Cycles of Time

I’ve been reading Roger Penrose’s new book, Cycles of Time. I’ll be quoting some excerpts to illustrate my post.

He proposes a cyclical theory of the universe, according to which the final phase of the universe resembles the initial phase, and therefore circles back to the beginning–to be reborn–like the ancient myth of eternal return. On his view, the universe has a recurring lifecycle.

In the course of his exposition he discusses the measurement of time, which is contingent on the existence of massive particles. Yet in his cosmology, black holes devour massive particles, leaving the universe, in its final stages, emitting massless radiation.

An implication of his cosmological model, as I understand it, is that every time the universe is “reborn,” it resets the clock.

An ironic consequence of his cosmology is that it resembles a secularized version of omphalism, with its distinction between prochronic time and diachronic time. Cyclical time rather than linear time.

My immediate point is not to defend either omphalism or conformal cyclical cosmology. My point, rather, is that no scientist would attack Penrose’s theory because it’s “deceptive.” They might attack his theory on other grounds, but not because it’s “deceptive.”

They’d allow the universe to be whatever it is. That’s something to be discovered. Not something we prescribe or proscribe in advance.

It is important for the physical basis of general relativity theory that extremely precise clocks actually exist in Nature, at a fundamental level…for there is a clear sense in which any individual (stable) massive particle plays a role as a virtually perfect clock…any stable massive particle behaves as a very precise quantum clock, which “ticks away” with the specific frequency in exact proportion to its mass.

 

To build a clock we do need mass. Massless particles (e.g. photons) alone cannot be used to make a clock, because their frequencies would be zero; a photon would take until eternity before its internal “clock” gets even to its first “tick”!

 

According to a massless particle, the passage of time is as nothing. Such a particle can even reach eternity before encountering the first “tick” of its internal clock….To put this another way, it would appear that rest-mass is a necessary ingredient for the building of a clock, so if eventually there is little around which has any rest-mass, the capacity for making measurements of the passage of time would be lost.

 

Photons and gravitons are both massless, so it seems not unreasonable to adopt a philosophy, relevant to the very remote future, that since, in a very late stage in the universe’s history it would in principle be impossible to build a clock out of such material, then the universe itself, in the remote future, would somehow “lost track of the scale of time”…

R. Penrose, Cycles of Time (Alfred A. Knopf 2011), 93-94, 146, 150.