0
$\begingroup$

When something needs to inform its presence, such as the electromagnetic presence of charged particles , or the gravitational presence of particles due to their mass. Is this made by sending information of its existence propagated in space via some kind of electromagnetic waves or hypothesised gravitational waves.

So as a part of telling others of their presence to others, do the particles constantly lose their energy ? I understand that they could also gain energy in same way, but if a particle was completely isolated would it lose its existence and turn into pure energy over time ?

I understand that the mass and energy would together remain constant, but my question is that whether something would happen to a particle or would it remain a particle ?

$\endgroup$
  • $\begingroup$ Notice that if particles lost energy, they would disappear. $\endgroup$ – jinawee Oct 27 '13 at 10:14
  • $\begingroup$ So how do particles express their fields to fellow particles ? I believe em waves is the way to go and those are costly, I mean energetically. $\endgroup$ – Rijul Gupta Oct 27 '13 at 10:19
  • $\begingroup$ Comment to the question (v2): Are you really asking if there exists a stable elementary particle? $\endgroup$ – Qmechanic Oct 27 '13 at 12:26
  • $\begingroup$ @ Qmechanic : no I am talking about fields and propogation related energy of all particles which lead me to think of that question $\endgroup$ – Rijul Gupta Oct 27 '13 at 12:42
  • $\begingroup$ I think the OP may be asking : If the EM force is communicated by photons (equivalently, if it takes energy to sustain the EM field around an isolated charge), then why don't charged particles lose energy - and therefore mass? Shouldn't an isolated charge radiate all its mass-energy away? $\endgroup$ – sammy gerbil Jul 9 '16 at 3:37
3
$\begingroup$

Energy in physics takes many forms, that can be interchangeable during interactions. The law of conservation of energy holds for a summation of all the different energy manifestations of the system under study.

if a particle was completely isolated would it lose its existence and turn into pure energy over time ?

No . An isolated particle can have energy as its rest mass, can have kinetic energy if it is moving with respect to some coordinate system. There is no way to transfer its rest mass energy anywhere, unless through interactions ( and then it is not isolated) . An isolated particle is stable if it cannot decay to other particles. The electron for example, or a photon, can only disappear through interactions with other elementary particles.

You are probably confused by the simplified quantum mechanical picture of a charged particle continually exchanging virtual photons with other charged particles in the environment. Virtual photons are a useful calculational tool in getting the probabilities for the interactions of elementary particles. The virtual means that they do not conserve the energy momentum measure of their four vector, they are off mass shell, so energy conservation has no meaning in these exchanges.

In classical electromagnetism the fields of charged particles are stable, they do have an energy density but it is associated with the particle as its charge, and cannot be diminished by interactions. This is an observational fact. The boundary conditions of a problem with many charges will determine the composite fields, and any energy produced or lost comes from another form of energy than the field energy density of the individual electrons; it will probably be kinetic or potential energy to start with.

Macroscopically looking at live organisms, yes they continually exchange energy signals with the environment, energy which they have to replenish from other forms ( food).

Not elementary particles though

$\endgroup$
  • $\begingroup$ So when we charge something (initially uncharged) the charged body does not send electromagnetic waves to establish its field ? I am not sure that this is a correct explanation $\endgroup$ – Rijul Gupta Oct 27 '13 at 8:47
  • $\begingroup$ A charged body is either all positive or all negative. If all positive the charge is built up by the elementary charges residing in the ions of the surface. If negative it it the collective field of the electrons residing on the surface. In the process of charging there exist electromagnetic waves because changes in electric or magnetic field generate electromagnetic waves, but it is not the waves that establish the field. The energy for orienting all electrons on the surface comes from the current spent and ultimately from the generators that create the current. $\endgroup$ – anna v Oct 27 '13 at 12:39
  • $\begingroup$ The static field energy is coming from the combined/collective field of the electrons.(or ions if it is a positive charge). $\endgroup$ – anna v Oct 27 '13 at 12:40
  • $\begingroup$ And where is that field coming from (the collective field)? $\endgroup$ – Rijul Gupta Oct 27 '13 at 12:44
  • $\begingroup$ @annav It appears, you have not finished your last sentence of the answer. $\endgroup$ – user23660 Oct 27 '13 at 13:28
2
$\begingroup$

Anything when it needs to inform its presense such as electromagnetic presense of charged particles and gravitational presense of particles due to their mass does so by sending information of its existencs propogated in space via means of electromagnetic waves or hypothesised gravitational waves.

Not true. Maxwell's equations have wave solutions and static solutions. They are two different things. Similarly, the Einstein field equations have wave solutions and static solutions, and they're different things.

So as a part of telling others of their presense to others, do the particles constantly lose their enegy ?

No. Static fields don't transport energy.

$\endgroup$
  • $\begingroup$ So would you say that when a neutron turns into a proton and electron their electric fields are just set up in 0 time, and then are set up forever ? Since they are static. I mean in negligible time I understand, but you are saying because maxwells equations give static waves, they are already there ? That is surely wrong !! $\endgroup$ – Rijul Gupta Oct 27 '13 at 14:23
  • $\begingroup$ @rijulgupta: In your example, the electric dipole moment D is zero before the neutron decays, and then after the decay it begins to attain nonzero values. This causes a change in the field, which propagates outward as a wave. This is not a static example, since D is time-varying. $\endgroup$ – user4552 Oct 27 '13 at 15:09
  • $\begingroup$ And your point is ? I am simply talking about emission of information(of field) with energy, as informtion wouls travel via waves having energy, I go back to my question $\endgroup$ – Rijul Gupta Oct 27 '13 at 16:39

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.