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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.
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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...
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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?
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.