Why must an ether exist, in order to justify IUT? Cannot there simply be enough random matter in the universe to eventually filter out all light from the outer limits? Or, does the definition of ether include random matter?
An excellent question! There are two possibilities:
1) Light is matter in motion
It is true that the presence of “random matter” throughout the universe would lead to the absorption and therefore the reddening of light over distance. According to neomechanics (TSW, p. 127), each microcosm (portion of the universe) contains still other microcosms (submicrocosms). Thus, when two microcosms collide, some of the motion of the collider (high-velocity microcosm) is absorbed internally by the submicrocosms of the collidee (low-velocity microcosm). This does not happen in Newton’s mechanics, in which objects are considered either point sources of zero dimension or filled with inert solid matter or “filled” with completely empty space. Thus in Newton’s Second Law, all of the motion of the collider is transmitted to the collidee as a whole. Similarly, the corpuscular theory of light proposed by Einstein follows Newton’s lead. Massless particles of light (photons) are said to travel throughout the universe without losing any of their motion during collisions. With the caveat that if they do, this light would be re-emitted in exactly the same form after the collisions. From the standpoint of univironmental determinism, the Newtonian and Einsteinian idealizations cannot be correct. Nothing travels through the infinite universe without something happening to it.
2) Light is the motion of matter.
For light to be considered the motion of matter, it must have a medium for transmission, defined by 19th century physicists as the ether, with specific properties generally not considered to be “random matter.” As with the wave motion in other media (air, water, etc.), ether is responsible for the Doppler Effect and for absorption of motion over distance (red shift). Einstein’s early model assumed that the ether did not exist, with intergalactic space being completely empty. This was falsified by the discovery of the intergalactic microwave background radiation having a temperature of 2.7K. Completely empty space would have a temperature of 0 K. From the standpoint of univironmental determinism, light must be the wave motion within the dynamic medium traditionally referred to as the ether.
How this all fits together
INFINITY, as defined in TTAOS, is both microcosmic as well as macrocosmic. This means that every portion of the infinite universe contains submicrocosmic particles within microcosmic particles, ad infinitum. Similarly, it must contain supermacrocosms within macrocosms, ad infinitum. The upshot is that there is no completely empty space; nonexistence is impossible. The universe is infinitely subdividable and infinitely integrable (as in the calculus).