10-Year Study Reveals Electron Shape

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."

Comments

Units

[Nemyst]

I know the site is probably trying to be approachable, but what's wrong with saying 1e-29 m instead of this absurd measurement of 0.000000000000000000000000001 cm? This is getting close to the Planck length; no matter what you compare it to, it won't be a length you can intuitively grasp.

Re:Units

[Twinbee]

The 0.000...001 version maybe visually represents the amount better.

Re:Units

[Anonymous Coward]

From the reference article :
We obtain de = (2.4±5.7stat±1.5syst)×1028ecm, where e is the charge on the electron, which sets a new upper limit of |de|10.5×1028ecm with 90 per cent confidence.

Re:Units

[mattack2]

What's wrong with calling it mysterious? The theories say there should be equal parts matter & antimatter.. There doesn't seem to be.. So it's a mystery.. Thus, as an adjective, it is mysterious.

Re:Units

[M0j0_j0j0]

Or 6.21371192 × 10-33 miles , remember this is an international board ....

Re:Units

[CapOblivious2010]

It's not the size of your uid that counts - it's how you use it.

Re:Units

[Surt]

But it's USA-centric, per the faq.

Re:Units

[sumdumgai]

Easy for you to say.

Re:Units

[X0563511]

I think you could have left that short (heh) at "your UID doesn't fucking matter, you fucking cunt" and described it quite succinctly :)

(I've seen plenty of low-UID idiots)

Re:Units

[Ultra64]

Mysterious? Yes. Really.
http://en.wikipedia.org/wiki/Baryon_asymmetry

Re:Units

[superdave80]

It certainly measures MY length!

Re:Units

[blueg3]

It doesn't. Unfortunately, once you add lots of zeros (or, with the converse, a lot of 9's), people lose any sense of how big the number is. Granted, people also don't have a sense of what 10^29 is like, but if they're going to be lost either way, might as well use a standard that's helpful for people good with numbers.

Look at any Slashdot post, for example, where people talk about low probabilities. It'll be 0.00...01%, even if the actual number they use is dramatically, horribly wrong. (Something that's happened once in a hundred years, that's a 0.00000001% probability, right?)

Re:Units

[blueg3]

There should be more antimatter. There's not, as far as we can see. We don't know what happened to it. Hence, mysterious.

"Fate" is a bit unfair, though, since it properly refers to the future.

Re:Units

[davester666]

Heisenberg phoned and left a message saying all these numbers just MIGHT be slightly too precise...

Re:Units

[gl4ss]

it's a zero, point, lots of zeros and a one. it actually presents it pretty well, but better would be to present it with other sums in the region, like the size of some molecule or something - and present them with the point matched. then it's easy to see that something is 1000 times bigger than some other number. and use a fixed width font.

0.00000000000001
0.00000000000000001
0.0000000000000000001

1e-29 m sounds like a designer drug to most people nowadays, get used to it.

Re:Units

[Joce640k]

There's somebody out there who calls themselves "Situation"?

Do people send him packets of currants for his birthday then piss themselves laughing? I would.

Re:Units

[Waccoon]

All that tells me is that it doesn't fit on a calculator screen.

Re:Units

[roman_mir]

What next? Maybe we aren't really related to monkey? Maybe there really is a God?

to find out the answers to these, and other interesting questions, such as: are all ACs on /. trolls or are some ACs more trollish than others stay tuned to our program at "Kinds of Questions that Ass-hats Like to Ask".

Re:Units

[irtza]

nor the theory of general relativity provide an obvious explanation for why this should be so;

From your source. So, mystery it is?

Re:Units

[gmueckl]

Whether this statement (which in its general form covers more than just speed and location, but rather any two operators which are not commutative) does affect the measurements or not depends on the methods involved. But they will certainly have considered this before doing their experiments :).

Re:Units

[Muad'Dave]

It's about 618715 Planck lengths, actually. I had the same thought.

Re:Units

[willworkforbeer]

Close is relative, it is equal to almost 619,000 Plank Lengths.

http://www.unitconversion.org/length/centimeters-to-planck-lengths-conversion.html

Re:Units

[bipedalhominid]

Maybe we are related to a Monkey God?

Re:Units

[smolloy]

His uncertainty principle doesn't put any limits on how accurately we can know any one number. It puts a limit on how accurately we can know certain pairs of numbers (e.g. position and momentum). There is nothing in his principle that says we can't know one of those numbers *precisely*, as long as we are completely uncertain as to the value of its canonical pair.

Re:Units

[blueg3]

The uncertainty principle places no limits on how precisely you can measure a single quantity. It only places a limit on how precisely you can measure a pair of quantities (with some additional restrictions).

Re:Units

[louic]

1. 0.0000001
2. 0.0000000001
3. 0.000000000000000000000000001
4. ???
5. Profit!

Re:Units

[Grishnakh]

Luckily, you can get around the uncertainty principle by using a Heisenberg Compensator.

Re:Units

[dziban303]

Whoosh. Also, nice six-digit UID starting with 5. Get the fuck off my lawn.

Re:Units

[dziban303]

Idiocy wasn't the point, really. Some dude insinuating that the Good Ole Days were better, when he clearly wasn't around for the Good Ole Days, was the point. You get a "Also, nice six-digit UID starting with 5. Get the fuck off my lawn," too.

Electrons out of shape

[FishTankX]

I could just see it now.

The crystal latice questions the electron about it's excercise.

Electron: I'm in shape, round is a shape.

Under what conditions?

[blair1q]

Is it always round, even when it's tunnelling through a potential wall?

And I assume that by "round" they mean that every level curve of the probability amplitude has constant radius.

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?

Re:Under what conditions?

[Anonymous Coward]

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:Under what conditions?

[cheeks5965]

how is the electron supposed to tell where a certain constant on its level curve is relative to its own frame of reference?

Oooh electron, you got burrrned!

Re:Under what conditions?

[SETIGuy]

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:Under what conditions?

[quax]

Thanks for clearing this up.

I have a master of physics but skimming through the article I could not make heads or tail of what these guys actually measured.

Extrapolating from the dipole moment to the headline that the electron is perfectly spherical is just cringe-worthy.

Re:Under what conditions?

[jd]

So long as you don't know how fast it is moving, knowing where it is is fine. The exact rule is that the product of the level of uncertainty of the variables is a constant, not that the variables have to be unknown.

Re:Under what conditions?

[Your.Master]

Umm.

No, it's not stupid and it's not obvious. It applies to "everything" only in that everything is composed of quantum matter, but generally it doesn't apply meaningfully to macroscale objects.

The uncertainty principle isn't some soft and squishy rule-of-thumb that can be trivially applied to the contents of your refrigerator, it is a very specific physical inequality (or set of inequalities if you want to include things like energy-time, etc. along with position-momentum) which was the result of hundreds of years of modern science (following many thousands of years of pre-modern discovery).

I have to assume you don't really understand the Heisenberg uncertain principle if you make claims like this. Because there's no way it's "obvious" to any human that the minimum product of the uncertainties of the position and momentum of a particle in a measurement is 5.27285738 × 10^-35 kg m^2 / s.

Re:Under what conditions?

[blueg3]

No, they don't mean the wavefunction for an electron. What they undoubtedly mean is its "shape" as measured by scattering (e.g., colliding electrons with one another).

Re:Under what conditions?

[mathfeel]

It is important to distinguish the size of an electron versus the size of its trajectory under certain potential. Tunneling of electron (or electron under any long range potential) is not squeezing the electron into certain shape, but rather its position wave function: probability amplitude of where it can be. It provides NO information about what internal structure, if any, an electron has.
I believe by round it means one cannot distinguish any orientation of the electron. e.g. perhaps the experiment can measure quantity X as function of laser angle and found that X do not depends on angle at all to very good precision. This means the electron looks the same from all angle, inferring that it is "round".
One consequence of a non-round electron would possess a dipole moment. Judging from the article, I got the impression that they tried to measure the effect of electron having any dipole moment. A charge dipole would experience a torque in the field of the nucleus and therefore alter the electron's motion and make it "wobble". They did not observe any such wobble and this quantitatively allows them to put an upper limit on the dipole moment (if any) of electron.

Re:Under what conditions?

[Entropius]

It's at least sort of reasonable, though. An object with no dipole moment, no quadrupole moment, no octupole moment, etc., *is* spherical; the dipole moment is just the second term in a multipole expansion of the shape, the first one that describes perturbations away from sphericity.

They measured the dipole moment as nearly zero; it's reasonable to assume that if the dipole moment is zero then the higher moments are nearly zero, too.

Re:Under what conditions?

[Entropius]

The Heisenberg principle is just a consequence of a property of Fourier transforms that says that any signal localized in frequency space will not be localized in the original space. There is no magic there at all.

Where the magic comes in is the relationship between momentum and position, and energy and time, operators in QM. The position dependence of a momentum eigenstate is sinusoidal, so you use Fourier transforms to convert from the momentum eigenbasis to the position one. Thus, any state well-localized in the momentum basis will not be well-localized in the position one, and vice versa. This isn't because of any voodoo "uncertainty" that's unique to QM; it's a direct consequence of the fundamental way QM works and the way Fourier transforms work.

Re:Under what conditions?

[JonyEpsilon]

Yeah, it really is spherical in any sense that you can mean spherical. It can't have any higher order multipole moments because it only has spin 1/2. (So the Wigner-Eckart theorem tells you that all matrix elements with operators greater than spin 1/2 are necessarily zero.) Jony

Re:Under what conditions?

[AliasMarlowe]

The Heisenberg principle is just a consequence of a property of Fourier transforms that says that any signal localized in frequency space will not be localized in the original space.

It's a consequence of linear operators in general. Conceptualizing it in terms of the Fourier transform which localizes an invariant process very well in frequency and not at all in position may limit one's viewpoint. It's more informatively interpreted using time-frequency decompositions such as the Wigner distribution (or position-scale representations such as wavelet transforms), in which there is a direct trade-off between localization in frequency (or scale) and localization in time (or position).

Where the magic comes in is the relationship between momentum and position, and energy and time, operators in QM.

An even bigger magic comes from the applicability of mathematics to physics, which is an interesting philosophical issue in its own right. "How can it be that mathematics, being after all a product of human thought which is independent of experience, is so admirably appropriate to the objects of reality." - Albert Einstein.

Re:Under what conditions?

[V!NCENT]

That shit counts for everything... There is an infinite amount of situations to test, so you can't test them all, so you cannot prove anything. You can only assume that you've tested enough.

Maybe under a certain condition you can messure the size and location at the same time, but you just haven't tried all possible combination.

Re:Under what conditions?

[Noughmad]

There is at least one electron in Scotland, one side of which appears to be round.

Re:Under what conditions?

[Noughmad]

Ouch, I wasted a good opportunity for another Mathematician joke. The "There is" should be "There exists".

Re:Under what conditions?

[taiwanjohn]

Yeah, I'm no physicist, but even I was wondering about that whole "spherical shape" thing. Ever since high school, I've had the notion that electrons are probabilistic, with no "knowable" location or shape.

Re:Under what conditions?

[tehcyder]

The uncertainty principle isn't some soft and squishy rule-of-thumb that can be trivially applied to the contents of your refrigerator

So is the reason I couldn't accurately determine both the number and names of the cans of beer in my fridge last night simply that I was drunk?

Re:Under what conditions?

[tehcyder]

An even bigger magic comes from the applicability of mathematics to physics, which is an interesting philosophical issue in its own right. "How can it be that mathematics, being after all a product of human thought which is independent of experience, is so admirably appropriate to the objects of reality." - Albert Einstein.

What's so surprising about that? Human beings, human brains and human brains are part of reality too.

Re:Under what conditions?

[Seedy2]

Is that part of the Heineken uncertainty principle?

Re:Under what conditions?

[qubezz]

Fourier transform is the most stupid and obvious principle ever. Eigenvalues too. They apply to everything.

Re:Under what conditions?

[cpotoso]

Correction: spin 0 or spin 1 operators only. A spin 1/2 added to a spin 1 can give spin 1/2 or 3/2, hence an operator with spin 1 can have a non-zero matrix element between two spin 1/2 states. Note that two spin 1/2's always add to an integer spin (0 or 1).

Re:Under what conditions?

[JonyEpsilon]

Oops, yes, exactly right. I shouldn't post before I've had my cornflakes.

Re:Under what conditions?

[WastedMeat]

Actually, if you only have charge of one algebraic sign, there is always a convenient point of reference (a center of charge, analogous to a center of mass) from which there is no dipole moment. Any other point of reference would give you a dipole moment due to the displacement of the entire particle, not its internal properties. A distributed electric monopole is analogous to a mass, as far as deformations go; the first perturbation away from 'sphericity' would be to make it a subtle ellipse, which is a quadropole deformation. This is the lowest possible deformation in a mass distribution since a change in monopole moment implies matter/energy is created, and a change in dipole moment implies that the center of mass accelerates, and you are therefore looking at an incomplete picture.

What you are stating is analogous to a Taylor expansion in which, just because the linear coefficient is zero (i.e. you are expanding about a maximum or minimum), you assume all higher corrections are zero and the function is constant.

Re:Under what conditions?

[blair1q]

it's reasonable to assume that if the dipole moment is zero then the higher moments are nearly zero, too.

Is it?

The dipole moment is innately asymmetric.

The quadrupole moment can be symmetric.

If all they did was measure symmetry and find no asymmetry...

Re:Under what conditions?

[WastedMeat]

Although perhaps what is measured here is a dipole moment as defined from the center of mass. I guess that also makes sense.

Re:Under what conditions?

[StikyPad]

Mathematics aren't independent of experience; they're built on experience. They necessarily make certain predictions which can be extrapolated sans experience, but those predictions are a consequence of a foundation which, again, is based on experience and observation. Mathematics describe reality by intent, not by accident, and if they didn't, the maths would be revised.

Finally, crediting mathematics as a whole because a given formula perfectly describes a natural process is ignoring the infinite variations which do not.

Re:Under what conditions?

[blair1q]

"How can it be that mathematics, being after all a product of human thought which is independent of experience, is so admirably appropriate to the objects of reality." - Albert Einstein.

Because real objects follow logical processes, and math is logic. The "independent of experience" part is why it's purely logical and not prejudiced towards assumptions based on apparent constancy of observations, which, it turns out, is precisely why physics has to turn to math.

Re:Under what conditions?

[arisvega]

I have a master of physics but skimming through the article I could not make heads or tail of what these guys actually measured.

So who gave you that MSc?

Re:Under what conditions?

[Unequivocal]

This may sound dumb (I don't even know enough to know that), but do we know if the electron actually has a physical structure at all? Doesn't string theory (whatever that is) suggest that electrons are just elements of strings surfaced into 3-d from some n-d space? If so, what does round even mean? I'm really asking all these questions, but not sure if any experts will want to bother to provide answers or links to answers. Thanks.

Re:Under what conditions?

[pnewhook]

Right on sister.

Re:Under what conditions?

[pnewhook]

It is stupid. It simply states that you cannot measure two interrelated properties simultaneously to an arbitrary precision. Can you actually measure *anything* to an arbitrary precision? It's just one of these fudges to make up for the mistakes and fudges in quantum mechanics. When they figure out quantum mechanics correctly and tie everything together, the uncertainty principle will go away.

Re:Under what conditions?

[quax]

This is why this article is so ludicrous. Current understanding is that the electron doesn't have a structure and is a elementary particle with intrinsic spin. I.e. it is a point particle.

Within the precision of their measurements they did not find any higher order electric moments. If they did it'll hint at a sub structure and that'll be a rather major discovery.

This is good science but a terribly written article.

Re:Under what conditions?

[quax]

What probably happened is that the scientists tried to illustrate the incredible precision of their measurements by illustrating what that'll translate to for a classical charge distribution.

The author of the article who apparently didn't pay as much attention in high school as you did just ran with it and mistook the analogy for the real thing describing the electron as a perfect sphere.

Most current theories assume a tiny electron dipole moment and that's what motivates this slow motion goose chase.

If the electron had a dipole moment that'll either mean if has a sub-structure or it'll be the first point particle observed to have a dipole moment.

I am pretty disenchanted with the state of theoretical physics these days and I don't have much faith in any particular prediction.

Especially since the implications are pretty pro-found. It'll mean that parity invariance and time reversal invariance no longer hold.

So I am not holding my breath expecting an elementary electric dipole to be found any time.

Curious question

[gcnaddict]

What other possible shapes were theorized for an electron? What are these theories based on? What difference would an egg-shaped electron make in the grand scheme of things?

I know why we should care, but I wouldn't mind knowing what theories exist to justify different shapes.

Re:Curious question

[Anonymous Coward]

Egg shaped one throws away everything we know about quantum physics, in short. As solution to Schroedinger equation is spherical (in the lowest energy state),

Re:Curious question

[Relic of the Future]

There don't need to be any competing theories: we have *a* theory and it says "round". Technical capabilities improved so we can test that theory to higher precision. So we tested it. The theory still stands. But the absence of a competing model has ZERO to do with whether or not we should test the current theory.

If you want exactly two sides to every argument, go into political journalism.

If the test had come back negative, THAT would be interesting, and I assure you there would soon be plenty of theories (and then lots of tests!)

Remember, the most interesting phrase in science isn't "Eureka!", it's "Well that wasn't what I expected..."

Re:Curious question

[gcnaddict]

My good sir, I merely asked a few questions. I made no statement indicating an expectation of multiple theories, merely a query for any in the event that any happened to exist.

As an aside, it would do you wonders to investigate new methodologies of conveying written information. Your response, most notably the capitalization, the usage of asterisks for emphasis, and the snide remark about political journalism, appeared to have a not-terribly-subtle hint of condescension. As someone who wants to learn more, this is something I most certainly do not deserve after asking a benign question.

Re:Curious question

[blair1q]

Well, having now read TFA (i do that when i'm bored and the topic is ultra-geeky like electron shape must be), it seems all they could have been measuring here is the shape of the electrical and quantum fields around the electrons in not just an atom but a molecule (of the sexily named ytterbium fluoride).

So what they've done is proved solenoidality of both; i.e., that they obey the inverse-square law to an anal-retentive degree; i.e. that force = A*1/r^(2+x) where |x| 1e-29. We only know gravity's solenoidal to about 8 significant figures, for comparison.

Interestingly, the shape of the fields around the nuclei of the atoms in the molecule ought to have played some part. I wonder if they haven't accidentally also proved that nuclei are round to a similar degree.

Re:Curious question

[Anonymous Coward]

A much better article, with predicted numbers for how spererical the electron should be according to different theories:

http://www.newscientist.com/article/mg21028145.100-ultracold-measurements-reveal-shape-of-the-electron.html

Re:Curious question

[Anne_Nonymous]

>> What other possible shapes were theorized for an electron?

I was hoping they would be dollar sign shaped, so I could tell my father, "Well, as it turns out, you *are* made of money.".

Re:Curious question

[elashish14]

[talking out of my ass here, IANA physicist]

You'd expect an atom to be mostly spherical right? Well if you measure the radius of an atom, you'll find that it can fluctuate. Knowing by how much the radius of an atom fluctuates might, for example, give you an idea of the angular momentum or kinetic energy of its constituent particles. I presume that the size and shape of the electron could fluctuate in similar ways and might give an indication of what physics governs its mechanical properties.

What I'm getting at is that maybe the actual measurement of the electron's radius isn't what's so important; rather it's knowing the deviation in these measurements that might yield some interesting scientific value. Keep in mind that 1e-29m is still over 5 orders of magnitude larger than the Planck length so maybe if we make a little more progress, we'll start seeing some really interesting physics.

Re:Curious question

[Attila the Bun]

What they mean is that they have tested the symmetry of the electron and found it to be equivalent in all directions, like a sphere. The hair's-width thing is just an analogy to describe the degree to which that symmetry has been tested; the electron does not have an intrinsic size or shape. If there were any detectable asymmetry, that would imply that the electron and positron are not perfect opposites, and may explain why there is so little antimatter in the universe.

Re:Curious question

[Lord Kano]

But the absence of a competing model has ZERO to do with whether or not we should test the current theory.

The absence of a competing model increases the importance of testing the current theory.

LK

Re:Curious question

[lee1]

That seems to be just stupid headline writing. Nowhere in the body of the article do we encounter a scientist expressing surprise at the result.

Re:Curious question

[bigsexyjoe]

Well they tested it's "shape" by seeing electrons have any wobble. They apparently found no wobble. Meaning that they are either little spheres, or IMHO more likely they have no wobble because they have no size. There are good reasons to think they fundamental indivisible particles already; because of the uncertainty principle the constituents of such a small particle would have to have a lot momentum.

Re:Curious question

[fermion]

From what I can tell ia this has to do with Standard Model which predicts equal quantity of matter and anti-matter in the universe. As far as can be determined, there is an asymmetry that is hard to explain. One way to explain this asymmetry in the quantity of matter is if there was a physical asymmetry between the electron and positron. The asymmetry would not exist in the particles themselve, but in the virtual particles surrounding them.

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 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

[JonyEpsilon]

Good questions! This is actually one of the central motivations for measuring this is. The standard model of particle physics predicts that the electron will be round. But most physicists think that the standard model isn't the full story. The interesting thing is most of the proposed extensions/replacements to the standard model predict that the electron will be somewhat distorted. To give a concrete example, supersymmetric theories, which are viewed by many as the most promising avenue for extending our theories of physics, usually predict a distorted electron.

Re:Curious question

[blank axolotl]

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:

The electron is predicted to be slightly aspheric, with a distortion characterized by the electric dipole moment (EDM), de. No experiment has ever detected this deviation. The standard model of particle physics predicts that de is far too small to detect, being some eleven orders of magnitude smaller than the current experimental sensitivity. However, many extensions to the standard model naturally predict much larger values of de that should be detectable. This makes the search for the electron EDM a powerful way to search for new physics and constrain the possible extensions.

Re:Curious question

[straponego]

They were hoping electrons were shaped like Pac-man. This would where the antimatter went.

Re:Curious question

[werdnapk]

An ellipsoid (shape of the Earth) could have been another possible shape for an electron I suppose. The earth bulges due to gravity and centrifugal forces from it's spin. An electron spins too, but if it's a near perfect sphere then this spin doesn't appear to have any effect on its shape, nor does gravity... as far as we can tell so far I guess. Interesting.

Re:Curious question

[GrumblyStuff]

I have learned from an inside source that the electron in question was born in Kenya or Indonesia and is a muslim. The birth certificate it presented has some very serious flags indicating that the certificate was falsified!

Re:Curious question

[Eil]

One of the researchers was interviewed on NPR and he said that a round electron throws an unknown variable into a lot of unproven theories. Many scientists were apparently hoping for a significantly elliptical shape in order to make their calculations work out. (Sorry I can't provide a better description. I'm only regurgitating what I heard on the radio.)

One interesting bit is that they had been collecting data for over 10 years, but the researchers prevented themselves from looking at it before the experiment was over so as to not introduce bias into their final results. That's some scientific integrity right there.

Re:Curious question

[Anonymous Coward]

They don't mean the electron is a "round" object as a ball is round. Instead they mean the electron is "spherically symmetric".

But spherically symmetric only to a certain degree. The electron has a very, very small dipole moment, less than 10.5×1028e cm (i.e., pretty f'ing small), so it isn't _perfectly_ spherically symmetrical. Were the dipole moment zero then the electron would be perfectly spherically symmetric.

They actually state that the electron is "slightly aspheric". So there.

Re:Curious question

[Surt]

If your father is made entirely of electrons I'd be shocked to meet him.

Re:Curious question

[Vasheron]

Thank you that was excellent. Any chance you could answer my question?

Re:Curious question

[jd]

Actualyy, I find it a good question for the simple reason that if you spin an atom fast enough it becomes pear-shape. This is in part because they have internal structure. Thus, knowing if other shapes are possible/expected under any given condition tells you if electrons are believed to have internal structure or not and what that internal structure might be if one is believed.

Internal structure is sensible to assume since there must be Higgs bosons to provide mass and something else to provide charge. Since we know internal structures can be made to distort, it is equally sensible to ask how, when and what. This makes Relic's reply somewhat... odd, as well as a little OTT.

Even if we didn't assume that, we know that in physics all shapes are a result of minimum energy state. An object will always prefer the lowest energy state available to it. There is nothing in physics that requires this to be a sphere, and indeed in physics there are quite a number of shapes that are lowest-energy for some condition or another.

Finally, it is a truism that no scientist could even begin to function without a childlike curiosity and sense of wonder. Those in scientific jobs who lack such traits are not scientists, they are mere cataloguers of findings. But since when have they been the exclusive owners of adult curiosity? The lack of it is never good and those with lives where curiosity is discouraged are certainly living below their potential.

Re:Curious question

[jd]

Since electrons have mass, they can't be indivisible. They have, at the very least, to be divisible into a Higgs boson and whatever is left over.

Re:Curious question

[Artifakt]

When the term 'spin' was first coined for sub-atomic particles, it was chosen because it was thought to have some similarities to macro-scale situations. (this was 1925, by about 1928 when Paul Dirac used it, people were already arguing about whether 'spin' really had to correspond to anything physical about the particles shape. Still 'spin' behaves like a form of angular momentum in at least some ways.).
          The spin of an electron is 1/2. By that, if it was a macroscopic object, it would only look the same if it was rotated 720%. If you turned it around just once (360 degrees), it would look different. Some other particles have spin 1 or even 3/2, and the predicted carrier of mass itself, the Higgs boson, is predicted to be spin 2 (which means if it was a macroscopic object, you would have to rotate it only 180 degrees for it to look the same - A macroscopic object with that property might be shaped like a football or a cigar, if it was being rotated around a certain axis.). Obviously, there are no macroscopic examples of objects with classical spin less than 1, so an electron couldn't look like anything macroscopic in this model. Its shape would have to be something that can't exist in the macro world.
            A perfect sphere is spin infinite, or arguably doesn't have a spin at all, it doesn't matter how you rotate it, it still looks the same.
            Another idea was that an electron had to be an absolute point, zero size in all directions. If you go by the old Bohr atom model, Electrons orbit the nucleus like tiny planets, but physicists soon realised they had to be moving at tremendous percentages of the speed of light. So in the Bohr atom, a spherical electron would look distorted, tremendously flattened in the direction of motion. It would look almost like a pancake. This led to some problems when calculating what happens as multiple electrons orbit in shells around a single nucleus - in particular, it led to erroneous predictions about how heavier atoms than helium would emit various wavelengths of light in their spectra, and how atoms outer shells would form crystals, set the spacing between nuclei, and do a lot of other things (for examples, even how much energy it would take to fracture something or how fast two different metals weld together at a particular temperature come out different, if I remember my old physic classes),
          So that's a theory that says an electron can't be a sphere, unless (really odd idea from the 1930's) it stretches to compensate for relativistic distortion and stay a sphere when it would normally flatten. For other reasons, the Bohr atom model turned out to be inadequate and most modern physics works by treating the electron as a wave function, as in quantum mechanics, in all the cases where the Bohr model doesn't give accurate numbers for observational results.Obviously, the shape of a probabilistic wave function isn't a tiny sphere or anything else solid, more like a fuzzy shell around the nucleus.
     

Re:Curious question

[GospelHead821]

I'm mostly getting this from reading other comments in this thread but I think that what you're saying is incorrect. Here's why:
The Higgs Boson has never been detected; it is merely predicted by the Standard Model.
The Standard Model also predicts that the electron is NOT perfectly symmetrical, albeit at a scale 11 orders of magnitude smaller than what this experiment measured.
If the electron IS perfectly symmetrical, then the Standard Model is incorrect and will require revision. In doing so, perhaps the Higgs Boson would fall out or some other explanation for mass may arise. I'm certainly not good enough at physics to suggest how the model would have to change. All I'm really saying is that if a symmetrical electron could falsify the Standard Model, then it's circular to suggest that because of the Standard Model, we know a priori that the electron is divisible.

Re:Curious question

[Anonymous Coward]

welcome to the cutting edge of academia. most people who are in science, especially very technical areas, are extremely short on communications skills. Most of them live in a lab because that's where they feel most comfortable. There's a reason that all scientific papers are formulaic. People like feyman who can sit around a campfire and patiently explain things are very few and far between.

if it makes you feel any better, as a disinterested observer I doubt very much that he was flaming you.

Re:Curious question

[rrohbeck]

The Higgs boson creates a field. That doesn't mean that every particle contains a Higgs.

Re:Curious question

[niktemadur]

Impressive how language, any language, is such a flexible and volatile thing; how an added, subtracted or rearranged word can create noise in the attempt to convey information. Add to that the difficulty in suppressing the emotional inertia and current state of transmitter and receivers alike, as well as lack of universal consensus as to what a specific word can mean, and you get the idea as to how lossy a format the written word is.

In context, it sounds as if *impressively* would have been a better choice than *surprisingly*.

Re:Curious question

[Entropius]

Forgive me if this explanation includes some stuff you already know -- I have no idea what your background is.

***

Are you familiar with Taylor (or Maclaurin) series? The idea is that any (well-behaved) function can be written as a polynomial of the form A + Bx + Cx^2 + Dx^3 + Ex^4 + ... ad infinitum, and that when x is close to zero, this expansion is dominated by the first few terms. If you want to see if a given function is a constant, one way to do it is to show that the coefficients B, C, D, etc., are all zero. Unless you have a particular reason to suspect that you're at an inflection point, showing that B=0 strongly suggests that C, D, E, etc., are zero too for many physical systems.

It turns out that you can expand the shape of an object or the distribution of a field in something that resembles a Taylor series. The expansion terms are things called the "spherical harmonics"; you're probably most familiar with them as the shapes of the various hydrogen orbitals (s, p, d, f, etc.). It turns out that any shape (at least, any shape with a unique radius for a given latitude and longitude) can be written as a combination of these spherical harmonics. The process of calculating the coefficients corresponding to the different shapes is called a "multipole expansion" -- it's like a Taylor expansion for shapes. For something that is very nearly a sphere, this is dominated by the first few terms.

The first one of these spherical harmonics -- corresponding in a sense to the coefficient A above -- is just a perfect sphere. Its coefficient is called the "monopole moment". The second one (actually, there are three of them, corresponding to x, y, and z axes) are called "dipole moments", and they represent the leading-order deviations away from perfect sphericity. This dipole moment is what this experiment measured; they figure that if the electronic dipole moment is very nearly zero then all the higher-order moments are zero too.

Re:Curious question

[Entropius]

"Divisible" is a funny term. If you mean that in quantum field theory there is a vertex between an electron line and a Higgs, sure. But this doesn't mean that you can split an electron into a Higgs and "something else", any more than it means you can split an electron into an electron and a bunch of photons.

What it *does* mean is that every electron disturbs both the photon field and the Higgs field around it, and that by necessity some of the properties of what we call "electron" are actually related to the disturbances in these fields; in other words, you can't perfectly separate out the properties of the electron and the properties of the fields that it couples to. This is not a huge deal for electrons, since they only couple weakly to other quantum fields; the coupling constant is 1/137 (at low energy) with the photon field, and small to the Higgs field (if such a thing exists). It's a far bigger deal for quarks, where the coupling to the gluon field is large at low energy; you can't describe the properties of a quark in any meaningful way without considering how that quark affects the gluon field around it.

Re:Curious question

[pinkushun]

That small divergence could just be an indication of the variance from instrumentation readings on such a small scale. Perhaps that figure will narrow over move years of testing until it finally reaches zero divergence.

I bet however, just like the theory of relativity which can never reach the actual speed of light (the idea of infinity), the time needed to measure this to a zero-fault level would also take infinity. Possibly due to the observer disturbing the observed.

But I'm no physicist, just my wild guess :-)

Oh matter & antimatter aren't exact opposites, they behave the same way, but just that they have opposite charges.

Re:Curious question

[spiralx]

Thanks for the post, it's been far too long since I did my degree lol.

Re:Curious question

[rvw]

They were hoping electrons were shaped like Pac-man. This would where the antimatter went.

Yeah and then sue the electrons for copyright violation!

Re:Curious question

[FrangoAssado]

Just a small nitpick (to remind people that quantum mechanics is even weirder than that): when you rotate an electron by 360 degrees, its wavefunction gets the opposite phase (i.e., it's multiplied by -1), but other than that, it remains exactly the same. That means that if the electron is all alone, there's no way to tell if it's been rotated or not -- because probability is the square of the amplitude, and so an opposite phase will yield the same probabilities. It's only by interference of the wavefunction with other stuff that you'd be able to tell if the electron has been rotated or not.

Re:Curious question

[black soap]

Maybe only the round ones got measured? For all we know, the test procedure could have a bias toward only selecting round ones, or only testing them while they are round.

Re:Curious question

[b0bby]

NPR had one of the scientists on yesterday; he was saying that they were expecting it to be aspheric, as most theories predict. He was also saying that they had the computer hide the results until the end, to prevent any biases creeping in. They did something like 25 million measurements.

Re:Curious question

[b0bby]

Here's the link to the story:
http://www.npr.org/2011/05/25/136656087/what-shape-are-electrons-scientists-try-to-find-out

Re:Curious question

[qubezz]

This kind of humour is very polarizing...

Re:Curious question

[tibit]

I agree, yet on some level I think that understanding and communications go somewhat hand-in-hand. If there is someone who is supposedly very good in some field, yet can't explain his work, at least in terms of key concepts, to a semi-layman in that field, I start suspecting his/her real understanding.

I've run into plenty of people who seem very good at what they do, yet the truth is that they have limited grasp of the basics of their field -- they merely blindly reapply, in a formulaic style, whatever they learned/read some time ago. Common example of a person thin-on-understanding would be almost everyone who ignites computer language flamefests. It takes real understanding to be able to filter out usability and productivity breakthroughs offered by some programming platform from marketing speak and hearsay. Yet you often hear just the latter.

Re:Curious question

[tibit]

More seriously, though, a couple dozen of kilograms of electrons, confined to the volume on the order of a human being, would wreak quite a havoc on Earth. The electric forces would be quite astonishing -- probably larger than any gravity forces seen anywhere in the Solar System.

Re:Curious question

[Spectre]

If your father is made entirely of electrons I'd be shocked to meet him.

So much negativity in the forums these days.

Re:Curious question

[marcosdumay]

Those are some quite massive electrons you have around. Can you lend me a few for my cold fusion machine?

Re:Curious question

[StikyPad]

Bew-bew-bew wa-aa!

Re:Curious question

[jd]

I would consider "divisible" for these purposes to mean "if you impose sufficient and appropriate forces, you will see evidence of underlying structure" (since you can't have a composite if there's nothing doing the composing) and to mean "if you split the particle, you will yield something other than energy" (since all matter is ultimately energy) PLUS "if you reduce some particle to a single particle (that is not the original particle) and energy, there exists at least one particle that can be constructed from less than the energy released AND which fits the underlying structure you have revealed" (ie: if you can only see part of the underlying structure, you can nonetheless deduce part or all of the remainder from what you do observe with no contradictions).

So, if an electron has both an internal structure AND you can identify at least one component directly AND any components you cannot directly observe CAN be directly deduced from the observations, THEN an electron is divisible.

In the case of a proton, for example, you can break it into a quark-gluon soup (which would be the ideal, since you can then observe quarks and gluons independently) or you can observe the quarks directly and deduce the gluons from the fact that what remains fits the model for gluons correctly.

That the electron should, under extreme conditions, alter shape tells me that there is something that can obtain a lower-energy state than a sphere. You can't distort points, however, as there's nothing to distort. You can't achieve a lower energy state if there's one item present. How do you sort a unitary item? As for mass - an electron has a mass that is approximately 1/1836 that of the proton. Since ONLY the Higgs boson* gives the property of mass, you would require enough such bosons for the electron to have the mass it does.

*Agreed, this assumes the Higgs boson exists, which is not the case in alternatives to the Standard Model. However, under accepted methods, you assume H0 to be what you would expect under the accepted theory and H1 to be that the accepted theory is broken in some way. Thus, it is correct to assume the Higgs boson is valid and then work to find a case where it is NOT valid. The accepted theory, again under accepted methods, is ALWAYS the the theory that is as simple as possible but no simpler. ie: the simplest theory that still works.

The problem with gravity being weaker than other fields is, in my opinion, of no significance as far as whether the electron has structure. A fact can have many interpretations, which is why there are so many theories trying to explain it. With no meaningful information at present on why the fields appear to be of different strength, we can't even be sure they actually are. Some versions of supergravity suggest that they are not different but that the relative distance makes for the illusion.

Re:Curious question

[t_ban]

They were hoping electrons were shaped like Pac-man. This would where the antimatter went.

But would it where your went?

Amazing!

[Vasheron]

It's incredible that the shape of one of the most fundamental particles in the Universe has one of the simplest mathematical descriptions! Is it a coincidence or is there some deeper meaning to this fact?

Re:Amazing!

[blair1q]

They didn't measure the particle, they measured the forces between particles.

Re:Amazing!

[doshell]

You can use the exact same definition, except that the distance is defined according to the L-infinity norm instead of the Euclidean one!

Re:Amazing!

[Vasheron]

Can you suggest a better way of measuring the shape of an electron?

Re:Amazing!

[Surt]

The deeper meaning is simply that God is the laziest creator ever. Building everything out of the simplest possible shapes. Takes all the fun out of nature. Jerk.

Re:Amazing!

[MichaelSmith]

If the electron has a radius it must have a surface, so what is that surface made of?

Re:Amazing!

[blair1q]

Can you suggest a better way of measuring the shape of an electron?

What is the shape of a fan?

Is it a long and turbulent stream, or is it a flat figure-8 with a slight twist in it?

One is the shape of its force. The other is the shape of it.

Actually, it is associated with a third shape: A whirling disc of pain.

Re:Amazing!

[Vasheron]

We're talking about sub-atomic particles and something needs to interact with them in order for them to be detected. In the case of this experiment they were photons (the article mentioned using a laser). So in a manner of speaking they were "seeing" it. An aside, and what I was getting at, is that technically when we touch something we're feeling the Coulomb force, and touching something is also a perfectly valid way of determining it's shape.

Shape?

[Anonymous Coward]

Uh, call me naive but I thought that electrons were point-particles and had no shape (being single-dimensional).

--AC

Re:Shape?

[Warlord88]

First I studied they were particles, then I studied they are actually mixture of waves and particles. Then I studied you cannot actually pinpoint it at all, and all you can know is probability density of its existence in space. Now, I read that they are extremely round.
My mind is full of fuck.

Re:Shape?

[ChrisMP1]

Sir, I know you're trying to be polite, but you shouldn't hold back so. It is imperative that we right the incorrect whenever we see them on the Internet, or else the Internet might be (gasp!) wrong! Ugh... the very thought makes me shudder.

Re:Shape?

[bigsexyjoe]

This experiment shows they have no wobble. I think that's pretty consistent with them being point particles, don't you?

Re:Shape?

[doublebackslash]

This is simplified, don't take this completely literally, but get this first. I'll use a car analogy.

You and several other clowns are in a clown and some of them are juggling. You are driving so you can't look at them. You can't look because you are doing a precision maneuver with several other clown cars. As part of the act they are also exchanging juggling objects with other cars. Even though you can't look at the jugglers you can sense what they are doing due to the fact that their motions and transfer of momentum are throwing you off course. It is important that you stay on course to make the jump. God help you if you hit the ramp like like the last guy did, but the kids like to see this act up close.

If the jugglers are throwing around tennis balls your course will be effected differently than if they were throwing juggling pins.

Now, back in the world of the article you've got the same thing. Atoms with electrons flying around and shared by chemical bonds. The shape of the electrons effects the shape of the molecule. More specifically the shape of the charge around the electron effects the shape.

Don't try to watch the objects being juggled, watch the clown cars try to stay in formation on their way to the jump over lion pen.

It took a long time because the measurements are so delicately precise and spurious data had to be discounted and filtered from the signal. The measurements weren't averaged but they were mercilessly filtered and subjected to analysis to take the "noise floor" down this low.

I am not a physicist. Someone correct me or clarify if I was dead wrong. Thanks!

Re:Shape?

[XManticore]

You and several other clowns are in a clown

Sup dawg, I heard you like quantum physics, so I put a clown in your clown so you can juggle while you drive

Re:Shape?

[Nursie]

And now I don't know what my name is or where I live any more!

Re:Shape?

[jd]

The easiest explanation is that the particle has no fixed position but exists over a probability wave. It can be anywhere on that wave, with the probability equal to the value of the wave at that point. Thus, it is a particle and a wave, but cannot be treated as both at the same time (which is exactly what we observe). The certainty with which we know the position also decreases the certainty of its velocity since it will reside ANYWHERE on the wave on the next instant. Since velocity is rate of change of displacement, we cannot know the velocity. However, if your concern is with velocity, you can measure how far the wave has moved. In so doing, the exact position of the electron on the wave is known only by the probability and so is unknown. For all intents and purposes, it doesn't have both a simultaneous velocity and position in this description (which is also what we observe).

This is not the "standard model" (well, not unless I just reverse-engineered it in under a minute - and, if so, you can sent the Nobel prize to the following addres....) but it IS an easy-to-master description that explains Heisenberg's uncertainty principle, wave-particle duality, diffraction patterns with extremely low photon counts, quantum tunneling and many of the other strange effects described at that level.

Re:Shape?

[little1973]

Exactly. All the elementary particles are 0-dimensional , point-like particles. As they are 0-dimensional they cannot have a shape. Also, this means only head-on collisions are possible in particle accelerators.

Some geniuses, like Feynman, tried to model the elementary particles as 3-dimensional bodies, but to no avail.

Re:Shape?

[Richard Kirk]

I was wondering how they mananged to come up with the smoothness parameter. After all, we cannot tell how much a bump on the 'surface' of a ball would affect how it spins unless we know the radius of the ball, and how the mass is distributed through the bulk. There are also symmetric configurations of bumps that would give no measureable asymmetry because the effects would balance out. I now think I have figured it out. Suppose the actual 'shape' of the electron was two half-electron point masses at either end of a massless stick. This would give the biggest contrast in moment of inertia between the two spin axes, and this let them convert the experimental measurements into a length. This length does not tell us anything about the 'actual' shape of an electron, and the quotes around 'actual' are there because quantum theory does not necessarily admit to any 'actual' in the normal sense of thing at these dimensions. But it's a useful trick that allows them to express what they have found in familiar units of length. Hope this helps a bit.

all that wave particle jazz

[Sebastopol]

So.... it's a sphere when it is a particle?

For years, I've been trying to un-brainwash myself out of the early models of the electron as a little ball whirring around a nucleus, and convert to the probabilistic electron cloud model, as well as the wave/particle hybrid nature.

My head is about to explode. Can someone who is a physicist please chime in?

Re:all that wave particle jazz

[Daniel_Staal]

Your head exploding is a perfectly normal reaction to trying to comprehend modern physics. Carry on.

Re:all that wave particle jazz

[CrimsonS]

I'm no physicist but isn't the probabilistic model related to the position of electrons around the nucleus of an atom. It has nothing to do with the form of an electron.

Re:all that wave particle jazz

[NoSig]

It is neither a particle nor a wave, so there is no "when it is a particle/when it is a wave". Instead, it is something whose behavior is like that of a particle in some ways and like that of a wave in other ways, but it is never actually a wave or a particle. It is its own thing - the analogies to waves and particles are just there to aid understanding, they are not accurate descriptions. I imagine that what is meant is that the density of the probability field (or whatever the correct term is) decreases uniformly in all directions with distance - no direction is favored over another.

Re:all that wave particle jazz

[Johnny Mnemonic]

At what speed would it explode?

Are there maths that describe the pressure of metaphysical forces on matter?

Re:all that wave particle jazz

[Obfuscant]

At what speed would it explode?

To what degree is it spherical?

Remember, TMI equals width times girth divided by the angle ...

Re:all that wave particle jazz

[blank axolotl]

The electron cloud model is the more correct one.

They are using 'spherical' somewhat metaphorically.. what they are actually measuring here is the electron dipole moment. A particle with a nonzero dipole moment causes an asymmetric electric force: A water molecule, for example, has a large dipole moment, so you feel a different electric force when you are near the negative oxygen vs when you are near the positive hydrogen.

So, if the electron has a nonzero dipole moment, it means it is a bit asymmetric in its electromagetic properties, and in this paper they have found that the dipole moment must be very very small. As they point out though, the Standard model (the best model of subatomic physics we have) predicts that the electron _will_ have a tiny but nonzero electric dipole moment.

Re:all that wave particle jazz

[jd]

Since all matter is ultimately reducible to energy, and energy must travel at C, then it follows the brain must explode at 3.pi.C/7 m/s.

Re:all that wave particle jazz

[iris-n]

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

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?

Re:all that wave particle jazz

[rrohbeck]

"QED - The Strange Theory of Light and Matter" by Feynman has a very accessible description. A quantum is a particle that has a phase. He symbolizes that with an arrow on a clock face IIRC.

Re:all that wave particle jazz

[hendrikboom]

Whatever it is is spherically symmetrical.

Re:all that wave particle jazz

[im_thatoneguy]

So, makes more sense now?

Mayyyybe...?

So if something has a north/south polarity in magnetism we say it has a strong "Magnetic Dipole Moment"? Or more simply I would using my non-physicist vocabulary say it has a distinct Magnetic Polarity. Magnetic Moment = Amount of polarity?

So even though the electron obviously has an average electric charge some theories think it might actually be the product of a slightly + in addition to being mostly - field?

But this study found that there isn't any duality to the charge; it's to the best of our measurements completely singularly charged and therefore has no polarity or shape?

I'm getting thrown by "Bipole Moment" since I don't know what that means but I feel like it's important to your explanation. :D

I'm imagining a magnetic field in my head. If you could create a magnet that was only positive it would be a round field pattern. But if you had a bar magnet it would form the classic figure eight of magnetic fields and therefore not be 'spherical'?
http://www.windows2universe.org/spaceweather/images/bar_magnet_correct.gif

Am I understanding you correctly?

Re:all that wave particle jazz

[ArundelCastle]

I appreciate your post very much, but I'm also reasonably confident that I understand more about four dimensional objects on an enthusiast level than I do about electrons. That's a bit of a bummer.

Re:all that wave particle jazz

[Tim C]

...to the limit of our current ability to measure it. The Standard Model predicts that it is not spherically symmetrical.

Re:all that wave particle jazz

[gooneybird]

So, what you're really saying is that the electron is a.... wavicle?

example of wavicle math:
0.5particle + 0.5wave = 1 wavicle
0.5particle + -0.5wave = antimatter
-0.5partcile + -.5wave = antimatter
0.99particle +0.1wave = particle
0.1particle+0.99wave = wave
... simple enough....
Intuitively Obvious To The Casual Observer...

Re:all that wave particle jazz

[hendrikboom]

That's right, of course.

-- hendrik

Re:all that wave particle jazz

[radtea]

So.... it's a sphere when it is a particle?

Nope.

This stuff is hard to think about, and getting the classical models out of your head before it explodes is a worthy goal (although were that to happen I guess it would be like cranial popcorn for your zombie neighbours, assuming you have any...)

The problem with thinking about electrons as "things" with "properties" is that they aren't. The whole point of quantum physics is that the "things" it deals with don't share the ontological constraints that are required for genuine thingness. An ordinary thing like a rock is always under observation in the relevant sense, regardless of what any conscious observer is doing. As such it can't be in two places at once (it is local) and it can't behave in contradictory ways under incompatible experimental conditions because no two experimental conditions are genuinely incompatible, for a rock.

For an electron, this is not the case. Electrons for the most part cannot be observed, and when they are observed their interaction with the experimental apparatus makes some measurements entirely incompatible with others. As such, any model we have in our heads of "what an electron is doing when no one is able to look at it" is wrong: we literally cannot conceive of such a situation. Doing so would require us to violate the law of non-contradiction, because that's what electrons do.

We we can think about is how electrons behave in various well-defined situations. In those situations they do reveal something like "properties", but those "properties" mean "they behave like X under exactly situation Y", and don't generalize well to other situations.

The closest classical analogy in the present case might be to think of an electron as a very squishy ball, like an unbreakable soap-bubble. Under normal circumstances it's very hard to tell what the shape of the ball is because the least force acting on it distorts it. What these guys have done is make a precision measurement that says in the absence of any external forces the soap-bubble-electron has a shape that is, to a very high degree of precision, a sphere. You can then think of the wave-like properties as being wobbles in the surface of the soap-bubble as it moves, or something like that (any analogy of this kind is going to be at best woefully inexact and at worst misleading and wrong, so be cautious!)

There is a related measurement that looks at deviations from point-like-ness. Electrons have a "characteristic scale", the Compton wavelength, that is vaguely analogous to the relaxed radius of the soap-bubble-electron. But it turns out if you squeeze the soap-bubble by running another soap-bubble into it, instead of distorting the two bubbles shrink during the collision while remaining perfectly spherical, then bounce back to there original radius after it. This means that while the electron when left alone has a "radius" associated with it, when it scatters off another charged particle is appears "point-like" in the sense that the structure function never deviates from unity.

Again: these are analogies between apples and penguins, so use them with care.

Re:all that wave particle jazz

[Have Brain Will Rent]

It certainly wasn't the last thing he ever said about it but at one point Feynman was giving a lecture to a non-physics audience and suddenly paused and said [not verbatim] "Remember it is a particle, we talk about it as a particle when that is convenient and we talk about it as a wave when that is convenient {pause}... but it really is a particle." Might have been one of the NZ lectures.

Re:all that wave particle jazz

[iris-n]

Even laymen like OP see that there's something weird about saying the electron has a shape and is a sphere

Do you HONESTLY think that people like Sebastopol (189276) who have "been trying to un-brainwash [themselves] out of the early models of the electron as a little ball whirring around a nucleus, and convert to the probabilistic electron cloud model, as well as the wave/particle hybrid nature" are in ANY way representative of typical laypeople?

I think Sebastopol is representative of the typical layman that is interested in reading about the latest developments in modern physics. He remembers what he learnt in high school, has probably read a wikipedia article or two, and usually reads these quantum physics articles when they appear. So a electron as a little ball is contrary to everything he has ever learnt about the subject.

Here's what a typical layperson would say: "electrons? Oh, right, I vaguely recall something from physics class in school. Aren't they the negatively-charged ones?"

Sure, there'll be a lot of people who'll know some more than that. There'll also be a lot of people who know a lot less, though, and the amount of people who consciously try to understand things like "probabilistic electron cloud models and the wave/particle hybrid nature" probably amount to no more than a few percent of the general population.

You're forgetting that no more than a few percent of the general population is interested in this subject.

The Beeb, like other news sources, isn't trying to cater to people like Sebastopol, or me (another interested layperson). It's trying to cater to the man on the street, and the only options they have are either a) simplifying things to the point where the man on the street can actually understand a word of what's being said, or b) not reporting on it at all. You appear to be blaming them for taking the former approach (all the while also denigrating the average man on the street by insinuating that he doesn't know the Beeb is not presenting all the details and that if he becomes interested, he's too stupid to possibly look up things himself).

Science Daily is not taking approach 'a'. They are mangling the information until there's almost no relation to the actual results. They are inventing a story about roundness to make the subject appear more simple, but in doing so they are just obscuring the facts and confusing the reader. Allow me to xkcd you. I'm not against the rubber sheet kind of analogy (as long as you say that it is an analogy; actually Feynman has an analogy that is more correct and simpler, but I digress); but what they are doing here is saying that Einstein's theory is like fairies pushing the stars around to make it seem like gravity.

I'm not saying that they should give all the details (because oh the actual details are hideously complicated), I'm saying that they should have given less details. They have measured a fundamental property of the electron, called electric dipole moment, that has profound implications on our understanding of the physical world.

Now it's much easier for the interested reader to search "electric dipole moment" and find out what it is, and ask the interesting questions, like "how can it have an electrical dipole moment if it is a single charge without structure?", instead of the nonsensical ones I'm seeing here on slashdot, like

Is it always round, even when it's tunnelling through a potential wall?

And I assume that by "round" they mean that every level curve of the probability amplitude has constant radius.

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?

Re:all that wave particle jazz

[Sebastopol]

Thank you!

Re:all that wave particle jazz

[Sebastopol]

Thanks! You must be a teacher, yes?

Re:all that wave particle jazz

[iris-n]

So, makes more sense now?

Mayyyybe...?

So if something has a north/south polarity in magnetism we say it has a strong "Magnetic Dipole Moment"? Or more simply I would using my non-physicist vocabulary say it has a distinct Magnetic Polarity. Magnetic Moment = Amount of polarity?

Yes, you are mostly correct. We use the word dipole because there are monopoles and quadrupoles and octopoles and so on, so we need to differentiate between them to be precise. But the dipole moment is what corresponds to polarity, so you can understand the magnetic dipole moment as amount of polarity.

So even though the electron obviously has an average electric charge some theories think it might actually be the product of a slightly + in addition to being mostly - field?

No, no theory says it so. The origin of the predict electric dipole moment of the electron is very fundamental, and no one thinks that it is due to a slight + charge. The most simple example of a system that has an electric dipole moment is a combination of a + and a - charge, but that is by no means the only example. Things that have an electric dipole moment have an electric field like the one in the picture.

But this study found that there isn't any duality to the charge; it's to the best of our measurements completely singularly charged and therefore has no polarity or shape?

This study found that our best measurements can't see any polarity in the electric field of the electron.

I'm getting thrown by "Bipole Moment" since I don't know what that means but I feel like it's important to your explanation. :D

I'm imagining a magnetic field in my head. If you could create a magnet that was only positive it would be a round field pattern. But if you had a bar magnet it would form the classic figure eight of magnetic fields and therefore not be 'spherical'?
http://www.windows2universe.org/spaceweather/images/bar_magnet_correct.gif

Am I understanding you correctly?

Hmm no. The issue of the shape is that if the electron were a uniformly charged sphere (it isn't), and you distorted this sphere a bit, it would display an electric dipole moment. So by measuring the electric dipole moment one can measure how much the sphere deviates from a perfectly round sphere, as a perfectly round sphere has no electric dipole moment.

The issue is that the electron is not a uniformly charged sphere, so it's meaningless to measure its roundness through the electric dipole moment; and I think that it just obscures the issue, because you have to know a bit of electromagnetism to know that a imperfectly round sphere has a nonzero electric dipole moment.

Re:all that wave particle jazz

[jfengel]

So... this is really evidence against supersymmetry? That conclusion sounds like a big freaking deal, much bigger than "electrons are round". SUSY is leading candidate for the solution to the hierarchy problem, and I'm not sure what the runner-ups are because SUSY was so far in the lead.

Re:all that wave particle jazz

[iris-n]

Yes, this is evidence against SUSY. And I agree that this is much bigger than "electron shape".

But it is not huge, because their measurement was not precise enough to actually rule out SUSY; about alternative models, I prefer to stay silent, because this is not my area of expertise.

Re:all that wave particle jazz

[jfengel]

Cool. Thanks.

Re:all that wave particle jazz

[NoSig]

For one thing, particles collide (bounce off each other) while waves interfere (as when two ripples in an otherwise still pond meet).

Re:all that wave particle jazz

[bstoneaz]

Do not look at electron as a sphere. Size and dimensions are reported as the maximum values we can observe. No one has measured a minimum size. All this study stays is that it is very spherically symmetric. The measured size is inconceivably small. It may measurably only be a point. That said, I think the data conclusively shows free electrons are actually gigantic in size. It is like a wave on a pond, only the wave condenses to an end state. The double slit experiment is one example of this. Similar behavior exists in atoms. Electrons are not little balls moving around a nucleus, when they join an atom something new is formed that is best described as waves.

I Knew This 35 Years Ago

[perry64]

when I made a model of an atom in 7th grade science and used spheres for electrons.

But it didn't look as good as her's: http://jeaninallhonesty.blogspot.com/2009/12/how-lizzy-made-atom-model.html.

Re:flaw?

[kvvbassboy]

I didn't read the TFA, but that clears my confusion. I thought that they discovered that electrons were "deterministically" spherical.

puuurfect

[fragfoo]

Maybe its shape is indeed a perfect sphere and the "width of a human hair" is just a measurement error. How more precise they want to get, until its shape diverges a human hair from a perfect sphere when enlarged to the size of the galaxy? Is there an end to measurement errors? Am i making any sense? I think not, its late at night :x

Re:puuurfect

[blair1q]

It will no longer be possible to measure the error, when you are bald.

Re:puuurfect

[digitaltraveller]

Maybe there is something interesting to be learned about that 'measurement error'...

Re:puuurfect

[znigelz]

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:puuurfect

[ghmh]

Well, I came here to post the same thing. According to the third paragraph, the measurements were made:

"Using a very precise laser"

Then you ask about how they measured the lasers preciseness and how did they build the laser. You keep investigating and pretty soon after that the turtles (unfairly) end up getting blamed for everything.

Point particles

[barlevg]

Aren't electrons point particles? How can something be spherical if it has no radius?

Re:Point particles

[mfnickster]

"It's like Sputnik - spherical, but quite pointy in parts."

Re:Point particles

[Smigh]

Exactly my thought when reading the headline. What sense does it make to talk about the shape of a point?

Re:Point particles

[SETIGuy]

They are assuming that if it has no electric dipole moment, then in some way it is spherical. I'm not really sure I buy it, but I'm not a particle physicist. The electron has a magnetic dipole moment because of its intrinsic angular momentum (spin), but that spin is not due to any motions within the electron, it is an intrinsic property. I'm not sure why the electric dipole moment wouldn't also be an intrinsic property, unrelated to any internal structure an electron has.

Re:Point particles

[Entropius]

Other way around: if an electron did have an electric dipole moment, then that wouldn't necessarily mean that it is not spherical. But if it has no electric dipole moment, then that is strongly suggestive that it is spherical; otherwise you'd need the intrinsic dipole moment (analogous to spin) to exactly cancel the dipole moment due to the non-spherical shape.

Re:Point particles

[hendrikboom]

(a) Whatever iit it, it\s spherically symmetrical.
(b) A point is a sphere of radius zero.

-- hendrik

Re:Point particles

[barlevg]

This actually makes sense to me. Well, as much as spin makes sense in the first place. Is this what the experiment was actually measuring?

Re:Point particles

[Entropius]

Yep; the electric dipole moment of the electron.

Size of the solar system?

[Zandamesh]

What is the radius of the solar system anyway? Furthest planet (40 AU)? Furthest comet orbit (50000 AU)?

But more importantly, how much digits of pi would you need to describe this sphere accurately?

Re:Size of the solar system?

[wrathpwn]

Just off the top of my head, I'd say 32 digits of pi, but I'm probably wrong.

Re:Size of the solar system?

[CrimsonAvenger]

Furthest planet (40 AU)

Last I checked, the furthest planet is only 30 AU out.

Or are you one of those heathens who hold with the sacrilegious notion that Pluto is a planet?

Re:Size of the solar system?

[jd]

The formal edge of the solar system is at the end of the heliopause. Who cares how many you need, we've something like 3 or 4 trillion of them. It is essential that we design a GPU capable of handling floating point numbers to this accuracy.

Re:Size of the solar system?

[XiaoMing]

But more importantly, how much digits of pi would you need to describe this sphere accurately?

About three Libraries of Congress worth!

Re:Size of the solar system?

[forkboy]

But more importantly, how much digits of pi would you need to describe this sphere accurately?

ALL OF THEM

Human hair?

[hkz]

10^-27cm (the spherical error in the article) is 10^-29m. The upper bound on the electron's radius is 10^-22m (Wikipedia). The solar system is roughly 1.5*10^13m in radius (Wolfram Alpha), so 3*10^13m in diameter. If you'd inflate the electron to the size of the solar system, scaling by 3*10^35, the spherical error would be 3*10^6m, which is more than twice the diameter of Earth, according to my calculations.

Re:Human hair?

[blair1q]

Inhuman handwaving.

Re:flaw?

[kvvbassboy]

Also:

That's like saying the shape of the ocean is smooth as glass averaged over 10 years. Sure it's true

Citations needed.

Think about it. Taking a huge number of readings over 10 years and averaging them, could give any irregular polyhedron, but it turns out to be an elegant shape.

What about texture?

[i ate my neighbour]

Is there a tiny ( - )sign on its surface?

Relative comparison *wildly* off AFAICT

[Omega Hacker]

The numbers in the article don't work for me.....

Electron radius (wikipedia): 10^-22 meters
Article's claim of error-from-round: 10^-29 meters
Relative error: 10^7, or 0.1 parts per million

"Radius of solar system" randomly chosen as Eris's avg orbit fo 68AU (wikipedia): 1.017 * 10^13 meters
Relative error scaled to size of solar system: ~1.017 * 10^6 meters, or ~1017km

Now I don't know about you, but my hair isn't exactly 1000km thick, eh?

Avg thickness of human hair (answers.com): 0.1mm, or 10^-4 meters
Ratio by which Science Daily apparently cannot count: 10^10

Re:Relative comparison *wildly* off AFAICT

[JonyEpsilon]

We used the compton wavelength of the electron as the size scale for this analogy. You could argue that the 1/e radius of the electron/positron virtual particle cloud would be a better measure, and this is closer to the classical radius (off the top of my head, it's late here), which would give an accuracy measured in mm rather than microns. The 10^-22 number comes from interpreting ion trap measurements of the electron's g-factor, comparing them to QED theory. To some extent, the question of the electron's size depends on what you mean by size and how you might choose to measure it. Jony

Re:Relative comparison *wildly* off AFAICT

[VortexCortex]

Ah so, it's not completely subjective or wrong; It depends on how you measure it -- "Here that honey?! I'm above average length; It's just that not all of me goes inside you."

Re:Relative comparison *wildly* off AFAICT

[michelcolman]

You're just splitting hairs now. The readers of Science Daily, meanwhile, have moved on to an article about some celibrity's breasts.

Well, it must follow then..

[multipartmixed]

..that sub-electronic particles either do no exist, or they have no* mass. Otherwise the electronic equator would be at least a teensy* bit fatter, due to its spin.

*no and teensy are both about one over infinity. Plus or minus a tad.

Re:Well, it must follow then..

[shutdown -p now]

In the current model, electron has no deeper structure - it's truly fundamental, alongside photon, quarks etc.

Re:Well, it must follow then..

[camperdave]

At the quantum level, is "spin" really spin (as in angular displacement over time), or is it like the term "color" or "charm", just a term to denote an aspect of quantum weirdness? Quantum spin is always up or down. It's never clockwise or counter-clockwise.

Re:Well, it must follow then..

[hendrikboom]

"Charm" is a pretty arbitrary word.

"Color" is chosen because it has three primaries, but the term has no other relevance.

"spin", on the other hand, was chosen because the mathematics was awfully similar to the math for angular momentium.

Re:flaw?

[Anonymous Coward]

why? what did google say?

At last!

[roesti]

At last, the flat-electron rabble can finally give it a rest.

Re:So its like a dick then?

[scififan]

Thats depends on a dick. If its yours, that sure its about same size

Obligatory

[creat3d]

Scaled to the size of the Library of Congress, its shape would diverge from that of a perfect sphere by less than 0.00049 dead interns in the closet. Or 0.0033 homosexual affairs with assistants, for the Republicans...

Define "shape"

[shutdown -p now]

How, exactly, do you define the concept of "shape" for something like an electron?

I mean, for a macroscopic object, our "common sense" definition of shape is the boundary at which an outside interaction would feel resistance - if you poke it, that's where you feel the counterforce (weak as it may be). This is actually caused by molecules interacting between each other, but at that point already the concept of "poking" something is kinda hazy, since you already get all that quantum mumbo jumbo strong enough to be prominent. By the time you go down to electron, the common sense approach would break apart entirely; so what is the definition, then?

Re:Define "shape"

[creat3d]

Scale down your imaginary poking finger and the notion of shape will remain the same. Worked for me!

Re:Define "shape"

[shutdown -p now]

But my finger consists of molecules and particles as well. If I scale it down to that size, the "finger" is a particle as well. So now you just have two particles of unknown shape...

Re:Define "shape"

[shutdown -p now]

Not exactly. The "poking" in this case was done by a laser. You're correct that there's no single point where the electron starts, it's more like a field of interaction. So shape still has essentially the same meaning.

So there's no well-defined boundary, but rather the laser is just more likely to be deflected (or absorbed) as we direct it closer to the center of mass (with a 100% chance right at the center)?

If so, then it's not exactly what I'd describe as "spherical".

Re:Define "shape"

[blank axolotl]

The (differential) cross section of an atomic or subatomic particle is well defined and quite close to our idea of 'shape'. It tells you how a test particle being shot a the target 'bounces' off the target. For classical objects it reduces to our intuitive picture (ie, if you are shooting at a sphere, you know how your bullet bounces) but it applies to fuzzy particles too. Unfortunately the wikipedia pages on it are not very detailed and miss a lot. Also check out the 'scattering cross section' and 'rutherford scattering' wikipedia pages for more info.

Re:Define "shape"

[shutdown -p now]

Right, that's what I mean. With macroscopic objects, the interaction is either there or it's not. Here, we're rather talking about probabilities - you can't have two particles occupying exactly the same spot, but aside from that you just need to try longer (or shoot harder) to get more "overlap".

But that's not really shape in any common sense, and calling that "round" is quite a stretch. I understand what they mean - that probability of interaction decreases uniformly on all directions from the center - and I'm not sure what the best word to describe that is, but "round" just re-evokes the simplified and incorrect image of tiny spheres from the old days of primitives models of the atom.

Re:Define "shape"

[sayfawa]

A better description than shape of electron, is distribution of charge. Which is exactly what they are measuring. If the charge density were not uniformly spherical (or point charge) then there would be some "shape".

Re:Define "shape"

[creat3d]

You'd see the shape if all the universe was scaled down as well... maybe the solar system was a good example after all!

Re:Define "shape"

[blank axolotl]

Two other things are important that I forgot to note:

1. They are not measuring the 'shape' of the electron at all.. they are measuring its electron dipole moment. They are using the word 'spherical' metaphorically to mean 'symmetric' or 'with zero dipole'. So my comment about cross section, while answering your question, is actually irrelevant to the study.

2. Assuming zero electroc dipole (so the electron's electric field is symmetric) the electron actually has an infinite cross section, so in this case the cross section is not very intuitive anyway.

Intelligent Design with Balls!

[mevets]

The deeper meaning is that the FSMs meaty balls must also be as round and consistent as these electrons. It is a fulfillment of the recipe.

Re:Intelligent Design with Balls!

[Vasheron]

I was wondering if it had a deeper theoretical meaning, not a religious one...

What's even crazier

[straponego]

...is that God did that freehand.

Re:What's even crazier

[Waccoon]

Or maybe he used strings... joined by points in space.

All the anti-matter is...

[RL78]

"Imperial's Centre for Cold Matter aims to explain this lack of antimatter by searching for tiny differences between the behaviour of matter and antimatter that no-one has yet observed. Had the researchers found that electrons are not round it would have provided proof that the behaviour of antimatter and matter differ more than physicists previously thought. This, they say, could explain how all the antimatter disappeared from the universe, leaving only ordinary matter. Professor Edward Hinds, research co-author and head of the Centre for Cold Matter at Imperial College London, said: "The whole world is made almost entirely of normal matter, with only tiny traces of antimatter. Astronomers have looked right to the edge of the visible universe and even then they see just matter, no great stashes of antimatter. Physicists just do not know what happened to all the antimatter, but this research can help us to confirm or rule out some of the possible explanations."


Is it possible that we can't find anti-matter because it's all in one place?

Re:All the anti-matter is...

[camperdave]

How would they be able to tell the anti-matter from matter?

Re:All the anti-matter is...

[XiaoMing]

To the questions

Is it possible that we can't find anti-matter because it's all in one place?

How would they be able to tell the anti-matter from matter?

In reverse order:
Anti-matter and matter share the same mass, but different charge based on their antiquark composition. When matter and antimatter touch and combine, they annihilate each other and convert all of the mass into pure energy (photons). So one very easy way we can tell is basically, something that's as light as an electron but bends in the wrong way in a magnetic field as a normal electron would, or something as heavy as a proton doing the same thing.
Even more interesting, aside from nuclear anti-particles (antiproton, neutron, electron), you can make anti-atoms (like antihydrogen: antiproton + antielectron) and one day maybe even anti-molecules. (This is tough because we generate anti-particles with very high energy nuclear reactions, but we can only create molecular compounds at very low energies where quantum mechanics can come into play so that we have actual bound [anti]electorns etc.)

As for why they can't all just be hiding in the same place:
Since antiparticles effectively share the same properties (as far as we know! that's a very rough explanation of why people were hoping for a very deformed electron) as "normal" particles, for that theory to work we'd be effectively looking for a black hole, made completely of antiparticles, containing all the mass of the universe.
Now that thought experiment aside, what's really more interesting is that if antiparticles really _are_ perfect mirrors of normal particles with only a charge difference (i.e. possibly needing to study antielectron sphericalness to verify), then many theories suggest that the entirety of the universe should have annihilated itself into pure photons a long time ago, with no mass being left over to make up what we know it is today.
In fact, when a high energy photon interacts with matter and converts into matter, or when you have ZPE vacuum fluctuations, you're always creating both a particle and corresponding antiparticle (i.e. electron and antielectron).

So the big question people are basically trying to solve is three parts:

Matter and anti-matter share so many similar properties, they must have been created in equal proportions at the start of the known universe.
Matter and anti-matter always annihilate into pure energy, which then can convert back into matter and anti-matter.
Why has the universe not annihilated itself out of existence?

Re:All the anti-matter is...

[camperdave]

Why has the universe not annihilated itself out of existence?

Physical displacement? As far as I know (which, granted, is just pieced together from watching documentaries and surfing the web) a particle and antiparticle need to be in close proximity to mutually annihilate; close as in sub-atomic. A proton can't annihilate an antiproton that is half a metre away.

If that is the case, then when the universe was a seething mass of particle-antiparticle reactions you would undoubtedly get a situation where two particle-antiparticle creation events happen close to each other. Suppose the particle from reaction A annihilates the antiparticle from reaction B instead. That would leave the antiparticle from A and the particle from B, which could be far enough apart not to react. The expansion of the universe carries them farther and farther apart, and voila: naked matter in one corner of the universe, and naked antimatter in another.

Re:flaw?

[JonyEpsilon]

It took us ten years to build the experiment. We didn't average for ten years!

So an electron is not a sphere!

[bigsexyjoe]

This is incredible! Sure they might be almost spherical, but the shape is slightly off! This small difference could have profound theoretical implications. First it means that an electron has volume, second it means they might have an inner structure to create that shape. Very interesting indeed. Might lead to new physics.

Re:So an electron is not a sphere!

[VortexCortex]

I think you may be misinterpreting the summary. The precision of their measurements put an upper bound on deviations from perfectly sphericity. The electron can be no more than "the width of a human hair in the solar system" off from being a perfect sphere, or they would have measured it.

So... if the electron is more than ' "the width of a human hair in the solar system" off from being a perfect sphere' they would have measured the human hair instead? Huh, that actually makes sense...

Re:So an electron is not a sphere!

[LongearedBat]

That deviation is a maximum, so I think what they're saying is that if an electron is not a perfect sphere, then it deviates from being a perfect sphere by a very tiny amount. Electrons might still be perfect spheres, but we can't measure to perfection.

Round.

[Roachie]

Yea... its round. Thanks for the grant.

Re:Round.

[VortexCortex]

Yea... its round, as far as we can tell...

Thanks for the grant.

FTFY.

Re:Round.

[PPH]

Its shaped like a football.

What kind of football, you ask? Sorry. We'll need more grant money for that.

Re:Round.

[Roachie]

touche

How much more round could it be ...

[Anonymous Coward]

None more round

Radius?

[aa_trna_syn]

But what is the radius of the electrons?

Not a wave?

[Trogre]

If an electron is just a wave I might have expected it to be more, well, wavy.

Or is this "shape" representing a distribution of its possible locations?

Re:Not a wave?

[LesFerg]

No it's not a wave, or a particle. They are just a field-effect generated by our holographic projector.
And don't even ask how many sticks of RAM are being used to track them all.

I think I've seen this show before:Captain Obvious

[Anonymous Coward]

The story would have been much more interesting if went over the assumptions, and the holes in their methodology. Not just, "it doesn't wobble much so it must be very round". It seems like they are projecting some macro-world experiences into the micro-world.

Width of a human hair

[PPH]

From what part of a human, exactly? And would this hair be blond, perchance?

Good to know

[Osgeld]

I can use that in my nonsensical techno-babble

Or it is irregular in shape

[Anonymous Coward]

but spinning very very very very very very very fast.

LMAO

[Anonymous Coward]

As soon as I read the title I thought "Not shit, its round Einstein!", and then they confirmed its round. Someone has wasted their life, should have just asked Slashdot.

4D Shape

[Doc Ruby]

An electron's shape includes the path that it takes through the "electron cloud". And that path has to date never been plotted with any accuracy, only its overall probability densities in spacetime. It's a fractal (since time's dimension is not an integer), and so it depends in part on the size and shape of whatever measures it.

Re:round?

[X0563511]

Can you read? Well, you made it through the title at least.

OK, so you can't comprehend shit.

Reread it. It should be obvious.

what?

[Charliemopps]

The size of the solar system? Lets do away with unrealistic measurements... Compare it to something we can all understand like the library of congress.

But does it have volume?

[LUH 3418]

I've always imagined that elementary particles must be point-like, without any actual volume. Does this study contradict that notion?

It just seems to me that it wouldn't make sense for electrons to have a volume, because that would imply some kind of structure. Nobody ever seemed to suggest that photons actually have a "shape", other than a point.

Re:But does it have volume?

[StripedCow]

I imagined that too. Wikipedia contains some information on it, see http://en.wikipedia.org/wiki/Electron:

The electron has no known substructure. Hence, it is defined or assumed to be a point particle with a point charge and no spatial extent.

Variable shape?

[Walt Dismal]

I was under the impression that an electron is not a hard constant sized object but is a wave constrained to fit the boundaries of the quantum mechanical environment around it. Though variable, also cannot be compressed into infinite density either. I also thought, from chemistry, that the electron 'fits' into the various orbital states but that it's not a tiny sphere 'bouncing around' inside them but indeed a wave constrained within the orbital shapes. I would think an unconstrained wave in three dimensions is obviously symmetrical and hence spherical, but always morphs shape under the influence of any outside charge. So what really was measured here? Grandpa in the movie Moonstruck: "I'm so confused!"

Re:Variable shape?

[Intron]

Electrons are a charged particle. If they had point size, then they would have infinite energy density, which is obviously impossible. Since all electrons have the same charge, they are all the same size. As for the wave-particle duality, when you measure wave characteristics, you can think of it as a wave. When you measure particle characteristics you can think of it as a particle. The electron won't be offended.

As for what was measured, read the comment above about dipole moment. That's the best description.

Re:Variable shape?

[Walt Dismal]

My understanding is that actually, charge and size are not related by a constant. That is, electron size varies, hence density of an electron as occupied space to charge ratio varies, but it cannot vary to infinitely small size. The only thing stable about the electron is charge, but aside from that, it can assume different sizes. As Carver Mead notes "(I) agree with Einstein ... a lot of the confusion and counter-intuitiveness of quantum mechanics would go away if we stopped imagining elementary particles like electrons and protons as tiny points and instead saw them as waves with a boundary." And also Mead notes:

"The electron isn't something that has a fixed physical shape. Waves propagate outwards, and they can be large or small. That's what waves do. So how big is an electron? It expands to fit the container it's in. That may be a positive charge that's attracting it - a hydrogen atom - or the walls of a conductor. A piece of wire is a container for electrons. They simply fill out the piece of wire. That's what all waves do. If you try to gather them into a smaller space, the energy level (density) goes up. That's what these Copenhagen guys call the Heisenberg uncertainty principle. But there's nothing uncertain about it. It's just a property of waves. Confine them, and you have more wavelengths in a given space, and that means a higher frequency and higher energy. But a quantum wave also tends to go to the state of lowest energy, so it will expand as long as you let it. You can make an electron that's ten feet across, there's no problem with that. It's its own medium, right? And it gets to be less and less dense as you let it expand. People regularly do experiments with neutrons that are a foot across."

I note that Mead was a professor at Caltech and a friend and student of Richard Feynman. Also, Mead is neither an idiot nor crazy, and has been doing QM in solid state physics for decades.

Re:Variable shape?

[Walt Dismal]

Are we talking about position of center of mass of a particle, or position of wavefront edges at a boundary? Or are the definitions of shape and position in need of better description from a quantum mechanical probabilistic standpoint? If a 'particle' can only be described in terms of probability of occupation of a region of space by a wave, what happens to the term 'shape'?

Re:Variable shape?

[Intron]

Since electrons have mass, I guess you are ok with a singularity at the center of every electron, also.

Re:Variable shape?

[Intron]

Well, I knew there would be a reference for size-to-charge and size-to-mass ratio, here it is:
http://en.wikipedia.org/wiki/Classical_electron_radius

That's the classical physics view, anyway. Quantum physics may say that the electron is simultaneously a wave and a particle, but the particle mode still has to have definable characteristics.

Shed some light on this

[NicknamesAreStupid]

At what frequency would you need to have laser light in order to use it to detect an electron diameter (2 * 10^22), which is moving around at the speed of light. Even gamma rays have a wave length that is about 10^10 bigger than an electron. If you try to measure 'wobble' of a particle with a classical radius that is seven orders of magnitude larger than its quantum radius, then how could you assume that it 'wobbles' at all?

It may not be round; it may just be a perfectly symmetrical charge.

Other subatomic particles...?

[LongearedBat]

It would be interesting to know how the quarks that make up neutrons and protons behave. Do they cluster like a bag of bags of marbles (separate clusters), or cluster like a single bag of marbles (single cluster), or superimpose (one blob, probably spherical). Do these clusters stretch, especially in covalent bonds?

Do we perhaps already know?

Re:Other subatomic particles...?

[Have Brain Will Rent]

They move... constantly. Much of what was previously thought to be the rest mass of matter turns out to be mass generated/represented by the relativistic velocities of the quarks.

Obligatory XKCD

[Anonymous Coward]

Oblig: http://xkcd.com/895/

point

[StripedCow]

I thought the theory was that an electron is a point-particle (a mathematical perfect point, having zero diameter).

The Details Betray the Designer

[tinkerton]

No, in fact they found there was a systematic pattern in the deviation from a perfect sphere, and when they made a map of the surface pattern they found a Laura Ashley wallpaper flower pattern. This has lead to a lot of speculation on the intentions of the grand designer.

Processing....

[Panaflex]

Processing 10%...
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ERROR 42: What was the question?

Round?

[Owza]

Like hell its round

Re:round?

[Intron]

Is it round or spherical?

A sphere is a mathematical term for a surface at a constant distance from a point in three dimensions. A solid body might be better described as "round" rather than use math terms that you don't really understand.

Re:So its like a dick then?

[Geotopia]

"The experiment continues in the search for even greater precision."

If they've discovered so far that it's about as round as can be, why are they wasting their time looking for more precision!? Let's just say it's perfectly round and call it a day.

Or maybe they're like the yahoos posting above that can kill hours talking about the shape and size of things of no consequence!?

Re:equatorial speed

[Noughmad]

What does the fine-structure constant do with it?

That was a very good explanation

[Kupfernigk]

No mod points, but if I had you would have got one.

How big is a point?

[he-sk]

I was always under the impression that the electron was a 0-dimensional point, i.e. it has no size, just a charge.

I know, it doesn't sound intuitive, but then the table I'm sitting at mostly consists of vacuum, yet it feels solid when I knock on it.

Thinking about it, if the electron has mass it should also have a size. Ah, screw it, I'm gonna stick with computers and leave particle physics to the experts.

Pedantic Spheres (Re:round?)

[carlzetie]

Well, kinda. In common geometrical usage, a sphere is a three dimensional SOLID whose surface is as you described. That's how Euclid used the term, and it's how anybody who studied math to less than college level would use the term. In higher mathematical usage, an n-sphere is an n-dimensional object embedded in an (n+1) dimensional Euclidean space that satisfies the corresponding equation of constant distance from a point in that space. So a circle is a 1-sphere (a one dimensional line embedded in the two dimensional plane); the surface of a ball is a 2-sphere (a two dimensional surface embedded in three dimensional space); and 3-sphere is something you cannot picture because it's a three dimensional "surface" embedded in four dimensional space (and not, as some people mistakenly think, a ball). So if we're going to be strictly pedantic, you could say that the solid body is a sphere [common geometrical usage] or the surface is a 2-sphere [strict mathematical usage], but it's nothing but confusing to define "sphere" the way you did. Normally I'd just shrug and let this go, but since you used the phrase "rather than use math terms that you don't really understand"... In other news, The Pedantic Spheres will be the name of my next band.

Re:Pedantic Spheres (Re:round?)

[Anonymous Coward]

You're just wrong about Euclid. He defined a sphere by construction (of course) as:

"Def. 14. When a semicircle with fixed diameter is carried round and restored again to the same position from which it began to be moved, the figure so comprehended is a sphere.

Def. 15. The axis of the sphere is the straight line which remains fixed and about which the semicircle is turned.

Def. 16. The center of the sphere is the same as that of the semicircle.

Def. 17. A diameter of the sphere is any straight line drawn through the center and terminated in both directions by the surface of the sphere. "

Nowhere does Euclid consider a sphere to be a solid body.

Re:Pedantic Spheres (Re:round?)

[Ruie]

A ball is solid. A sphere is a surface of a ball.

Re:Pedantic Spheres (Re:round?)

[carlzetie]

Again: In higher mathematical usage, yes. In standard geometrical usage, no. At the risk of repeating myself, in topics such as Euclidean solid geometry, "sphere" means the same thing it means in common usage, i.e. a solid. Thus we talk about the volume "of" a sphere, not the volume "inside" a sphere. If you're going to use "sphere" in the higher mathematical sense as in topics that require you to distinguish carefully between the surface ("sphere") and the space bounded by the surface ("ball"), you are better off avoiding the term entirely and using something more specific such as 2-sphere. If there's one thing worse in a Slashdot thread than people who don't know what they're talking about, it's people who think they know what they're talking about (or equally, people quoting Wikipedia out of context)

Re:Pedantic Spheres (Re:round?)

[carlzetie]

Def. 14 precisely defines a solid body as the volume swept out by the area of the semicircle.

Re:Pedantic Spheres (Re:round?)

[Ruie]

I don't see anything wrong with sticking to modern definitions. How else will the public learn them ? Math education in schools is not improving for sure..

Re:round?

[CrispyZorro]

Is it round or spherical?

I thought it was shaped like a dash. Damn you high school Physics! I guess next they'll tell me molecules aren't the same size as ping-pong balls.

Doesn't prove it's round

[Old Wolf]

They just proved that it was not a not-round shape. That doesn't mean it is round. It seems to me a simpler explanation is that the electron has /no/ shape or structure.

Planck Length?

[Draque]

"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." I'm highly skeptical of the entire article. That measurement would be well under the Planck Length. Below that, isn't all geometry and spatial measurement meaningless? I'm asking, rather than asserting.

What is an electron actually made of?

[shilly]

So, a question to the physics gurus here: what is an electron actually made of? Is the answer simply "matter"? And if so, what is that? Or is this a "turtles all the way down" kinda thing?

Re:What is an electron actually made of?

[marcosdumay]

They are made of electrons. Exactly one of them for each.

Re:Curious question -- square anti-electrons.

[scharkalvin]

Actually anti-electrons (positrons) are SQUARE. As you all know, you can't fit a square peg in a round hole.

Plank

[rubycodez]

a standard Plank Length in the U.S. is 8 feet.

Re:round?

[justNoperator]

or a non-edged cube?

Red

[SnarfQuest]

Ok, they talk about how they tell how round it is, but why don't they tell us how they know electrons are red?

"In any sense that you can mean spherical"

[quax]

Only in the sense that a point particle is spherical. The meaning that the article suggested i.e. imagining the electron as an actual spherical charge distribution - say with the classical e radius - is completely misleading.

Re:"In any sense that you can mean spherical"

[JonyEpsilon]

I don't know why people are so convinced the electron is a point particle. A point particle is an idealisation, one that even theory essentially rejects these days (in as much as the bare electron is a theoretical fiction which can't, even in principle, be considered separately from the vacuum polarisation it induces). I don't think it's particularly misleading to think of a ball of charge either - there's no evidence to suggest this isn't the case! I stand by my comment, and the title of my paper: I don't see what else what terms like "shape" and "spherical" can mean in this context, if one restricts oneself, as one must as a physicist, to things that can be measured.

Re:"In any sense that you can mean spherical"

[quax]

A point in physics is not the same as an idealized mathematical point. Point particle means it physical attributes live on the scale of the Plank length. Of course you are free to imagine the electron as a classical ball of charge but there are good reasons why physicist tend to no longer cling to that picture. It doesn't make sense to imagine a differentiated shape on a scale where space itself does not have a sub structure anymore.

Having a ball shape means that you have a cross section that you can actually probe - but that is exactly what is missing for point particles (and not for lack of trying).

In the context of the article the whole thing gets even more convoluted because the measurement was done on bound electrons in a molecule. These electrons are not localized and rather represent a charge distribution in a molecular orbital. It is the electrons charge that make the orbitals. Of course the latter themselves have higher order electric moments and all that was determined by the 10 years data gathering is that no intrinsic electron dipole moment contributes to them.

Re:"In any sense that you can mean spherical"

[JonyEpsilon]

I think I'm not quite making my point: there's simply no sense in talking about attributes on the scale of the Plank Length, or the electron missing a cross section. The fact of it is that we simply don't know what's going on in the electron and that's all speculation.

What we do know is that it, electromagnetically, has a magnetic dipole, a charge monopole, and - as best we can tell - no charge dipole. The electromagnetic properties are the shape in the only sense that anyone ever really uses the word shape. So its shape is round.

If you want a picture in your minds eye of what we know about the electron, with the understanding that this is just a picture and the theory is the authoritative description, then a ball of charge is, in my opinion, closer to our current theories than a mysterious point particle. You bring up the classical charge radius above: this is precisely the radius that electron-positron virtual pairs can be created, and in a meaningful sense is something like an electron radius. (Although note that they have set limits on the charge radius by comparing the measured magnetic g-factor with the QED calculation, this is the 10^-20something that wikipedia quotes, but this really measures something different - I think you need to be more specific than just saying size at this length scale).

I understand the complications due to the electrons being in molecules - if you haven't twigged yet, JonyEpsilon == J.J. Hudson == first author of paper under discussion - but it doesn't have any real bearing on what we're talking about.

Hope that makes sense :-)

Re:"In any sense that you can mean spherical"

[quax]

The electromagnetic properties are the shape in the only sense that anyone ever really uses the word shape. So its shape is round.

When physicists talk amongst each other and refer to the electron having a round shape they will exactly mean and understand what you stated. I don't take any issue with that shorthand in a published article abstract or title.

But I think the confusion in this /. thread is testament to the fact that if you have a popular science article using this phrasing accompanied with a blue billiard ball picture this is not what a more or less informed public will perceive.

Communicating the peculiarities of QM to the public is a daunting task. We don't know with certainty if an isolated electron is indeed a point particle (in the physical sense) or has an actual spatial charge distribution above the Plank length (although I don't like the latter assumption because it adds complexity and a hidden variable :-)

What we know for certain is that the electron is "not from this world" i.e. the macroscopic world of cause and effect.It behaves for the most part like anything but a blue billiard ball. Yet, this poorly written and illustrated dailyscience.com article inadvertently reinforces this misconception. IMHO the somewhat mysterious point particle image does a much better job a conveying to the unsuspecting public that we are in fact dealing with a very different realm when describing the humble electron.

Not that good popular science writing comes easy. Translating science to prose is always fraught with danger. "Lies to children" is how Terry Pratchett so aptly called it in what I consider the best popular science book. In this regard I think the point partical image works very well because the mathematical point is an abstraction that everybody is familiar with and kids learn very early about (my 6 year old learned about 3d shapes and 2d in kindergarten. He then asked me about 1d shapes and concluded that there is only one).

Piss poor pop science writing is a pet peeve of mine (the current state of theoretical physics doesn't help in this regard). So the dailyscience.com write-up and even worse /. summary rubbed me all the wrong way.

Your experimental work is quite impressive and I am looking forward to the the further refinement and zeroing in on the elusive electron dipole moment. It deserves the limelight and attention that it gets.

Not sure how much control or influence you have on the treatment that your work gets on popular science sites like dailyscience.com but if you can influence them I urge you to include appropriate caveats in their write-ups to not get people stuck on the image of an electron as blue billiard ball.

Do it for the children! :-)

Re:"In any sense that you can mean spherical"

[JonyEpsilon]

http://www.youtube.com/watch?v=3wHKBavY_h8

:-)

Jony

Re:"In any sense that you can mean spherical"

[quax]

Thanks! Made my day.