Physics Help Forum Is every electron unique?

 Philosophy of Physics Philosophy of Physics Forum - Philosophical questions about our universe

 May 9th 2017, 01:55 AM #1 Member   Join Date: Apr 2017 Posts: 46 Is every electron unique? Let's imagine a simple thought experiment. There is a container with hydrogen and a container with helium. Let's take some atoms from both containers and detach electrons from them. Then mix those electrons. Is there any way to tell for sure which electrons come from helium atoms and which ones come from hydrogen atoms? If not, is it still correct to think that every electron (or any other particle) has its individual story? Last edited by Fox333; May 9th 2017 at 01:58 AM. Reason: grammar
 May 9th 2017, 11:16 AM #2 Senior Member   Join Date: Aug 2010 Posts: 383 To answer your question, no. All electrons are identical and there is no way to distinguish one from the other. In fact, the physicist, Richard Feynman, once presented a theory (perhaps tongue in cheek- he was a little odd) that all electrons are identical because there is only one electron! Imagine drawing a graph showing electrons, and positrons, moving along a line, the x- axis, with the other axis the time axis. The electron initially moves "to the right" (on the x-axis) and "up" (toward the future on the time-axis) while a positron moves "to the left" and up. They meet at some x, t point and destroy each other in a burst of energy. But farther "to the right" that positron originated in a burst of energy that created the electron-positron pair to begin with. You could follow that electron further to the right until it disappeared. Now cover that with another piece of paper that has a horizontal slot cut in it. Place it at the bottom and slowly move it up the time axis so that the horizontal slot shows a specific time. Instead of lines, representing the paths of the electron and positron, we see dots representing the electron and positron at that time. Now remove the top paper and look at the electron-positron lines again. According to Feynman, we can think of that zig-zag line as a single electron moving back and forth in time, seeing the electron moving backward in time as a positron!
 May 9th 2017, 11:32 AM #3 Senior Member   Join Date: Apr 2015 Location: Somerset, England Posts: 995 This is actually a very good question and I'm sorry to say that the answer is both yes and no. To explain this apparent paradox it depends what you mean by the same or different or unique. Every electron in the universe is the same as every other in that it could replace any other electron without any outward difference being apparent. But an electron accelerated to high velocity in a particle accelerator has more apparent mass than one treading a more pedestrian path in a cathode ray tube. But both enjoy the same rest mass.
May 10th 2017, 02:10 AM   #4
Member

Join Date: Apr 2017
Posts: 46
 Originally Posted by HallsofIvy In fact, the physicist, Richard Feynman, once presented a theory (perhaps tongue in cheek- he was a little odd) that all electrons are identical because there is only one electron!

Yeah, I heard of it. I would like to go farther and I personally think that the concept of "the same" or "another" doesn't have any sense for particles.

 Originally Posted by HallsofIvy Imagine drawing a graph showing electrons, and positrons, moving along a line, the x- axis, with the other axis the time axis. The electron initially moves "to the right" (on the x-axis) and "up" (toward the future on the time-axis) while a positron moves "to the left" and up. !
Do you mean, a positron moves to the left and down? It if moves backward in time?

Last edited by Fox333; May 10th 2017 at 02:14 AM.

May 10th 2017, 03:05 AM   #5
Member

Join Date: Apr 2017
Posts: 46
The post seems rather long, but the last paragraph is most important. You might want to start from it, if you want to keep it brief.

 Originally Posted by studiot To explain this apparent paradox it depends what you mean by the same or different or unique.
That's the point. In macro scale every object seems to be unique, cause there is no two absolutely identical objects. Moreover, macro scale objects are constantly changing. So, every objects seems to be unique even regarding to itself in different moments of time.

I think the concept of "the same" or "another" is a human thing (derived from animals). An animal has ability to recognize objects which are significant for it, among many similar objects. Like a pet can recognize its owner. Humans are much more advanced in it. We can label every macro object and track it in time. As long as those objects are constantly changing, a paradox appears. It's known as the ship paradox, invented by the Ancient Greek (if we replaced every detail of a ship gradually, will it still be the same ship or another ship?).

And here's the essence. Stable particles are another case. They can't change. Theoretically we can track a single electron in time, and say that the particle is "the same" if it has a continuous projection on the t axis. But if we lose its track we can't restore its history anymore. A paradox again. But what if the spacetime isn't continuous, but discrete? And each (x,y,z,t) coordinate point of the particle is like a "new" particle? The "old" particle exists only in particular (x,y,z,t) coordinates. So, there is no "the same" electrons and "another" electrons. They are "another" in every particular instant and has no history.

May 10th 2017, 04:28 AM   #6
Senior Member

Join Date: Apr 2015
Location: Somerset, England
Posts: 995
 Originally Posted by Fox333 The post seems rather long, but the last paragraph is most important. You might want to start from it, if you want to keep it brief. That's the point. In macro scale every object seems to be unique, cause there is no two absolutely identical objects. Moreover, macro scale objects are constantly changing. So, every objects seems to be unique even regarding to itself in different moments of time. I think the concept of "the same" or "another" is a human thing (derived from animals). An animal has ability to recognize objects which are significant for it, among many similar objects. Like a pet can recognize its owner. Humans are much more advanced in it. We can label every macro object and track it in time. As long as those objects are constantly changing, a paradox appears. It's known as the ship paradox, invented by the Ancient Greek (if we replaced every detail of a ship gradually, will it still be the same ship or another ship?). And here's the essence. Stable particles are another case. They can't change. Theoretically we can track a single electron in time, and say that the particle is "the same" if it has a continuous projection on the t axis. But if we lose its track we can't restore its history anymore. A paradox again. But what if the spacetime isn't continuous, but discrete? And each (x,y,z,t) coordinate point of the particle is like a "new" particle? The "old" particle exists only in particular (x,y,z,t) coordinates. So, there is no "the same" electrons and "another" electrons. They are "another" in every particular instant and has no history.
Why chose the complicated model?

Remember all these descriptions are just models and all models are imperfect somehow.

Here is another model of discontinuous existnece.
It was written as a joke for another purpose but it demonstrates the principle if you think about it.
There is a powerpoint in the zipfile called clickme.

Compare how the clickem box moves with your discontinuous electron.

Have fun.
Attached Files
 clickme.zip (3.5 KB, 5 views)

 May 10th 2017, 04:43 AM #7 Member   Join Date: Apr 2017 Posts: 46 I'm not sure if I opened it correctly. There is no text in it, only some slides with "Click me Quick". But it's not clickable.
 May 10th 2017, 05:17 AM #8 Senior Member   Join Date: Apr 2015 Location: Somerset, England Posts: 995 You need to actually run the powerpoint.
 May 10th 2017, 11:04 AM #9 Member   Join Date: Apr 2017 Posts: 46 Yeah, I was in hurry and forgot to run it. It is a good example. For me it seems like that box is "the same box", that moves very fast from one corner to another. Is it an illusion of moving?
 May 15th 2017, 12:20 PM #10 Member   Join Date: Apr 2017 Posts: 46 I made 1 minute presentation which represents that "the same" is just an "artificial" human concept. If you are interested please watch it. https://drive.google.com/file/d/0B_i...ew?usp=sharing For some reason, it doesn't work in google presentation as well as it supposed to do. Please use Microsoft Office if you can. Last edited by Fox333; May 15th 2017 at 12:26 PM. Reason: adding information

 Thread Tools Display Modes Linear Mode

 Similar Physics Forum Discussions Thread Thread Starter Forum Replies Last Post nathsa Electricity and Magnetism 2 Jun 17th 2013 08:18 AM DKseed Advanced Electricity and Magnetism 1 Jun 15th 2011 10:28 AM missyc8 Electricity and Magnetism 1 Dec 1st 2009 10:46 PM werehk Electricity and Magnetism 3 Jul 16th 2008 06:27 AM Aryth Special and General Relativity 6 Apr 17th 2008 06:03 AM