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Mystery of the Shrunken Proton
ananyo writes "The proton, a fundamental constituent of the atomic nucleus, seems to be smaller than was previously thought. And despite three years of careful analysis and reanalysis of numerous experiments, nobody can figure out why. An new experiment published in Science only deepens the mystery. The proton's problems started in 2010, when research using hydrogen made with muons seemed to show that the particle was 4% smaller than originally thought. The measurement, published in Nature, differed from those obtained by two other methods by 4%, or 0.03 femtometers. That's a tiny amount but is still significantly larger than the error bars on either of the other measurements. The latest experiment also used muonic hydrogen, but probed a different set of energy levels in the atom. It yielded the same result as the Nature paper — a proton radius of 0.84 fm — but is still in disagreement with the earlier two measurements. So what's the problem? There could be a problem with the models used to estimate the proton size from the measurements, but so far, none has been identified. The unlikely but tantalizing alternative is that this is a hint of new physics."
Maybe they mixed imperial with metric units in some part of the process. At least they could had enjoyed to get back home and say "Honey, i shrunk the proton"
that it was the cold water.
Welcome to the Panopticon. Used to be a prison, now it's your home.
The universe it growing (including our meter sticks) and the proton is staying the same size.
I was moderately excited.
It just works.
Subway Corporate announces that their foot-long measurements were unfortunately based on accepted assumptions of larger protons.
"He's using a quantum encryption scheme! That'll take hours to break!"
It's old physics that we haven't figured out yet, but thought we had.
If the universe is expanding everywhere, and if this included the space between protons and atomic particles, then this result would be due to the length we use to measure being larger than it was before. So it's possible that the proton isn't getting smaller, but that everything else in the universe is expanding with the expansion of the universe. Is there anything that precludes this as a possibility?
-- ssoorrrryy,, dduupplleexx sswwiittcchh oonn.. -Quote found on actual fortune cookie.
I hadn't realised the recession was this bad!
Might we not just be mistaking precision (low variance in repeated measures) for accuracy (distance from ground truth)?
This appears all the more likely given that indirect methods of measure are needed for such extreem cases!
It's possible that we are all smaller now than at any specific point in the past. Just as space-time may speed up, slow down or, go up or down, unbeknownst to us, it can also shrink or expand.
It is probable that the mystery of Quantum Mechanics lies in the fact that sub-atomic particles are in-between two worlds. In that they are abiding by two separate laws, two separate realities, at the same time.
I assume though that as these particle are tied to you, if they are in another universe, the occupants there observe that they display odd properties (like dark matter possibly?)
Extraordinary results require extraordinary proof. How many hair-brained theories were generated to explain the Pioneer trajectory aberration.
that's why old people shrink !
everthing seems smaller that you are going away from, perhaps the signal is fading fast
Maybe the additional 4% was just lens flare.
The extra mass of the muon is holding it in a tighter orbit around the nucleus. We've been kidding ourselves with all this Higgs Boson crap.
Meth. It's Meth.
I hate it when my heroine is full of protons.
There are two types of people in the world: Those who crave closure
As in all hard science, the results are not nearly as fascinating as the methods. It could be that we are measuring two different quantities. Or that some mistake was in the calculations, which is what many seem to expect. If the accepted value is not accurate, we may expect to see the measured size of the proton slowly shrinking over time until a new consensus value is reached.
As always a single measurement is simply that. A single measurement, a guess, a data point.
"She's a scientist and a lesbian. She's not going to let it slide." Orphan Black
My first idea would be that the muon does indeed shrink the proton. After all, the proton is not some solid body, but consists of interacting charged quarks. The muon has a higher probability to be inside the proton (that's exactly why it is useful for measuring its size), and thus lowers the charge density there (it adds some negative charge density to the proton's positive charge density). The electrostatic repulsion inside the positively charged proton should certainly affect its size; decreasing that repulsion due to the partial screening by the muon should therefore allow the proton to shrink a bit. Not much, but maybe enough to explain the difference.
No, this one is global shrinking.
But maybe it is connected with the kilogram prototype losing weight. :-)
Short answer is that I suspect the physics is not new, but something related to something we think we qualitatively know, but we don't really know how to bound the computational errors correctly in a complicated system.
AFAIK, the QED computation techniques that are used to compute bound state of a proton (often modified ordered pertubation methods) aren't particularly convergent so many shortcuts are taken (e.g., use orders of different quantities like non-relativistic velocity, etc). By using a muon and a proton (instead of an electron and a proton), we are essentially replacing something we know more about (the electron) with something we know less about (muon), to try and compute something about something we don't know much about (the proton). Since we don't know much about protons yet, I believe most computations of the bound state are currently just assuming things about them (charge is a point source, nothing about quarks). I haven't read the paper yet, so it's hard to know what they are doing in the QED corrections.
Maybe there is a slight chance that this simplistic system (muon+proton) can macroscopically exhibit something that hints that QCD confinement inside a proton or muon isn't perfect (e.g, the heavy quarks sortof show themselves in a way that we can measure) which would be some interesting new gluon physics that is currently beyond our particle collider reach. But in some ways this might just show us that the QED based adjustments we are making aren't good enough for the real system and we need some even harder to dream up QCD adjustments and it's hard to say that this would definitly be new physics, but perhaps just new math on old QCD physics....
Now, they tell me.
Please do not read this sig. Thank you.
If the mass is unchanged then the previously measured radius was more than likely the result of less than perfect calibration of the equipment, much like erroneously reported FTL neutrinos.
Were the previous measurements done in Texas? If so, everyone knows that it has been scientifically proven that "everything is bigger in Texas"
Have gnu, will travel.
I have no idea what muonic hydrogen is, but I have decided that I like the word "muonic" and all its derivatives.
Anyway, FTFS (didn't' RTFA, obviously) it appears that the "shrunken" measurements were all made on protons in muonic hydrogen, and those measurements disagree with measurements/calculations based on unmuonised protons. Could it be that the muonic state or muonising process somehow causes the shrunken result? Shouldn't the next step be to repeat the experiment, but using some other unmuonate medium and compare those results?
Muonic. Mmmmm-uuuuuuu-onic. Mu.
Well the universe is constantly expanding, its an illusion of that.
"The unlikely but tantalizing alternative is that this is a hint of new physics."
It's just like we learned in math and science class in school. If your experiment or equation doesn't result in what you were predicting, claim it was accurate and make some shit up. Like dark matter for example. Some guys sitting here on Earth with computers and telescopes didn't measure the mass of the ENTIRE UNIVERSE quite right so...must be magical invisible matter we just made up on the spot! Protons shrunk? Must be new laws of physics.
Obviously, the beings running the simulation just changed a constant. Or maybe the computer our universe is currently running on has a manufacturing flaw in some of its hardware.
I think a proton is shaped like a dodecahedron, so of course it's going to measure up to 4% less depending on it's orientation.
That was the turning point of my life--I went from negative zero to positive zero.
because if *everyone* does the experiment and the results don't match up with the theory, then there's something missing in the theory.
In this case, taking the same measurement two different ways results in two different numbers, and the theory says they should match.
You'd shrink too... it's cold out there in the aether.
Well, that's what he's telling the other particles...
You have the right to remain sentient. If you give up the right to remain sentient, you will be elected to public office
I was thinking about this one. I thought that we could redefine the kilogram using a certain number of atoms of silicon-28, but looks like even that won't do, if the protons themselves are gonna lose mass. Only thing I'm wondering - if the protons are becoming lighter, are electrons, neutrons and other sub-atomic particles becoming equally heavier to compensate, or are all of them losing mass, which is transforming into energy using E=mc^2? Maybe at a point, it will all become energy, and there will be no protons left.
Inflation
I'm going to demonstrate my own stupidity (and lack of willingness to RTFA) ...
What changes with this measure? I'm sure it has loads of things which it might affect, but I have no idea.
So, what does a slightly smaller photon translate into?
Lost at C:>. Found at C.
Especially when they have beauty and charm. Or maybe my my hadron is just strange......
Protons are not the size our current model suggests.
Gravity doesn't work on large scales the way our current model suggests.
We can't observer dark matter and dark energy the way our current model suggests.
There's literally hundreds of other examples, but am I the only one who thinks the problem is our current model?
I'm willing to wager dark matter/energy don't even exist. They are just made up to make the computer model work. Ridiculous.
I hold very few opinions. I hold information based on observation and fact. If you wish to disagree, please use facts.
No idea whether this is garbage or has already been taken into account.
In large scale orbiting systems, equivalent measurements relating to size are based on centre of masses, where the masses also govern the force controlling the orbit.
In hydrogen atoms the masses still determine the orbit, but the forces are mediated by the charges rather than by the masses directly as gravity, which may not be in the same place as the masses and may be to some extent free to move in relation to the centre of mass
Looking at this classically - which is very wrong of me - in both electronic and muonic hydrogen, the centre of charge of both the proton and the electron or muon rotate about a fixed point in much the same way as the centres of mass in a 2 body orbital system move around a fixed point between the centres of mass at distances governed by the ratios of the squares of the masses. But in the atomic system if the mass of the proton and its charge can have different centres, the mass of the proton can remain more nearly in the same place, leaving the proton's centre of charge some freedom to orbit the proton's centre of mass and placing the mass centre of the proton nearer the combined charge centre of the orbiting proton and electron or muon pair.
Given that the muon is much heavier than the electron, the orbit is smaller thus the combined charge centre of the proton muon pair will be much closer to the centre of mass of the proton. This means that the protons centre of charge always remains closer to the centre of gravity. Thus the centre of gravity of the proton is not needing to move so much in a muonic hydrogen atom
Or maybe the centres of mass and charge of a proton are separated by a fixed distance and in muonic hydrogen, the mass does not need to swing around so much to accommodate the orbit.
It would be hell to solve in classical mechanics - never mind quantum mechanics.
I was thinking about this one. I thought that we could redefine the kilogram using a certain number of atoms of silicon-28, but looks like even that won't do, if the protons themselves are gonna lose mass. Only thing I'm wondering - if the protons are becoming lighter, are electrons, neutrons and other sub-atomic particles becoming equally heavier to compensate, or are all of them losing mass, which is transforming into energy using E=mc^2? Maybe at a point, it will all become energy, and there will be no protons left.
What are you smoking. I think we'd notice that amount of energy being released!
I don't think anyone said anything about the proton's mass, just the radius.
A difference of 4% in the previously measured mass would be a much bigger story.
The radius, on the other hand, has much less significance -- it even depends heavily on an arbitrary definition, since a proton doesn't have a definite boundary.
Did they check the cables...? Perhaps, it's a loose one.
It's not correct to think of objects as being passive points attached to an actively expanding grid which carries them along. Objects (masses) are primary participants in the shaping of spacetime and not simply being dragged along. In other words, we shouldn't think of the expansion of the universe as causing faraway galaxies to move away from us. Rather, the fact that faraway galaxies are moving away from us is the expansion of the universe (and not a symptom). Everything is moving apart from each other. Galaxies are coasting away from us due to inertia, causing the expansion to continue. (Dark energy, or cosmological constant, is causing the expansion to accelerate by altering the geodesics that these galaxies are following.)
With this picture in mind, it should be more clear that the expansion of the universe won't cause a ruler or the Sun to expand.
The muon sits much closer to the nucleus than an electron, so the charge of the muon is perhaps changing the shape of the proton, "squeezing it". Since the proton is made up of charged quarks, the ground state orbitals for the quarks could be somehow modified by the nearby muon charge. I'm totally guessing of course.
May be someone just didn't tighten a fiber optic cable somewhere.
Why are some people so jumpy on the news of one experiement's measurement of a quanity that contradicts all earlier evidence? I'm not trying to be an asshole, but sorry, haven't we learned our lesson yet? I will concede that they have data dating to 2003, so we could have a real thing there and it is good to give them time to review their stuff. Still, apparently no other measurement has shown anything similar, or I'd assume that they'd have mentioned something in the article, granted they know about or even have read about other discrepancies in the literature on the size of the proton that are eerily familiar.
So, let's wait and see if anyone else can repeat it. If so, then God, are we fried.
From time to time someone comes along and redefines a thing. On an abstract level we suppose they are discussing the same object when they have essentially changed the subject. The old definition still has permanence in our original conceptualization. This is a part of being human. To be aware of the contrasting and sometimes contradicting results as a phenomenon of definition and the technique used to test the definition is to be scientific.
An operational definition generates variation in the way one measures a thing. This is not an isolated procedure because at some point there is variation in the tools applied and a variation in the users’ technique of applying the tool. It may be that the tool itself is a fixed mathematical abstraction, in which case one still must acknowledge the variation from the original definition simply because the mathematics are different.
On another level there is the machine architecture, which can be engineered to have arbitrary precision. This leads to the question of the accuracy in the computer science when dealing with numbers that are so small as to create what is called catastrophic cancelation. Do scientists actually compute the mathematical results or do they rely on the computer science? This level is a check or a question since the precision can be adjusted to the desirable state.
I find it hard to believe that our historical science and measurement for the size of a proton has been wrong by 4% up until now. It is more likely that we have changed the way in which one makes measure of protons. It is likely that sometime in the future new operation definitions will be deployed and the proton will collapse or expand according to the new methodology.
We've probed protons with electrons and with muons. How about using tau leptons next? If only the durn things would exist long enough...
And then, after those, what to use?