Just out of curiosity: on a scale of 1 to 10, how confident are you in what you just wrote ? Can you provide one link to back it up ? The link will help us reach your level of enlightenment
Sorry it took so long to get back to you.
On a scale of 1 to 10, it's a 10. Background: Physics 149, 151, 152, and 269. (That's a refresher Physics for them's that's been away from it for a while; then the two standard Physics for engineering majors that more-or-less start with Newton and work their way up some of the relativity equations involving time dilation; and the Physics that gets into serious elecromagnetics with Maxwell's equations. Throw into that a couple of courses in chemistry (and the labs), and the dedicated electromagnetics courses in "Basic" and "Antenna Theory" and, well, one gets a pretty good appreciation for How It All Hangs Together. Including the quantum electronics that one runs into in chemistry these days, what with orbitals and all. Not to mention that, as a EE, one typically gets into deep dives into how, say, semiconductors
actually work and why it's stated, for example, that ceramic capacitors are made out of ferroelectric insulators.
Add to that some, what is it, some 40 years of actually working in the field on some pretty hairy stuff..
But, consider this, for example: A photon hits an atom. If the atom's not ionized (and maybe even if it is), some electron(s) or others in the shell(s) around the nucleus are going to jump up a level or three; then, after a time, emit a photon and jump back down. Everything from why, say, a red-colored object
looks red to the the inner workings of atomic clocks work on this basis, not to mention biological systems (that means
you) all over.
Trick is: Photons may travel at Ye Speed Of Light, but they very definitely
have mass. Energy of a photon is h*f, where h is Plank's constant, f is the frequency in Hertz. Then, the mass of the photon, by Einstein, is m(rel) = E/(c*c), where c is speed o'light.
So, when that atom gets hit by the initial photon, it goes from its base mass to the base mass + the photon mass. It may stay in that state for from near-zero time to forever; come the time it emits a photon, that photon carries away mass.
But chemical reactions are all about moving from one energy state to another; in a higher energy state, an individual molecule (or a collection of them) has absorbed energy and gained mass; in fact, all chemistry is based upon the idea that one is trading quanta of energy around via photons and, yup, all those photons have mass.
One sees this, "Photons carry mass around" with what are termed "Solar sails". Spread out a thin, reflective surface face-on to something bright, like the sun; photons bounce right off, and the momentum (that is, PhotonMass*SpeedOfLight) of the photons doing this get transferred to the solar sail, which then sails off that-a-way. There's been a number of NASA funded experiments with this since, while the acceleration is low, It Doesn't Let Up. And one doesn't have to carry fuel around to change vector.
Thing is, though, the mass changes are ridiculously tiny compared to the energies absorbed and given off by chemical reactions, so it's kind of excusable that Nobody Noticed What Was Going On until Einstein and his compatriots finally nailed it in the 1910's or so. And then all the mysteries of How The Heck That Flaming Ball of Gas In the Sky Got So Old If It Was "Just" a Chemical Reaction kind of got laid bare, and the conversion of the mass of four hydrogen atoms (and their electrons) into the mass of one helium atom and its two protons, two neutrons, and pair of electrons provided the answer.
That's enough on this for one day, and sorry that it's in the Investment Forum. I mean, people were joking around about the weight variation of a charged battery vs. an uncharged one with respect to an ICE semi's weight of fuel in its tank, and acting like figuring out the mass variation of the BEV version was some inscrutable problem.. when, as it happens, it's not an inscrutable problem, it's pretty simple, if one knows the amount of energy involved. It's not every day one can pull out E=mc^2 and solve
an automotive problem. Which is pretty funny, when one thinks about it.