Pair Production

[texta]

Consider a closed system in which a positron and electron are the only members.

The positron and electron collide producing two gamma ray photons.

What is the velocity of each photon?

[cincirob]

texta: Consider a closed system in which a positron and electron are the only members.

The positron and electron collide producing two gamma ray photons.

What is the velocity of each photon?

cinci: The speed of light.
*********************

[texta]

texta: Consider a closed system in which a positron and electron are the only members.

The positron and electron collide producing two gamma ray photons.

What is the velocity of each photon?

cinci: The speed of light.
*********************

Speed of light relative to what?

[cincirob]

texta: Speed of light relative to what?

cinci: Relative to anybody who measures it.
***********************

[CCC]

The speed of light is funny like that. Anything travelling at lightspeed relative to one observer automatically travels at lightspeed relative to all observers...

[CANGAS]

Cheez. This is interesting. And getting interestinger and more interestinger.

There are only, in a postulated closed system, a limited gallery of observer candidates.

All of established physics, be it Newton or Einstein brand, has been developed from study of a system (Universe), which is controversial re whether it is closed or open.

We cannot be certain about if our theories, derived within a controversial system, hold true in a specifically defined system.

[cincirob]

CANGAS: Cheez. This is interesting. And getting interestinger and more interestinger.

There are only, in a postulated closed system, a limited gallery of observer candidates.

All of established physics, be it Newton or Einstein brand, has been developed from study of a system (Universe), which is controversial re whether it is closed or open.

We cannot be certain about if our theories, derived within a controversial system, hold true in a specifically defined system.

cinci: Thanks.
******************

[CANGAS]

CANGAS: Cheez. This is interesting. And getting interestinger and more interestinger.

There are only, in a postulated closed system, a limited gallery of observer candidates.

All of established physics, be it Newton or Einstein brand, has been developed from study of a system (Universe), which is controversial re whether it is closed or open.

We cannot be certain about if our theories, derived within a controversial system, hold true in a specifically defined system.

cinci: Thanks.
******************

For what?

With no specifically defined system, the limited gallery of observers may judge their velocity/speed to be anything from zero to infinite.

[OZLOFT]

The speed of light is funny like that. Anything travelling at lightspeed relative to one observer automatically travels at lightspeed relative to all observers...

Quite right CCC, and the reason it does so is due to the Doppler Ensemble nature of light. The gamma-ray photons created by the collision of positron and electron move away in opposite directions, their 'gamma-ray' intensity evident only to an observer at rest to the collision. Were the observer moving rapidly in one direction or the other he would observe a resultant emission photon from the collision at a wavelength proportional to his relative velocity i.e. relative to the collision.
There is no question about spacetime warps or other such nonsense. Even Blathers will have to admit here that the two gamma-ray photons are moving away from each other at twicethe speed of light though he will only admit half this value. The radio-wavelengths of the Doppler Ensemble comprising each photon are of course moving away from each other many thousands of times the speed of light! As you can see, once we dump SR, we can start to understand things objectively and physically without intruding all the relativity-based nonsense.
Yours faithfully
OZLOFT

Apologies to everyone for having to reedit/insert the highlighted words.

[texta]

Hi Guys,

Sorry for my delayed reply, i've been quite busy with work lately.

If all motion is relative, then the only meaningful velocity we can assign to each gamma ray is one which is measured relative to an observer. I think that most relativists would say that gamma rays are not valid observers. That's fine, but we still need to define the behaviour of the two gamma ray photons. In this closed system after the collision there are no observers.

If we are to insist that the rays move at the speed of light, while at the same time stating that the rays themselves do no constitute observers, then we must conclude the existence of an absolute reference frame. I find it odd that the people most in opposition to an absolute reference frame are the first to assume the velocity of C upon the gamma rays. In effect it's an argument for an absolute frame of reference.

At this stage I see only 3 valid answers to my question:

1) The closed system is not physically possible.
2) The existence of an absolute frame of reference.
3) The validity of EM radiation as an intertial observer.

I think that answers 2 and 3 will lead to logical contradictions in SR. For answer 1 I can imagine scenarios that will lead to most odd results when such a pair production happens very far from valid observers. Also for 1, some logical reasoning must be produced which invalidates the possibility of the closed system.

I suppose another option is to assume that every question asked can be answered without thought. If a question arises which would require the use of our brain perhaps it's best to answer with 'ere be dragons, or equivalently "relative to anybody who measures it".

Personally I prefer well thought out answers.

[OZLOFT]

Greetings once again, texta!

Hi Guys, Sorry for my delayed reply, i've been quite busy with work lately.

If all motion is relative, then the only meaningful velocity we can assign to each gamma ray is one which is measured relative to an observer. I think that most relativists would say that gamma rays are not valid observers. That's fine, but we still need to define the behaviour of the two gamma ray photons. In this closed system after the collision there are no observers.

If we are to insist that the rays move at the speed of light, while at the same time stating that the rays themselves do no constitute observers, then we must conclude the existence of an absolute reference frame. I find it odd that the people most in opposition to an absolute reference frame are the first to assume the velocity of C upon the gamma rays. In effect it's an argument for an absolute frame of reference.

At this stage I see only 3 valid answers to my question:

1) The closed system is not physically possible.
2) The existence of an absolute frame of reference.
3) The validity of EM radiation as an intertial observer.

I think that answers 2 and 3 will lead to logical contradictions in SR.

Your underlined words are a bit of a shocker, texta. I would have thought that the negative MM experiment would have knocked over all notions of an absolute reference frame! So keep up to date by looking at the Doppler Ensemble thread! Why? Because the absolute reference frame and Newtonian absolute space lead to paradoxes of their own.
Yours faithfully,
OZLOFT

[CCC]

If all motion is relative, then the only meaningful velocity we can assign to each gamma ray is one which is measured relative to an observer. I think that most relativists would say that gamma rays are not valid observers. That's fine, but we still need to define the behaviour of the two gamma ray photons. In this closed system after the collision there are no observers.

You know, this is starting to look to me a lot like the old question; if a tree falls in a forest and there's no-one there to hear it, does it make a noise?

If there are no observers, and the lack of observers is a fundamental part of the setup, then this is not going to be testable, is it?

[texta]

Greetings once again, texta!

Hi Guys, Sorry for my delayed reply, i've been quite busy with work lately.

If all motion is relative, then the only meaningful velocity we can assign to each gamma ray is one which is measured relative to an observer. I think that most relativists would say that gamma rays are not valid observers. That's fine, but we still need to define the behaviour of the two gamma ray photons. In this closed system after the collision there are no observers.

If we are to insist that the rays move at the speed of light, while at the same time stating that the rays themselves do no constitute observers, then we must conclude the existence of an absolute reference frame. I find it odd that the people most in opposition to an absolute reference frame are the first to assume the velocity of C upon the gamma rays. In effect it's an argument for an absolute frame of reference.

At this stage I see only 3 valid answers to my question:

1) The closed system is not physically possible.
2) The existence of an absolute frame of reference.
3) The validity of EM radiation as an intertial observer.

I think that answers 2 and 3 will lead to logical contradictions in SR.

Your underlined words are a bit of a shocker, texta. I would have thought that the negative MM experiment would have knocked over all notions of an absolute reference frame! So keep up to date by looking at the Doppler Ensemble thread! Why? Because the absolute reference frame and Newtonian absolute space lead to paradoxes of their own.
Yours faithfully,
OZLOFT

I understand what you are saying but I disagree. The null MM experiment could not detect motion of Earth through a luminiferous aether. That's not the same as an experiment proving without doubt that there is no absolute reference frame.

If we set up a valid thought experiment based on emperical evidence and it leads to the logical conclusion of an absolute reference frame, it means that Einstein's relativity is invalid. If it leads to a contradiction in Newtonian mechanics then it means that Newtonian mechanics is invalid too.

The question is about the validity of the thought experiment and the conclusion of that experiment. It's not good to get too attached to a particular idea in science, whether it be SRT or doppler ensemble theory.

[texta]

If all motion is relative, then the only meaningful velocity we can assign to each gamma ray is one which is measured relative to an observer. I think that most relativists would say that gamma rays are not valid observers. That's fine, but we still need to define the behaviour of the two gamma ray photons. In this closed system after the collision there are no observers.

You know, this is starting to look to me a lot like the old question; if a tree falls in a forest and there's no-one there to hear it, does it make a noise?

If there are no observers, and the lack of observers is a fundamental part of the setup, then this is not going to be testable, is it?

I think it's not a matter of testability. It's a matter of logical deduction.

If we accept as truth the following:

Light is always propagated in empty space with a definite velocity c which is independent of the state of motion of the emitting body.

Then in my experiment the two gamma ray photons must propagate with velocity C. However, in my experiment there are no inertial frames of reference, so the velocity is relative to something inherit in space itself.

If we give any velocity other than C to the two photons, then the postulate is false.

What do you need to test to show logical reasoning?

[OZLOFT]

In reference to my critique of MM, texta, you replied:

I understand what you are saying but I disagree. The null MM experiment could not detect motion of Earth through a luminiferous aether. That's not the same as an experiment proving without doubt that there is no absolute reference frame.

Yet it is certainly very strong evidence for that. In order to justify an absolute reference frame (ARF) you have to find some convincing evidence to the contrary. What's your poison here - the cosmic background radiation? The "fixed stars?" Newton's absolute space? (The latter is implicit in your reply to CCC above).

If we set up a valid thought experiment based on emperical evidence and it leads to the logical conclusion of an absolute reference frame, it means that Einstein's relativity is invalid. If it leads to a contradiction in Newtonian mechanics then it means that Newtonian mechanics is invalid too.

I am not aware of any thought experiment that leads to the logical conclusion of an ARF ; you'll have to enlighten me here. There is a thought experiment that VERY DEFINITELY invalides Newtonian/Lorentzian mechanics however, and it involves the notion of length contraction! (And I hope too that not just yourself but even Dearth Vaguer will hearken to it too, since it will straighten out his dim and droopy light-sabre and let him slash out effectively once more at the bewildered herd of believers in an absolute reference frame for motion who so infest this website!)

The question is about the validity of the thought experiment and the conclusion of that experiment. It's not good to get too attached to a particular idea in science, whether it be SRT or doppler ensemble theory.

Very true, texta, but we have to search to find which theories do NOT lead to logical paradoxes and discard the remainder. Not only Einsteinian and Lorentzian relativity but Newtonian absolute space is in this category!
Yours faithfully,
OZLOFT