The famous equation of Einstein is usually interpreted as “matter is bottled-up energy.” This interpretation is not quite right!
gives the impression that the mass can be converted to energy. This interpretation is not quite right either.
Einstein’s mass/energy equivalence is meant to express the fact that the gravitational force acts on the total energy of an object. The total energy of an object includes its rest-mass but does not mean that mass can be converted to energy.
Rest-mass can be converted to energy under certain circumstances but even that is open to interpretation. For example, when we collide an electron and a positron 2 photons emerge. Electrons and positrons have rest-mass. Since the emerging photons do not have a rest-mass we can claim that we converted the rest-mass into energy in the form of photons. Others might argue that we converted particles with nonzero-rest-mass into other particles with zero-rest-mass.
What is happening in nuclear reactions? Are we not converting matter into energy? No, we are not! We are simply releasing the “interaction energy.” We are releasing the energy contained in the force that holds protons and neutrons together. We are not converting matter into energy.
The rest-mass is as mysterious as the energy. Matt Strassler refers to the rest-mass as “mass-energy.” We now know that there is a universal Higgs field and the elementary particles get their rest-masses from this Higgs field. But, we also know that the composite particles such as protons and neutrons DO NOT get their rest-masses from the Higgs field. Also, the Higgs field cannot explain the numbers associated with the masses of elementary particles. The Standard Model of elementary particles which includes the Higgs field concept cannot explain why electron’s rest-mass is 0.510998928 +/- 0.000000011 Mev.
I am thinking that the rest-mass must be related to curvature. I am referring to the curvature of the primordial fabric of the universe which is more fundamental than space-time-matter. I am thinking that there are intrinsic flows (threads) in this fabric and when a closed-loop is formed in a fundamental thread the rest-mass manifests. But, I don’t have a quantitative theory yet. There will be no scientific progress until a theory explains why electron’s rest-mass is 0.510998928 +/- 0.000000011 Mev without introducing more free parameters.
The goal is to have a theory with minimum number of free parameters.
In the Standard Model of particle physics there are 18 free parameters. There will be 7 more free parameters if the neutrino rest-masses turn out to be non-zero. In the Standard Model the rest-masses of the elementary particles are free parameters. The “free parameter” means that we measure the rest-mass and set the “free parameter” to the measured value without any fundamental understanding.
Getting back to the “matter is bottled-up energy” misconception, I think the matter (rest-mass) is the “bottle” itself.
From the spiritual philosophy point of view it is useful to remember that Shrii Shrii Anandamurti described matter as “Known I.” My commentary on this can be found in “Knower I, Doer I, Done I, Known I.” The main point of that article was that the “soul” has to be explicitly mentioned in any theory, even in theories of matter.