Does My Wrist Watch Physically Beat Slower?

[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.