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plant
2015-Sep-04, 02:08 PM
Decades ago i read about this spooky theory of John Wheeler's that there is ONLY ONE electron in the universe, moving forward in time and then backward in time (what we see as a positron).
Does anyone still think this is possible?

https://en.wikipedia.org/wiki/One-electron_universe

... reminds me of the short story "The Egg".. which despite being an atheist i rather like :-) .. just googled him, turns out he is the same bloke who wrote "The Martian".

https://www.reddit.com/r/Frisson/comments/1a07cy/short_story_the_egg_by_andy_weir/

Amber Robot
2015-Sep-04, 04:50 PM
Would this require there existing an equal number of electrons and positrons in the universe? If so, that seems inconsistent with the observation that the universe is primarily composed of matter and not anti-matter.

Ken G
2015-Sep-04, 09:29 PM
ETA: on second thought, you're right, if there's only one electron that is doing all this, then there'd have to be an excess of only one electron over all the positrons, and that's not seen. It doesn't sound like it wouldn't work, without a lot of help.

JohnD
2015-Sep-04, 09:47 PM
Forget electrons and positrons, what about all the protons?

Or can the single electron double, as if it were a repertory player doing second roles, act as all the electrons around any nucleus that mean the atom isn't charged?
Else, all of matter would fly apart, no?

John

swampyankee
2015-Sep-05, 05:36 PM
Decades ago i read about this spooky theory of John Wheeler's that there is ONLY ONE electron in the universe, moving forward in time and then backward in time (what we see as a positron).
Does anyone still think this is possible?

https://en.wikipedia.org/wiki/One-electron_universe

... reminds me of the short story "The Egg".. which despite being an atheist i rather like :-) .. just googled him, turns out he is the same bloke who wrote "The Martian".

https://www.reddit.com/r/Frisson/comments/1a07cy/short_story_the_egg_by_andy_weir/

I think the positron was the same electron moving backwards in time. I'm wondering if legs were being pulled.

ShinAce
2015-Sep-05, 07:34 PM
That's correct. It was a thought experiment proposed by Wheeler to (Feynman?).

When they were working on QED, the fact that electrons are indistinguishale became an issue when considering that the equation should be symmetric with respect to time.

Wheeler proposed that we had been looking at an electron moving forward in time as a single electron which can spawn electron-positron pairs. Instead, imagine the X and Y axes are space coordinates. Let the Z axis be time. Now draw a line representing an electron up through Z, then turn around and come down through Z, then back up. Now.... what we want to know is how many electrons there are. So we need to take XY planes and intersect our drawing. If we start low enough, we only intersect a single elctron. As we move up, there's now 2 electrons and a positron. Further up still and we find only a single electron. This 'one' electron tracing a path back and forth through space and TIME looks exactly like an electron which spawns particle pairs which then annihilate. The pictures are equivalent and help guide us toward a description that is symmetric with respect to time.

That's my understanding of the one-electron universe. It's been years though, so take that with a grain of salt.

Ultimately, Wheeler's insight was profound, as it usually is.

Ken G
2015-Sep-05, 07:53 PM
That's my understanding of the one-electron universe. It's been years though, so take that with a grain of salt.Yes, that's my understanding too, but note it preserves the net number of electrons over positrons, and that number has to be "1" to have a one-electron universe. That's what seems to break down, the number must be way bigger than 1, unless our universe is constantly exchanging particles with vast pockets of antimatter. That seems to be ruled out by the absence of the X-rays created every time the positron "turns around" back into the electron. So it might make sense to say that positrons are electrons that have been scattered back in time by an X-ray moving back in time, but it doesn't make sense to say it's all the one electron. And to say the former, one still needs a source of backward-in-time particles at some future boundary, whether they be X-rays or positrons. It might make more sense to expect no such source, such that if you go forward in time far enough, you'll have nothing but electrons and photons moving forward in time, with no more interactions that look like anything moving backward in time-- other than perhaps virtual particles that don't require a source.

ShinAce
2015-Sep-05, 09:21 PM
Correct. It was a theoretical idea to deal with virtual particles and particle pair production/annihilation. It was never able to explain why we have a universe full of electrons.

In other words, it was used to explain the behaviour of electrons, not their existence. This is easy to miss considering it talks of new particles coming into existence and then disappearing.

This is Wheeler saying "There is no spoon."
Anyone who hasn't seen that scene from The Matrix needs to watch it:
https://www.youtube.com/watch?v=uAXtO5dMqEI

Ken G
2015-Sep-06, 12:04 AM
Yes, that's a nice scene, I'd say it's a pretty intentional reference to this image by Escher: http://www.theassc.org/files/assc/escher-hand-with.jpg

JohnD
2015-Sep-06, 07:52 PM
If I ask my question in a different way, do you think that anyone will answer?

If there is only one electron, what ensures that all the atoms in the universe that are not ionised are neutral?
JOhn

malaidas
2015-Sep-06, 08:09 PM
A very good point john

ShinAce
2015-Sep-06, 08:37 PM
If I ask my question in a different way, do you think that anyone will answer?

If there is only one electron, what ensures that all the atoms in the universe that are not ionised are neutral?
JOhn

I don't see where you're going with that.

By definition, if an atom is not ionized, it is neutral.

Are you trying to say that if there's an extra electron in the universe, then surely there must be an atom with an extra electron out there somewhere?

Ken G
2015-Sep-07, 12:28 AM
If there is only one electron, what ensures that all the atoms in the universe that are not ionised are neutral?
The real constraint on the "one electron universe" seems to be that there is always one more electron than positron. There's plenty of electrons to keep the atoms neutral, but only if there are also anti-atoms.

plant
2015-Sep-07, 03:54 AM
could someone explain the arguments against this...?
have i got it right...?

an electron (moving forward in time) spontaneously releases a gamma ray photon, and switches itself to moving backwards in time (what we see as a positron), which then releases another burst of gamma rays and switches to moving forward in time as an electron again?

are the arguments against this that:
1) we don't see the universe full of gamma rays?
2) we don't see enough positrons?

is that correct?

ShinAce
2015-Sep-07, 07:24 AM
Gamma rays hitting each other is one way to produce an electron-positron pair. If that pair annihilates, it will release gamma rays. The electron and positron are real particles and can be detected.

However, it is possible for an electron-positron pair to be produced without any gamma rays to begin with. They will annihilate, but no gamma rays will be produced. Worse yet, you will not obsserve the electron or positron, because they are virtual particles. The virtual positron could even annihilate with an existing electron, thus promoting the remaining virtual electron to real electron. The electron has just teleported.

The backwards in time is used to explain virtual particles. And virtual particles are needed to explain quantum effects.

JohnD
2015-Sep-07, 09:17 AM
I don't see where you're going with that.

By definition, if an atom is not ionized, it is neutral.

Are you trying to say that if there's an extra electron in the universe, then surely there must be an atom with an extra electron out there somewhere?

ShinAce, maybe you should read the OP.
I did and then looked at the Wiki entry (nice slant on Feynman!). Wheeler's premise was that all the electrons in the Universe are identical because they are all the same electron, travelling along an infinite world line.
Feynman didn't like it, but did the idea that they travel both ways and are a positron in reverse time. So he stole it.

The article didn't explain why he didn't like the single electron idea. My question is, all atoms are neutral (unless ionised, but that is a special case) so how does ONE electron neutralise the positive charge on myriads of protons?
The whole Universe would be positively charged, and matter would fly apart, unless the protons are an equally unique Proton.
How could the eminent Prof Wheeler entertain this thought for a moment? Before his brain flew apart.

KenG,
Your comment is equally obscure to this poor student. One more electron than positrons? How is that 'known'?

John

Ken G
2015-Sep-07, 01:00 PM
an electron (moving forward in time) spontaneously releases a gamma ray photon, and switches itself to moving backwards in time (what we see as a positron), which then releases another burst of gamma rays and switches to moving forward in time as an electron again?The gamma rays are not spontaneously released, there had to be a gamma ray already moving backward in time, which "scatters" forward in time as the electron "scatters" backward in time and becomes a positron. The key point is, the net number of particles moving forward and backward in time is conserved (though virtual particles can be elevated into real ones by energy exchange), so if it is supposed to be "all the same electron" (to explain the indistinguishability of electrons), then you cannot have a net excess of more than one forward-moving electron over all the backward-moving positrons. But the possibility of virtual particles muddies the water a bit-- perhaps Wheeler thought this through already, and what he was saying is that there is some strange tendency for the forward-moving electrons to be real, and the backward-moving positrons to be virtual instead. I'm not sure how that could work out to get a correlation between real/virtual and forward/backward, but maybe that's what Wheeler was saying.


are the arguments against this that:
1) we don't see the universe full of gamma rays?
2) we don't see enough positrons?

is that correct?Yes, it seems hard to explain all those real electrons going forward in time-- they would have had to get back in time to emerge again via a virtual positron, when there isn't the same flux of virtual electrons moving foward turning into real positrons moving backward.

Ken G
2015-Sep-07, 01:14 PM
Your comment is equally obscure to this poor student. One more electron than positrons? How is that 'known'?
We know that when we look at real particles, we see lot of electrons everywhere, and very few positrons. But if it's all the same particle, then the differential between electrons going forward in time and positrons going backward, at any given time, cannot be more than one particle either way. Since we know the real particles are electrons, not positrons, this would require that the particle be virtual more often when it was a positron than when it was an electron. Bringing in protons just says we need lots of real electrons to neutralize their charge, but we know this, we are saying we know we have to have a lot of real electrons and we don't have a lot of real positrons.

But it occurs to me that maybe Wheeler was saying something else. Maybe Wheeler was saying that the universe has a boundary in the future and a boundary in the past, and these boundaries are equated, so that a real particle can cross the future boundary and end up back at the past boundary. Then there is no limit on the excess of electrons over positrons, for you are only conserving the flux of electrons, you are not saying the net flux cannot exceed one. All the electrons we see are then the same electron, that has cycled through the timeline of our universe many many times. The problem with that would seem to be how to get a connection, and what would determine the number of times the electron cycles around.

Steady State
2015-Sep-07, 05:32 PM
If proton decay (https://en.wikipedia.org/wiki/Proton_decay) is possible, then the the positrons may be mostly in the guise of protons which eventually decay into positrons and neutral particles.

There may have been an asymmetry in the early universe which, rather than simply producing a slight excess of matter over antimatter, produced eg more neutrons than antineutrons.

There's no problem with gamma rays going forward or backward in time since photons are identical to antiphotons.

There's no need for even one electron.

Think of creating a real (ie not virtual) electron/positron pair which later annihilates. Total number of electrons at any time = 0.

There's a lot of problems in taking this idea further as Feynman etc found, but I'm not aware of anything to indicate it's impossible either.

JohnD
2015-Sep-08, 08:24 AM
Nooooooooooooooo!
Please answer my question!
ONE electron, with ONE negative charge, lets call it The Electron.
How many protons in the Universe? Eddington tried to calculate that, and assumed that there were an equal number of electrons.
Given that The Electron is true, then the net positive charge of the Universe is Nedd minus one, a situation that is palpably untrue.

Please destroy my logic, but at least address it.
John

Ken G
2015-Sep-08, 02:13 PM
If one holds there is just one electron, one is certainly also going to hold there is just one proton. Remember, the whole point of the "just one" picture is to explain indistinguishability. Hence, any particle that is indistinguishable from others of the same type would be regarded as the unique example of that particle, everywhere in the universe. There is no problem with total charge, in the "just one" model the fact that there are very nearly the exact same number of protons and electrons is just a feature of how that one electron and one proton function. I don't know how they could function to make that work, but then I also don't know how you get more electrons than positrons in that model. If Wheeler thought it through, I don't know what he had in mind, and I believe that is why Feynman rejected the idea on the whole. (Above someone said he "stole" the idea, but in the book of his that I read on the issue, he clearly said Wheeler came up with the idea, and Feynman didn't think it could work, but that it was a cute idea.)

JohnD
2015-Sep-08, 03:22 PM
Ah! Thank you Ken! So it's One Electron, One Proton, and I presume One Neutron.
But an electron is an electron is an ....
Protons are two up and one down quark.
Wheeler would not have had quarks to think about, but with TWO up quarks per proton there could not be One Up Quark. Could there?

JOhn

Grey
2015-Sep-08, 05:04 PM
Wheeler would not have had quarks to think about, but with TWO up quarks per proton there could not be One Up Quark. Could there?Sure there could. It just would have had to go backward in time (manifesting as an anti-up quark) at some point, meet back up with itself, and then travel forward in time again with itself and the only down quark around (on one of its many trips forward in time) to form a proton with.

Think about it like an extremely convoluted time travel story, with the electron as the protagonist. Whenever it looks like there are two electrons together, it's really just that the electron has travelled back in time, and met back up with its former self. It works just as well with any particle. The problem really is that, since a particle travelling back in time manifests as its anti-self while doing so, we're left to wonder where all the antiparticles are. If, as Ken G suggests, Wheeler was imagining that particles could cross from the end of the universe to the beginning of the universe, that would solve that issue, and we're left with a technically possible (if perhaps a bit silly) model.

JohnD
2015-Sep-09, 09:13 AM
OoooooooooooooKay!
I think.
As is so usual in theoretical physics, the thought experiment can explain much, but at the cost of 'violating' common sense and the macro view.
Roll on, Beyond the Standard Model!

John

plant
2015-Sep-09, 10:47 AM
... could it be possible that there are more positrons somewhere else in the universe to even up the positron/electron numbers.. presumably they wouldn't have to be in the same region .. as the positron could also travel in space as well as backwards in time and be seen by us to be in a different location?

... is there any way that this sort of theory could be considered 'non - scientific' by being non-falsifiable NOW, but with future technology/physics be able to be theoretically disproved at some point in the future?

... also... who is to say that other 'realities' could experience time in reverse i.e our electrons would be seen as positrons moving backwards in time... or is the arrow of time an emergent property of thermodynamics that can only go 'one way'....

Ken G
2015-Sep-09, 01:57 PM
... could it be possible that there are more positrons somewhere else in the universe to even up the positron/electron numbers.. presumably they wouldn't have to be in the same region .. as the positron could also travel in space as well as backwards in time and be seen by us to be in a different location?There are other things that could happen as well-- instead of going to a different location, the positron could be virtual. So you could have the "one electron" tend to be real when it is going forward in time, and tend to be virtual when going backward in time, having passed off its energy to something else that "scatters off it." I just don't know the details of what Wheeler had in mind here. I guess what it all boils down to is, how many inconveniences or "cluges" must one tolerate to buy the conceptual advantages of having all indistinguishable particles be the same one particle, and is it worth it?

JohnD
2015-Sep-10, 07:57 AM
Quote Feynman in his Nobel lecture, quoting (from memory) Wheeler in his famous phone call:
"Feynman, I know why all electrons have the same charge and the same mass." "Why?" "Because, they are all the same electron!" And, then he explained on the telephone, "suppose that the world lines which we were ordinarily considering before in time and space - instead of only going up in time were a tremendous knot, and then, when we cut through the knot, by the plane corresponding to a fixed time, we would see many, many world lines and that would represent many electrons, except for one thing. If in one section this is an ordinary electron world line, in the section in which it reversed itself and is coming back from the future we have the wrong sign to the proper time - to the proper four velocities - and that's equivalent to changing the sign of the charge, and, therefore, that part of a path would act like a positron."
I found this quote here, where the author discusses the Wheeler theory:
http://io9.com/5876966/what-if-every-electron-in-the-universe-was-all-the-same-exact-particle
He relates how Feynman contradicted Wheeler's proposition, by pointing out that "there aren't as many positrons as electrons." "Well, maybe they are hidden in the protons or something" replied Wheeler, a lame response, I have to say. The article goes on the defend the Wheeler reputation, and after all, it's the wild ideas that spark others! But why has this Single Electron idea persisted, when even a theorist who could countenance the wildest ideas discounted it at once? Even if he did 'steal' a rider to it!
JOhn