What a headline. Should someone talk to the author, make sure they're doing ok?
Feel free! I don't see the problem with it, though.
Physicists finally nail the proton’s size, eliminating an anomaly
31–40 of 115 posts
Re: Physicists finally nail the proton’s size, eliminating an anomaly
#32I 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?
From my admittedly entry-level understanding, particles like electrons, quarks and gluons are largely considered to be points with energy fields. So, not exactly "stuff", but the stuff that "stuff" is made out of.
Re: Physicists finally nail the proton’s size, eliminating an anomaly
#33I 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?
I guess it's hard to say, because we don't know what we don't know. The famous example is Newtonian physics which seemed to perfectly explain everything.... until new tools and methods came out that were capable of showing it break down under extreme circumstances. That's how we ended up with Einsteinian physics, where it accounted for the old model and the new observed discrepancies. So... how do we know that we wil…
Although Einstein apparently knew about the Michelson-Morley experiment, it's unclear how much his development of relativity depended on it. He seems to have moved on to being motivated mainly by rationalist abstraction and the use of gedanken experiments, rather than actual experiments. The predictions of relativity were then confirmed by later observations and experiments.
"On the role of the Michelson-Morley experiment: Einstein in Chicago" http://philsci-archive.pitt.edu/4778/1/Einstein_Chicago_Web2...
It seems that the development of quantum mechanics has been much more driven by experimental results, although there are exceptions, such as Dirac's prediction of the positron.
Re: Physicists finally nail the proton’s size, eliminating an anomaly
#34so, a failure in measurement sparked a mystery which went on for decades. i wonder how often that happens in science ;P
All the time! People propose hypotheses, supported by some preliminary data, and then they need to be tested. Some problems are easy, some take years or decades to be overturned. It's messy sometimes, but that's how science is supposed to work!
Re: Physicists finally nail the proton’s size, eliminating an anomaly
#35I 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?
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…
"the harder it is to find flaws in the Standard Model, the harder it would be to use such new physics in engineering."
I think that is very likely, but not necessarily guaranteed. I use similar logic with regard to FTL and time travel; if physics has not quite entirely ruled it out, the window is getting smaller and smaller, and is already to the point it's entirely plausible that even if it's theoretically possible there may be no conceivable engineering path to get to it, even for a hypothetical civilization that can fling black holes around.
However, we can't entirely rule out the possibility that some new physics will come along that will reveal how to easily "flip" matter into anti-matter (there seems to be no fundamental reason why this is impossible, it's just... too hard to be useful), or enable the creation of some state of matter or energy that may be exceedingly unlikely to be created naturally [1], but once created could be leveraged into something useful, or other such things. Stabilized muon fusion [2]? Relatively & QM fusion will certainly reveal something new about gravity; it can't be entirely ruled out that it will in some way be useful to engineering. (Although in this particular case, remember we can eliminate not just the "scientific" theories, but also observe engineers have yet to blunder into anything that seems to indicate any manipulation of gravity in any sensible way. Every real-world device ever built is also a test that shows that particular device must not be doing large-scale gravity manipulation.) Will quantum computers reveal some limit of reality's ability to calculate, and will that limit somehow itself turn out to be useful? Maybe.
Still, I tend to think that as much fun as flights of fancy about time travel, FTL, or bizarre alien tech can be, that the most likely hypothesis by far is that we are indeed very unlikely to discover anything in particle physics anymore that will be of any engineering value.
But I wouldn't counsel disappointment. There's still a lot of room at the bottom. We're not going to run out of technology in our lifetimes. If particle physics bores you, check out what's going on in materials science. They're making qubits sing and dance on command. It may still not build UFOs, but they're doing weird stuff in there.
[1]: As a sort of example, see: https://en.wikipedia.org/wiki/Strangelet#Dangers (Stranger Danger has nothing on Stranglet Danger.)
Re: Physicists finally nail the proton’s size, eliminating an anomaly
#36I 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?
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…
If applying the new physics requires gigantic particle accelerators, sure.
But maybe it's under a completely different rock, that we haven't thought of turning over.
Re: Physicists finally nail the proton’s size, eliminating an anomaly
#37I 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?
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 observer inside the shell, will she be attracted to the center of mass of the shell? No, let's see why.
We know that gravitational field falls of with distance squared ( 1 / r^2 ). Consider a random observer position, and a random direction. Now consider a cone tipped at the observer with the random direction as its axis, and also consider a second cone with the same cone angle but the opposite direction as its axis. So the observer position is where the 2 cone tips meet. Then consider the distance between the observer towards each patch of the spherical shell. The area (and thus mass) of this patch will scale with the distance squared, so if one patch is say 3 times further away than the other, it will be 9 times weaker due to 1 / r^2 gravitational fall off, but also 9 times heavier due to geometric scaling of the patch, so gravity due to the patches will cancel, and since the direction of the axis was arbitrary, the gravity of each part of the shell will be balanced by the gravity of a corresponding opposite part of the shell.
So when you are in an elevator halfway down the radius of the hypothetical spherical Earth, all the layers of Earth above you will cancel gravitationally, and the gravitational field will only be due to the mass of the Earth that is contained in the sphere up to your altitute with respect to the center of the Earth.
Similarily, when the electron is far enough from the (assumed spherical) proton, we can somewhat pretend the proton is a point particle. but when the electron is inside the proton, then the effective charge of the proton will be lower because of all the charge of the proton that is farther from the proton's center than the electron is invisible to the electron (since the electric field also falls of like 1 / r^2 ).
I hope that answers the question?
Re: Physicists finally nail the proton’s size, eliminating an anomaly
#38so, a failure in measurement sparked a mystery which went on for decades. i wonder how often that happens in science ;P
Worse are the "best explanations" that get adopted as if they were real observations with militant fervor, something we're seeing with Dark Matter and Energy today. It's gotta be difficult to make progress sometimes when most of your field insists that their best theory must be the correct one.
Please. Millions of dollars are spent every year researching alternative theories and modifications to GR that eliminate the need for Dark Matter and Dark Energy.
The problem is, and has always been, that these alternative theories are never as accurate or precise as GR and their observational evidence is never as good as what we have for DM and DE.
It's not a conspiracy that scientific consensus is that they both exists, and no one is preventing research into alternatives being done. Significantly more money goes into research that accepts their existence, yes, but that's because most scientists do as well. What outcome do you want? To force scientists to work on theories they don't put any stock in? There is still plenty of interest in research papers written by people advancing alternate theories. Good ones are widely read by the entirety of the community, but you make it sound like the scientific community is actively suppressing anyone from researching anything that casts doubt on the existence of dark energy and dark matter, and that's just not true.
Re: Physicists finally nail the proton’s size, eliminating an anomaly
#39This was a great writeup. Accessible, yet I feel like I learned some genuine not-dumbed-down science.
Quanta has a lot of good articles like this one, definitely worth looking at every now and then.
Re: Physicists finally nail the proton’s size, eliminating an anomaly
#40I 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?
"Radius" is a distance at which something stops happening, defining a boundary between some "inside" and some "outside".
Interactions between particles, waves, fields, etc. are quantized, which means there is a set of distances at which a given interaction can happen, and a set of distances at which it can't. This creates a boundary, often spherical, which can be described as having some "radius", and thus some "diameter".
Depending on the interactions you choose, a particle might have multiple diameters, or even boundaries with different topologies, but they're usually somehow related to each other for any given particle.