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Physicists finally nail the proton’s size, eliminating an anomaly

quantamagazine.org

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Re: Physicists finally nail the proton’s size, eliminating an anomaly

#61

Post by blhack »

ur-whale wrote: post #21

I wish a physicist could explain here how the very notion of "diameter" has any meaning for an object whose size (IIUC) belong entirely to the quantum realm. Is the hydrogen atom two hard little balls of matter orbiting one another, as we were taught in primary school, or are they a probabilistic soup with various, vaguely localized extrema? If the latter, how do you even define the notion of diameter?

This is true for every physical object though. You cannot tell me with perfect certainty the width of a ball of tungsten, because the edges aren’t actually rigidly defined. In fact: it doesn’t really have an “edge” the way you might think of it geometrically. Just a boundary across which forces start interacting with each other.

Re: Physicists finally nail the proton’s size, eliminating an anomaly

#62

Post by btown »

chasd00 wrote: post #56
DoctorOetker wrote: post #37

Earlier quoted context omitted.

Consider a perfectly spherical earth, and a vertical tunnel perforating it through the center, with an elevator in the tunnel. suppose you are halfway towards the center, coming from the surface, and you pause the elevator. How strong will the gravitational field be? Can we pretend all of Earth's mass is concentrated in the center? No, let's see why. Consider a perfectly spherical hollow shell of mass, and an observe…

forgive my ignorance, but don't you have to assume uniform density in both cases? It seems to me the person in the earth elevator halfway down would feel more gravity toward the center of the earth because there's actually more mass due to the higher density. In a similar way, the proton would have higher mass toward the center because of the higher wave amplitude.

Yep, due to non-uniform density it's much more complicated. https://en.wikipedia.org/wiki/Gravity_of_Earth#Depth includes a graphic that shows how it varies.

Re: Physicists finally nail the proton’s size, eliminating an anomaly

#63

Post by AnthonBerg »

WhitneyLand wrote: post #50
conistonwater wrote: post #11

> If the discrepancy was real, meaning protons really shrink in the presence of muons, this would imply unknown physical interactions between protons and muons — a fundamental discovery. Hundreds of papers speculating about the possibility have been written in the near-decade since. This reminds me of a joke. An experimental physicist walks into a theoretical physicist's office with a really cool experimental result,…

The clever thing about these kinds of jokes as when it happens in politics is, they manage to mock two groups of people such that each group reads the joke and tends to laugh because they infer it as poking fun at the other group.

We laugh even if it is rotated by 180 degrees.

Re: Physicists finally nail the proton’s size, eliminating an anomaly

#65

Post by nategri »

cthalupa wrote: post #42
Sharlin wrote: post #20

Earlier quoted context omitted.

Not really sure about that. Physicists are getting really frustrated by the fact that the LHC has found exactly the missing piece that the SM predicted (the Higgs) and zero evidence of any physics beyond that, anything that would get us closer to quantum gravity. No strings, no supersymmetry, not even any hints as to the nature of dark matter. All it has done is give new lower bounds to the energy scales at which som…

>For all we know, we might need a solar system size collider to attain the required energies. We just need to observe the collisions happening at these energies - we don't necessarily need to produce them ourselves. Some physicists are starting to think about how we might be able to observe naturally occurring collisions at these energy levels rather than producing them ourselves.

IIRC that only buys you 2-3 orders over LHC energy.

Re: Physicists finally nail the proton’s size, eliminating an anomaly

#66

Post by ChuckMcM »

colechristensen wrote: post #55
pavel_lishin wrote: post #2

What a headline. Should someone talk to the author, make sure they're doing ok?

There is a certain philosophical dissatisfaction with the standard model and it just keeps getting confirmed over and over, nobody can seem to find any significant new physics because possible discrepancies keep getting eliminated one by one. Hope dies is maybe a bit florid, but it's a bit real if you don't take it too seriously.

Yup, pretty much. Now if they could just use the standard model to explain dark matter/energy or the inconsistencies in the cosmic age evidence, or what ever the non-fundamental physics but really interesting problem is.

I wonder if we figure out how to regrow a damaged heart into a healthy heart with a simple injection and 10 weeks of physical therapy if hope will die in all those cardiologists out there who no longer are able to push the boundaries in heart transplant surgery or heart substitutions.

What is the effect on people who have spent their lives becoming an expert in a field or subject which now seems to be "done." I could imagine they might lose hope.

Re: Physicists finally nail the proton’s size, eliminating an anomaly

#67

Post by adrianN »

skrebbel wrote: post #23
qws wrote: post #10

Earlier quoted context omitted.

Someone please help correct my intuition here: the harder it is to find flaws in the Standard Model, the harder it would be to use such new physics in engineering. Basically I'm curious whether continuing failures to find new physics can be taken as evidence that, if and when we find the new physics, it will be very difficult to apply. I'm not against science for its own sake, however. Just more of an engineer than a…

Don't forget that our engineering ability grows as well. I guess that when Einstein proposed his relativity theories, it seemed totally inapplicable. But fast forward a few decades, and we got GPS which wouldn't work without them.

Much more impressive are the gravitational wave detectors.

Re: Physicists finally nail the proton’s size, eliminating an anomaly

#68

Post by striking »

whatshisface wrote: post #6
Bostonian wrote: post #4

I think in some areas of physics, such as high-energy physics, there is not much left to discover. The Standard Model works. What branches of physics are likely to see progress?

The standard model lacks gravity.

I would like to believe this is a double entendre.

Re: Physicists finally nail the proton’s size, eliminating an anomaly

#69

Post by DoctorOetker »

lisper wrote: post #27
ur-whale wrote: post #21

I wish a physicist could explain here how the very notion of "diameter" has any meaning for an object whose size (IIUC) belong entirely to the quantum realm. Is the hydrogen atom two hard little balls of matter orbiting one another, as we were taught in primary school, or are they a probabilistic soup with various, vaguely localized extrema? If the latter, how do you even define the notion of diameter?

That is an excellent question! The definition is somewhat arbitrary, but still has some real physical significance. In actual fact, a proton is a field, so it doesn't have sharp boundaries. But the amplitude of the field still dies off very rapidly with distance from the center, so you can pick some arbitrary small value and say "the point at which the amplitude becomes less than this value is the radius of the proto…

> One of the biggest problems in physics right now is that there are no experiments (except possibly this one) whose results are at odds with the Standard Model.

If we say that new physics comes from inconsistencies (either between theory and experiment, or simply within a theory), then there is plenty of new physics to be done, for example the pretense that an electron is a fundamental particle results in the inconsistency with predicted infinite mass. (I claim to have a solution, but I am sitting on it because I believe with a bunch more effort it can explain the dimensionless number that relates planck charge with electron charge, essentially explaining planck's constant and QM in quasiclassical terms...)

Re: Physicists finally nail the proton’s size, eliminating an anomaly

#70

Post by moonbug »

lisper wrote: post #27
ur-whale wrote: post #21

I wish a physicist could explain here how the very notion of "diameter" has any meaning for an object whose size (IIUC) belong entirely to the quantum realm. Is the hydrogen atom two hard little balls of matter orbiting one another, as we were taught in primary school, or are they a probabilistic soup with various, vaguely localized extrema? If the latter, how do you even define the notion of diameter?

That is an excellent question! The definition is somewhat arbitrary, but still has some real physical significance. In actual fact, a proton is a field, so it doesn't have sharp boundaries. But the amplitude of the field still dies off very rapidly with distance from the center, so you can pick some arbitrary small value and say "the point at which the amplitude becomes less than this value is the radius of the proto…

except for an explanation of 96% of the universe's mass
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