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Mike Tarbutt
Imperial College London's Dhiren Kara adjusts the laser system used to measure the shape of the electron.
The most precise measurements of the electron ever made suggest that it's perfectly spherical to an accuracy of less than
In this case, we're actually talking about the "shape" of the electron's interactions with electric fields rather than whether it's a non-spatial point particle or a tiny vibrating string. Those concepts are fine in other contexts, but for the laser experiment conducted by researchers at Imperial College London, size (and shape) matters. The measurements, which were 10 years in the making, are reported in this week's issue of the journal Nature.
If the physicists had seen an irregularity in the electric dipole moment — that is, the orientation of the electron as it spins in an electric field — that would have lent support to some of the non-standard models in particle physics. One example is the idea that an extra supersymmetric particle (a.k.a. "sparticle") exists for every particle we know about in the standard model. Another example is the view that the interactions involving matter are just slightly different from interactions involving antimatter ... which would explain why we see virtually no antimatter in the universe around us.
The fact that the electron seems so perfectly round suggests that the search for "new physics" at Europe's Large Hadron Collider might be harder than some scientists had hoped. That meshes with the LHC's initial findings ... or, should I say, the non-findings of exotic phenomena such as microscopic black holes and supersymmetry. The LHC is still ramping up its data collection rate, however, and physicists say it's way too early to guess at what they'll find or not find.
In any case, the results reported in Nature are considered an observational tour de force.
"We're really pleased that we've been able to improve our knowledge of one of the basic building blocks of matter," research team member Jony Hudson said today in a news release. "It's been a very difficult measurement to make, but this knowledge will let us improve our theories of fundamental physics. People are often surprised to hear that our theories of physics aren't 'finished,' but in truth they get constantly refined and improved by making ever more accurate measurements like this one."
In a Nature commentary, University of Michigan physicist Aaron Leanhardt noted that the previous best attempt to detect the electron's electric dipole moment was reported by other researchers in 2002, by making fine-scale measurements of electrons in a beam of neutral thallium atoms. The Imperial College team pushed the envelope by measuring the motion of electrons in ytterbium monofluoride molecules, using highly precise laser pulses.
If the electrons were not perfectly round, their motion would exhibit a slight wobble, like a spinning top that's running down. As a result, the shape of the ytterbium monofluoride molecules would be distorted. But the physicists saw no sign of such a wobble. Instead, they determined that any variance from perfect roundness, stated in terms of centimeters, would have to be less than 10.5 times 10 to the -28th power times e, where e is the charge of the electron.
"This means that if the electron was magnified to the size of the solar system, it would still appear spherical to within the width of a human hair," Imperial College said in its news release.
Hudson and his colleagues aren't finished yet. They report that they're working on new techniques that could make even finer measurements of the electron, allowing them to "probe for new particle physics at tens of tera-electronvolts." In comparison, the top collision energy achievable at the LHC is a mere 14 tera-electronvolts, or 14 TeV.
It's mind-boggling to think that ultra-fine measurements of electrons can guide physicists' investigations at the highest energies achievable on earth. That perspective is what led Leanhardt to hail the Imperial College team's effort as a significant push into the frontiers of physics.
"Experiments of this genre reach far beyond the realm of atomic, molecular and optical physics: they can be viewed as low-energy windows on the high-energy soul of the cosmos," he wrote.
More about the frontiers of physics:
- What's a hadron? Take a tour of the particle zoo
- Fundamental cosmic constant now seems shifty
- Particle discovery has the physics world buzzing
- Higgs boson rumor as elusive as the particle itself
In addition to Hudson, the authors of "Improved Measurement of the Shape of the Electron" include D.M. Kara, I.J. Smallman, B.E. Sauer, M.R. Tarbutt and E.A. Hinds.
You can connect with the Cosmic Log community by "liking" the log's Facebook page or following @b0yle on Twitter. Also, give a look to "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.
Leave a Comment:
an expert is somebody who knows more and more about less and less...until he knows everything about nothing...which is what we have on display here....
I found the amazing roundness of the electron reminiscent of the Platonic ideal of a sphere. It was both intellectually and esthetically stimulating to find such near-perfection in a disordered universe.
Sorry it is too big a concept for you...
thankyou for your expert comments
dobnoi, dobnoi, dobnoi,
The essence of knowledge is, having it, to apply it; not having it, to confess your ignorance. - Confucius
I came up with this theory that the the atom was comprised of perfectly spherical particles which accounted for the perfect refraction rate of light months ago. I should have been a physicist because this is no news to me.
I got something else to share with you too that you're going to "find" out with your experiments. You ready? ... Soon you're going to find out that the particle that gives "mass" to everything resides in the neutron. Let's give you a few more years to figure that one out.. then give me a call, but don't leave me off the list when it comes to the Nobel Prize, because when you find out the neutron-gravity particles exists there... you can thank me for it.
As far as I'm concerned, most of you physicists suck and think too mathematically and don't use your imagination enough.
-CM
@CavemanStyle
Um, I really hate to break this to you but the neutron has mass, as you say,
So yes, you are 100% right, the particle that gives rise to mass IS in the neutron, very imaginative on your part.
I thought the whole point of working those horrible Schroedinger's equations was to prove that the electron collapsed into a certain state when you measured it. If it weren't spherical there would be pretty dire implications for oh xyz coordinates. Of course, they still have torque.
Dobni:
I must disagree. History itself tells us that man's quest for knowledge is inherent in all of us. To seek to determine the very reason for our existence was born out of millions of years of evolutionary growth. The need to know.
The smallest particles envisioned by the Science of Particle Physics will be the keys to unlock the mysteries of the Universe. The quest for knowledge of anything and everything is 'hardwired' into us and it can't be deleted from our very being. The study of the infinitely small IS the key to every question we have about the construct of the Universe. I am sorry if you can't see that need.
The smallest particles envisioned by the Science of Particle Physics will be the keys to unlock the mysteries of the Universe
my friend your words above are the very definition of HUBRIS and I thank you foir so beautifully voicing the standard fallacy so clearly. Man will never unlock the mysteries of the universe - he just doesn't own the right equipment for it and never will.
Oh corpuscular wonder, what hath thou wrought?
To say that the smallest particle will answer big questions is naive. It is a reductionist that cannot truly love, nor ever truly know pain.
Yes William I agree. Let's stop waisting our time trying to understand the universe around us. Let's instead catatonicly enjoy the pleasure and knowledge that the bible provides.
We won't unlock many mysteries if we don't manage our Earth better.
Personally, I do find it fascinating that we have tools that allow us to appreciate creation at this level. However, it's not that surprising considering that anything less perfect would make a less stable platform for existence. Magnified over the expanse of the Universe may well have made it impossible in the first place. It exists, therefore it is most likely perfect. It is perfect, therefore it most likely exists. [Conjecture.]
You would agree, Dobni, that if everyone had your attitude we wouldn't be here in our A/Cs, typing away on our computers?
Sure we have only touched the surface, but we have only been here a very short time, and not only that we have religion. So we as humans expanding just this much in such a short time and with such needless useless weight is something to be proud of. Just think as religion shrinks and the common human starts thinking deeply about the world around him/her instead waiting and preaping for death all their life.
enthusiasim and excitement are off the charts here... gonna need some new charts.
I was happy to maybe learn something about electrons not sure I have... in that gibbly-gook fanboy text.
awesome, I once did the milikan experiment and extended it out to the charge on a quark or 1/137th e- if you will, in the late 70's my high school physics teach directly told me that quarks were only a theory...great, my penn state profs were a bit more enthusiastic though, thank god. At this diameter, his measurements are nearing the diameter of the quark confinement bag, it is something to think that quark-quark bonds are so tight that the experimenter found no deviation in spherical diameter, I hope more scientists duplicate his experiment and publish the results, I eagerly await confimation!!....kudos to the scientist and his team, imagine the perserverance it takes to make such an accurate measurement, even in a well funded lab (pop quiz, with out checking above, chime in if you caught the lab's name)....and better still, imagine the kahunaus you gotta have today, when such peer review can come from all over academia when NATURE is so ubiquitous (online in every continent, even the frozen ones)...his findings will stand I am sure, and hopefully the people such as dobni above will have as small an affect on his (or any other) scientific ambitions as the dimensions of the measurements he made....awesome dude, take it one more decimal point if you can!!! (I actually counted em before typing, just be sure, I understand the logs reasoning for not placing it in sci notation, not everyone who reads at a fifth grade level knows sci notation...hehehe..)..thanks alan, now it's off to read the whole paper!!
I don't think electrons are composed of quarks. They are fundamental particles not know to have any constituents.
@William Dobni
1) We already have unlocked many great mysteries of the universe
2) The point isn't to necessarily to find the ultimate truth, it's to get closer to it
3) I find it hilarious that you are using a modern computer and the internet to challenge man's quest for knowledge. Do you have any idea the amount of modern physics that goes into making your trite comment possible? It's very disingenuous to criticize our advancement of knowledge and to then take advantage of it. Make up your mind.
1. If this is the accuracy to the true value, what is the precision of this measurement?
2. How many parameters were there is the measurement system?
No the measured value was
(−2.4 ± 5.7stat ± 1.5syst) × 10−28e cm. Be careful not to confuse accuracy and precision which are two completely different things - you can be incredibly precise but not accurate (think of 3 darts clustered on a particular number which is not the bullseye), likewise you can be accurate but not precise (think of the darts spread all over the dart board but on average they are centred around the bullseye).
This measurement is incredibly precise but that is not why this is the first experiment of its kind in ten years or so. The measurement took so long because the scientists had to ensure accuracy - ensuring all systematic errors had been accounted for. There were 9 parameters (or thereabouts) which were switched during in the experiment. Also many other supplementary measurements were taken to ensure accuracy. Finally the experimentalists were 'blinded' from the final result so that they could not intentionally or unintentially bias the result.
Small Joe, thank you for your concise, clear explanation, it made sense even to a non mathamatical person... me!
Why would they suspect that the interactions from a point particle would be anything but perfectly spherical? If that was the case, would we also be able to define a specific direction in space for electron spin? Also, I'd think our universe would work completely different than it does if electrons had asymmetric interactions.
That's part of the point. A whole lot of theoretical physics concerns itself with questions of 'Well, what if such and such were the case? How would that affect reality as we know it?' then the experimentalists go and do their work to verify if indeed such and such is the case.
A couple of possibilities were alluded to in the article, if electrons did not have a perfectly spherical dipole moment... But in fact, it appears that they do, so we don't need to spend more time and energy chasing down that that particular dead end path.
This is a good writing, containing helpful material which ultimately enhances the interest of the reader in that particular topic. Keep it up :)
it sickens me to see such a dearth of confidence in human faculties, especially from the lips of those who have so clearly abandoned there's....
Don't be deceived by the liberal left wing media! These so called mythical electronscannot be near perfect spheres - unless you are a socialist! Socialism I tell you. If you believe that electrons are spheres, then you are buying into the lie and drinking the koolaid! Electrons are the second biggest hoax perpetrated on man!!!
(In all seriousness, I find this article very interesting. Subatomic physics are cool beyond cool because all of the conventional physics we know in the world around us start the break down the deeper you look. Fascinating read.)
Also physicist pen the coolest names.......leptons, gluons, quarks, tau particles, etc.
WAVE GOODBYE
-- James Ph. Kotsybar
An electron, so perfectly round
it could spin without wobble or sound,
was measured carefully
at fixed velocity,
but its position couldn't be found.