What Shape Are Electrons? Scientists Try To Find Out
ROBERT SIEGEL, host:
From NPR News, this is ALL THINGS CONSIDERED. I'm Robert Siegel.
MICHELE NORRIS, host:
And I'm Michele Norris.
When school kids make models of atoms and they have to represent the electrons whizzing around the atom's nucleus, they usually reach for things like Ping-Pong balls, round things. But are electrons really spheres? The answer to that question has important implications for understanding the nature of our universe.
And as NPR's Nell Greenfieldboyce reports, scientists have made their best effort yet to discern the shape of these subatomic particles.
NELL GREENFIELDBOYCE: This new method of determining the shape of an electron is so precise that it boggles the mind. Johnny Hudson is a physicist at Imperial College London. He says just imagine if you took a teeny electron and enlarged it to the size of the solar system.
Professor JOHNNY HUDSON (Physics, Imperial College London): We've measured its shape with an accuracy equivalent about one human hair. It's a stupendously accurate measurement. You can't even think about how accurate it is. I think it's got a lot of decimal places.
GREENFIELDBOYCE: It took six people a dozen years to do it. They developed a measuring system that uses red and green lasers. It gives their lab an unearthly glow. And inside their apparatus, they created a special molecule that is orbited by a single, lonely electron.
Prof. HUDSON: We then take the molecule, and then we send it into a region where we have some electrically charged plates.
GREENFIELDBOYCE: The test was to see if the electron would start to wobble because that would tell them how round it really was.
Prof. HUDSON: To give you an analogy, right. If I put a perfect spherical ball on my desk, it wouldn't flop over one way or the other because it's a perfect sphere. Every way up is just as good. Where if I put an egg on my desk, it would fall over onto its side. And so it's just the same thing. If the electron is not round, then any force on the electron might make it turn.
GREENFIELDBOYCE: They checked this not once, but about 25 million times. And in order to be really precise, they had to shield this sensitive experiment from very tiny interferences that could mess it up. How tiny?
Prof. HUDSON: The example I always like to give is if you think hard, then all the neurons in your brain fire. And actually, if you put a magnetic field sensor on your head, you can detect that change in magnetic field. And actually, that change in magnetic field would be enough to completely ruin our experiment.
GREENFIELDBOYCE: So do you all just make sure that you don't think during your experiment?
Prof. HUDSON: We just - absolutely no thinking in the lab is the rule. Yeah.
GREENFIELDBOYCE: That's a joke, obviously. One thing that was forbidden in the lab for a long time was seeing the results. Hudson and his colleagues had their computer system hide the data to make sure the team stayed unbiased. Then one day, they all gathered in an office, hit a button and finally learned the answer.
Prof. HUDSON: As best we can tell, you know, to our experimental precision, the electron seems to be round.
GREENFIELDBOYCE: The result is reported in the journal Nature. And it isn't just a bit of esoteric trivia. Hudson says many theorists don't want the electron to be round. It throws off their calculations. They're counting on a slightly aspherical electron to explain things, like why antimatter has pretty much disappeared since the creation of the universe billions of years ago.
And Hudson says as physicists take their best shot at developing a Grand Theory of Everything...
Prof. HUDSON: They almost always predict that the electron won't be round, that actually it should be noticeably distorted.
GREENFIELDBOYCE: Now, it's possible that even this new experiment was still not sensitive enough to detect that distortion. Dave DeMille is a professor of physics at Yale University.
Professor DAVE DEMILLE (Physics, Yale University): It's fantastically impressive that they've been able to make this measurement more precise than it has been before.
GREENFIELDBOYCE: But he says we need something even more precise. DeMille says what's exciting to him is that this is a new way of probing an electron's shape. He has some ideas for tweaking the approach.
Prof. DEMILLE: We and a few other experiments are projecting that we might be able to get sensitivities that's a factor of a hundred, a thousand, maybe even in the long-term, 10,000 times better.
GREENFIELDBOYCE: And he says pushing it that much further should reveal any bulges or dents that would make the theorists happy.
Nell Greenfieldboyce, NPR News.
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