Equivalence of mass and energy
The equivalence of mass and energy is reflected in Albert Einstein's equation E = mc². He coined the concept of equivalence in order to circumvent the same of equality. The energy E can be converted into the mass m and vice versa by means of equivalent transformations. He probably avoided the concept of equality because it could also mean identity. However, total energy and mass are not identical, you can see that in the units. Mass is calculated in kg and the total energy in joules, or in elementary particle physics also as eV, because the charge multiplied by the voltage gives the electrical energy.
Absolute theory and E = mc²
Albert Einstein actually only defined this equation for the radiation output, a radiation quantum has the energy of m * c². However, according to absolute theory, the equation has a more general meaning. So one can easily derive from it the equivalence of space and time and that the absolute speed in the universe must always be equal to c. Albert Einstein also assumed a fundamental meaning of c in the course of the theory of relativity, as he defines space-time as a vector (x, y, z, ict), which means that the time vector of the three space vectors is multiplied by the product of the imaginary number i the speed of light and multiplied by time. Equivalence of mass and energy means, of course, that energy and mass grow and shrink in the same proportion and not, as is often wrongly assumed today, that there is a conversion of mass into energy.
Equivalence of rest mass and rest energy
The terms of rest mass and rest energy defined by Einstein, i.e. the mass and energy that a particle would assume if it were absolutely at rest, are equivalent. E (0) = m (0) * c² applies. Since m = m (0) divided by the relativistic root, one can also bring energy and rest energy into harmony. E = m * c² = m (0) * c² / sqrt (1 - v² / c²). This shows one of the few weaknesses of Einstein's theory of relativity. If the objects came in absolute rest, then the energy would be = 0 because there would be no velocity component. Accordingly, the popular belief that these values correspond to values in absolute calmness are flaws. In absolute rest, mass and energy are equal to 0. Accordingly, rest mass and rest energy must always be equal to 0, regardless of how fast a particle is. But since one can define the Division by Zero, the mass - rest mass relationship always produces meaningful results from an absolute point of view, since the speed is always equal to c from an absolute point of view. Calculation example: m (0) always n * 0, v² / c² always 1: n * 0 / sqrt (1 - 1) ² = n * 0/0 = n. This corresponds to the possible states for the mass.
Equivalence is equality in absolute theory
Albert Einstein coined the term equivalence. He opened the back door that there would be a conversion of mass into energy. From a purely technical point of view, this is correct: for example, atom fusion can release high-energy photons from two elements, which can be used to generate heat and generate energy from it. But strictly dogmatic, this is wrong. You cannot convert joules into kilograms and vice versa. Einstein's statement is that a mass in kilograms corresponds to an energy content and thus an energy. This means that the two numerical values (of course based on the constant c²) are the same. In contradiction, because the absolute theory answered the question of the conversion of mass into energy in the negative, one can speak of equality. In logic, equality is a place above equivalence, because it excludes conversion. However, the concept of equivalence is at best imprecise, but not wrong. However, there is then another level above the identity. So that things are the same and not the same. Here I think that there is still a difference in mass and energy so that both cannot be seen as identical. But here too the equals sign allows for both. But to understand the equivalence of mass and energy E = mc² as a quasi chemical reaction equation, so that one can be converted into the other, is wrong. Correctly, mass and energy are the same.