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B Is it possible that an electron can have a negative mass?

  1. Jul 19, 2017 #1
    I have this brain worm and it's been bugging me for ages. I don't know enough about anything to be able to answer this but when I heard a theory that an electron can be in 2 places at once but then appears to be in a specific location when observed I started wondering how this could be possible. Is it possible that electrons have negative mass and if so could they then travel faster than the speed of light? Ep = mga would look interesting too as both m and g would be negative values? HELP!!!

    Any thoughts?
  2. jcsd
  3. Jul 19, 2017 #2


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    You'll see that description in many pop-sci books and articles, but it's somewhere between seriously misleading and just plain wrong. Sadly, when it comes to quantum mechanics there are very few reliable sources that aren't at least college-level textbooks.

    You might want to see if you can find the book "Sneaking a look at god's cards" by Giancarlo Girardi. It's no substitute for a real text book (and the two or so years of college-level math needed to get through the textbook) but it's reasonably user-friendly, doesn't demand a lot of math, and is way more accurate than whatever you were reading.
    Last edited: Jul 19, 2017
  4. Jul 19, 2017 #3


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    It is not possible, sorry. It would violate several fundamental laws of physics.
  5. Jul 19, 2017 #4


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    My thoughts on this is that, why haven't you look up all the numerous electron accelerators around the world and double check and see if they have reported finding such a thing?

    The thing about physics is that you simply can't come up with an idea and not even entertain the possiblity of checking for experimental evidence. That should have been the very FIRST thing that you should have done, especially when the facilities that deal with such effects are almost everywhere! There might even be an electron accelerator in your doctors' office!

    And oh, to be clear, the electrons do not have negative mass.

  6. Jul 19, 2017 #5
    I can't see how that would answer my question. Are you saying that someone somewhere knows how fast an electron orbits the nucleus in all or any atoms and in all of the electron's possible energy states?
  7. Jul 19, 2017 #6
    With all due respect Drakkith, how do we know that all of these fundamental laws apply in the quantum world? Do photons lose energy in gravitational redshift etc?
  8. Jul 19, 2017 #7


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    We have extremely accurate measurements of the electron mass. It is known to better than 1 part in a billion. And it is clearly positive.
    Quantum mechanics is the basis of all these fundamental laws (apart from General Relativity, which is not relevant here). Does quantum mechanics apply to quantum mechanics? Yes.

    Unrelated to the electron question: Objects with a negative mass cannot move faster than the speed of light.
  9. Jul 20, 2017 #8
    Thanks mfb, a clear constructive answer.
  10. Jul 23, 2017 #9
    Also, to clarify on this, @Nugatory is right that this statement is very, very misleading. This is what the author means:
    An electron, at any given moment, can have a probablitlty of being at point a, while simultaneously having a probablity of being at point b. The electron is NOT in two places at once, though. Technically, the electron is in a superposition of being at point a and point b. But note that this superposition has to do with probability.

    Here's a classical analogue (I could use Schrödinger's cat but I feel that this one connects more to "two places at once"): you, at random, throw a ball into a box. You have no idea where in the box the ball landed. Now, this box is designed (with slopes and such) that any ball thrown into the box can go down hole a or hole b, and it will always go down one of those holes. Hole a leads to California and hope b leads to New York. After enough time for the ball to reach its final destination, I now ask you where the ball is. The answer is that the ball has some probablility of being in California and some probablility of being in New York. These places are so, extremely far apart, yet the ball could be in either one of them. The ball is in a superposition of being in California and being in New York, and you don't know which one until you look for the ball. Popsci books will call this superposition the ball being in both places at once. Well, you can see how that is misleading.

    I've always liked this explanation: a particle in a superposition is not in one place or the other, it's NOT in both, but it is also not in neither.
  11. Jul 23, 2017 #10
    With all due respect, your classical analogue will cause more confusion; there are no "classical" analogues to describe quantum phenomena!
  12. Jul 24, 2017 #11


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    The mass of the electron is measured and well known to 8 digits. It's not negative.
  13. Jul 25, 2017 #12
    1. How is the mass of the anti-electrons in the Dirac's ocean - vacuum, provided they have negative energy and m = E/c²?
    2. Whatever the answer to question 1., what is the physical meaning of a body having a negative mass? have it a negative inertia? Acceleration opposite to force? And about gravitational mass? A negative mass would attract or repel another negative mass? And would attract or repel a positive mass? Why have positrons and the other antiparticles a positive mass? If neither antiparticles have negative mass, how can physicists admit anything having negative mass?
  14. Jul 25, 2017 #13


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    Positrons have positive energy. Their mass has been measured to 1 part in 100 million, and it is clearly positive as well (and identical to the electron mass within the uncertainties).

    A negative mass, in the way mass is used, would imply that it accelerates against the direction of applied forces. It would still fall down in gravitational fields, as the mass of the test particle does not matter for its motion. How it would act as a source of the gravitational field is unclear.
    Why not? Everything has zero or positive mass.
    We didn't find anything with negative mass yet.

    Some quasiparticles can accelerate against the direction of forces, but that is only a phenomenon seen in a medium with very special properties, and you do not have actual particles with negative mass.
  15. Jul 25, 2017 #14
    I believe there are concepts in Quantum Electrodynamics or QED that suggest the so-called 'bare' mass of the electron may be negative. The mass that we can measure is supposedly the 'bare' mass dressed up with interactions with the quantum vacuum that makes it finite and positive. If, and it's a very big if, probably an impossible if, if one could isolate such 'bare' mass without destroying the universe, one might be able to build Alcubierre Warp bubbles or Stargates according to prof. James Woodward. But all this is so highly speculative at this point and I only mentioned it because it relates to your question as to breaking the speed of light.
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