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The Proton Just Got Smaller
inflame writes "A new paper published in Nature has said that the proton may be smaller than we previously thought. The article states 'The difference is so infinitesimal that it might defy belief that anyone, even physicists, would care. But the new measurements could mean that there is a gap in existing theories of quantum mechanics. "It's a very serious discrepancy," says Ingo Sick, a physicist at the University of Basel in Switzerland, who has tried to reconcile the finding with four decades of previous measurements. "There is really something seriously wrong someplace."' Would this indicate new physics if proven?"
"'The difference is so infinitesimal that it might defy belief that anyone, even physicists, would care"
Does this sentence bother any one else? Just me?
In fact, the correction is about 2% (from 0.8768(69) fm to 0.84184(67)fm; one femtometer is 10^{-15} metres). Yes, the absolute magnitude of the difference is small compared to everyday things, but that's meaningless. More importantly, this difference is more than 5 standard deviations, so this is unlikely to have happened by chance.
> 4% sure does seem significant. But more interesting is that the measurement is thought to be much more precise because of the method of measurement.
No. The interesting thing is that the proton size is now shown to be different than expected from theory. Which means that the theory is wrong. Which is the first step in exciting new physics.
And of course, there's that stupid cat-in-a-box thing...
Not relevant in this case. The uncertainty is between two different measurements, say, mass and momentum. You don't care about the momentum in this case, so the uncertainty in the momentum can be as high as you like. (In this case they're measuring radius rather than mass, but the uncertainty principle governs many different pairs of measurements.)
Doesn't it seem more likely that it's just not possible to get an accurate measurement with the electron -- like measuring a grape with a yardstick instead of a micrometer?
It's more like trying to measure an watermelon with a yardstick rather than a grape. The muon is heavier by a factor of 200, so the energy levels are higher, making them easier to detect with precision. The energy levels of the electron are very small and fine, making them hard to measure with precision.
It's more likely that our ability to measure has improved.
You're conclusions are only going to be as accurate as your ability to weigh, or measure.
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In other words, it's a "that's funny..." kind of moment.
"The most exciting phrase to hear in science, the one that heralds new discoveries, is not 'Eureka!' (I found it!) but 'That's funny...'"
-Asimov
No, such a size is not defined. But it could be, if it were a useful measurement. It would have to be defined in relation to the gravitational fields in the neighborhood, which would make it around the same radius as the L1 Lagrange point. Voila, we have defined a gravitational 'size', and it can even be represented graphically.
Nothing exists unless someone has defined it; by the same token, anything can be defined in some way.
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But if all that checked out and you still had this discrepancy, you'd start to wonder if your ruler and your micrometer were really measuring the same units.
The grape analogy is not a particularly good one. Consider instead a peach analogy. With an electron you're looking at it from 20 m away. With a muon from 10 cm away.
At 10 cm you're going to be vastly more sensitive to the detailed structure of the peach. What at 20 m looked like it could be characterized adequately by a single radial parameter is now clearly a copmlex shape that doesn't even have a very sharp boundary, being covered with fuzz and all.
By far the most likely explanation of this result is something slightly wrong with our understanding of the tails of the proton's structure function, not anything as deep as physics beyond the standard model.
Massive neutrinos aside--as they require only the most minor tweak in the form of off-diagonal elements in the KM matrix--physics beyond the standard model is a bit like fusion power: we've been a few years away from detecting it for the past thirty years... It's gotta be out there somewhere, granted, but I'll be shocked if this experiment is the smoking gun.
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I love science, but it always seems like I know less than yesterday.
Perhaps the used the fudge factor. Just subtract or add to any other mass in question the fudge factor of 4% as needed to get the answer everyone thinks it should be to make the theories work to ones benefit.
The journalists who write about science often use bad, confusing, or just plain nonsensical terms. But it's almost always the journalists, and you can't really fault them for dumbing down their story to appeal to the largest group of readers.
Sure I can. Because it breaks the story, making it false. This confuses the readers further and makes the story have less value than not running the story at all. Yes I know the REAL job of newsies is to attract eyeballs to sell to advertisers. But they pay for the eyeballs by offering information, so "dumbing down" the story until it's worse-than-useless is outright fraud. (And it's a big part of why the old news media are dying.)
English is a very expressive language. It's usually possible to come up with wording that can get the meaning across just as clearly and just about as tersely. For instance, in this case the proton didn't just "get smaller" i.e. suddenly change size. "New measurement technique finds protons unexpectedly smaller." is my first attempt - and I'm NOT an expert in such composition. News writers are SUPPOSED to be experts in this, so there's no excuse for them.
Slashdot had an article and discussion on this - and science popularization - a few days ago.
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This is, in fact, usually true. As the saying goes, "The more you know, the more you know you don't know." If you picture the sum of all knowledge as a rectangle and the sum of your knowledge as a circle inside that rectangle, the boundary of that circle represents what you know that you don't know. As the circle grows, so does the boundary and your awareness of how little we actually understand. Sorry for the long-winded exposition on your comment; I just find that concept fascinating
My high school physics would quote Fitzhenry: "the larger the island of knowledge, the longer the shoreling of mystery".
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