Does My Wrist Watch Physically Beat Slower?

[PeterDonis]

No I mean 30 seconds in the missile frame.

That's not possible with any of the numbers you've given; a curve going from t = 30 seconds on the Earth's worldline to t' = 30 seconds on the missile's worldline would be timelike, not spacelike. In fact it will be timelike for a missile traveling at any speed fairly close to that of light (off the top of my head I think all that's required is a gamma factor of 2, which requires a missile speed of 0.866c).

Because if it reaches the missile at say 1 sec or 25 seconds (let's say it travels continuous and no target), it can produce a scenario where Earth can receive it before sending out.

Not if the tachyon always travels at the same speed in the ether frame. It's easy to show this: just work the problem in the ether frame. There are two possible cases in that frame: Earth and missile both moving in the same direction, and Earth and missile moving in opposite directions. It's straightforward to show for each case that if the tachyon travels at a fixed speed w relative to the ether frame, the Earth can't receive it before it sends it. And since both events occur on the Earth's worldline, their time ordering is invariant; if the signal is received after it's sent in the ether frame, it's received after it's sent in any frame. Work it out.

Now does it mean 30 seconds on Earth and 30 seconds on the missile are simultaneous to the aether frame?

They can't possibly be if the missile is traveling at any significant fraction of the speed of light, because the two events will be timelike separated, not spacelike separated. Only spacelike separated events can be simultaneous in any frame.

How do you make the aether frame simultaneous to it when they are in relative motion. This is what I was trying to understand.

I think you're going at it the wrong way around. Try what I suggested above: work the problem in the ether frame, treating the tachyon speed w as an unknown, but fixed in that frame. Work it out and you will find that the tachyon signal can't be received on Earth before it is sent for *any* tachyon speed w greater than 1, including speed w = infinity (i.e., the tachyon travels instantaneously in the ether frame).

 

[Tomahoc]

That's not possible with any of the numbers you've given; a curve going from t = 30 seconds on the Earth's worldline to t' = 30 seconds on the missile's worldline would be timelike, not spacelike. In fact it will be timelike for a missile traveling at any speed fairly close to that of light (off the top of my head I think all that's required is a gamma factor of 2, which requires a missile speed of 0.866c).



Not if the tachyon always travels at the same speed in the ether frame. It's easy to show this: just work the problem in the ether frame. There are two possible cases in that frame: Earth and missile both moving in the same direction, and Earth and missile moving in opposite directions. It's straightforward to show for each case that if the tachyon travels at a fixed speed w relative to the ether frame, the Earth can't receive it before it sends it. And since both events occur on the Earth's worldline, their time ordering is invariant; if the signal is received after it's sent in the ether frame, it's received after it's sent in any frame. Work it out.



They can't possibly be if the missile is traveling at any significant fraction of the speed of light, because the two events will be timelike separated, not spacelike separated. Only spacelike separated events can be simultaneous in any frame.



I think you're going at it the wrong way around. Try what I suggested above: work the problem in the ether frame, treating the tachyon speed w as an unknown, but fixed in that frame. Work it out and you will find that the tachyon signal can't be received on Earth before it is sent for *any* tachyon speed w greater than 1, including speed w = infinity (i.e., the tachyon travels instantaneously in the ether frame).

So back to my original question. A tachyon aborting signal sent at 30 secs that travels always at the same speed in the ether frame can't reach the missile in time (which takes only 2 secs to reach tau ceti). Do you agree? Bottom line is. Tachyons with velocity fixed in the aether frame is an inefficient or not effective method to abort any signal (assuming normal light speed not enough to abort it (I know I gave wrong figures which makes it reacheable but ignore this as this Is not my main inquiry or concern).

Anyway. How many seconds in the missile frame can it receive the Earth signal which is sent at 30 seconds assuming tachyons velocity (instantaneous in our case) is fixed relative to aether frame. How do you solve for it?

 

[Dale]

Again, it should be emphasized that the basis of Lorentz's (and Poincare's, et. al.) derivations make LET significantly different than the Einstein-Minkowski theory of special relativity, notwithstanding the common mathematical feature, i.e., Lorentz transformations.

Do you agree that the common mathematical feature, the Lorentz transform, is what each uses to make all of its experimental predictions?

 

[PeterDonis]

So back to my original question. A tachyon aborting signal sent at 30 secs that travels always at the same speed in the ether frame can't reach the missile in time (which takes only 2 secs to reach tau ceti). Do you agree?

The missile only takes 2 seconds *in the missile frame*. It takes longer in the Earth frame--how much longer depends on the speed of the missile and the distance in the Earth frame to Tau Ceti. I've made this point repeatedly.

As for your question, I've given you enough information already to work out for yourself under what conditions a tachyon pulse can or cannot reach the missile in time; you can work the entire problem in one frame (I worked it in the Earth frame). Have you read through the worked example I gave?

Bottom line is. Tachyons with velocity fixed in the aether frame is an inefficient or not effective method to abort any signal, assuming normal light speed not enough to abort it.

No, this is not true. I've already stated that repeatedly as well. By definition, tachyons travel faster than light in any frame; that means that you can't assume that if a light pulse can't get there in time, a tachyon pulse can't get there in time either. You have to work the numbers and see.

How many seconds in the missile frame can it receive the Earth signal which is sent at 30 seconds assuming tachyons velocity (instantaneous in our case) is fixed relative to aether frame. How do you solve for it?

Again, have you read through the worked example I gave? It included an inequality that relates the time the Earth signal is emitted (30 seconds in your case, but I left it as a variable so you could try different values if you want), the distance to Tau Ceti, the speed of the missile, and the speed of the tachyon, all in the Earth frame. If this inequality is satisfied, the tachyon can catch the missile before it hits Tau Ceti. That gives you a good starting point to answer other questions.

 

[Tomahoc]

The missile only takes 2 seconds *in the missile frame*. It takes longer in the Earth frame--how much longer depends on the speed of the missile and the distance in the Earth frame to Tau Ceti. I've made this point repeatedly.

As for your question, I've given you enough information already to work out for yourself under what conditions a tachyon pulse can or cannot reach the missile in time; you can work the entire problem in one frame (I worked it in the Earth frame). Have you read through the worked example I gave?
No, this is not true. I've already stated that repeatedly as well. By definition, tachyons travel faster than light in any frame; that means that you can't assume that if a light pulse can't get there in time, a tachyon pulse can't get there in time either. You have to work the numbers and see.
Again, have you read through the worked example I gave? It included an inequality that relates the time the Earth signal is emitted (30 seconds in your case, but I left it as a variable so you could try different values if you want), the distance to Tau Ceti, the speed of the missile, and the speed of the tachyon, all in the Earth frame. If this inequality is satisfied, the tachyon can catch the missile before it hits Tau Ceti. That gives you a good starting point to answer other questions.

Have you forgotten something. To avoid the missile sending the signal back to Earth's past. It has to receive it at 30 seconds too. So the aether frame in our scenerio acts like delay buffer. Because if it receives it less than that. It can send the signal to Earth before Earth sends it. In our examples. Remember We are dealing only with scenerio where tachyons velocity is fixed to the aether frame so don't go back to the old assumptions that the tachyons velocity is frame dependent (which is what make you worked example or inequality valid).

 

[PeterDonis]

To avoid the missile sending the signal back to Earth's past. It has to receive it at 30 seconds too.

Not if the tachyon velocity is independent of the emitter's motion. See my post #51.

don't go back to the old assumptions that the tachyons velocity is frame dependent (which is what make you worked example or inequality valid).

No, it isn't. My worked example assumes that the velocity of the tachyon emitted by the Earth is fixed at w in the Earth frame, which will be true only if the tachyon velocity is independent of the state of motion of the emitter (since the missile is moving in the Earth frame). Since we don't know if the Earth frame is the aether frame, we don't know if the speed w is the same as the (fixed) tachyon speed in the aether frame, but that doesn't matter; all we need to know is that w is fixed. (My example doesn't even analyze the trajectory of a return tachyon emitted by the missile; for that case, see below.)

It is true that there is a case my worked example doesn't cover: the case in which the tachyon emitted by the Earth goes backwards in time in the Earth frame (or the tachyon emitted by the missile--but they can't both go backwards in time in the Earth frame, for the reasons I gave in post #51). But that's easy to fix; as I said before, just work the problem in the aether frame instead (since the tachyon can't go backwards in time in that frame--the fastest it can travel is instantaneously), and add a nonzero velocity e for the Earth. Then, as I said before, there are two cases to cover, the case where e and v (the missile velocity) both have the same sign (i.e., Earth and missile are moving in the same direction) and the case where e and v have opposite signs (i.e., Earth and missile are moving in opposite directions). It is straightforward to extend my worked example to cover this case, which also allows you to extend the analysis to the return tachyon emitted by the missile as well.

 

[Tomahoc]

Not if the tachyon velocity is independent of the emitter's motion. See my post #51.



No, it isn't. My worked example assumes that the velocity of the tachyon emitted by the Earth is fixed at w in the Earth frame, which will be true only if the tachyon velocity is independent of the state of motion of the emitter (since the missile is moving in the Earth frame). Since we don't know if the Earth frame is the aether frame, we don't know if the speed w is the same as the (fixed) tachyon speed in the aether frame, but that doesn't matter; all we need to know is that w is fixed. (My example doesn't even analyze the trajectory of a return tachyon emitted by the missile; for that case, see below.)

It is true that there is a case my worked example doesn't cover: the case in which the tachyon emitted by the Earth goes backwards in time in the Earth frame (or the tachyon emitted by the missile--but they can't both go backwards in time in the Earth frame, for the reasons I gave in post #51). But that's easy to fix; as I said before, just work the problem in the aether frame instead (since the tachyon can't go backwards in time in that frame--the fastest it can travel is instantaneously), and add a nonzero velocity e for the Earth. Then, as I said before, there are two cases to cover, the case where e and v (the missile velocity) both have the same sign (i.e., Earth and missile are moving in the same direction) and the case where e and v have opposite signs (i.e., Earth and missile are moving in opposite directions). It is straightforward to extend my worked example to cover this case, which also allows you to extend the analysis to the return tachyon emitted by the missile as well.

I've been analyzing your statements the past couple of hours. But if both the Earth and missile travels opposite from each other at say 0.9999c (or whatever), and you are watching in a station at middle of them. And you are in the ether frame. Then when Earth sends instantaneous signal after 30 seconds to missile, and missile sends another at the same 30 seconds. Then they can both receive it instantaneously at 30 seconds. In this case, their time is somehow synchronized, contrary to what you said it can't be synchronized bec they are timelike and not spacelike, may I know your comment?

 

[PeterDonis]

may I know your comment?

If you keep on changing the parameters, of course you're going to change the answer. Now it appears that "30 seconds" means "30 seconds in the ether frame", which is different than 30 seconds by Earth's clock or 30 seconds by the missile's clock. So you're talking about signals being sent between different events than the ones we were talking about before. These two events *are* spacelike separated (because they both occur at the same time, 30 seconds, in the ether frame).

 

[Tomahoc]

If you keep on changing the parameters, of course you're going to change the answer. Now it appears that "30 seconds" means "30 seconds in the ether frame", which is different than 30 seconds by Earth's clock or 30 seconds by the missile's clock. So you're talking about signals being sent between different events than the ones we were talking about before. These two events *are* spacelike separated (because they both occur at the same time, 30 seconds, in the ether frame).

Ey if its 30 seconds at ether frame, it is also 30 seconds at both Earth and missile. If not, what time then??

 

[Vandam]

You have a serious obsession with solipsism. I am not a solipsist, if you believe that I have EVER made statements indicating that then please point them out and I will retract or explain them.

If you are not a solipsist, meaning you believe in an outside real world, then relativity of simultaneity leads automatically to Block universe.

On the LET interpretation, the primed coordinates correspond to coordinate assignments that the moving observer would make. LET says that those assignments are not the "true" coordinates, but it still gives them a perfectly well-defined meaning.

What physical meaning? We talk physics on this forum.

I already have, repeatedly. I just did it again, above. But you either can't understand or refuse to accept that LET is an *interpretation*, just as the "block universe" is an *interpretation*.

No. observational evidence leads to block universe. See below.

Do you agree that the common mathematical feature, the Lorentz transform, is what each uses to make all of its experimental predictions?

What are 'experimental predictions'? What is 'experimental evidence'?

Observation.

The LT matches what you observe. Indeed.

But what do you observe?

In order to observe an event (f.ex. a clock showing specific time indication), that event has to exist before you observe it and lightbeams travel from that event to your retinae. (If you refute this it is pointless to talk about 'observation'. What is left is only the image of an event you 'see' in your brain as a mental awareness with no cause or origin creating that image. Solipsism.)

Hence the experimental or observational evidence gives us information of that's going on in our 3D world. A 3D world that exists before you 'observe' any events of it, because we have to wait until the lightbeams reach our retinae.
The fact we do not know yet (now) what happens out there in our 3D world 'now' doesn't mean there are no specific events out there in 3D world.

What do the LT transformations tell us?

Green coordinates tell us that in the 3D world of Mr Green with wristwatch 0.5, event A is at .5 distance. The experimental/observational evidence for Green tells us that event A is simultaneous with his wristwatch .5 (event E), which means those two events are/were both part of one 3D world. (3D world = simultaneous events. Non-simultaneous events can never be part of one 3D world.)

The experimental/observational evidence for Red tells us that event A is simultaneous with event R, which means that they are/were both part of one physically real 3D world, a different one than Green's 3D world. That only makes sense in SR, not LET.

LT and the experimental/observational evidence shows that LET is wrong, but SR correct.

Of course you can say that the observational evidence is correct in LET if you consider red's observational evidence an illusion, a mathematical fiction. But is this physics? Lorentz knew the LT were problematic in his ether context. (I will not repeat his quote.)
Einstein's contribution was to solve that problem by changing the illusion into reality so to speak.
It means the relativity of simultaneity is not only a mathematical exercise on your calculator on the kitchen table, but a description of what is really happening with and in the real physical 3D worlds in 4D spacetime. Experimental and observational experiment (f.ex Einsteins train experiment) show us Block Universe.

 

[Vandam]

It's more than that; the moving guy also thinks that the clock of the guy at rest relative to the ether is ticking slower than his. "Time dilation" in this sense is still symmetric. It's just that LET gives a privileged status to the guy at rest relative to the ether; his perception is the "true" one, and the perception of the moving guy, who thinks the guy at rest's clock is ticking slower, is an "illusion".

Can you show us how that (bold) works?
So the moving guy is from his illusion bubble observing slower ether time? Gets too philosophical for me.

You say 'thinks'.
I'm interested what is out there in 3D space. Physics. Not what he thinks. Nor illusions.

(Or are you going to tell me that 3D world is an illusion? Be carefull. If you do, you are a solipsist)

 

[Dale]

If you are not a solipsist, meaning you believe in an outside real world, then relativity of simultaneity leads automatically to Block universe.

No, it doesn't. LET is a counter example. Another counter example would be a universe where any arbitrary spacelike 3D surface is "real" and the postulates of relativity hold locally, such an example could be made compatible with GR and therefore a much better candidate for "reality" than the block universe. There could well be other counter examples.

What are 'experimental predictions'? What is 'experimental evidence'?

An experimental prediction is the value expected on some specific measuring device in a given setup. Experimental evidence is the actual value obtained on the measuring device in a given setup.

E.g. a particle accelerator produces a stream of atoms moving at v relative to the laboratory. When measured at rest those atoms emit radiation with a characteristic frequency f0. What frequency, f, will be measured from the moving atoms with a receiver at rest wrt the lab mounted perpendicular to the stream?

Both the block universe and LET will use the LT to determine the experimental prediction which is the expected value of f. Since they both use the LT to calculate it they must unavoidably both obtain the same value for f.

Therefore the actual measured value of f can either confirm both LET and the block universe or it can contradict both. It cannot possibly confirm one and contradict the other since they both predict the same value of f.

Can you provide a counter-example? Any experiment where LET uses the LT to predict some measured value and where the block universe uses the same LT to predict some different value? It seems like a patently false claim to me.

I think that all you can do is to make a strawman LET which doesn't use the LT to make its predictions or continue to make irrelevant philosophical or historical objections about LET.

 

[Dale]

Can you show us how that (bold) works?

Easy. The laboratory has a set of local rods and local clocks which are synchronized using light signals in the laboratory frame. According to LET these are related by the LT to the true time and space coordinates in the ether frame. I will denote local coordinates as the primed coordinates and the aether coordinates by unprimed variables.

A clock at rest at the origin of the ether frame has a constant position x=0. So by the LT in the lab frame it reads time:
t' = γ (t-vx/c²) = γt

Since γ>1 the aether clock appears to run slow according to the local clocks.

 

[bobc2]

Easy. The laboratory has a set of local rods and local clocks which are synchronized using light signals in the laboratory frame. According to LET these are related by the LT to the true time and space coordinates in the ether frame. I will denote local coordinates as the primed coordinates and the aether coordinates by unprimed variables.

A clock at rest at the origin of the ether frame has a constant position x=0. So by the LT in the lab frame it reads time:
t' = γ (t-vx/c²) = γt

Since γ>1 the aether clock appears to run slow according to the local clocks.

So, what is the justification for using the Lorentz transform in this context (it is easy to show the justification in the context of Einstein-MInkowski)?

 

[Dale]

So, what is the justification for using the Lorentz transform in this context (it is easy to show the justification in the context of Einstein-MInkowski)?

Please don't avoid my question of post 53: Do you agree that the common mathematical feature, the Lorentz transform, is what each uses to make all of its experimental predictions?

The justification is that it is a postulate of the theory that local frames are related to the ether frame by the LT. And, of course, that postulate is supported by the data.

 

[bobc2]

Please don't avoid my question of post 53: Do you agree that the common mathematical feature, the Lorentz transform, is what each uses to make all of its experimental predictions?

I have never denied the commonality of the Lorentz transformations in both interpretations of special relativity. I've noted that more than once. So, I think I will present a new interpretation of special relativity using the Lorentz transformations as a postulate (I can think of a number of arbitrary possibilities)--now, that proves that Einstein-Minkowski is not necessarily the correct interpretation.

The justification is that it is a postulate of the theory that local frames are related to the ether frame by the LT. And, of course, that postulate is supported by the data.

DaleSpam, the Lorentz theory is not based on that postulate, it was originally based on an ad hoc derivation of the Lorentz transformation for times to account for the negative speed of light experimental results. They were derived for special cases (the length contraction may have later been added on as a postulate--I don't remember for sure). Einstein-Minkowski is a foundational theory that is applied for the most general case. It is not surprizing that Lorentz's electron theory should be compatible with Einstein's general theory for electrodynamics. Actually, Lorentz's original formulations had error's that were corrected by Poincare' and others. And Poincare' actually carried Lorentz's theory into the more general arena (which I think was a departure from the original intent of the theory) and understood the Lorentz transformations to form a group (I believe it was Poincare' who coined the term Lorentz transformation).

 

[PeterDonis]

Ey if its 30 seconds at ether frame, it is also 30 seconds at both Earth and missile. If not, what time then??

The Earth and the missile are both moving in the ether frame, so t = 30 seconds in the ether frame is *not* t' = 30 seconds in the Earth frame or the missile frame. You keep on switching numbers around so I'm not sure which numbers you are thinking of for this example, but if we take 0.9999c as the speed of the Earth and the missile in the ether frame, then gamma is about 71, so t = 30 seconds in the ether frame corresponds to t' = 30/71 seconds, or about t' = 0.42 seconds in the Earth frame or the missile frame. So a tachyon that travels instantaneously in the ether frame, and is launched at t = 30 seconds in the ether frame, will hit the Earth (or the missile) when the Earth's clock (or the missile's clock) reads about 0.42 seconds.

 

[PeterDonis]

Looking back over my previous posts, I found a couple of errors that need to be corrected:

a curve going from t = 30 seconds on the Earth's worldline to t' = 30 seconds on the missile's worldline would be timelike, not spacelike. In fact it will be timelike for a missile traveling at any speed fairly close to that of light (off the top of my head I think all that's required is a gamma factor of 2, which requires a missile speed of 0.866c).

I was wrong here. If the Earth and the missile both set their clocks to zero when the missile is launched, then the two events "Earth clock reads 30 seconds" and "missile clock reads 30 seconds" (each event located on the appropriate worldline, Earth's or missile's) will *always* be spacelike separated. So I was wrong to say that a light pulse launched from Earth when Earth's clock reads 30 seconds could ever reach the missile before the missile's clock reads 30 seconds.

However, I was still correct in the original example (when I assumed the missile's speed was 0.99c) when I said a light pulse launched from Earth when Earth's clock reads 30 seconds would reach the missile before the missile hits Tau Ceti (at a distance of 12 light years in the Earth frame). That's because if the missile's speed is 0.99c, the missile will take a lot longer than 30 seconds, by its own clock, to reach Tau Ceti. That is, I was wrong to assume that the missile's time of flight, by the missile's own clock, would be only 2 seconds if the missile's speed was 0.99c.

So I also got this wrong:

in the missile's frame, the time between launch and the President issuing the order is *much* less than 30 seconds; in fact it's 30 seconds divided by the time dilation factor, which is something like 10^8)

The time dilation factor for v = 0.99c is only about 7, so the time between launch and the President issuing the recall order, in the missile's frame, is 30/7 seconds, or about 4.3 seconds. That doesn't change the rest of my conclusions; the light pulse will still catch the missile well before it reaches Tau Ceti (since, as I said, that result is an invariant and I derived it in the Earth frame without using any values in the missile frame). The missile's time of flight, by its own clock, will be the time of flight by Earth's clock, 12/.99 years, divided by gamma = 7, or about 1.7 years; and 4.3 seconds is still *much* shorter than that, so in the missile's frame, Earth is still much closer than Tau Ceti when the light pulse is launched.

 

[PeterDonis]

the Lorentz theory is not based on that postulate, it was originally based on an ad hoc derivation of the Lorentz transformation for times to account for the negative speed of light experimental results.

Originally, yes. But once again, don't confuse the physics with the history of the physics. You say later on in this same post that the theory was later modified; when we talk about "LET" in terms of the physics (as opposed to the history of the physics) we are talking about whatever the "best current version" of the theory is. That would seem to be this:

And Poincare' actually carried Lorentz's theory into the more general arena (which I think was a departure from the original intent of the theory) and understood the Lorentz transformations to form a group (I believe it was Poincare' who coined the term Lorentz transformation).

In other words, the "best current version" of LET covers the "more general arena" and is therefore mathematically equivalent to what you are calling "Einstein-Minkowski" SR. Since both are mathematically equivalent, it's pointless to talk about which "postulates" each one uses. You can derive "Einstein-Minkowski" SR *without* taking the LT as a postulate, if you pick your other postulates appropriately. The point is that each theory contains a mathematically self-consistent system, and it's the *same* system, mathematically, in both theories.

 

[Dale]

I have never denied the commonality of the Lorentz transformations in both interpretations of special relativity. I've noted that more than once.

OK, then the conversation should really be concluded. Since they both use the LT for all of their experimental predictions then all of their experimental predictions must be identical. Since all of their experimental predictions must be identical there can be no experiment which could distinguish between the two.

Do you disagree in any way with that chain of reasoning? If so, please explain.

So, I think I will present a new interpretation of special relativity using the Lorentz transformations as a postulate (I can think of a number of arbitrary possibilities)--now, that proves that Einstein-Minkowski is not necessarily the correct interpretation.

Exactly. Now you are getting the idea. There can always be more than one way to interpret the same equation, so there will always be multiple interpretations which cannot be distinguished empirically and therefore no interpretation can claim to necessarily be the correct one.

DaleSpam, the Lorentz theory is not based on that postulate, it was originally based on an ad hoc derivation of the Lorentz transformation for times to account for the negative speed of light experimental results. They were derived for special cases (the length contraction may have later been added on as a postulate--I don't remember for sure). Einstein-Minkowski is a foundational theory that is applied for the most general case. It is not surprizing that Lorentz's electron theory should be compatible with Einstein's general theory for electrodynamics. Actually, Lorentz's original formulations had error's that were corrected by Poincare' and others. And Poincare' actually carried Lorentz's theory into the more general arena (which I think was a departure from the original intent of the theory) and understood the Lorentz transformations to form a group (I believe it was Poincare' who coined the term Lorentz transformation).

All of those are excellent philosophical/historical reasons for prefering the block universe interpretation of the LT over the LET interpretation of the LT.

 

[Tomahoc]

The Earth and the missile are both moving in the ether frame, so t = 30 seconds in the ether frame is *not* t' = 30 seconds in the Earth frame or the missile frame. You keep on switching numbers around so I'm not sure which numbers you are thinking of for this example, but if we take 0.9999c as the speed of the Earth and the missile in the ether frame, then gamma is about 71, so t = 30 seconds in the ether frame corresponds to t' = 30/71 seconds, or about t' = 0.42 seconds in the Earth frame or the missile frame. So a tachyon that travels instantaneously in the ether frame, and is launched at t = 30 seconds in the ether frame, will hit the Earth (or the missile) when the Earth's clock (or the missile's clock) reads about 0.42 seconds.

Oh I thought the time in the Earth frame and aether frame is the same. How do you compute for time in the aether frame. For example. The instantaneous tachyons moving with fixed velocity in the aether frame is launched at t = 30 seconds in the Earth frame to the missile..

What would be the corresponding time in the aether frame?

 

[PeterDonis]

Oh I thought the time in the Earth frame and aether frame is the same.

You said quite a few posts ago that you wanted to have the aether frame be different from the Earth frame, so that's what I was assuming.

How do you compute for time in the aether frame.

You have to first know which frame it is. If you know which frame is the aether frame, you can just use the Lorentz transformation to find any times or distances you like in that frame, if you know them in some other frame (like the Earth frame).

The instantaneous tachyons moving with fixed velocity in the aether frame is launched at t = 30 seconds in the Earth frame to the missile..

What would be the corresponding time in the aether frame?

It depends on which frame is the aether frame; see above. Since nobody has an actual physical theory that says which frame is the aether frame, there's no way of really answering these questions. I've said that repeatedly already.

 

[bobc2]

OK, then the conversation should really be concluded. Since they both use the LT for all of their experimental predictions then all of their experimental predictions must be identical. Since all of their experimental predictions must be identical there can be no experiment which could distinguish between the two.

Do you disagree in any way with that chain of reasoning? If so, please explain.

Given the assumptions you've been making, your logic seems valid. While my intuition tells me that too much significance is given to the Lorentz ether theory, I still haven't performed the due diligence in digging through the sequence of papers by Lorentz, Poincare', Heaviside, and others that would be required to correctly assess the basis for LET in its final form. I'm not sure Lorentz's original rationale for advancing the stationary ether (with the electric field states) was carried through with all of the revisions of the theory that occurred over some 10 or 15 years.

Perhaps this means I should yield the point to you for now. I don't think my colleague Vandam would back away so easily. I can understand how he would be so tenacious in discounting LET (remember his citing Lorentz's own resignation) and affirming the 4-dimensional universe as physical reality.

I realize that the attempt to distinguish between LET and Einstein-Minkowski is considered a philosophical endeavor, but this is where I disagree. My intuition is that physicists have not performed the due diligence on the physics side in identifying the correct theory. I'm not sure that the search for an experimental program yielding the distinction has been fully explored. I've cited the results of entanglement experiments, but it is clear that respondents here have not understood the thrust of my argument.

Anyway, this is a good point to let this discussion take a rest.

 

[Tomahoc]

You said quite a few posts ago that you wanted to have the aether frame be different from the Earth frame, so that's what I was assuming.



You have to first know which frame it is. If you know which frame is the aether frame, you can just use the Lorentz transformation to find any times or distances you like in that frame, if you know them in some other frame (like the Earth frame).



It depends on which frame is the aether frame; see above. Since nobody has an actual physical theory that says which frame is the aether frame, there's no way of really answering these questions. I've said that repeatedly already.

If the aether frame is the common origin where both Earth and missile left at 0.9999c then we can use your gamma factor of 71 and aether t = 30/71 seconds, or about aether t = 0.42 seconds, do you agree?

If the aether frame is elsewhere. Do you believe it is still possible to consider it as a common origin?

About aether as a concept. Do you think Aether is connected with physical interpretation of everything. So if there is aether, then particles have definite positions before measurements and the universe is really solid? Does aether signify or stand for gross physicality?

 

[PeterDonis]

My intuition is that physicists have not performed the due diligence on the physics side in identifying the correct theory. I'm not sure that the search for an experimental program yielding the distinction has been fully explored.

I'm not sure where one would start, particularly since, as you have already pointed out in this thread, nobody is seriously pursuing LET as an alternative theory. The math of SR has been extremely well confirmed by experiment, within its domain of validity, and in so far as an "interpretation" is required at all, everybody in the field seems to be using the Einstein-Minkowski interpretation. That's not to say that everybody in the field would agree with the strong claims about the "block universe" that some have made; but I think everybody in the field (or at least almost everybody) would agree with the weaker claim that 4-D spacetime is a good model at an appropriate level of approximation.

I've cited the results of entanglement experiments, but it is clear that respondents here have not understood the thrust of my argument.

This probably deserves its own thread, possibly in the quantum physics forum instead of this one.

 

[PeterDonis]

If the aether frame is the common origin where both Earth and missile left at 0.9999c then we can use your gamma factor of 71 and aether t = 30/71 seconds, or about aether t = 0.42 seconds, do you agree?

I think I understand what you mean here, but your way of phrasing it can be misleading. A frame is more than just an "origin". What I think you mean is: the aether frame is a frame whose origin is the event on the Earth's worldline at which the missile is fired, and in which the Earth is moving in one direction at 0.9999c and the missile is moving in the opposite direction at 0.9999c.

If the aether frame is elsewhere. Do you believe it is still possible to consider it as a common origin?

This is why I think your way of phrasing things above can be misleading. The "common origin" of the Earth and the missile is an invariant; it's the event on the Earth's worldline at which the missile is fired. The definition of that event doesn't depend on which frame you're in.

As far as where you place the origin of the aether frame, I don't think it matters, since a translation in space and/or time (which just shifts the origin without doing anything else) doesn't change any of the physics. But of course taking that attitude to its logical conclusion would lead you to discard the aether frame altogether and just use standard SR, since Lorentz transformations also don't change any of the physics.

About aether as a concept.

I don't think "aether" is a single well-defined concept; various people use it to refer to different ideas. As I've said before, I'm not aware of any currently viable physical theory that uses the concept, so I don't think your questions about it as a concept can be answered.

 

[Tomahoc]

I think I understand what you mean here, but your way of phrasing it can be misleading. A frame is more than just an "origin". What I think you mean is: the aether frame is a frame whose origin is the event on the Earth's worldline at which the missile is fired, and in which the Earth is moving in one direction at 0.9999c and the missile is moving in the opposite direction at 0.9999c.



This is why I think your way of phrasing things above can be misleading. The "common origin" of the Earth and the missile is an invariant; it's the event on the Earth's worldline at which the missile is fired. The definition of that event doesn't depend on which frame you're in.

As far as where you place the origin of the aether frame, I don't think it matters, since a translation in space and/or time (which just shifts the origin without doing anything else) doesn't change any of the physics. But of course taking that attitude to its logical conclusion would lead you to discard the aether frame altogether and just use standard SR, since Lorentz transformations also don't change any of the physics.

You mean someday a billion years from now if it was discovered that tachyons really use the aether frame and its velocity is fixed to it and we can contract Andromeda instantaneously. It doesn't matter where the aether frame is? (you described that "a translation in space and/or time (which just shifts the origin without doing anything else) doesn't change any of the physics)? Is it valid here?

I don't think "aether" is a single well-defined concept; various people use it to refer to different ideas. As I've said before, I'm not aware of any currently viable physical theory that uses the concept, so I don't think your questions about it as a concept can be answered.

 

[PeterDonis]

You mean someday a billion years from now if it was discovered that tachyons really use the aether frame and its velocity is fixed to it and we can contract Andromeda instantaneously. It doesn't matter where the aether frame is?

It would matter in that case, yes (more precisely, it would matter what state of motion the aether frame was in--i.e., what its speed was relative to other frames like the Earth frame--see further comments below). But if we made such discoveries it would not just be an addition to our current theories; it would falsify them, because it would allow causal connections between events that are spacelike separated. Our current understanding of causality does not allow for that.

(you described that "a translation in space and/or time (which just shifts the origin without doing anything else) doesn't change any of the physics)? Is it valid here?

A translation (moving the origin of a frame without changing anything else) doesn't change the speed of anything relative to any frame, nor does it change the meaning of "instantaneously".

 

[Tomahoc]

It would matter in that case, yes (more precisely, it would matter what state of motion the aether frame was in--i.e., what its speed was relative to other frames like the Earth frame--see further comments below). But if we made such discoveries it would not just be an addition to our current theories; it would falsify them, because it would allow causal connections between events that are spacelike separated. Our current understanding of causality does not allow for that.



A translation (moving the origin of a frame without changing anything else) doesn't change the speed of anything relative to any frame, nor does it change the meaning of "instantaneously".

You said earlier above it would matter, then below.. you said it doesn't change anything. So why does it matter? Maybe to synchronize the tachyon stations on Earth and Andromeda?

Right now. If one of the public speaks about tachyons or FTL... scientists would immediately yell.. "Relativity forbids it"... inquiring further.. you will hear the reasoning... "because FTL can violate causality"... not many of the public can argue ".. but the tachyons velocity is fixed relative to Aether frame so no causaity violated and instantaneous signal across the universe possible"... anyway.. how many percentage of physicists are familiar with this reasoning that "if the tachyons velocity is fixed relative to aether, instantaneous signalling is possible without causality violation?", all of them? or are there portions who haven't heard or thought of the possibility?

 

[PeterDonis]

You said earlier above it would matter, then below.. you said it doesn't change anything.

No, I said that whether "it" matters depends on what "it" is. You have asked about a number of different things in different scenarios; there isn't one single answer that applies to all of them. I have said that repeatedly.

In the particular post you quoted, I even stated explicitly what matters: the *speed* of the aether frame, relative to other frames of interest (like the Earth frame) matters. The *placement of the origin* of the aether frame does not matter.

but the tachyons velocity is fixed relative to Aether frame so no causaity violated

No, that's not correct. You even quoted my statement of why it's not correct: "it would allow causal connections between events that are spacelike separated. Our current understanding of causality does not allow for that." Please read what I post more carefully before asking questions or raising issues that I've already addressed.

What fixing the tachyon speed relative to an aether frame *does* avoid is having closed causal loops. But avoiding closed causal loops is not sufficient to avoid violating causality period.

how many percentage of physicists are familiar with this reasoning

I don't know how many physicists have spent time thinking in detail about these things, but nothing I've said in this thread would be at all difficult for physicists in the field to understand. There have been a number of physics papers published on tachyons, so they are not an unfamiliar concept.

As far as what I said above about causality, the principle I gave--that spacelike separated events cannot be causally connected--is used everywhere that relativity is used in physics. Violating that principle would be a *huge* issue; all sorts of things in various fields depend on it.

 

[Tomahoc]

No, I said that whether "it" matters depends on what "it" is. You have asked about a number of different things in different scenarios; there isn't one single answer that applies to all of them. I have said that repeatedly.

In the particular post you quoted, I even stated explicitly what matters: the *speed* of the aether frame, relative to other frames of interest (like the Earth frame) matters. The *placement of the origin* of the aether frame does not matter.



No, that's not correct. You even quoted my statement of why it's not correct: "it would allow causal connections between events that are spacelike separated. Our current understanding of causality does not allow for that." Please read what I post more carefully before asking questions or raising issues that I've already addressed.

What fixing the tachyon speed relative to an aether frame *does* avoid is having closed causal loops. But avoiding closed causal loops is not sufficient to avoid violating causality period.

Causality is related to time ordering, correct? Events at spacelike is not causality connected because it takes time for light to travel. This is why I think causality can be violated if they are connected at spacelike. But our tachyons moving fixed to aether frame changed that. Isn't it tachyons can connect events that are spacelike separated, this is the context of what I mean tachyon would avoid causality violation. Why, how do you define or what is the context of your "causality violation"?

I don't know how many physicists have spent time thinking in detail about these things, but nothing I've said in this thread would be at all difficult for physicists in the field to understand. There have been a number of physics papers published on tachyons, so they are not an unfamiliar concept.

As far as what I said above about causality, the principle I gave--that spacelike separated events cannot be causally connected--is used everywhere that relativity is used in physics. Violating that principle would be a *huge* issue; all sorts of things in various fields depend on it.

 

[PeterDonis]

Causality is related to time ordering, correct?

Yes; on our current understanding, the time ordering of causally connected events must be invariant--i.e., it must be the same in every frame.

Events at spacelike is not causality connected because it takes time for light to travel.

No; they can't be causally connected because their time ordering can be different in different frames. Adding tachyons doesn't change that.

 

[Tomahoc]

Yes; on our current understanding, the time ordering of causally connected events must be invariant--i.e., it must be the same in every frame.



No; they can't be causally connected because their time ordering can be different in different frames. Adding tachyons doesn't change that.

Do you mean "adding tachyons does change that" or "doesn't change that"? Because earlier you stated "But if we made such discoveries it would not just be an addition to our current theories; it would falsify them, because it would allow causal connections between events that are spacelike separated. Our current understanding of causality does not allow for that".

So adding tachyons does change that. So your "doesn't" was a typo?

 

[PeterDonis]

Do you mean "adding tachyons does change that" or "doesn't change that"?

Adding tachyons doesn't change the fact that the time ordering of spacelike separated events is not frame invariant.

Because earlier you stated "But if we made such discoveries it would not just be an addition to our current theories; it would falsify them, because it would allow causal connections between events that are spacelike separated. Our current understanding of causality does not allow for that".

Allowing spacelike separated events to be causally connected would force us to modify all of the theories we have (which, as I said, is a lot of them) that assume that the time ordering of causally connected events must be frame invariant.

To see how drastic this would be, consider a commonplace causal phenomenon: I throw a baseball that breaks a window. If the baseball were made of tachyons, then in some frames those events would be in reverse order: to observers at rest in such frame, it would look like the window spontaneously reassembled itself as the baseball moved through it towards my hand.

 

[Tomahoc]

Adding tachyons doesn't change the fact that the time ordering of spacelike separated events is not frame invariant.



Allowing spacelike separated events to be causally connected would force us to modify all of the theories we have (which, as I said, is a lot of them) that assume that the time ordering of causally connected events must be frame invariant.

To see how drastic this would be, consider a commonplace causal phenomenon: I throw a baseball that breaks a window. If the baseball were made of tachyons, then in some frames those events would be in reverse order: to observers at rest in such frame, it would look like the window spontaneously reassembled itself as the baseball moved through it towards my hand.

But remember ordinary matter including light is frame dependent. Only the tachyons are not. So ordinary matter are not affected. Ordinary matter time ordering of causally connected events are still frame invariant even if there are tachyons.

If you still mean it. Try giving an example where baseball and tachyons are separate entities and how the former can be affected. All I know is that only tachyons emission and detection would have this time ordering affected.. not the ordinary matter.

 

[PeterDonis]

But remember ordinary matter including light is frame dependent. Only the tachyons are not. So ordinary matter are not affected. Ordinary matter time ordering of causally connected events are still frame invariant even if there are tachyons.

Yes. So what? If tachyons are allowed, then there are still going to be causally connected events that are spacelike separated. It doesn't matter that not *all* causally connected events are spacelike separated; having *any* of them be so is enough.

Try giving an example where baseball and tachyons are separate entities and how the former can be affected.

If tachyons can't affect objects that aren't tachyons, and vice versa, then tachyons effectively don't exist; there's no way to detect them and no way to affect them, because we and all of our scientific instruments aren't made of tachyons, we're made of ordinary matter. There's no point in discussing tachyons if they can't interact with ordinary matter; we can simply ignore them.

 

[Tomahoc]

Yes. So what? If tachyons are allowed, then there are still going to be causally connected events that are spacelike separated. It doesn't matter that not *all* causally connected events are spacelike separated; having *any* of them be so is enough.



If tachyons can't affect objects that aren't tachyons, and vice versa, then tachyons effectively don't exist; there's no way to detect them and no way to affect them, because we and all of our scientific instruments aren't made of tachyons, we're made of ordinary matter. There's no point in discussing tachyons if they can't interact with ordinary matter; we can simply ignore them.

Even without tachyons there are some problems with inconsistency. Going to the train example and 2 lightnings hitting both ends. It is said in:

http://www.rafimoor.com/english/SRE.htm

"Suppose we put two photoelectric cells at point P on the train where the two flashes of light meet in the man’s frame. One of the cells is directed to the front of the train and the other to the back. Now we connect the cells to a bomb in a way that if the two cells are illuminated simultaneously the bomb explodes. In the man’s frame the bomb will explode. In the woman’s it will not since in her frame the flashes meet by her and not at point P."

The woman is the one sitting on the moving, the man on the station at point P. The website didn't answer if the woman is dead or not. So do you think it explodes? The website didn't give details of what happen at the end. Just look at the illustration as the lightning and train example is classic. So there are some frames it explodes and some frames it doesn't? If not.. does it explode or not?

 

[Dale]

Even without tachyons there are some problems with inconsistency. ... So there are some frames it explodes and some frames it doesn't?

No, there are no problems with inconsistency, and there are no disagreements between frames on whether or not it explodes.

Similar problems are often given as homework in introductory relativity classes.

 

[PeterDonis]

Now we connect the cells to a bomb in a way that if the two cells are illuminated simultaneously the bomb explodes.

The word "simultaneously" is being used here in a different sense than you are interpreting it; it does not refer to two spacelike separated events, but to a single event--a single point in spacetime--at which two things happen (each cell receives a flash). A better way of phrasing how the cells are connected would be: "if the two cells receive light beams at the same spacetime event, the bomb explodes". That phrasing makes it clear that whether or not the bomb explodes is frame-invariant. See further comments below.

In the man’s frame the bomb will explode. In the woman’s it will not since in her frame the flashes meet by her and not at point P."

No, this is not correct. The two flashes do *not* meet by the woman; the woman sees the flash from in front of her *before* she sees the flash from behind her. The two flashes meet at point P even in the woman's frame; the difference is that in the woman's frame, point P is moving, whereas in the man's frame, point P is at rest.

does it explode or not?

It explodes.

 

[Tomahoc]

The word "simultaneously" is being used here in a different sense than you are interpreting it; it does not refer to two spacelike separated events, but to a single event--a single point in spacetime--at which two things happen (each cell receives a flash). A better way of phrasing how the cells are connected would be: "if the two cells receive light beams at the same spacetime event, the bomb explodes". That phrasing makes it clear that whether or not the bomb explodes is frame-invariant. See further comments below.



No, this is not correct. The two flashes do *not* meet by the woman; the woman sees the flash from in front of her *before* she sees the flash from behind her. The two flashes meet at point P even in the woman's frame; the difference is that in the woman's frame, point P is moving, whereas in the man's frame, point P is at rest.



It explodes.

Not so fast. Prior to the paragraph. It is said that "That is, while the man measures the light from the front getting to the woman before the light from the back, the woman sees the light from both sides simultaneously.".

The website especially mentioned that the woman sees the light from both sides simultaneously. So dead or alive, that is the question.

 

[PeterDonis]

Prior to the paragraph. It is said that "That is, while the man measures the light from the front getting to the woman before the light from the back, the woman sees the light from both sides simultaneously.".

Please read more carefully. The statement in quotes is a *hypothetical*, which the author later shows to be false. He is *not* stating it as an actual conclusion of relativity.

[Edit: The same is true of the statement I said was incorrect: "in the woman's frame it will not since in her frame the flashes meet by her and not at point P"--it is also part of the hypothetical, which the author later shows to be false.]

 

[Tomahoc]

Please read more carefully. The statement in quotes is a *hypothetical*, which the author later shows to be false. He is *not* stating it as an actual conclusion of relativity.

[Edit: The same is true of the statement I said was incorrect: "in the woman's frame it will not since in her frame the flashes meet by her and not at point P"--it is also part of the hypothetical, which the author later shows to be false.]

Ok. I'll look into them. For now. I'm looking for web sites that illustrates what you mentioned that "If tachyons are allowed, then there are still going to be causally connected events that are spacelike separated. It doesn't matter that not *all* causally connected events are spacelike separated; having *any* of them be so is enough.".

Know any such website with spacetime diagrams of tachyons and effects on causality to get me busy this weekend.

Or maybe an actual example you already knew. If the baseball is made up of normal matter and throws into a windows. If no tachyons, there is no frames where the order is reverse? If there are tachyons flying alongside.. how come it can be reverse? I get the essence, but want exact details of how the worldline details work that can make the ordering reverse or chaotic. Thanks.

 

[PeterDonis]

For now. I'm looking for web sites that illustrates what you mentioned that "If tachyons are allowed, then there are still going to be causally connected events that are spacelike separated.

This follows from the definition of tachyons: they travel faster than light. That means they travel on spacelike worldlines, so successive events on a tachyon's worldline are spacelike separated.

If the baseball is made up of normal matter and throws into a windows. If no tachyons, there is no frames where the order is reverse?

If the baseball is made of normal matter, then it travels on a timelike worldline. The time ordering of events on a timelike worldline is frame invariant. (The same is true of the ordering of events on a lightlike worldline, so a "baseball" made of photons would be the same in this respect as a baseball made of normal matter.)

If there are tachyons flying alongside.. how come it can be reverse?

Please read carefully. I didn't say "a baseball with tachyons flying alongside it"; I said "a baseball *made of* tachyons". That means the baseball itself is moving faster than light.

I get the essence, but want exact details of how the worldline details work that can make the ordering reverse or chaotic. Thanks.

See above. The time ordering of events on a spacelike curve is frame-dependent. That's just a basic fact about spacelike curves.

 

[Tomahoc]

Adding tachyons doesn't change the fact that the time ordering of spacelike separated events is not frame invariant.



Allowing spacelike separated events to be causally connected would force us to modify all of the theories we have (which, as I said, is a lot of them) that assume that the time ordering of causally connected events must be frame invariant.

To see how drastic this would be, consider a commonplace causal phenomenon: I throw a baseball that breaks a window. If the baseball were made of tachyons, then in some frames those events would be in reverse order: to observers at rest in such frame, it would look like the window spontaneously reassembled itself as the baseball moved through it towards my hand.

Ah. As long as closed causal loop is solved by tachyons moving fixed in aether frame. There is no problem about reverse order. I mean. When you rewind your video tape or fast forward them. It is just in the function. One knows that window doesn't spontaneously reassemble. So if a frame shows that. We can say "Ah, it's just an artifact"... unless you want to argue that what happens in a frame actually happens such that the window spontaneously reassemble? But then we can just say to ignore it... and just treat the normal ordering as actual with the reverse order virtual like virtual particles.. just an artifact effect.

 

[Dale]

Given the assumptions you've been making, your logic seems valid.

Good, I am glad that you agree with that much at least.

While my intuition tells me that too much significance is given to the Lorentz ether theory

Honestly, I don't place any significance on LET, it is merely the most well-known counter example to the Vandam's false claim that the experimental evidence we have to date can only be interpreted as a block universe and not as any other interpretation as well as his other false claim that the relativity of simultaneity implies a block universe.

I can understand how he would be so tenacious in discounting LET (remember his citing Lorentz's own resignation)

Lorentz's disavowal of LET is historical trivia and not relevant to the question of whether or not the evidence supports it. Science isn't a popularity contest, the only vote that counts is nature's.

I'm not sure that the search for an experimental program yielding the distinction has been fully explored.

If you wish to continue the search then this is where you need to focus your efforts. The task is fairly clear: find an experiment where LET predicts X and block-universe predicts Y with X≠Y. I don't believe the task is possible, for the reasons stated above, but at least it is clear.

What you can say that is not overstepping is that the evidence is consistent with a 4D universe. You can also talk about the many aesthetic, practical, and philosophical advantages of the block-universe approach over other approaches, like LET. If you don't claim that the block universe is the only interpretation supported by the evidence then your drawings and explanations would be quite beneficial, I think. And there is certainly nothing wrong with simply stating that it is your clear personal preference.

 

[PeterDonis]

One knows that window doesn't spontaneously reassemble.

But how do we know that? Because we always see the events in the same order: throw baseball, then window breaks. If baseballs made of tachyons were commonly observed, and we commonly saw the events in the opposite order, we might not be so confident that we knew which order was the "right" one.

unless you want to argue that what happens in a frame actually happens such that the window spontaneously reassemble?

Part of the standard physical interpretation of a frame is that "what happens in a frame actually happens", yes. There is no room in the standard interpretation for some observations made in a frame to be "artifacts".

and just treat the normal ordering as actual with the reverse order virtual like virtual particles

Since you mention virtual particles, it's worth bringing up the point that if we include quantum mechanics, we can no longer say that tachyons can actually transmit information or causal influences faster than light. See here:

http://math.ucr.edu/home/baez/physics/ParticleAndNuclear/tachyons.html

The same is actually true of virtual particles: virtual particles in quantum field theory can travel faster than light, but they can't be used to transmit information or causal influences faster than light, for the same sorts of reasons as tachyons can't be used that way as explained in the article above.

 

[jk22]

I think there are experiments checking the constancy of the speed of light no matter what the motion of the observer is in the so called emission theory (see Wikipedia), for example by measuring the speed of sun light during spring and autumn or from binary star systems and no significant difference could be found.
Another way to test it is the Sagnac interferometer that uses rotating mirrors.