Particle creation and annihilation and the remaining fields problem

[heldervelez]

The OP experiment is not addressed by actual theory. By the time of GR development it was thought that matter did existed since ever and no one imagined that matter could vanish into photons.
The problem was never formulated and of course it was never answered in the actual knowledge.
The challenge remains: An answer is needed.

 

[Gokul43201]

To the OP: You haven't exactly asked a question. What is your question? You seem to be implying that your thought experiment demonstrates a violation of some conservation law. Which one? Please be clear and explicit.

 

[malawi_glenn]

The OP experiment is not addressed by actual theory. By the time of GR development it was thought that matter did existed since ever and no one imagined that matter could vanish into photons.
The problem was never formulated and of course it was never answered in the actual knowledge.
The challenge remains: An answer is needed.

Gravity is not related to rest-mass but to the stress-energy tensor, photons feel gravity. The particle which is annihilating on your 'experiment' does so after interaction with its antiparticle and thus create photons. Energy is conserved, no discontinuity in gravitation field.

So there is no challenge remaining

 

[heldervelez]

To the OP: You haven't exactly asked a question. What is your question? You seem to be implying that your thought experiment demonstrates a violation of some conservation law. Which one? Please be clear and explicit.

http://en.wikipedia.org/wiki/Electron-positron_annihilation" are in complete energetic balance (*) .
Therefore, in each experiment, we start and end with 2 photons whith equal energy.

(*) quote...
Matter creation is the process inverse to particle annihilation. It is the conversion of massless particles into one or more massive particles. This process is the time reversal of annihilation.
...
matter creation is allowed by momentum conservation law
...
end-quote

At the beginning and at the end the energy in photons are perfectly equal in both experiments.
By theory, also in both experiments, the energy on matter-antimatter pair particles (electron-positron pair, or neutron-antineutron,...) is also equal.


Comparing the experiments, we can stop talking about the quantities that are equal on both (photons and matter-antimatter particle pair).

The experiments (initial products and final outcomes) can be compared
( 2 photons) -> (pair+Field1) -> ( 2 photons) -- total time of exper. 1 let's say 1 time unit.
( 2 photons) -> (pair+Field2) -> ( 2 photons) -- total time of exper. 2 let's say 2 time unit.

taking off what is equal we can write :

Field1 is equal to Field2
or
Field1 is different from Field2

(Field1 and Field2 are abreviations of Space+Field on experiment 1 and 2)

Do we agree until now?

-----------------------------

next post I will say that the correct assertion is
Field1 is different from Field2

implying that energy content of particle pair at end of experiment 1 MUST be different of energy content of particle pair at end of experiment 2. This is an unexpected result.

 

[malawi_glenn]

What is the field, gravitational field or electromagnetic field?

 

[heldervelez]

Electrons and positrons have mass and generate gravitational effects. Tiny effects that I think not measurable by us.

To make the experiment simpler, and more clear we can choose the gravitational field.
It is not canceled and it has long range effects.

The observers are located in the center of mass where the two photons collided and the pair was produced, in both experiments. And they can measure the effects.

Looking around from that positions the worlds are equal.

 

[malawi_glenn]

If we consider gravity, there is no problem at all since gravity is assigned to energy, not mass as indicated in post #33.

 

[heldervelez]

But in post #34 we get rid of photons because the net effect in both experiments are equal.
...
But now I see your point and I have to prepare myself.
I see a 'wasp nest' now.
I do know that photons 'feels' gravity as you said, in the sense that they will follow the geodesic that curved-space imposes by gravitation. Also that 'gravitation gravitates' as 'the field has energy' (as I also say).
But I do not know if photons contribute to gravity field.
I did found a lot of threads on this forum about the subject, and a lot of discussion and no consensus.

By http://www.bartleby.com/173/" I see that the equivalence of inertial mass with gravitational mass is the basis of GR formulation. On that Einstein paper I saw no reference on photons as possible gravity sources.

When I wrote the OP I was not considering that photons could have inertial mass (neither gravitational mass). And I see now, that you consider the opposite.
By experimentation it seems almost impossible because we can not assemble zillions of photons to measure. (the 'almost' word is there just in case). But this is not the point in question.

This week-end I will study the arguments against my position.

 

[malawi_glenn]

Consider a container filled with photons, the container will have mass. That is the "experiment"

 

[Vanadium 50]

If photons fall to Earth (as has been measured) but do not themselves generate a gravitational field, momentum conservation is violated.

 

[heldervelez]

Consider a container filled with photons, the container will have mass. That is the "experiment"

Have energy for sure (water: compare water vapour with ice, they are the same but not alike) and a mass equivalent (another way of expression of energy).

 

[heldervelez]

I was wrong when I wrote that photons have not inertial mass. Yes they have inertial mass (i.e. bend on accelerated frames) and have gravitational mass (i.e. bend on gravitational fields).
About beeing or not responsables themselves as sources of gravity field is more critical.
I need more readings (In GR it is said yes, I found it on the 1916 papper), but do we have an experimental confirmation? It could be done, to prove or disprove, the assertion that light are sources of gravity (independently of GR saying so).
With extreme power lasers of today and try to bend the trajectories of UCN (ultra cold neutrons) beam.
Does anyone know of an experiment that proves that light is source of gravitational effects ?

May be old fashion but I represent a 'field' with some sentences.
Field means a need for the existence of a gradient.
Without gradient there is no 'field'.
Field means also: the ability of action on a distance, timely of course, not instant action!
Without fields the universe would be static.
With instant action at distance, the universe would be magical, without laws. No cause, no consequence, no previous nor next events.

Suppose all space of universe filled with photons.
Then the distribution of energy thru space has to be considered uniform, and the space has plenty of energy. Is this gravitational energy ? To me is energy, but not 'field'.

May be we wish to call it gravitational energy. But to me is enough call it energy.

Suppose that below is a representation of an infinite world of equal particles at rest and with a isotropic and constant distribution of mass.
Each particle remains at rest, and keeps at rest, and see no 'field'.

...
...
... ...........
... ...........
... ...........
... ...........
... ...........
... ...........
... ...........
... ...........
... ...........
... ...........
...
...

I see energy, (mass) (or gravitational energy ?) but I do not see field.

The same for a universe of photons.
Photons are not 'localized' like we 'think' about 'particles'.
What is the configuration of the gravitational field associated to a photon ?
(With a definite mass we remember the rubber sheet association)
The photon also as 'c' speed. How do field 'spread' in the space around 'what?'.
Having zero rest mass and traveling at 'c' speed, makes photons the limiting case for all other positive finite masses, not one of them. How gravitons (*) could interact with a wavefront moving a 'c' ?

(*) I do not like the gravitons idea. It has to have some other, more appealling ways of explaining gravitational interactions. Why the need of gravitons if it is the space that is 'bended' and the natural path for anybody is to follow the geodesic? The space itself makes the road from where there is no chance to deviate.

Later I will continue the OP experiment. This post was to express some difficulties with the notion of field (may be I'm old fashion) , and that, it is not clear why and how light contributes to gravity.

"Usually photons are not confined in a container, aka mirrored box"

I will try to continue the thread even if we disagree with the above questions.

 

[malawi_glenn]

heldervelez, we can help you find a modern textbook on GR - in 1916 there was not so many proofs for GR, but now we are 90 years later! GR is one of the best proven theories in physics, Einstein was not elected "person of the century" by Times for nothing.

So, yes, you are a bit old fashioned. You should study modern GR (Einsteins theory + applications + observational / experimental verifications). And you should also study modern Quantum Field theory.

Then you can start to study Grand Unification theories and Theories of Everything -> the reason for 'why we want' gravitons is that GR is a NON QUANTUM theory and everything else is Quantum theory (strong force, weak force and electromagnetism). So one would like to have a quantum theory of Gravity as well.
Then we have shown that the weak force and electromagnetism are really ONE force, but this is only manifested at very high energies -> Electroweak unification. So one would like to unify all forces into one. String theory is the most studied candidate for this.

So this was some introduction to what contemporary physics is.

 

[heldervelez]

https://www.physicsforums.com/showpost.php?p=1899079&postcount=1" points to a document were are done all the calculations that prove my point.

This kind of problem is not addressed in textbooks, and we have to do the homework.

The textbooks AFAIK only addresses the fields already settled in space for ages, as if matter had an infinite age and as if the field had an infinite speed of propagation. We may consider theese points as details, not written in the equations and make all the difference.

The formalism involved is nothing more than plain electromagnetism.

Tha calculations are 'facts'/evidence. The author's conclusions/paradoxes I do not share. A priori they are out of the scope of the discussion.

I made my case(*) if the calculations are not proved wrong.

Calculate the energy that fills two infinitesimal shells, centered at the mass/charge point, traversed at times t1 and t1+dt and t2 and t2+dt by integrating in those volumes the energy density (electrostatic, magnetic, or gravitational field) of a propagating field, at 'c' speed.
The distance to the center is, say, x1 and x1+c.dt for the first shell and x2 and x2+c.dt for the second shell.

Resulting :
E1=Energy within the 1st shell = Konstant * c*dt /((x1 + c*dt) * x1)
E2=Energy within the 2nd shell = Konstant * c*dt /((x1 + Dx +c*dt) *( x1 +Dx) )
resulting »» 0 < E1 < E2

beeing Dx = x2 -x1 (distance between both shells)
Konstant = Q^2/(8*pi*eps0) beeing Q the charge
the Konstant will have other value for the gravitational case.

-----------------------
Turtur, Claus W. (2007).
Two Paradoxes of the Existence of electric Charge.
arXiv:physics/0710.3253 v1

Abstract
A thought experiment is considered in which somebody observes an electrical charge, moving with constant speed relatively to a given frame of reference, in which the observer is in rest. Let us further assume that no electric fields and no magnetic fields interact with this moving charge, so that there is no force acting on the charge. Consequently it keeps constant speed.
But the moving charge itself produces a magnetic field within the reference frame. Because the moving charge does not alter its speed and thereby its energy, it can not emanate any power. But the generated magnetic field contains energy, and we can calculate the power being emanated from the moving charge, which we find to be not constant as a function of time. The existence of this energy and the alteration of the power is a first paradoxon of the magnetic field.
If we follow the trace of a specified element of volume containing field energy, a further calculation proves, that this contents of energy decreases during time. This unexplained loss of energy as a consequence of the mere propagation in space is a second paradoxon of the magnetic field.

by
Prof. Dr. Claus W. Turtur
University of Applied Sciences Braunschweig-Wolfenbüttel

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(*) I have made a mistake when I invoked the energy conservation of the problem. As calculations showed I was wrong.

My sincere tanks to Mr malawi for the fairness,
and with a bit of irony , also the solicitude in pointing me 'a modern textbook on GR'. I do know that GR and SR are valid, but the details..., probably are not written on any textbook.