1 pat dolan | Relativity can't be true because in the Twins Paradox... | Sunday 24 November 2019 |

2 tjrob137 | Re :Relativity can't be true because in the Twins Paradox... | Sunday 24 November 2019 |

3 tjrob137 | Re :Relativity can't be true because in the Twins Paradox... | Sunday 24 November 2019 |

4 tjrob137 | Re :Relativity can't be true because in the Twins Paradox... | Sunday 24 November 2019 |

5 tjrob137 | Re :Relativity can't be true because in the Twins Paradox... | Monday 25 November 2019 |

6 tjrob137 | Re :Relativity can't be true because in the Twins Paradox... | Tuesday 26 November 2019 |

7 tjrob137 | Re :Relativity can't be true because in the Twins Paradox... | Tuesday 26 November 2019 |

8 tjrob137 | Re :Relativity can't be true because in the Twins Paradox... | Tuesday 26 November 2019 |

9 pat dolan | Re :Relativity can't be true because in the Twins Paradox... | Tuesday 26 November 2019 |

10 Sylvia Else | Re :Relativity can't be true because in the Twins Paradox... | Tuesday 26 November 2019 |

11 Ned Latham | Re :Relativity can't be true because in the Twins Paradox... | Tuesday 26 November 2019 |

12 Sylvia Else | Re :Relativity can't be true because in the Twins Paradox... | Tuesday 26 November 2019 |

13 tjrob137 | Re :Relativity can't be true because in the Twins Paradox... | Wednesday 27 November 2019 |

14 Sylvia Else | Re :Relativity can't be true because in the Twins Paradox... | Thursday 28 November 2019 |

15 tjrob137 | Re :Relativity can't be true because in the Twins Paradox... | Thursday 28 November 2019 |

16 tjrob137 | Re :Relativity can't be true because in the Twins Paradox... | Friday 29 November 2019 |

17 Sylvia Else | Re :Relativity can't be true because in the Twins Paradox... | Friday 29 November 2019 |

18 Sylvia Else | Re :Relativity can't be true because in the Twins Paradox... | Friday 29 November 2019 |

19 Sylvia Else | Re :Relativity can't be true because in the Twins Paradox... | Saturday 30 November 2019 |

20 tjrob137 | Re :Relativity can't be true because in the Twins Paradox... | Sunday 1 December 2019 |

21 tjrob137 | Re :Relativity can't be true because in the Twins Paradox... | Sunday 1 December 2019 |

22 Sylvia Else | Re :Relativity can't be true because in the Twins Paradox... | Monday 2 December 2019 |

23 tjrob137 | Re :Relativity can't be true because in the Twins Paradox... | Monday 2 December 2019 |

24 tjrob137 | Re :Relativity can't be true because in the Twins Paradox... | Monday 2 December 2019 |

25 tjrob137 | Re :Relativity can't be true because in the Twins Paradox... | Wednesday 4 December 2019 |

26 Sylvia Else | Re :Relativity can't be true because in the Twins Paradox... | Sunday 8 December 2019 |

27 tjrob137 | Re :Relativity can't be true because in the Twins Paradox... | Tuesday 10 December 2019 |

28 tjrob137 | Re :Relativity can't be true because in the Twins Paradox... | Saturday 14 December 2019 |

29 tjrob137 | Re :Relativity can't be true because in the Twins Paradox... | Wednesday 18 December 2019 |

30 tjrob137 | Re :Relativity can't be true because in the Twins Paradox... | Thursday 19 December 2019 |

31 tjrob137 | Re :Relativity can't be true because in the Twins Paradox... | Thursday 19 December 2019 |

32 tjrob137 | Re :Relativity can't be true because in the Twins Paradox... | Thursday 19 December 2019 |

33 tjrob137 | Re :Relativity can't be true because in the Twins Paradox... | Friday 20 December 2019 |

34 tjrob137 | Re :Relativity can't be true because in the Twins Paradox... | Sunday 29 December 2019 |

35 tjrob137 | Re :Relativity can't be true because in the Twins Paradox... | Monday 30 December 2019 |

36 Michael Moroney | Re :Relativity can't be true because in the Twins Paradox... | Tuesday 31 December 2019 |

Relativity can't be true because in the Twins Paradox....

315 posts by 25 authors

https://groups.google.com/forum/?fromgroups=#!topic/sci.physics.relativity/Vzr4XFUJIO

Relativity can't be true because in the Twins Paradox both twins share the same relative velocity with respect to one another. So they should both age at the same rate. Why didn't people see this back in 1905? Sheesh!

On 11/23/19 5:12 PM, pat dolan wrote:

> | Relativity can't be true because in the Twins Paradox both twins share the same relative velocity with respect to one another. So they should both age at the same rate. |

This is just plain wrong. One twin moves inertially and the other does not.

> | Why didn't people see this back in 1905? |

Because they actually understood the theory. YOU DON'T.

Tom Roberts

On 11/23/19 9:05 PM, Julio Di Egidio wrote:

>> | T ? v( 1 - x'˛) dt < T, a simple exercise in math. 0 |

> |
You see, that's the part that is symmetrical... |

No, it is not "symmetrical" between the twins.

First, let me write this equation more properly and describe what its symbols mean:

T (elapsed proper time) = ? v( 1 - (dx/dt)˛) dt 0

Where (x,t) are coordinates of an inertial frame, the integral is taken over the worldline of the twin being analyzed, dx/dt is the velocity of the twin's worldline with respect to the inertial frame used (a function of t), and T is the earth frame's coordinate time elapsed between departure and reunion. Note this uses units with c=1 (e.g. time in years and distance in lightyears).

Apply this to the earthbound twin in the earth's inertial frame [#]:

(elapsed proper time of earthbound twin) = T

because (dx/dt)˛ = 0 for this twin.

Apply it to the traveling twin in the earth's inertial frame [#]:

(elapsed proper time of the traveling twin) < T

because (dx/dt)˛ > 0 for this twin. The actual value depends on the details of the scenario; ALL scenarios obey this inequality because (dx/dt)˛ must be greater than zero for the traveling twin to travel.

[#] In the twin paradox with the traveling twin's speed an appreciable fraction of c, the earth's non-inertial motions are completely negligible.

Tom Roberts

On 11/24/19 4:21 AM, Engr. Ravi wrote:

> |
Here is a symmetric way to do the twin paradox experiment proposed by Tom Roberts.
The proposed experiment has never been performed, since physicists are too scared that it could collapse STR. |

The "experiment" in that thread was proposed by YOU, not me. And it is not "symmetric" at all. You REALLY need to learn how to read.

Moreover, as I said in that thread:

"It is not feasible to perform this particular experiment, because for all currently available clocks the systematic errors will greatly exceed the predicted effect."

Don't blame me for YOUR failures to understand.

Tom Roberts

On 11/25/19 3:33 AM, Zeb Dee wrote:

> | [The twin paradox has] been observed! |

Yes. Many times. All are consistent with the predictions of SR/GR.

> | There are now clocks so accurate the effect can be measured by just walking across a room and back again. |

Hmmmm. You couldn't actually carry one, though.

Tom Roberts

On 11/24/19 6:13 PM, pat dolan wrote:

> | there is no lack of interest, enthusiasm, vim or vigor in this forum for defending relativity against all gainsayers, |

You confuse "defending" with "explaining".

Relativity needs no "defense", it is already solidly established, and nothing anybody has ever said in this newsgroup affects that.

> | [...]as the arguments and demonstrations against the theory become more sophisticated and terse. |

You mean they become more ridiculous. No "argument or demonstration against relativity" here has ever been "sophisticated"; "terse" is irrelevant.

> | Why do I not engage my team? |

I'm not sure what you are asking, but any volume of Heidegger is unlikely to help. Because all you have are misconceptions and fantasies. That's no different from all the other cranks, fools, and idiots around here.

Tom Roberts

On 11/24/19 9:46 AM, Julio Di Egidio wrote:

> | length contraction and time dilation are MUTUAL, |

Between inertial frames, yes. But in the twin paradox being discussed that does not hold, and there is no such "symmetry".

> | What the heck do you think relativity even means?! |

I think it means that all physical processes are locally Lorentz invariant. That implies that between inertial frames the coordinate transformations are Lorentz transformations. That implies the formula I gave earlier in this thread (for elapsed proper time) is correct. That implies that the traveling twin has a shorter elapsed proper time between departure and reunion than does the earthbound (inertial) twin.

> | In the earth's inertial frame in both cases?? |

Yes. Because that is the simplest calculation to make. Remember the formula I gave is valid ONLY for inertial coordinates.

> | You must be fucking kidding... |

Nope. YOU are just too ignorant to understand, and too stupid to STUDY. You demonstrate your ignorance in every post you make around here.

Tom Roberts

On 11/25/19 6:36 PM, pat dolan wrote:

> | [...] |

So you are just trolling. Goodbye.

Tom Roberts

You phony, Tom Roberts. I asked you about a perfectly plausible physical scenario. I made no claims, I contradicted no aspect of relativity.

If you do that (and accelerate them back similarly) then SR does indeed predict that they'll be the same age when they meet again. Sylvia.

In the frame of the starting point. Gotcha.

How can he speak for other people? Sylvia.

On 11/26/19 11:28 AM, Julio Di Egidio wrote:

> | On Tuesday, 26 November 2019 07:24:24 UTC+1, tjrob137 wrote: |

>> | On 11/24/19 9:46 AM, Julio Di Egidio wrote: |

>>> | length contraction and time dilation are MUTUAL, |

>> |
Between inertial frames, yes. But in the twin paradox being discussed that does not hold, and there is no such "symmetry". |

> |
That does not hold *globally*: and you still have explained nothing. |

Still, the mutual "length contraction" and "time dilation" between inertial frames does not hold for non-inertial frames. Such as the traveling twin.

>>> | What the heck do you think relativity even means?! |

>> |
I think it means that all physical processes are locally Lorentz invariant. That implies that between inertial frames the coordinate transformations are Lorentz transformations. |

> |
That is completely a misrepresentation. |

No, what I said is the essence of relativity. It may be phrased more generally than you have seen before, but local Lorentz invariance most definitely _IS_ the core of relativity.

> | Your very insistence on inertial frames is a misrepresentation. |

Please read what I write, and not your personal fantasies. I said NOTHING about "insisting on inertial frames". Yes, I only mentioned inertial frames, but that does NOT imply what you tried to infer. Moreover, from the fact that the coordinate transformation between inertial frames is the Lorentz transform, you can calculate what the transform is to any non-inertial coordinates of your choosing.

>> | That implies the formula I gave earlier in this thread (for elapsed proper time) is correct. |

> |
Correct but irrelevant: you have simply snipped the whole point. |

In a discussion of the twin paradox like this, what I said is directly relevant.

But you seem to be changing the topic without mentioning that you are doing so. I am not clairvoyant.

> | If two particles zip past each other, *at any single moment* all distortions are symmetrical (and indeed Lorentzian), aren't they? |

What "distortions" do you mean? Neither "length contraction" nor "time dilation" is a "distortion", they are simply the direct effects of geometrical perspective.

When a friend stands a foot away from you, they look tall. When they are 100 yards away they look much shorter. Your friend is not "distorted" in any way, this is just different geometrical perspectives.

But yes, at the instant of their closest passing they can be analyzed using each one's instantaneously co-moving locally inertial frame. Between those frames both "time dilation" and "length contraction" are mutual. But that simply does not apply to the entire trip in the twin paradox.

> | Of course, it's a point of locality I am raising, |

I don't know what you mean by that.

> | I must confess the more I get into SR the more I recover a notion of absolute time: as just equivalent to proper timeSince |

There is nothing "absolute" about proper time, in the usual sense of "absolute". After all, every worldline has a completely different notion of proper time. Applying the label "absolute" to the fact that any worldline's proper time is invariant is a HORRIBLE pun on that word -- the word "absolute" includes connotations and implications that do not hold. In particular, "absolute time" implies a universality that is simply not present.

> | Namely, all reference clocks tick the same way in any frame, not even just the inertial ones... (at least in SR, I still don't know about GR). |

This is also true in GR. Think about why this is so: in SR the first postulate (the PoR) implies that the laws of physics are the same in any inertial frame. In GR, SR is valid locally, at every point of every manifold. As a clock is quintessentially local, the laws of physics governing the ticking of a clock are the same, regardless of how it might be moving or where it might be located. So, every clock advances by one second in indicated time when its worldline increases its proper time by one second -- that is what these words mean. This is not limited to inertial worldliness.

Tom Roberts

When Einstein published his paper in 1905, he was little known. There is no way that what he proposed would have been accepted if it hadn't

On 11/28/19 2:27 AM, Sylvia Else wrote:

> | Anyone now thinking that Einstein's paper relating to special relativity contains multiple obvious errors is just deluding themselves. |

Hmmm. It does indeed include an error of fact: he assumed the earth is spherical, when in fact it is an oblate spheroid, and the distinction directly affects his comparison of clocks at equator and pole. This was not known in 1905; nor was the "gravitational time dilation" (which was recognized BY EINSTEIN in 1911).

In the 1905 paper, of course, this was merely a side comment about an effect of the theory; it does not undermine his theory at all.

Tom Roberts

On 11/28/19 1:43 PM, Michael Moroney wrote:

> | I think it is the OBSERVERS of the clocks who have to be stationary relative to each other, not the clocks themselves. |

It is impossible to synchronize two clocks not at rest in the same inertial frame, except in certain special circumstances. Observers have nothing to do with it. Note also that synchronization is frame dependent (which is one indication they must be at rest in the same frame).

The "clocks" of the GPS are arranged to be in one of those special circumstances, for synchronization in the ECI frame (only).

The "clocks" of the GPS are not standard clocks. Each one is modified for its altitude and motion wrt the ECI, so each always displays the ECI coordinate time where it is located. Some modifications are in the hardware, and some are in corrections uploaded to the clock, broadcast to the receivers, which apply them.

Tom Roberts

On 29/11/2019 4:46 am, Thomas Heger wrote:

> | Am 28.11.2019 um 16:06 schrieb Tom Roberts: |

>> | On 11/28/19 2:27 AM, Sylvia Else wrote: |

>>> | Anyone now thinking that Einstein's paper relating to special relativity contains multiple obvious errors is just deluding themselves. |

>> |
Hmmm. It does indeed include an error of fact: he assumed the earth is spherical, when in fact it is an oblate spheroid, and the distinction directly affects his comparison of clocks at equator and pole. This was not known in 1905; nor was the "gravitational time dilation" (which was recognized BY EINSTEIN in 1911). In the 1905 paper, of course, this was merely a side comment about an effect of the theory; it does not undermine his theory at all. |

> |
There are several errors and some of them are severe. The main error was, that he used a wrong method for synchronization between two observers in relative motion. The 'real thing' would be like to 'ping' the other observer, measure the delay of the reflected signal, divide the result by two and add the value to a time-signal received from the other observer. |

This would require an assumption about how clock rates are related for relatively moving observers, and at this point in the paper, there would be no justification for such an assumption.

Einstein avoids making any such assumption by basing his definition of whether clocks synchronize solely on what the clocks show at well defined moments, being when a light ray leaves or arrives where the clock is.

And it is only a definition. It does not purport to impose any restriction on the way the universe behaves.

Sylvia

This is a significant misinterpretation of what is in the paper.

In "§ 2. On the Relativity of Lengths and Times", the times t_A, t_B, and t'A (using your representations) are the times in the stationary system, and also the values displayed by the clocks at A, B, and A, respectively when a light ray leaves A, is reflected at B and returns to A.

They are not times in the moving system, and are not intended to be. As far as the observers in the moving system are concerned, they are just abstract values displayed by clocks, which can be plugged into the equation that, by definition, tests whether the clocks synchronize.

There is no manipulation of time here, because the only times under discussion are those of the stationary system.

Sylvia.

> | 1) Mainstream physicists have always been happy that "§ 1. Definition of Simultaneity" relates to clocks stationary in the "stationary" system of coordinates - that when Einstein talks about "at the point A of space there is a clock", the clear prima-facie interpretation of that statement is that the clock is fixed at A's (x, y, z) coordinate (and ditto for "there is at the point B of space another clock ") |

Einstein is concerned here with the situation where the observer is stationary relative to the clocks. Although he later talks of a stationary system, he's not giving it any special status - it's just terminology he's using to identify what we would now refer to as a particular reference frame.

> |
2) TH reckons this is incorrect, that instead Einstein was talking about one or the other (or both) clocks are moving |

All clocks are moving relative to something.

> |
3) TH points out that "this method is not correct" for moving clocks - in other words, that the equations in that section are incompatible with the idea of moving clocks - which he therefore attributes to Einstein making a foolish mistake in using moving clocks. |

It's not a method at all. It's a definition of what Einstein means by synchronize. It also fits our everyday notions of how synchronized clocks behave.

It means that if I have two clocks, one next to me and one a long way away, and next to the remote clock there is suitably aligned mirror, then if I look at the remote clock through a telescope, I'll see the time it shows and the time my local clock shows in its reflection. If I call the time I see in the reflection of my local clock tA, the time I see shown by the remote clock tB, and the time I see when I look directly at my local clock t'A, then if the clocks are synchronized, then tB will be halfway between tA and t'A.

None of these are measurements of time, they are just observations of what the clocks show.

Whether the clocks and I are moving relative to some other frame (and we always are anyway), is completely irrelevant.

> |
4) This error could have been avoided if Einstein had intended his statements like " a STATIONARY clock located at the place of the event, this clock being synchronous, ... with a specified STATIONARY clock" to not refer to "moving" clocks as asserted in (2) ..... 5) But instead to refer to STATIONARY clocks, which as per (1) mainstream physicists have always been happy to accept. |

Again, there are no such things as stationary clocks. There are only clocks that happen not to be moving relative to some arbitrarily chosen frame.

On 12/1/19 3:01 AM, Thomas Heger wrote:

> | A clock is a device, which is assumed to measure time. But time and clocks are not the same. |

Of course not -- the concepts are incommensurate.

> | This is similar to other measuring devices, like - say - a Volt-meter. |

Yes, a volt-meter is not a voltage. DUH!!!

> | Similar with clock: the readings of a clock are not time. Time is the stuff, which clocks measure. |

Hmmm. In physics, "time is what clocks measure" [Einstein and others],
because:

a) we need a precise definition

b) in every experimental test of a theory that involves time,
a clock is used to measure it.

c) in every instrument, process, and technique involving time,
a clock is used to measure it.

> | So we need some sort of metaphysical explanation to what entity we want to express with the term 'time'. |

Only in your fantasyland. In our everyday lives there is no problem and the usual, rather casual, meaning of "time" is sufficient. In physics, TIME IS WHAT CLOCKS MEASURE.

So you are free to go off into your fantasyland and speculate endlessly about "some sort of metaphysical explanation to what entity we want to express with the term 'time'". The rest of us will use the usual meaning in our everyday lives, and the physicists' meaning in physics. There _IS_ no problem here, and your wild speculations will not affect anything except your personal mental state.

Defining the meter in terms of the second and a defined value of the vacuum speed of light is the most convenient, and the most accurate way to define it. Definitions cannot be "circular", they simply are [#]. But of course using these definitions makes measuring the vacuum speed of light useless -- that's not a problem as we already know its value in meters/second, having been measured many times in many ways before this redefinition of the meter (in 1983).

[#] Hint: only ARGUMENTS can be circular (in this sense).

Tom Roberts

On 12/1/19 5:58 AM, Sylvia Else wrote:

> | [... constructing two different clocks] Since you are someone who can build very precise clockwork clocks, you would expect your two clocks to continue to measure time with the same relationship. You would not expect this to change just because you have moved to a different place, or accelerated for a period of time. |

"Expectations" have proven to be unreliable at best. But this is what is observed -- THAT is what matters in physics.

Heger's speculations in his fantasyland are irrelevant.

Tom Roberts

You claim to have read Einstein's paper, but then you come out with something like that. If you read the paper, you certainly did not understand it, because there is no such assumption. I have to wonder whether the numerous "mistakes" you claim to have found are actually nothing more than conflicts between relativity and your own notions of how things should be.

> |
Therefor rigid rods are not a good tool to make precise measurements of distances. They are also not very practicable for larger distance, like to distant stars. So we need other tools for cosmology, while rods may eventually be useful on the surface of planet Earth. This leaves us with the question: how long is actually a meter? |

Unless we need to know the lengths of things in metres, we don't care how long a metre is.

> |
We could use light as tool, but than we need something else to define the second (other than light in vacuum). |

An assumption that was actually made in relativity is that the laws of physics are the same for all observers. This means that determining time and distance by means of things we can actually measure is a reasonable approach. The result will match our experience, including for things like our heart rate, how quickly we age, and how tall we are.

You are not the first person to want to rescue some kind of conventional (as in pre-relativity) view by way of some other definition of time and length but what you end up with is something that is undetectable by way of any experiment whatsoever, and terms representing your new definitions will inevitably cancel out in any formulation that predicts the results of things we can measure. They serve no purpose.

Sylvia.

On 12/1/19 11:10 AM, Thomas Heger wrote:

> | The 'gamma factor' of SRT stems actually from the Doppler effect, |

This is just plain false. You REALLY do not understand basic physics.

In SR, gamma comes from the geometrical relationship between two inertial frames moving relative to each other. But it is really the Lorentz transformation that is involved, snf gamma is merely a part of it.

Tom Roberts

On 12/1/19 6:15 PM, Sylvia Else wrote:

> | I have to wonder whether the numerous "mistakes" [Heger] claim to have found are actually nothing more than conflicts between relativity and your own notions of how things should be. |

No need to wonder, the "mistakes" he discusses are CLEARLY just that -- conflicts with his preconceived notions of how things "ought" to be. Those notions of his simply do not correspond to the world we inhabit.

Tom Roberts

On 11/29/19 1:05 AM, Michael Moroney wrote:

> |
I was thinking of an SR situation where a clock was moving relative to an
observer and his clock at .866c (gamma=2) but the moving clock ticked twice as
fast as the observer's clock. The observer would see one tick on the moving
clock for every tick of his local clock and they could be synchronized, at
least as far as the observer was concerned. (an observer with the moving clock
would disagree!)
Would this be one of the special situations? |

Yes, with care. But remember the moving "clock" is not really a clock, because it does not advance 1 second whenever its worldline increases its proper time by 1 second.

The general idea is to arrange for a moving "clock" to always display the COORDINATE time of a specific frame, wherever it is located. Then in that frame it can be synchronized with standard coordinate clocks at rest in the frame. This is what the GPS does in the ECI frame.

Tom Roberts

I can recognise gibberish when I see it.

> |
To understand the implicit assumptions of Einstein in his text 'On the Electrodynamics of Moving Bodies' from 1905 it is best to read this text. see here: http://www.fourmilab.ch/etexts/einstein/specrel/www/ TH |

So you're claiming that they're in there, and expect me to find them. That's a cop out if ever there was one.

If you know what they are, then list them.

Sylvia.

On 12/9/19 1:43 PM, Thomas Heger wrote:

> |
He wrote, that a spherical wave emitted in one FoR would still be a
spherical wave in a moving FoR.
The equations he used are for expanding spheres, which have as center the zero point. But it is obviously impossible, that the same spherical wave centered around the zero point of a FoR at rest is also centered around the zero point of a moving FoR. |

The problem is YOURS -- you CLEARLY did not understand the paper at all.

He showed that the vacuum speed of light is c in EVERY inertial frame. So a spherical light wave in one frame is spherical in every frame, including the moving one.

I grant you that this is not obvious until one has read and understood the paper (or an SR textbook). But it is OBSERVED now, and in 1905 it was a consequence of his postulates.

In frames moving relative to the source there are Doppler shifts that are NOT constant around the sphere, but the location of the wave is spherical when observed simultaneously in the frame.

Tom Roberts

On 12/14/19 11:20 AM, Thomas Heger wrote:

> | I personally think, that SRT is full of errors. |

Except that the math underlying SR has been proven to be as self-consistent as is Euclidean geometry, and as is real analysis. The "errors" you discuss are all YOURS, and are unrelated to SR.

Tom Roberts

On 12/10/19 8:08 AM, Thomas Heger wrote:

> |
The part of his text we are discussing is this:
quote: "At the time t = = 0, when the origin of the co-ordinates is common to the two systems, let a spherical wave be emitted therefrom, and be propagated with the velocity c in system K. If (x, y, z) be a point just attained by this wave,then x˛ + y˛ + z˛ = c^2t^2. Transforming this equation with the aid of our equations of transformation we obtain after a simple calculation xi^2 + eta^2 + zeta^2 = c^2tau^2. The wave under consideration is therefore no less a spherical wave with velocity of propagation c when viewed in the moving system. This shows that our two fundamental principles are compatible." end quote But that is blatant nonsense!!! |

No, it isn't. It is simple algebra. Are you unable to do simple algebra?

Take his initial equation: x^2 + y^2 + z^2 = c^2 t^2 And substitute his transform: tau = beta (t - v x / c^2) xi = beta (x - v t) eta = y zeta = z with beta = 1 / sqrt(1 - v^2/c^2), and I have looked ahead in the paper to omit factors of phi(v) (= 1). The way to proceed is to first compute the inverse transform: t = beta (tau + v xi / c^2) x = beta (xi + v tau) y = eta z = zeta(This is a straightforward but tedious exercise in algebra.) That now substitutes directly into the initial equation. One finds that the cross terms (in tau xi) cancel, and when the xi terms are collected on the left and the tau terms are collected on the right, the beta^2 in each cancels out and one is left with: xi^2 + eta^2 + zeta^2 = c^2 tau^2 AS CLAIMED. Note in particular there is no v in this equation.

Alternate derivation: start with his final equation, substitute in his transform, and simplify to obtain his initial equation. Hint: since v is absent in BOTH equations, its value does not matter, including +v or -v.

> | The moving FoR k is moving with velocity v along the X-axis of K. |

Yes, that is the physical situation being described (by Einstein, in the paragraph you quoted).

> | So a sphere in K centered around the zero spot of K should move in k to the direction of smaller xi (xi is equivalent to x on the X-axis of K, but moving). So a moving FoR k would make xi smaller, if the same wave is measured in k. iow: the sphere is moving to the left in k, if higher values of x run to the right in K for higher values. |

NO! You STILL have not understood the basic property of SR: light propagates with speed c in EVERY inertial frame. It does not matter how "nonsensical" that YOU think it to be, that is what is predicted by SR. There is NOTHING you can do to change the theory or its predictions. But you CAN do some studying and LEARN how this comes about.

The main point you seem to be missing is that in K he is describing the positions (x,y,z) of the sphere at constant time t in K. But in k he is describing the positions (xi,etx,zeta) of the sphere at constant time tau in k. THESE ARE DIFFERENT SETS OF EVENTS.

> | But I cannot find any term containing v in his equation for the sphere in k. |

Because there isn't any. The sphere propagates ISOTROPICALLY with speed c in k. Just like it did in K.

Tom Roberts

On 12/18/19 4:58 AM, Thomas Heger wrote:

> | Am 18.12.2019 um 04:25 schrieb Tom Roberts: |

>> | You STILL have not understood the basic property of SR: light propagates with speed c in EVERY inertial frame. It does not matter how "nonsensical" that YOU think it to be, that is what is predicted by SR. There is NOTHING you can do to change the theory or its predictions. But you CAN do some studying and LEARN how this comes about. |

> |
Sure: LIGHT propagates in any inertial FoR with c. |

And so does the spherical LIGHT wave discussed by Einstein.

> | But we were talking about a spherical centered around the zero spot of the non-moving FoR K. This wave is observed from the moving FoR k. |

Yes.

> |
You could have it the other way round and emit the wave at x', which
is the center spot of the moving FoR k and observe that wave from the
non-moving FoR K.
But you cannot have both with the same wave, since the waves emitted in these situations are not the same. |

This is just plain not true FOR THE POSITIONS OF THE WAVE AT VARIOUS TIMES IN EITHER FRAME K OR FRAME k.

We discuss ONLY the positions of the spherical wave, NOT the Doppler shifts of various parts of it. The POSITIONS of the wave do not depend on whether the source is at rest in K or in k; the Doppler shifts do depend on that -- BUT THAT IS IRRELEVANT IN THIS DISCUSSION.

> | The reason: if you emit a wave centered around a certain zero-spot, this wave would not be centered around the zero spot of a moving FoR, moving in respect to that spot. |

This is not true. Since the "zero spots" of both frame coincide when the wave is emitted, and since light propagates with speed c relative to EVERY inertial frame (including both K and k), the LOCATIONS of the wave, when observed SIMULTANEOUSLY IN K will be a sphere in K centered on K's "zero spot". And also, the LOCATIONS of the wave, when observed SIMULTANEOUSLY IN k, will be a sphere in k centered on k's "zero spot".

This OUGHT to be obvious, because as you said above: "LIGHT propagates in any inertial FoR with [speed] c." -- this includes both K and k.

Just LOOK at it from the perspective of frame k: at time t'=0 a spherical light wave is emitted at x'=y'=z'=0. This light wave propagates outward with speed c, so at any time t'>0, the wave will be a sphere with radius c*t'. Note that anything having to do with frame K is COMPLETELY IRRELEVANT here, including whether the source is at rest in K or in k (the Doppler shifts depend on that but the positions DON'T).

> | This should be obvious! |

No. You are implicitly thinking of Galilean relativity. But this is SR, and one MUST use Lorentzian relativity.

> | But Einstein used a nasty trick to hide this: |

Not at all. You are obsessed with an IRRELEVANCY.

> | he declared that only one single sharp pulse created both waves, when both zero-spots coincided. The problem with this assumption is, that pulses with zero rising time are physically impossible. |

This is a GEDANKEN, and such real-world limitations simply do not apply.

> | You cannot possibly claim, the moving FoR would 'grab' the emitted wave and take it away. |

No FoR can "grab" anything. What we are discussing is how the two FORs DESCRIBE THE POSITIONS OF THE SPHERICAL WAVE. In SR both frames describe it as a sphere, because as you said "LIGHT propagates in any inertial FoR with [speed] c."

> | since single sharp pulses with zero rising time are physically impossible |

You need to learn basic physics. The "spherical wave" Einstein discussed can be implemented in the real world in several ways: A) Consider it to be the leading edge of a long wave. B) Make it a normal light wave emitted over such a short time that all the detectors see it as a single pulse. For instance, a 1 nanosecond long light pulse will appear in photomultiplier tubes as a short pulse, but contains over 40,000 wavecrests (modeling it as a wave).

But I repeat: this is a GEDANKEN and such real-world limitations do not apply. You are obsessed with an IRRELEVANCY, and have completely missed the real lesson: the wave is a sphere in BOTH K and k.

Tom Roberts

On 12/18/19 8:39 PM, Ned Latham wrote:

> | There are infinitely many inertial frames of references possible moving in infinitely many directions at infinitely many speeds... |

Sure.

> | So light "propagating" at c in these infinitely many frames of reference is "propagating" at infinitely many speeds, including FTL, in the FoR of the source. |

No. You need to learn basic logic: you applied "light propagates in any inertial FoR with [speed] c" to the "infinitely many frames", but did not apply it to ALL of the frames -- you omitted the frame of the source. So your claim here is complete nonsense.

You have completely missed the point: light propagates isotropically with speed c relative to EVERY inertial frame. This OF COURSE includes the FoR of the source.

In his 1905 paper, Einstein shows how velocities transform from one inertial frame to another. His derivation EXPLICITLY SHOWS that light propagating with speed c relative to frame A also propagates with speed c relative to frame B, INDEPENDENT of the relative velocity of frame B relative to frame A. A and B are arbitrary, so this applies to EVERY inertial frame.

It does not matter how "crazy" you think this is, or that it is "good for a giggle", that is what SR predicts. More importantly, that is WHAT IS OBSERVED.

Tom Roberts

On 12/18/19 11:30 PM, Ned Latham wrote:

> | in ordere to falsify my conclusion, that's what needs to be done. The scenario develops FTL in the FoR of the source, not any of those infinitely many others. |

You really are an idiot, and CLEARLY do not understand basic logic (much less basic physics).

In making your silly "conclusion" you accepted the statement "LIGHT propagates in any inertial FoR with c", but did not apply it to the FoR of the source. Applying it to the FoR of the source is all that is needed to falsify your "conclusion"; that is of course included in what "any" means.

Tom Roberts

tjrob137

On 12/19/19 10:59 AM, Ned Latham wrote:

> | Tom Roberts wrote: |

>> | Ned Latham wrote: |

>>> |
in ordere to falsify my conclusion, that's what needs to be done. The scenario develops FTL in the FoR of the source, not any of those infinitely many others. |

>> |
You really are an idiot, and CLEARLY do not understand basic logic (much less basic physics). In making your silly "conclusion" you accepted the statement "LIGHT propagates in any inertial FoR with c", but did not apply it to the FoR of the source. |

> |
Once again for the physicist: it does not propagate at the source. |

That does not even make sense. (You repeated it, so it is not a typo.)

The light most definitely does propagate IN THE FoR OF THE SOURCE. You accepted the statement "LIGHT propagates in any inertial FoR with c", and applying that to the FoR of the source CLEARLY falsifies your claim.

What part of "any" don't you understand?

Tom Roberts

On 12/11/19 4:21 PM, ahj...@gmail.com wrote:

> | SR never has indicated inertial nor non-inertial frame. |

Sure it has, right from the start -- Einstein's "system of coordinates in which the equations of Newtonian mechanics hold good" is his rather archaic way of specifying what we now call an inertial frame.

> | The mathematics of the Lorentz transform never makes a distinction between the inertial and non-inertial frames. |

Certainly one can apply any transform to any coordinates -- the issue is whether that is useful, remembering "garbage in, garbage out". In particular, the Lorentz GROUP is restricted to inertial frames. It is the group that really matters in modern physics.

Tom Roberts

On 12/30/19 2:14 PM, Thomas Heger wrote:

> | Am 29.12.2019 um 18:55 schrieb Tom Roberts: |

>> | On 12/11/19 4:21 PM, ahj...@gmail.com wrote: |

>>> | SR never has indicated inertial nor non-inertial frame. |

>> | Sure it has, right from the start -- Einstein's "system of coordinates in which the equations of Newtonian mechanics hold good" is his rather archaic way of specifying what we now call an inertial frame. |

> |
Actually he wrote, that a frame of reference where the equations of Newton are applicable is called 'stationary' ('ruhend'). |

Your phrasing here is disingenuous at best -- he did NOT say that.

In the first paragraph of I.1, after selecting an arbitrary inertial frame, he actually said "we call it the 'stationary system'" -- his reason for doing that is "to distinguish this system of co-ordinates verbally from others which will be introduced hereafter".

IOW: "stationary" is a LABEL, with no semantic content. He could have used the label "bltzfq" instead of "stationary", and there would be no change in the argument. (But it would not have confused poor readers like you.)

If you cannot understand the important difference here, then you are not able to read with sufficient accuracy to understand this subtle and complex paper. Specifically, above you imply a universality that is not present in the paper -- there is just ONE system labeled "stationary" but several other frames of reference. Your errors here have colored and confused your entire appreciation (or lack thereof) of SR.

> | In SRT we have only constant velocities, hence no acceleration. Which is what we call 'inertial'. |

There is considerably more to "inertial" than that.

> | So SRT covers only FoRs, which are at rest - by definition. |

His PAPER only dealt with inertial frames, but the theory can handle accelerated systems just fine. Note that he EXPLICITLY used frames that are moving relative to his "stationary" frame, so your "at rest" is NOT PRESENT in the paper -- it is YOUR FANTASY, and illustrates your personal CONFUSION.

I repeat: you REALLY need to learn how to read. Carefully and accurately.

Tom Roberts

Thomas Heger

> | Am 31.12.2019 um 10:49 schrieb Thomas Heger: |

>>>>>> | SR never has indicated inertial nor non-inertial frame. |

>>>>> | Sure it has, right from the start -- Einstein's "system of coordinates in which the equations of Newtonian mechanics hold good" is his rather archaic way of specifying what we now call an inertial frame. |

>>>> |
Actually he wrote, that a frame of reference where the equations of Newton are applicable is called 'stationary' ('ruhend'). |

>>> |
Your phrasing here is disingenuous at best -- he did NOT say that. |

>> |

> | Sure he did: |

> | quote |

> | "I. KINEMATICAL PART § 1. Definition of Simultaneity Let us take a system of co-ordinates in which the equations of Newtonian mechanics hold good. In order to render our presentation more precise and to distinguish this system of co-ordinates verbally from others which will be introduced hereafter, we call it the “stationary system.” |

"Stationary system" was just a name for what we now call frames, plus it is inertial because of the bit about Newtonian mechanics holding good. Using the phrase "stationary system" is a bit unfortunate now since a few people (esp. cranks) interpret it as some absolute rest frame.

> | If a material point is at rest relatively to this system of co-ordinates, its position can be defined relatively thereto by the employment of rigid standards of measurement and the methods of Euclidean geometry, and can be expressed in Cartesian co-ordinates." |

> | /quote |

> | from |

> | "ON THE ELECTRODYNAMICS OF MOVING BODIES" By A. EINSTEIN June 30, 1905 |

> | (Ok, he wrote 'hold good' instead of 'applicable'. But that difference shouldn't be a big deal.) |

Be careful which translation was used and how faithful it is to the original German.

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