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Particle creation and annihilation and the remaining fields problem

  1. Nov 13, 2008 #1
    lets simulate this simple experiment:

    creation followed by annihilation of 2 equal particles of type P, here named P1 and P2. (*)
    assuming the precursors before creation as usual, and also residuals as usual after annihilation.
    The question is about the remaining fields, gravitational and/or electromagnetic.

    Let 's' = Space and 'f' = Space With Field
    (they are physically different, for sure demonstrated by a test particle )

    -- Experiment P1
    T0 P1 created...........: p1 ssssssssss
    T1 field expands........: p1 fsssssssss (at c speed)
    T2 .........expands.....: p1 ffssssssss
    T3 P1 annihilated.......:....fffsssssss
    T4 .......... expands...:....sfffssssss

    -- Experiment P2 (far away of experiment 1, for sake of simplicity)
    T0 P2 created...........: p2 ssssssssss
    T1 field expands........: p2 fsssssssss
    T2 .........expands.....: p2 ffssssssss
    T3 ..........expands....: p2 fffsssssss
    T4 ...........expands...: p2 fffsssssss
    T5 ............expands..: p2 fffffsssss
    T6 P2 annihilated.......:....ffffffssss
    T7 ............ expands.:....sffffffsss
    T8 ............. expands:....ssffffffss

    Being equal the precursors in the creation and the residuals after annihilation on both experiments we have two different 'Space And Field' .

    The quantity 'Space And Field' is dependent on particle antiquity.

    And so, if the particles are equal in the beginning they must be different in dead, or 'free lunch' is permitted in physics!

    (*) assuming, for instance, two photons <-> electron/positron pair, and equal energy on start of both experiments.

    What is the correct answer to this physical problem :confused:
  2. jcsd
  3. Nov 13, 2008 #2


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    You mean that the field is left even after the particle has been annihilated?

    This is related to the question: if the sun suddenly dissapears, when will the earth notice?
  4. Nov 13, 2008 #3
    After the source of gravity/electromegnetic field has vanished the field already present in the space, continues propagating, at c speed.
    Fields dont get annihilated, by no means.
    And even without the presence of the source they can perform work on any test particle.
    As noted in the post, the account of 'space with field' is different on both experiments, and as they are physical realities, they must also be accountable on net energy balance.
    Usually on learning, and teaching, the annihilation and creation of particles, the problematic associated with the fields is missing from discussion.
    I'would like to see some reasoning about this theme in this forum.

    a perturbing conclusion is that all particles of type P are not equal.

    I presume that you know that if our Sun could 'somehow' suddenly vanish, our Earth will keep moving in a strait line and abandon the regular orbit, at the same instant that the Sun became invisible ( +-8 minutes after 'puff' -- distance Sun-Earth at c speed).
    this fact is only partially related to the enunciated question.

    the ultimate question is:
    all particles of type P are not equal.

    my sensibility prevents me from accepting some kind of answer saying that the fields have no energy, because they had to have 'something'. Beeing so, 'something' must be accountable.
  5. Nov 13, 2008 #4


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    Will the gravity dissapear at earth be removed at the same instant as the sun disapears. That was the analogy -> Will field exist, even without a particle/source?
  6. Nov 13, 2008 #5
    not at the same instant that 'Sun disapears' but delayed by the propagation of light/ gravity. There is no such thing as 'instant action at distance', c speed is the limit to propagate any physical quantity/effect.

    Beeing so, fields does not vanish. They propagate.
    As they spread into space at c speed in the presence of the source, also they keep spreading at c speed after extinction of the source, forever .
  7. Nov 13, 2008 #6


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    but the intensity goes to zero... ;-)

    I can't really see what your question is, since P2 is annihillated at a later time than P1, thus the fields will be different? I dont know what you are after here.
  8. Nov 13, 2008 #7
    of course 'quantity of space with field' at the end of both experiments are different.
    lets put side by side a simple representation at the annihilation
    let Space be = space without field ; Field = space with field; (field has intensity > 0)
    p1-puff/FieldFieldFieldSpaceSpaceSpaceSpace (be space 1-dimmensional, no crisis)
    later on ...
    p1 not anymore here/SpaceFieldFieldFieldSpaceSpaceSpaceSpace
    later on ...
    p1 not anymore here/SpaceSpaceFieldFieldFieldSpaceSpaceSpace

    later on ...
    p2 not anymore here/SpaceFieldFieldFieldFieldFieldFieldSpaceSpace
    later on ...
    p2 not anymore here/SpaceSpaceFieldFieldFieldFieldFieldFieldSpace

    as can be seen on this simple 1-dimensional sketch the fields propagate (clearly seen in red) from the point were particles used to be. The source of the field 'mutes' when particles vanished. But there is no vanishing possible on the field already present on space.

    at the end of experiment 1 one have ...FieldFieldField... propagating away
    at the end of experiment 2 one have ...FieldFieldFieldFieldFieldField... propagating away

    we can assume that the precursors of particle p1 and p2 are quantitatively equal (two photons of x energy)
    by theory the resultants after the annihilation of both experiments are equal.
    beeing so,
    with this experiment I have to state
    propagating FieldFieldField = propagating FieldFieldFieldFieldFieldField
    or else I am prepared to admit that particles after annihilation are'nt just equal on both experiments.

    until now I've not seen no clarification on this issue,
    and, as you, I'm also perplexed why it seems you cannot understand the problem as it is stated.
    Everyone assumed that patrticles of type P have allways equal mass.
    But it cannot be asserted without proof, and with respect of quantities (mass) the most we can test by experiment is allways within some limits, as small as we can get.

    But I do not know of any experiment well succeded to prove that 2 distinct neutrons have equal mass. We can put them as slow as possible, 'freeze' them,..., can we state they are equal ?
    ... measured half-time is allways within some dispersion.
    ... and why not the rest-mass of particle neutron be between X-delta, X+delta ?
    really, absolutely, and not just the measured value ?

    Wikipedia : Neutron mass 1.67492729(28)×10−27 kg
    NIST (CODATA) Value 1.674 927 211 x 10-27 kg ,
    Standard uncertainty 0.000 000 084 x 10-27 kg ,
    Relative standard uncertainty 5.0 x 10-8,
    Concise form 1.674 927 211(84) x 10-27 kg ,
    (wikipedia has different values from CODATA)

    This uncertainity could represent two things:
    the allways present uncertitude in the measure thecnique.
    AND the possibility, that neutrons have different rest-mass.

    And I maintain that not all particles of type P are equal. (at rest, i.e. same energetic condition).

    Nobody has to 'believe', we are talking on physics.
    Does anyone have any evidence that proves that all neutrons have equal rest-mass?
    I suppose you know the answer.

    Back to the experiment 1 versus experiment 2, please.
    Check the experiments conditions, and pinpoint any error, if possible.
  9. Nov 13, 2008 #8


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    Now I have no idea what you are talking about, and your post is really not structured at all.

    Do you for the first know how particles are detected in a particle detector for instance?
  10. Nov 13, 2008 #9
    If, as you said 'I have no idea what you are talking about' is more reasonable to leave
    this discussion. Dont waste any more time, yours and mine.

    Someone will understand the question as posted initially.

    ( By the way, I'm electronic engineer from the IST of Lisbon, 5 years superior study, 54 years old,
    and, you know, most problably I dont have a clue about electrons, neutrons, particles, fields, intensities, detectors,... name it,... )
  11. Nov 13, 2008 #10


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    Since I am particle physics student, I only suggested that you perhaps should stress what you think is the paradox/anomaly in your example.

    The picture you have drawn is not related to how you detect particles in a detector, you are assuming that the reason for that the different values of the measured field are due to particles beeing annihilated at different time, thus you'll get diffent values. But this is not related to a real physical situation - how you detect particles in a detector.

    And then you raised a discussion on how one can "be sure" that two neutrons are equal since you can't really get the same value, is a question that is related to philosophy of science in general. Since it is more symmetric to assume that all neutrons have same rest mass, and the fluctuations are just due to experimental resolution, that position wins over the situation that the neutrons themselves have a intrinsic restmass deviation.

    Same holds for your example on particle annihilation along the path of flight, how would this example relate to reality? What is the mechanisms for the annihilation and what is your device for detecting the field?

    And just for your information, you dont establish the mass of particles by measure their gravitational interaction, but you probably knew this..
  12. Nov 13, 2008 #11
    in the first post I've described a conceptual experiment were detectors are not needed, for sure.
    But, conceptual or not, is a physical question, and what I stress, again, is the unexpected result that at annihilation of pairs P1 and pairs P2 they MUST have different content (energy).
    I understand that in particle physics, usually disregards to the propagated fields. After all you are 'only' talking about 'particles', not the outside ordinary electro/ /gravitationaly emited fields. In the Feynman diagrams they are ommited.

    I'm prepared to discuss the experiment as stated above,
    and, as the experiment sugests ,even contrary to our expectations, we cannot say as you did '..it is more symmetric to assume that all neutrons have same rest mass'.

    if you are a student, try to check with your teachers, but keep in mind that is extremelly difficult for a theacher to assume that it has no answer.
    I found no answer in the theory.
    Everyone is assuming all particles of type P are just equal.

    In the beginning of experiment (time T0) pair P1 = pair P2 and by the moment of annihilation pair P1 NOT= pair P2.

    You call it anomaly/paradox, but I know that it is not so.
  13. Nov 13, 2008 #12


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    As malawi_glenn already pointed out, your question appears similar to the question of "Will the gravitational force experienced by earth cease to exist at the same instant as the sun disappears".
    Since you didn't address the analogy, I'm going to guess that you don't understand that this is an actual question with an undefined answer.
    The answers you might get will involve either spacetime geometry response (in GR) or virtual photon/graviton exchange (in a QFT).
    This is one (if not the major) underlying reason that there is no unified field theory.
    Neither idea would seem to support a need for mass variance between particles of the same type.
  14. Nov 14, 2008 #13
    the remaining fields become light. this is nothing new. its the same principle behind how antennas work. a field is created which then tries to collapse but because it lags behind the current it has nowhere to go and so becomes light.
  15. Nov 14, 2008 #14


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    No I didn't call that an anomaly/paradox, I asked why you think it is?

    Now let's turn to your fictional experiment, what is causing the particles to annihilate just like that? Is that mechanism needed to be added ad hoc? How would you prepare your experiment?

    One does not detect particles with antennas in particle physics experiments :)
  16. Nov 14, 2008 #15
    I recomend 'back to basics' elecrostactic
    we hava a charge/mass, we have a stationary electromagnetic/gravitational field.
    as there is now way of instanct action at distance the fields will occupy the space at c speed,
    test particles at different distances will notice the field at different times.
    the electrons set the field, that is spreading in space, and they are not radiating a single photon.
    in the experiment the remaining fiels surely doesnt become light (photons), they simply continue propagating.
    far way from the preexisting source, now vanished, relalivity teaches that the source is still 'visible'.
    we dont need to invoke antennas, test particle is enough.
  17. Nov 14, 2008 #16
    as in the first post:
    two photons <-> electron/positron pair, and equal energy on start of both experiments

    on both experiments:
    creation ......................................., radiate fields....,... annihilation
    two photons -> electron/positron pair ,..................,-> two photons
    by theory the energy of the 2 initial photons is the same as the 2 final photons

    as a conceptual experiment, no one needs to prepare that. Theory and imagination are enough. But beeing conceptual it is a physical problem, with physical consequences and meaning.
    When I say that for me it is not an anomaly neither paradox I'm refering to the meaning and consequences as already stated:

    The quantity 'Space And Field' is dependent on particle antiquity.
    And so, if the particles are equal in the beginning they must be different in dead, or 'free lunch' is permitted in physics!
  18. Nov 14, 2008 #17

    Vanadium 50

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    If you are talking about electric fields, you can't have a particle of one charge annihilate without it's antiparticle of equal and opposite charge. That means far away the field is zero, unlike what you have drawn in your first message.
  19. Nov 14, 2008 #18
    electron and positron have mass and so gravitational fields uphold, and the problem stands as stated.

    I think I understand your difficulties. As particle physics you concentrate in 'particles' ignoring fields, invoking virtual-photons for this, gravitons and gluons for that,...
    look around : your PC was invented, designed, computer languages invented, sensors, detectors, actuators, even at LHC it was electronic engineers that have created almost all apparatus.
    Before focus have moved to particles it was centered in fields. Electromagnetism is fruitfull from the beggining.
    And an electronic engineer as no problem in understand this post as formulated.
    You can allways think that spacetime around each particle was modified by gravity and expanding at c speed, during the time each pair was 'alive',
    the problem stands as stated ab initio.
  20. Nov 14, 2008 #19


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    i) I thought we was dealing with electrodynamics, not electrostatics.

    ii) Then if we can't prepare this experiment, maybe we should not draw so many conclusions regarding your example on the neutron mass etc.

    Physics is more than "proofs" and "evidence", its a matter of symmetry and beauty.

    Are you maybe referring the the process of virtual particle exhange?
    The experiemtn you are reffering to is a photon into a e+e- pair which annihilate to form a photon again? You must specify your experiment, what is beeing annihilated with what etc, otherwise one can rule out your reasoning by argument that particles don't annihilate just like that. So situation is ruled out from symmetry reasons.
  21. Nov 14, 2008 #20

    Vanadium 50

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    If you never intended to talk about electromagnetism, why did you yourself bring it up?

    As far as arguing how much smarter electrical engineers are than physicists, I don't think that adds any clarity at all.
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