Protons Aren't round

drox writes "USA Today reports that protons are ovoid rather than spherical, as most of us learned in school." In related news, thousands of high school science labs have thrown out a bunch of little plastic balls.

Comments

Not surprising

[andfarm]

As the protons are moving at such high speeds in the nucleus (disregarding for the moment the fact that their speed and location are rather hard to determine exactly), this is an expected result.

Why? Relativity. Objects moving at high speeds appear contracted along the axis of their movement to observers in a "fixed" reference frame.

No surprises here, move on, move on...

How can it have shape?

[therealmoose]

How can a proton have definate (or semi definate) shape? Shape can only be observed by sight (and protons are much smaller than the wavelength of light and don't just bounce high energy electo-magentic radiation), or by collision. Protons do not collide in the normal way, they either repulse like-charged particles by the electroweak force or attract them. So, how can the shape have any meaning?

Re:How can it have shape?

[rjh]

A related question: a proton doesn't even have a distinct location, so how can it have a shape? The answer is to change what you think "shape" means. When quantum physicists talk about the shape of a proton or an electron or what-have-you, they're actually talking about a probability distribution.

Let's take a very simple probability distribution. (Real physicists will take great umbrage at how I'm simplifying things--so just let me defend myself by saying this is a gross simplification.) Let's say that the proton has a 95% chance of existing within X distance of a given point in space (i.e., within X along all three direction axis). That probability distribution is spherical; the region of 95% probability is spherical in area.

Let's say the proton has a 95% chance of existing within X distance along the x axis, Y distance along the y axis and Z distance along the z axis. Suddenly, you no longer have a spherical probability distribution; the probability distribution is longer along one axis than another.

In the case of the proton, the "shape" of the proton is ovoidal.

Remember, pretty much all of your observations about the macro universe are totally inapplicable at the quantum level. Even the Second Law of Thermodynamics doesn't apply at the micro level like it does on the macro. So before you say "it can't have a shape"... make sure that you're not trying to apply your macro concept of "shape" to the micro.

Hey, that's nothing...

[kawika]

I have a paper from Hendrik Schon here that says they're shaped like tiny little cheddar cheese goldfish. Who would you believe, USA Today or Bell Labs?

Junk Post

[rjh]

In the article it said quarks travel at around ninety percent of the speed of light. So, tell you what, let's compute just how much more massive those quarks are. Fire up your LISP interpreter. We're taking a trip into Mathemagicland.

In LISP notation...

(defun relativistic-mass (m v) (/ m (sqrt (- 1 (/ (* v v) 1)))))

(relativistic-mass 1 .9)
2.294157


... So as you can tell, relativity tells us that at ninety percent of c, an object is only going to have two and a quarter times its normal mass. I don't see how you come up with the notion that "if the quarks are traveling relativistically, then the proton's mass must be near-infinite, thus quarks aren't traveling relativistically". If anything, your science is just as much junk as the USA Today article you're blasting.

Only one radially symmetry

[bagsc]

The implication that the proton doesnt have three radial symmetries is pretty sweet - we now _know_ that the proton can support two axes of rotation, meaning that they can store rotational energy, that we could only assume if protons were perfectly radially symmetric (and therefore completely indistinguishable from their non-rotating kin). This has thermodynamic implications, the degrees of freedom are increased if the proton can store rotational quanta, and possibly increasing our understanding of plasmas. How can any right-thinking geek find this banal?

Re:I still dont get it...

[JohnsonJohnson]

I think a more accurate statement is the probability density of the location of the proton has an ovoid appearance. Just as only the s orbitals of electrons have a spherical distribution and the others take on some rather remarkable shapes.

An additional caveat is the electrons scattering was used to probe the proton. So the primary interaction was electromagnetic with a very small weak component. Protons may have a different "shape" when viewed by a neutrino since neutrinos do not couple with the electromagnetic field. This is a guess though and I am not qualified to make that statement more precise.

Finally, the obvious question is how do we define a "top" for a proton, ie, how do we know which direction the ovoid is oriented in? The answer is since a proton has a nonzero spin it assumes one of two diametrically opposed orientations in a magnetic field and we can use the axis formed by those directions to define "up". Finally, thinking about it that way, since quarks also couple to the electromagnetic field as well as interacting with each other through the strong force, it's not that surprising that a proton has a shape, it may be a result of the complicated interactions between the quarks. Then again, no one has done the calculation (which is fiendishly difficult and impossible to do analytically since it's a pretty general 3 body problem) so maybe it's a little unjust to call the result unsurprising.