Revisions/additions made August 27 2022; for addition, see below.
In 1905, Einstein (age 26) wrote five papers on physics that have fundamentally shaped how physicists today see the cosmos. In looking at what this reality might be, Einstein was old school. Rigden says that Einstein sought to decode God's created universe (As Rigden quotes Einstein: "'I want to know how God created this world...I want to know His thought, the rest are details'"). Overall, Rigden provides an excellent introduction to Einstein.
In March 1905, Einstein laid out his theory about the particle nature of light, the emission of which is energy creation from mass and the absorption of which by a receiving body is the conversion of energy back to mass. In June, Einstein wrote his theory of special relativity. In this theory, only the speed of light is absolute. Conceptions of space and time, once commonly thought as absolute, are always relative to a (moving) frame of reference. As a logical extension of this new conception, Einstein presented his theory that space (length) contracts and time shortens as velocity moves closer to the speed of light. In September, in a three page paper, Einstein established the identity of energy and mass (locked up energy). The mass of a body is a measure of its energy. As a mass radiates energy, it loses mass and energy content. Radiation transports mass between the emitting body and the absorbing body.
Rigden notes the central role of entropy in Einstein's thought where the natural cosmos process moves from low entropy states (order, where everything is in place, has a place) to high entropy states (disorder). Understood this way, a pre-big bang scenario suggests that the tightest, most compact state possible is pulled together by gravitational force. Rigden also says that Einstein's particle theory of light provides enough force to kick out an electron of a receiving body. This produces a light quantum, something the previously prevailing wave theory (continuous, as opposed to discontinuous particle, energy) could not do because of insufficient energy.
Rigden says that both energy and mass are hard concepts to define. That reassures the reader somewhat, but is also frustrating. Rigden says that the speed of light brings energy and mass together (nature, he says, or Einstein says, does not distinguish between mass and energy). In pre-big bang scenario, is ultimate reality energy, with mass (via cooling) coming subsequently? Rigden repeats what others have stated that Einstein's general theory of relativity reveals that space and time are curved by gravity, adding that the general theory "has replaced the gravitational force...with warped space time." This is not clear. As stated, it suggests that a large, pulling gravitational force has been replaced by "warped space time" as if it is the latter that is the new cosmic force. It is easier to understand this by making a massive gravitational body the independent variable, and space time the dependent variable. Also, if a massive gravitational body is the independent variable, how did it form in the first place? Rigden does touch on this point.
August 27, 2022 Addition:
Rigden refers to “the oneness of mass-energy…as masses vanish into energy and masses reappear from energy.” (1) If mass-energy is one, and if mass is the degree of concentrated energy, which is matter in its various configurations, and if energy is that which is liberated from matter, then energy seems to be the primary cosmic component that comes in the concentrated or free/liberated form. (2)
If mass-energy are one, then the different “mass” characterizations – inertial, gravitational, rest, massless - are confusing unless these are understood in terms of what mass (degrees of energetic content) is or does. Thus, inertial mass is movement in place or straight-line movement across spacetime. The straight-line movement in turn encounters depressions in spacetime from a large gravitational presence that creates lines of movement that inertial mass follows (gravitational masses’ accelerating effect). Is rest mass that “rest” component when a body is free of accelerating influences? Photons (light) are said to be massless, but that’s the rest mass of an object, which is not light because it moves at c. But light is said to have inertial mass as well consisting of kinetic energy and its straight-line movement that resists acceleration as long as it’s understood that light’s movement can be and is accelerated by gravity. Light then, carries mass with it as liberated (from matter) energy.
If mass-energy contains two components (degrees of concentrated energy, and energy itself, respectively), how best to conceive of oneness? Is the single cosmic component energy that consists of (a) matter (congealed energy, concentrated mass) and (b) radiation (light, the energy liberated from matter, yet retaining inertial mass, kinetic energy of motion)? Alternatively, is it that Total Energy consists of (a) rest mass (bound energy in matter, amount/degree of energy) and (b) kinetic energy (liberated energy from matter that with speed increases an object’s inertial mass)? Or, is the oneness mass-energy consisting of (a) matter, and mass as substance, or (b) energy without matter but mass, as motion? (3)
(1) He quotes Einstein’s ‘“Mass is energy in reserve.’” Then Rigden writes that “radiation transmits inertia (mass) between emitting and absorbing bodies.” And, while energy is intangible and mass is tangible, Einstein’s E=MC squared “joins them as one” (“The equation E=mc sq. connects intangibility and tangibility and, by making them equivalent, joins them as one. Energy and mass are different and it is the speed of light that brings them together.”) It seems that ‘Rigden is saying something along the line of the following: Energy is that which moves (in a rest state or in straight-line motion), and mass is different only in the amount of energy a body contains. Rigden follows his statement above with a discussion of anti-matter that also unites matter and energy in the following way: “[W]hen a particle meets its anti-particle, they annihilate each other and the two masses become energy,” so that “Creation – energy to mass – and annihilation – mass to energy – go back and forth indiscriminately.”
(2) “Ask any physicist to identify the most important concept of physics and the answer is likely to be ‘energy’…Perhaps this is why physicists choose to write Einstein’s September equation as E=mc squared, where the energy, E, is the subject of the equation.” Yet, Rigden goes on to say, “Einstein did not write his equation this way; rather, he made mass the subject of the equation: m=E/c squared.” Thus, applying Einstein’s formulation on mass-energy equivalence, mass is the central concept, which suggests that all cosmic properties have varying amounts of energy? (I don’t know why E is capitalized and m is not, and if this is significant).
(3) And is this type of breakdown consistent with all matter being both a particle (tangible, material, substantive) and wave (intangible, immaterial, not substantive) duality?