Endnotes
Note 5: Beyond protons and neutrons to other hadrons
- Quote: The strong nuclear force is so overwhelming that you will never find a quark or gluon on its own; each is permanently trapped inside a proton or a neutron.
- Endnote: They can also be trapped inside other short-lived cousins of protons and neutrons, which are generically called hadrons and lend their name to the LHC.
- Discussion
Note 6: Binding energy can be negative
- Quote: When it comes to rest mass, the whole can be greater than the sum of its parts. (It can also be less than the sum of its parts, as is the case in many familiar contexts.)
- Endnote: In nuclei, atoms, chemical bonds, and planets around stars, the stored energy that holds the system together is negative.
- Discussion (coming soon)
Note 7: Proton mass from Higgs field?
- Quote: The Higgs field gives quarks and anti-quarks their rest masses, but it doesn’t provide us with much of our own. Any ordinary object obtains the majority of its rest mass through the efforts of the strong nuclear force.
- Endnote: The Higgs field’s role in a proton’s rest mass, and thus in yours, depends on which question you ask. The standard way to interpret the question, which I’ve used here, assumes that we leave the strong nuclear force’s strength the same while we switch off the Higgs field; then the Higgs field contributes a small fraction of a proton’s mass. But in a more subtle interpretation, the Higgs field’s role can be substantially larger.
- Discussion (coming soon)
Note 8: Black holes made from photons
- Quote: Once particles are imprisoned, their motion energy is trapped, too, and contributes to their prison’s rest mass even if they have no internal energy of their own.
- Endnote: Gravity provides another example of an object with rest mass made from objects that have none. A black hole is formed from objects whose mutual gravitational pull traps them in an embrace too tight for them to escape. In principle, a black hole could be made purely from photons, in which case the black hole’s rest mass would stem entirely from the photons’ trapped motion energy.
- Discussion (coming soon)
Note 9: Why lower electron rest mass leads to larger atoms
- Quote: If we somehow made the electron’s rest mass a thousandth of what it is today, atoms would grow a thousandfold, becoming so flimsy that you and I would evaporate away even at room temperature.
- Endnote: The cause of atoms’ growth is something called the quantum uncertainty principle, which I’ll briefly mention later. It assures that with a smaller rest mass, an electron finds its position in an atom more uncertain, causing it to spread out. This makes the atom larger and the electron easier to dislodge.
- Discussion (coming soon)
Note 10: Removing the electron’s mass
- Quote: If instead the electron’s rest mass dropped to zero in an instant, the impact would be more spectacular: you and I and all other ordinary objects, including Earth, would explode. The detonation would pale compared to a thermonuclear blast, but it would still heat our planet and its creatures far above a survivable temperature.
- Endnote: The power of the explosion and the temperature reached depend on how much of the electron’s lost internal energy is released into the explosion, and that depends in detail on how we turn off the Higgs field. It doesn’t matter much; it’s deadly no matter what you choose to do.
- Discussion (coming soon)
Note 11: Electrons without the Higgs field
- Quote: Shrinking the electron’s rest mass slowly down to zero, we’d find that even in the cold of outer space, all electrons would escape from their nuclei. As particles of zero rest mass, they’d go sailing off into the universe at the cosmic speed limit, much like starlight. . .We are truly dependent upon the electron’s rest mass, small as it is; were it to disappear, nothing in or on Earth would last an eyeblink. This, in turn, highlights our secret reliance upon the Higgs field. If it didn’t exist, or if it hadn’t switched on so it could play its important role, atoms would never have formed.
- Endnote: I’m cheating very slightly here. Depending on exactly how the Higgs field’s effect is removed, electrons’ rest masses might become zero or might instead merely drop by a factor of several billion. Either way, our atoms would disintegrate even in the void of deep space, ripped apart by the (suddenly ferocious) photons of the CMB.
- Discussion (coming soon)
