-
Question: Since space and time are the same is it that whatever happens at different positions in space should take place at different time? If what I think is correct consider an electric dipole, the charges are at different positions in space then, can there be electrostatic attraction between the charges even if they are individually present in different time?
- Keywords:
Comments
rajathjackson commented on :
Sir, I actually didn’t ask about simultaneous events. I read an article about an experiment in which physicists could entangle two particles at different time. First I was amazed but then I thought that since space and time are the same and particles can be entangled even if they are at different positions in space there is no wonder that this can happen even if the particles are at different time. So, thinking in this manner is it possible that there can be electrostatic force between charges at different time?
rajathjackson commented on :
Among the forces of nature(before unification) weak and strong nuclear force has the restriction of its range, the electrostatic force has the restriction that the particles/objects should be charged but gravity seems to have no restriction. Only mass comes in its equation(and also distance but it has infinite range) and from the answers of a previously asked question I could know that gravity affects even massless particles like photons. So, does gravity have any other type of restriction or is it that the gravity always keeps on acting till time ends on all bodies ?
Jack commented on :
Hi Rajath,
I’m still not so sure I’m following you — do you mind linking to the experiment in which things were entangled at a distance? It’s usually only possible to create entangled pairs where things are created in an entangled state, and then move apart.
Are you asking if the electrostatic force can change as a function of time? All the forces are independent of time (ish), and all act on particles with a charge — electric charge is the charge that the electrostatic force cares about, and it comes in ± quantities; the weak force cares about something called weak hypercharge, and the strong force cares about colour. Mass is directly analogous to the electric charge, but for gravity — and it only comes in a positive variant, unlike every other force.
rajathjackson commented on :
Her’s the link sir-http://news.sciencemag.org/sciencenow/2013/05/physicists-create-quantum-link-b.html
rajathjackson commented on :
To make it more clear what I’m thinking about consider the following. I have a body with charge Q1 at time t1 and then I neutralized it. At another instant of time t2 I have another body with charge Q2. Can there be electrostatic forces of attraction between the charges Q1 which was present at time t1 and Q2 which is present at time t2(remember that at time t2 there is no charge Q1 as I had neutralized the first body) i.e can there be EM force between charges that don’t exist at the same time like there can be entanglement between particles which do not exist at the same time as given in the article that I linked you to?
Jack commented on :
Thanks for the link and clarification! So, first of all, you can’t ‘neutralise’ a charge on a fundamental level — you can only introduce another equal and opposite charge into the system. The reason something like Xeon appears electrically neutral is because its positive nuclei and negative electrons create an electric field that goes to zero outside the atom’s radius quickly (I believe).
Now, onto what you’re asking: the answer is roughly yes (!), and the best example of this is to be found in Feynman’s doctoral thesis — which won him the nobel prize. I’ve actually got a copy of it in front of me, and am frantically digging through to find a good description — hang on a second…
Jack commented on :
The system at hand is an electrical charge interacting with itself through a mirror. It’s a fact of electromagnetism that if you put a charge next to a sheet of metal, the metal creates a ‘mirror charge’ that acts, to all intents and purposes, as if an opposite charge was placed equidistant from the mirror as the first one. The problem is that there’s no fundamental direction for the axis of time — the micorsocopic phenomena in nature are symmetric with respect to the interchange of past and future. This requires that the solutions of Maxwell’s equations used in computing the interactions between these two charges be waves (i.e. light) travelling in both directions, known as the ‘advanced and retarded’ waves, where the electron has to ‘care about’ both photons going to its image and coming from its image, called advanced and retarded waves. This sounds very paradoxical, and plays with our notion of causality. It also results in a difficult equation, where stuff requires a term that depends on things both now, and things a while ago.
Feynman himself sort of joked about this in his Nobel lecture: in his own words, he said:
“First, he said, let us suppose that the return action by the charges in the absorber reaches the source by advanced waves as well as by the ordinary retarded waves of reflected light; so that the law of interaction acts backward in time, as well as forward in time. I was enough of a physicist at that time not to say, “Oh, no, how could that be?” For today all physicists know from studying Einstein and Bohr, that sometimes an idea which looks completely paradoxical at first, if analyzed to completion in all detail and in experimental situations, may, in fact, not be paradoxical. So, it did not bother me any more than it bothered Professor Wheeler to use advance waves for the back reaction – a solution of Maxwell’s equations, which previously had not been physically used.”
Nature is pretty damn weird.
— Jack