10-Year Study Reveals Electron Shape 370
lee1 writes "In a 10 year long experiment, scientists at Imperial College have made the most precise measurement so far of the shape of the electron. It's round. So round, in fact, that if the electron were enlarged to the size of the solar system, its shape would diverge from a perfect sphere less than the width of a human hair. The experiment continues in the search for even greater precision. There are implications for understanding processes in the early universe, namely the mysterious fate of the antimatter."
Re:Under what conditions? (Score:2, Informative)
And, uh, what did they do about that Heisenberg thing? If you can't tell where the electron is relative to your frame of reference, how is the electron supposed to tell where a certain constant on its level curve is relative to its own frame of reference?
The measurement was indirect --- they didn't observe the electron but instead observed the lack of any distortion in the shape of the molecule. I guess this observation does not require them to pin point the position of the electron.
Re:Curious question (Score:5, Informative)
These virtual particles are tiny compared to atomic matter and exist for short amount of time, such a short amount of time thier very existence is below the uncertainty thresholds. They are a consequence of the fundamental uncertainty in position and momentum. They are created out of the vacuum.
So the question the experiment attempts to answer is does the electron behave like an object that reacts symmetrically in all dimensions, or is there so aberration, that is, is it not a perfect sphere. To a very high accuracy the paper claims that it is a sphere.
However that is not the full story. The paper is based on the idea that the aspherical shape would be larger than the standard model predicts. Adjusted models predicts a larger aspherical aberration. Since this experiment did not detect large aberrations, these other models, extensions of the Standard Model seem to be less than accurate. Form what I read, the standard model predictions are orders of magnitude lower than current sensitivity [nature.com] so it remains unclear if the electron acts like a sphere or something that is almost like a sphere.
What this experiment does is provide a novel and fascinating method to probe subatomic particles, as well as establish an upper limit on how big the abberation could be. Good science.
Re:Curious question (Score:5, Informative)
Actually, according to the paper the electron is aspheric in many theories, including the standard model (the best theory we have). From the article abstract:
Re:Under what conditions? (Score:5, Informative)
Is it always round, even when it's tunnelling through a potential wall?
I think that the way they are translating the physics into English is awful. I'm not sure I fully understand their method, but I'll try to restate. What they actually found was that they electric dipole moment of the electron was very small. It it were not that small, they would have seen changes in the wave function. From there they go to stating that if the electron can be modelled as a charge distribution or a charged object, that object would be spherically symmetric with dipolar radial deviations of less than that very small number. But more precisely, the wave function of an electron behaves as if it represents a particle that has a electric dipole moment less than 1.05E-27 ecm.
If course you couldn't actually make measurements to determine whether that dipole moment is a property of a physical shape of the electron or is an intrinsic property. Nothing we have can probe those size scales, and if you could you'd have particle antiparticle pairs popping up everywhere from the energy of the collisions. You might even create a new universe at those energies. Everything we've done so far suggests that the electron has no structure, but that's on much larger scales/lower energies.
Re:puuurfect (Score:5, Informative)
No matter how high of an order you go for an approximation, there will always be a truncation error. That is the problem with using infinite series to represent physical models.
Re:all that wave particle jazz (Score:5, Informative)
No it's not. Your head exploding is a perfectly normal reaction to trying to comprehend the piece of shit that passes as scientific journalism nowadays. I'm a physicist and after reading the article I still had no idea about what the researches discovered. At least Science Daily had the original reference so I could look up. Even more appalling is BBC's coverage: http://www.bbc.co.uk/news/science-environment-13545453 [bbc.co.uk]
They both only said "lasers" about what the group actually measured. As if the measurement technique were as relevant as what they were actually measuring. Even laymen like OP see that there's something weird about saying the electron has a shape and is a sphere. Of course, this makes absolutely no sense. This talk about sphere is a semiclassical analogue that someone in the 20's once thought that could be true and was quickly disproved. What they measured was the electron's electric dipole moment. What is that?
Imagine a small bar magnet, with south and north poles. This is what we call a magnetic dipole. The strength of the magnet (measured in a standard way) is what we call magnetic dipole moment. Now imagine that instead of south and north poles, we have negative and positive electric charges. This is an electrical dipole, and it's strength is likewise the electrical dipole moment.
Now the beauty of the electron is that despite not being a small bar magnet, it still displays a strong magnetic dipole moment, which we call spin. Originally people thought that it could be explained by postulating a structure on the electron (an electric charged spinning sphere gives rise to a magnetic dipole moment, hence the name spin), but quickly we found out that it couldn't be so. We have no explanation for it, it is what it is, just a property of the electron.
But what the electric dipole moment? The electron is a single charge, so it can't be an actual electrical dipole. But despite this, the Standard Model predicts that it has a very small electric dipole moment, too small to be measurable. But Supersymmetry predicts that it is quite larger, and even measurable, and these folks' measurement showed that Supersymmetry's prediction is probably wrong.
Ok, but why did they call it measuring the roundness? Analogously with the spinning sphere model for the magnetic dipole moment, a distorted sphere gives rise to an electric dipole moment. But calling it measuring the roundness makes as much sense as saying that when we measure the magnetic dipole moment (spin) we are measuring the speed with which the electron spins about itself.
So, makes more sense now?