Energy in physics feels analogous to money in economics. Is a manmade medium of exchange used for convenience. It is the exchange medium between measureable physical states/things.
Is energy is real in the same way money is? An incredibly useful accounting trick that is used so frequently it feels fundamental, but really it’s just a mathmatical convenience?
Small aside: From this perspective ‘conservatipn of energy’ is a redundant statement. Of course energy must be conserved or else the equations are wrong. The definition of energy is it’s conservation.
Interesting, I thought energy is photons themselves. Or is energy a group of those particles that pop out, like what you mentioned. Or is it a side effect from those that pop out?
The matter does get converted into those photons.
Said another way:
The things go from being a couple of spin-half particles/antiparticles to a flurry of spin-one photons.
Everything is energy. How big the energy is and how it moves is really all the difference between photons and mountains. Took a recent Veritasium video for that to really click for me.