a system [inertial reference frame(s)] moving in free space.”
The only question of importance here is, whether the postulate anticipates a measurement of motion such as the measurements presented here. If so, then, res ipsa loiquitor. If not, then some adjustment or explanation is due from any agency understood, by anyone. Perhaps a peripheral question would be,

“Does a frame of reference need the characterization of it being a physical entity as a necessary characteristic satisfying the definition of a frame of reference?”

In looking at the expression for velocity repeated here,
V = [Xn+1 ─ Xn]/[tn+1 – tn]
We see only that a distance must be measured between the Xn with the corresponding times that the measured entity was located at those points. However, this would be a limitation to the definition, which must be seen in the context of the expression as a whole − velocity is a calculation of the difference in distance traveled during the time frame indicated. The distance traveled by the frame need not be the actual trajectory used in the measurement − the distance moved by the entity must merely equate to the distance used in the expression. In the determination here the distance moved was not measured directly by stop-watch and meter stick, rather, the time-of flight of a light pulse was manipulated to determine the distance the entity holding the transponders [the light emitter/absorber and clocks] moved.

The conclusion is that VA is not a statement relating to any theoretical motion construct that is vitally concerned with relative motion and the prohibition against determining absolute velocity as if there were a preferred frame of reference from which all velocity may be measured. Clearly, such a frame, would be most difficult to produce as Vg = 0, as taken in an absolute sense, means zero motion with respect to all entities in the universe. The earth is not a frame of reference of zero velocity, but such a reference is not necessary in order to determine the terms used in the V = [Xn+1 ─ Xn]/[tn+1 – tn] expression. If a question exists regarding two frames of inertial reference and determining the velocity of each as contrary to the impossibility postulate, the present system is likewise inapplicable as only one frame was necessary here [with the possible addition of the on board probes used as ‘extra inertial frames’ in the various cases discussed. Even the first case, which shows a B frame of reference as seen in Figure 1, was irrelevant in the calculations even though the B frame transponder was utilized in the data manipulation.].
The Integration of Absolute VA = 0 Is Not Expressly or Implicitly Utilized Here
This subject was discussed above and little can be added here except to say that the definition of velocity, by it very terms, does not implicitly or explicitly, require a showing of a reference to some physical frame of reference can be measured.
The concept of “absolute VA = 0” is not an issue in the present context of the measurement of velocity. As understood, ‘absolute zero’ refers to an entity, an inertial frame, in a particular velocity state. The concept is abstract only in the sense of the difficulty in actually reaching such a state, which must, if it is absolute, be zero with respect to all moving objects in the universe – think of adjusting the relative motion of just one inertial frame with respect to all the moving stars and stellar entities − some trick. The measurement of velocity with respect to (X0,t0) is the starting point of a measurement and (X4,t4) is the end point of the measurement, and the measurement of time results in a determination of distance light travels. Velocity, VA is not meant to be, and was not, measured with respect to an inertial frame, as a relative velocity. By definition, V = (X1 – X0)/(t1 – t0), the measurement is a difference in length of light travel divided by the time-of-travel, V = ΔX/Δt, anyway one looks at it.

The velocity determined has merit in its own ‘frame of physical models’ and does not encroach upon any conclusions of any existing theory of motion.
With all the claimed experimental support for SRT/GR, how could this use of light distances in determining velocity be significant in relativity theory? Restricting the discussion to the postulate that only relative motion can be detected between two inertial frames moving in free space, it might seem that a clash is apparent − we cannot hide the fact that the velocity of an inertial frame was determined by using the time-of-flight of a light pulse measured at critical points in the total motion of the pulse as described. If the determination of velocity is deemed in conflict with any existing theory of motion then those theories must be held up to the light of the velocity measured here in order that the conflict may be resolved.

It can not be stressed that the system employed, has not, to this writer’s knowledge, been employed in previous systems, theoretical or physical.
.
Bibliography
1. “The Handbook of Astronautical Engineering”, Chapter 11, ‘Relativistic Rocket Mechanics’, H. H. Koelle, Ed., 1st Edition, Introduction by W. von Braun, McGraw-Hill (1961).

 

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geistkiesel;

The observer/device makes spatial measurements from its own
ref. frame using its own clock, which is altered by the
motion. The o/d and all things within this frame are also
altered to the same degree by the motion, thus all processes
appear normal within this frame.
The spatial measurements for objects outside this frame are
consequently distorted, thus SR requires transformations to
make a moving frame conform to a 'rest' frame, eg. length
(coordinate) transformation and velocity addition.
All you can get is a relative simultaneity, a relative
clock synchronization, and a constant c for the two-way speed
of light.
Since light speed is independent of the source motion, it can
only be constant to space itself (an unkown).
A zero speed object would therefore have to be at 'rest'
with respect to space itself, not all other objects.
A fixed spatial point of emission is theoretically sound,
but of no value in practical measurement. If you referenced
a point in space, you could never use it again, because all
things are in motion (we live in a dynamic universe). It's
like marking a spot on the surface of the ocean and trying
to return to it.
Your idea depends on finding a fixed point in space,
and this is currently not possible.

 

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It's a repeat of his last thread that was disposed of.

 

Hello geistkiesel

Would it not be easier to add an additional cog to the common cog and mirror set up used to measure the speed of light. If both cogs are synchronized to turn at the same speed and the second cog has a phase adjustment then it would be easy to see if the speed of light is the same in both directions to and from the mirror. All that would be needed is a set up that would allow a return path around the second cog and a detector at the mirror to indicate when light passes through both cogs.

If there is a change in detection when switching between return paths then the "lab" frame is moving with respect to the emission point of the light. IE the actual distance the light travels between the cogs in the outbound direction is different than the distance traveled between the cogs on the return from the mirror.

It may even be possible to measure the speed of the "lab" frame given enough experimental data by varying the distances between cogs, mirror distance, and cog(s) rotational speed.

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This sounds familiar. I seem to remember a very similar experiment described in this very site only a few years ago.

Who was the writer? Maybe you know who wrote it back then here.

 

While sitting in my North Garden this late afternoon and contemplating life, the universe, and everything, I happened by pure random luck (as far as I know) to remember this quote of yours. It took me all of ten seconds (approximately; I was not carrying [a stopwatch]) to concoct and perform and evaluate a thought experiment which seems on first blush to undeniably contradict you.

I suggest that you explain, if possible for you to do so, in sufficient comprehensible detail, why you imagine that "this is currently not possible".

PS: "phyti", in my pronunciation comprehension, sounds like "Petey". Are you related to the famous "Pete", indigenous to this site? Not that there is anything wrong with that.

 

I find no fault with your reply re SRT. From acceleration/time data the frame clock may calibrate its clock to agree with any frame of reference.

One can determine clock distortion from acceleration/time data, w'o exchanging information with its home port embankment. For Va << c the distortion you refer to will vanish.

There are no zero speed objects. The only entity vaguely approximating V = 0 is the point (X0, t0). I would never attempt to use the point again. The'point, at least you agreed that a "point in space is theoretically sound", is the point where the initial emission occurred. From acceleration/time data the A frame could navigate back to (X0, t0) without reference to any "space-marks".

The sum total of the data are the three time measurements, t0, t2, and t4, which are all the data that is required to calculate Va as described.

Or, simply add a few emissions/absorption and calculate the Va for all the point along

Then I will never find that point in space
The fixed point in space, (x0, t0), is not an entity subject to a physical search at, least not on my space-ship. owever, may b e hollden point, h

 

Geistkiesel;

Nothing like sitting near the garden listening to the turnips
ripening!
Your earlier post on this subject was quite recent,
so you only get credit for short term memory.

We are all related if we research the past.
Your pronunciation is wrong but that's not relevant.

Motion is a derived concept using position, another 'relative'
concept. No experiment or manipulation can make a relative
concept into an absolute concept. Since all our concepts are
by definition relative, i.e. in terms of something else,
there are no truly absolute ones. Even if space was understood
as a 'fixed' medium/matrix of elements that governed the
propagation of light, the gravitational motion of mass,
generation of virtual particles, etc., the speed of light
would still be 'relative' to that structure.
My suggestion would be to remove the 'absolute' from such
concepts. Absolute implies the notion of independent of all
things, but what would that be? It certainly can't be a
mental construct/concept as noted. It might be labeled as
the Herman velocity, etc.

After finding the book "The Strange Story of The Quantum",
I realized it's not the quantum that's strange, it's our
concepts.

Excuse me for not posting a physics explanation, there is
usually someone else who will.

From your last post:

How do you travel back in time?

 

phyti seems to be responding to my post, but, addressing G. And, reading phyti's post, such confusion may not be atypical.

In physicsforums there is a member who is registered as "phyti" and who has also signed at the bottom of posts "Pete".

You have not addressed my specific question. Of course that is your initiative. This is not some kind of super-formal Inquisition. This is just a kind of a big friendly club where friends can get together and compare opinions about important physics stuff. While having fun. You have said it yourself.

My question to phyti was: Explain in satisfactory detail your claim that a specific point in space cannot be returned to. My hastily contrived gedanken shows me that such is possible. The best I can guess from your rather purely (and pitiful) poetic post, phyti, protesting my positional assertion, is that you are relying on semantics. Not on any kind of logical, mathematical, physics, or, factual argument. Just your word games.

G. has plainly said that such point re-acquisition is not germane to his position or to the validity of this thread. Therefore I will not press this issue because I do not want to injure his exposition in any way. But, just between you and me, phyti, why don't you start a new thread and try to convince me and all of us that a specific point in space cannot be re-acquisitioned? In terms of physics principles. Not phyti's pathetic poetry.