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Richard Krooman


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What proof is there that electrons are particles?

Hello TED,

I'm not a physicist but the field interrests me...
And something within physics strikes me as very strange.
Namely that electrons are particles...

In the stuff I've been thought electrons were depicted as being 'small round things in an orbit around an atom'. And I can accept that were it not for the other observation that molecules are groups of several atoms being held together by the attraction and repulsion of the atoms and electrons.

It seems to me that you can always create a situation where the electron (if it is a particle) will collide with either other electrons or with other atom-nucleus'.

Therefor to me it seems a lot more logical that the "electron" is actually a force or a field rather than a particle.

But I am hoping that someone would have a link or an explanation which can show me why an electron is actually a particle.

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  • Jan 30 2013: I have a master's degree in Physics. The answer to your question is a little on the far out side, but I'll do what I can to get a clear explanation in under the character limit. The answer is that all subatomic "particles" including the electron have the characteristics of both a particle and a wave. This is going to be a little hard to believe but, the experiment you are doing determines whether you observe a particle or a wave. Edward is correct. In the Crooke's Tube experiment the electron exhibits the characteristics of a particle. However, Louis de Broglie posited in his 1924 one page Ph.D. thesis that matter could behave as a wave. An experiment, which was conceptually equivalent to the double slit diffraction experiment that proves light is a wave, was done with electrons and it was found that de Broglie's hypothesis was true. He won the 1929 Nobel Prize for his work.

    As a result of this, it doesn't make sense to think of the electron as being a particle that flies around inside of molecules. It is really neither truly a particle nor a wave.
    • Jan 30 2013: Well Robert,

      I am a guillable person... and to be honest I don't see why it would be hard to believe that electrons are neither particle nor wave (but have properties of both).

      However... then why have I been thaught that it is a "tiny ball moving around a spherical tiny nucleus like mad"?
      Couldn't they at least say that they are not sure what it is?

      Because all explanations I've ever heard start of by saying that an electron is a really small ball moving around an atom.... Heck even on TED there is an animated movie explaining atoms / particles in that way.
      • Jan 30 2013: I see it all the time, too. If you really wanted to explain all of the concepts and math behind quantum physics it would take several years of training and even then most people have a hard time with some of the concepts. I haven't told you the weirdest of them. I've been out of college for several years and I still have a hard time picturing some of it even though I think I understand it much better now than I did then. I can only conclude that the reason we are shown the "little balls" is partly popular culture and partly as a gross over simplification of the really strange stuff that is actually happening.
        • Jan 30 2013: Strange because to me everything seems so much more simple when the idea of "tiny objects" gets removed from the picture.
      • Jan 30 2013: If you get "tiny objects" removed from the picture, you'll face the question : what is real ?
        • Jan 30 2013: don't we already face that question?

          Anyway for me it is not a large step to go from "gas like atoms/molecules" to a solid object... because it just means that the force they have pulling them together is greater than the force pressing on it.

          Won't you agree that if you think of the world just as forces.... that it means that:
          a solid = more internal force than force trying to 'seperate it'.
          a liquid = slightly more internal force than force trying to "seperate it" however when you apply extra force you can split it.
          a gas = such a weak force that it gets seperated and eventually forms a mixture based on several properties.
      • Jan 31 2013: Yes , we do, but people usually don't like 'what is real ' kind of questions.
        I've just tried to explain why people prefer ' tiny objects ' to stay in the picture ; maybe because it is something that can be 'hold', it gives human psychy the comfort of understanding.
        • Jan 31 2013: well I once learned they were tiny objects... but eventually I got so much discomfort in observing a dissimilar reality that I wrote a post about it here (see above ;)).

          And if I as a 'normal person' can already figure this out try to imagine how many people are being misslead because their teachers told them that electrons and atoms are similar to different types of balls moving around influencing eachother.
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    Jan 30 2013: Here is a link: http://physics.weber.edu/carroll/honors-time/duality.htm

    There are sites devoted to physics where actual physicists will answer your questions! The American Physical Society is one where the explanations you get will be entirely reliable.
    Here is a site that will direct you to reliable sites aimed at the non-specialist: http://pdgusers.lbl.gov/~aerzber/aps_particle.html
    This is an area where there are lots of misunderstandings among those who are not physicists.
    • Jan 30 2013: Thank you for the links.

      It is funny... I was actually typing the post after just having watched an old lecture from Feynman on another site.
      In that he basically talks about the duality your first linked page is about.
      That talk seemed to heavily object the idea that "electrons are particles" (in the sense that they are physical objects).
      Peter Lindsay above already commented on that that particles don't have to be physical (solid objects) in physics but merely individually measurable quantities.

      I'll look into the other site tomorrow as it seems like a decent place to start a search from, but today I unfortunately don't have the time to start the search ;).
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        Jan 30 2013: I hope you get the sort of explanation and elaboration through some of the links that can advance your thinking as far as you like.

        I know you know, Richard, that Conversations is not super reliable for scientific explanations, but I think sometimes people new to the site think Conversations is the TED speakers talking.

        I had a bona fide quantum physicist look at some of our little physics discussions here a few weeks ago and his reaction gave me the idea of always posting links to the real authoritative sources when someone asks a physics question.
        • Jan 30 2013: I don't expect any of my "conversations" on TED to lead to any 1 specific scientific answer.
          But when enough people read / think about the question there is a really high chance that someone will be able to either give you the answer or link you to an answer.

          In this case my problem is that the answers that I had been given in the past seem to be very difficult to combine with some more recent information. (as recently I've been watching some more physics lectures from Walter Lewin / Richard Feynman)

          I've already had quite a few posts here describing things that, to me, make a lot of sense. Now it's up to me to see which (if not all) explanations seem most plausible. (where here plausible would mean most broadly supported by science)

          What kinda freaks me out the most though is that within a few hours from posting this... I've already seen an explanation that pretty much tells me that what I've learned in the "physics" class in highschool was wrong.
          That is quite upsetting (if it's true) that the scientific world moves this slow and that I got thought something that has been disproven for more than 60 years (at the time that I learned it).

          Anyway I'll try to read up on the subject and see what happens with the newly gained knowledge :)

          Thanks again for your feedback.
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        Jan 30 2013: Some things we probably learned from outdated sources, and other things we may not remember well.
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    Jan 30 2013: http://www.youtube.com/watch?v=DfPeprQ7oGc

    Though I don't necessarily agree with the conclusion that the wave collapses to form reality. I am more with those who say that it is more probable that reality (all particles) are always wave energy.
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    Jan 30 2013: a particle in physics is a similar concept to words in a language. nobody really knows what a word precisely is, but there are things that somehow stick together, mostly unchanged, rarely created or abandoned. and we call them words. similarly, there are things often appear either 1 or 2, but never a half or 0,9. they look similar, in fact they look the same. they rarely appear or disappear, though they can sometimes. so they deserve a name. and since they seem to be localized, indivisible, simple ... hence we classify them a "particle". these are just names. labels. don't mean anything. the important thing is the actual theory (mathematical model) that describes the behavior of stuff.
    • Jan 30 2013: I disagree with the important thing being the actual theory / mathematical model.

      For me the concepts are much more important. We can make mathematical models while not understanding anything. But when you understand something it is (for some people at least ;)) easy to make a mathematical model out of it.

      In the lecture of Feynman that I watched yesterday he explains that the Mayans civilisation could very accurately predict (by counting) when the planet venus would be where in the sky. But they had no idea that it was another planet.

      For me it is much more important to know that there is a planet out there than it is to know exactly when it will be visiable.
      Same for all other parts of physics... I find it more important to know why reactions occur than which.

      You could say that
      "What happens" = observation.
      "How it happens" = math.
      "Why it happens" = understanding.

      Although both the what and the how are important... I'm much more interrested in the why :)
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        Jan 30 2013: well, at least i tried
        • Jan 30 2013: ehhhhhh...
          I think I gave you the wrong impression.... I agree with what you said except for what I point out in my reaction.
          I'm gratefull for your post :)
    • Jan 31 2013: Good point ! language bears the quality of a code, it separates into two what is really one.
      Math is actually doing the same, i am not sure it can be viewed this way , but math is probably in a better position here. It doesn't supply the division with a description, iow. it doesn't language it, the more abstract, the more real, paradoxically :) But even mathematics, if you take Kurt Goedel, is an uncertain enterprise.
      Nothing is secure.
  • Jan 30 2013: Since everything may be viewed in many ways Maybe there are no easy explanations, but as noted earlier you are talking about physics which has a very well-developed and quantitative explanation.
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    Jan 30 2013: They have measurable mass and a measurable amount of charge, which means that you can positively identify a single electron. In physics the term particle really only means something you can count. It need not have a physical presence like a ball or a brick.
    • Jan 30 2013: so basically you're saying that it can be the case that the stuff I was thaught is not completely accurate?

      For me it is similar to the difference between gas and a solid (I know that in this case it is a strange analogy).
      I always thought that electrons were small solid things in a space... but now that I've thought things through I realize that it makes much more sense to think about them as if they are gasses within a space.
      I know that both analogies are wrong... but it is easier to think about things we can both visualize than talking in terms of forces/fields.
    • Jan 30 2013: by the above post I mean that the drawings in textbooks hint towards the atom and the electron being physical objects (like a ball) which are just really really small.

      It might be better to look at it with a view of only forces rather than objects?
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        Jan 30 2013: Yes, in the current "standard model" the only reason for the existence of particles is to explain the minimum amounts of certain forces or characteristics. An electron is a known amount of mass and a known amount of charge that occupies a known amount of space. Mind you this applies to all particles. A proton for example is composed of three quarks. A quark is a known amount of mass, a known amount of charge plus a known amount of color charge that occupies a known amount of space. The little balls are just used to make it feel more real. Your gas analogy would be useful as a stepping stone. A little blob of non-descript "gas" that has measurable characteristics is quite a good analogy.
        • Jan 30 2013: I would've loved to be in your physics class Peter.

          Thanks I think it's pretty clear to me already. Just the idea that they are not "tiny solid objects" helps me understand a lot more of physics.
          Although it also gives rise to many other questions but I'll figure it out :)
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    Jan 30 2013: Here is one example. In the "Crookes Tube" it can be demonstarted that a beam of electrons will be deflected by an object placed in their path resulting in a shadow where they would otherwise have collided with the surface of the tube. This was done in the late 1860's.