4 ms·

They may have been so into their own bellybutton lint that they were very concerned about the difference between bound quarks on a QCD lattice compared to just

They may have been so into their own bellybutton lint that they were very concerned about the difference between bound quarks on a QCD lattice compared to just elmer's gluing 2 free neutrons and 2 free protons together or something like that.

marcosdumay 5y ago
Yes, I have heard a lot of times how atom nuclei and alpha particles aren't made of protons and neutrons. It's always on this sense. Some times the difference is relevant (and people dealing with radioactivity see those times more often than others), but some people insist on the pedantic distinction even when it isn't.
- adrian_b 5y ago
  The binding energy of protons & neutrons into nuclei is less than 1% of their mass, so the energy required to separate a nucleus, like an alpha particle, into all its constituent protons and neutrons, is negligible in comparison with the energies required for interactions so intense that they would generate any other hadrons except protons and neutrons, for example pi mesons, which would expose the inner structure of protons and neutrons. This is an important feature of nature, whose consequence is that the most convenient way of understanding the world is that the first approximation, which is useful for almost all practical purposes, is to consider everything as composed of protons, neutrons and electrons, which are bound by strong, electromagnetic and gravitational forces and that there are also positrons (antielectrons), which can be generated in sufficiently intense interactions and which will annihilate with electrons. Only for few purposes it is necessary to go beyond this and take into account that there are many other hadrons composed of quarks, besides protons and neutrons, and that there are also other leptons. The distinction between these 2 level of approximation is important and whoever likes to think that alpha particles as not being made of protons of neutrons fails to get it. Of course, for many purposes you can ignore the strong nuclear forces and you can consider the surrounding world as being made of electrons and of a little less than 300 kinds of long lived nuclei, which are bound by electromagnetic and gravitational forces. At this other level of approximation, you should ignore the proton-neutron composition of any nucleus, but when you talk about alpha particles, you normally mean helium nuclei having a kinetic energy high enough to not be negligible in comparison with the binding energies of nuclei, so you are not in a situation when you can ignore the nuclear compositions. In any physical model, it is important to specify clearly which is the level of approximation at which it works. Mixing randomly various levels of approximation of the structure of things is usually a bad strategy.
  - lamontcg 5y ago
    Yes, but very smart people are often hyperfocused on their own particular bellybutton lint like I said. For someone whose whole job revolves around the quark structure of nuclei they may see it important enough to "correct" someone who only thinks of nuclei as protons and neutrons flying around each other in relative isolation like planets. Add a dash or ten of Asperger's (we're talking about nuclear physicists here) and that's how you wind up with an expert "correcting" a non-expert about a casual fact which is 99.9% correct. Thinking that the expert was too dumb to know that fact is probably the wrong interpretation. Thinking that the expert was making a social/communication mistake is probably the right one.

marcosdumay 5y ago

Yes, I have heard a lot of times how atom nuclei and alpha particles aren't made of protons and neutrons. It's always on this sense. Some times the difference is relevant (and people dealing with radioactivity see those times more often than others), but some people insist on the pedantic distinction even when it isn't.

adrian_b 5y ago
The binding energy of protons & neutrons into nuclei is less than 1% of their mass, so the energy required to separate a nucleus, like an alpha particle, into all its constituent protons and neutrons, is negligible in comparison with the energies required for interactions so intense that they would generate any other hadrons except protons and neutrons, for example pi mesons, which would expose the inner structure of protons and neutrons. This is an important feature of nature, whose consequence is that the most convenient way of understanding the world is that the first approximation, which is useful for almost all practical purposes, is to consider everything as composed of protons, neutrons and electrons, which are bound by strong, electromagnetic and gravitational forces and that there are also positrons (antielectrons), which can be generated in sufficiently intense interactions and which will annihilate with electrons. Only for few purposes it is necessary to go beyond this and take into account that there are many other hadrons composed of quarks, besides protons and neutrons, and that there are also other leptons. The distinction between these 2 level of approximation is important and whoever likes to think that alpha particles as not being made of protons of neutrons fails to get it. Of course, for many purposes you can ignore the strong nuclear forces and you can consider the surrounding world as being made of electrons and of a little less than 300 kinds of long lived nuclei, which are bound by electromagnetic and gravitational forces. At this other level of approximation, you should ignore the proton-neutron composition of any nucleus, but when you talk about alpha particles, you normally mean helium nuclei having a kinetic energy high enough to not be negligible in comparison with the binding energies of nuclei, so you are not in a situation when you can ignore the nuclear compositions. In any physical model, it is important to specify clearly which is the level of approximation at which it works. Mixing randomly various levels of approximation of the structure of things is usually a bad strategy.
- lamontcg 5y ago
  Yes, but very smart people are often hyperfocused on their own particular bellybutton lint like I said. For someone whose whole job revolves around the quark structure of nuclei they may see it important enough to "correct" someone who only thinks of nuclei as protons and neutrons flying around each other in relative isolation like planets. Add a dash or ten of Asperger's (we're talking about nuclear physicists here) and that's how you wind up with an expert "correcting" a non-expert about a casual fact which is 99.9% correct. Thinking that the expert was too dumb to know that fact is probably the wrong interpretation. Thinking that the expert was making a social/communication mistake is probably the right one.