Why neutrons and protons are modified inside nuclei

Yes.

Nucleons and quarks represent internal degrees of freedom (DoFs) inside the nucleus resp. proton that can receive momentum-energy from a scattering electron. This is measured as a loss of the sum of the kinetic energies of the electron and its target.

At low energies, the transfer to internal DoFs is negligible, so the scattering is elastic. At higher energies the transfer is relatively large, so the scattering is inelastic.

At sufficiently high energy, the nucleus disintegrates into components and new particles, and in the target's centre-of-momentum frame the sum of all their kinetic energies matches the change of the electron's. But at even higher energy there is again an apparent loss of kinetic energy, so there must be further internal DoFs within the components. Those are in the proton.

The higher energy scatterings are "deep".

As one does deep inelastic scattering, the proton's internal DoFs absorb electron momentum-energy. At sufficiently high energy levels the proton disintegrates into many new particles.

There are also differences in the scattering angle -- the amount by which the scattered electron is deflected from its beam path. Scattering angles are low in elastic scattering, and high in inelastic scattering. This gives further information about the internal DoFs.

For more see Mott scattering, deep inelastic scattering, and the parton model.

Yes, exactly. At low energies we can see that most of the atom's mass is in a nucleus. At medium energies we see that there are proton and neutron sized lumps in the nucleus. At very high energies we can see that the protons etc have quark sized lumps inside them. (Full disclosure: FWIW I took a physics course from one of the professors on the team which discovered gluons.)

Uranium loses "unexplained" unaccounted for mass other than leaving behind Barium and Krypton. ELI5 continuing.

What is that mass? What are its properties if you capture enough of it?

Does it behave like "a mass of quarks"? Does it behave like an element? What are the constraints on that mass?

It's funny that I have to talk about electroweak interactions to a guy who knows what a quark is. Perhaps they also know what a boson and fermion are.

The entity known as neutron has an interesting property that causes a different set of bosons to be emitted when it's broken out than as if just random quarks were torn out. The color constraint does not explain it.

It does not stop at any size. It just becomes impossible to measure. And it's not a toggle, it's the both at the same time.

The wavelength is inversely proportional to the momentum. As the momentum of the object increases, the wavelength decreases. For a human sized object the wavelength is already magnitudes smaller than Planck length (10^-35 m)

> a coffee cup does not toggle between being a wave and a particle

Neither does an electron, for that matter.

Particles such as electrons, protons, etc, are quantum objects. They're not waves. They're not particles. They are quantum objects - which means they have some wave-like properties, and some particle-like properties, but really are something else altogether.

The human brain is not wired to have an intuition into the world of subatomic particles. (Just like with the 4-dimentional geometry, one has to go through an extensive training in order to have an inkling of such intuition.) All these spheres, point-like particles, waves, etc. are mathematical models at best.

You might be interested in Pilot Wave Theory. It tries to reconcile wave/particle duality by claiming there is a real physical particle at all times in an attempt to get around the strange idea of everything being a probablistic wavefunction (the Copenhagen interpretation).

It explains some things pretty intuitively (double slit experiment), but from what I can tell it becomes too convoluted for other things.

Mass can be related to energy with E=mc^2, and you can get some idea of its relation to wavelength and wave collisions.

I think a smallest wavelength is unlikely, because it would put an upper bound on energy. The only side-effect of increasing the energy density (ie a lot of energy in a small space, like a very low-wavelength photon) is the formation of a black hole. I think the question of whether photons (massless) can form them is one of those quantum-gravity issues that are awaiting a theory.

I struggled with it until I thought that these things aren't particles or waves in the way that we think of them. They don't flip back and forth. They are one thing that is simultaneously both a particle and a wave and they are like that all the time. They're not particles and waves. They're particle-waves, or wave-particles. It's neither a wave nor a particle and neither is it both things simultaneously. Instead, it shares many properties of both. It is it's own thing. We don't have a better word or description for it because there isn't a good analogy in the normal macroscopic physical world we're used to. It appears contradictory to us only because we don't have a good analogy for it.

However, we do understand that things can be two things at once. Say I take an metal marble that has been painted blue. We have an object with two distinct properties. Now we can say that the marble is metal, and we can test it is by feeling it or using a magnet. And we can say that it's blue, and we can test that it's blue by shining a light on it and measuring the light that comes off of it. But our marble doesn't stop being blue just because we're using a magnet, and it doesn't stop being metal just because we're shining a light on it. However, we can't tell that it's blue by using a magnet, and we can't shine a light to tell if it's metal. Indeed, we can even think of more properties. A marble is spherical, but we could also have a blue metal cube.

The universe isn't tricking us or making something switch between two states of being. Our tests are just limited. When we get to a subatomic level, our tests and interactions are so limited that you can't test for more than one property at a time because every test interferes with what we're testing. You have to pick the one you want to look at. That's where the uncertainly principle comes in.

As far as I'm aware, the reason that we can't develop any test that can break the uncertainty principle is because everything we could potentially test with is, itself, a part of the wave-particle system. Since experimentation requires measurement (of course), and every measurement requires interaction (it does), and every interaction in the universe is either wave-like or particle-like and it's never both (they are, AFAIK), then no matter how smart we build our system we can't measure for both at once because everything we can build is inherently limited to this restriction because everything is in this system.

It's like baking a cake. Say you want to know two things: Is the oven temperature right, and is the cake completely cooked through? If you want to know if the cake is cooked, you'll have to open the oven and stick a tester into the cake. But, if you open the oven, you've let all the heat out. You can't do both at the same time, because one test interferes with the other. Even if you check the temperature and then test the cake, you've still changed the system. This is not a perfect analogy, of course, but it kind of gets you thinking along the right lines.

I'm no expert in this field, however, and I'm sure someone will be along to correct my misconceptions.