Monday, April 13, 2020

The Nature of Physical Reality, Part I: Time

Like as the waves make towards the pebbled shore,
So do our minutes hasten to their end;
Each changing place with that which goes before,
In sequent toil all forwards do contend.
William Shakespeare

The moving finger writes,
and, having writ, moves on.
Nor all thy piety nor wit,
Shall lure it back to cancel half a line. 
Nor all thy tears wash out a word of it.
The Rubaiyat of Omar Khayyam, translated by
Edward Marlborough FitzGerald

Time is not an illusion: it is a record of change in an evolving system, whether that be the unfolding of the universe, the progression of the seasons, or the vibration of the crystal at the heart of a quartz clock.

Before the creation of the universe there was no time. But after the Big Bang, stuff happened: first a fireball of quarks and photons exploding; then particles from the expanding plasma condensing; these, upon further cooling, cohering as atoms, mostly hydrogen plus a little helium; the clouds of gas collapsing under their own gravitation; the atoms fusing to heavier elements and heating the first stars to incandescence; the stars forming into gravity-bound spiral galaxies; the galaxies separating from one another in an ever expanding universe; the stars, their fuel of light elements exhausted, imploding violently to create the heaviest elements and spewing the remnants into space; stellar ashes aggregating into meteors and planets, some to be captured in orbit around new stars, our sun included; the process of universal evolution continuing, so far as can be told, without end. Thus the universe is the ultimate clock, its multifarious transformations marking the hours in the life of the world.

As the universe unfolds, so also do its components. Galaxies and stars evolve, as do planets, the latter both geologically and climatically. Planets may also acquire life, the evolution of which may result in the emergence of intelligent creatures able to fashion clocks and calendars providing measures of date and time more convenient for the regulation of life than natural processes, astronomical or geological.

The notion of events as the measure of time, seems odd to those conditioned by a scientific culture to view time as the measure of events. The notion of time outside of the world of events and having a reality of its own is reinforced by the subjective notion of time: our sense of the ongoing present, and receding past. But the subjective notion of time results from the workings of the mind, which constitute a process in evolution. The conscious mind, flowing continuously from idea to idea, as influenced both by internal processes and sensory input, serves as its own clock.

That it is the stream of consciousness which provides our sense of the passage of time is evident from the fact that when unconscious, for example, between the time  — as instructed by the anesthetist — to begin counting, and reaching perhaps to the number two or three, until the time consciousness returns amid the seeming chaos of a dimly lit and crowded recovery room, there is no sense whatever of the lapse of time.

The common use of language, according to which clocks measure time, further reinforces the misconception that time has a reality independent of events. But, in fact, clocks do not measure time, of which there is no known means of sensing, but only the evolution of their own internal workings: the swinging of a pendulum; the unwinding of a spring; the vibrations of a crystal.

A mistaken belief about the reality of time may also arise from the notion that time forms part of the ultimate fabric of the universe. So far as we understand it, reality consists in a succession of events in a three dimensional space. Thus to identify a particular event it is necessary to specify a point along the three spatial dimensions. But because what happens at every point throughout the universe evolves, identification of a specific event requires that it be time stamped. Thus time is often referred to as the fourth dimension in a space–time continuum. But time has no more reality than the spatial dimensions, fore and aft, left and right, up and down, none of which have a reality in the absence of the events that they map.

The Block Universe: Image source. In the block universe, each of our
moments are not forever"changing place with that which goes before,"
neither does the Moving finger of Omar Khayyam move, but both  remain  
forever fixed like the frames of a movie on a reel of celluloid. Only in 
perception, do our moments "in sequent toil all forwards do contend."
A curious consequence of the notion of time as the fourth dimension, is the idea that just as every event located in space at a particular point on the temporal axis, co-occurs, so every event located at a particular point in three-dimensional space must co-occur at every point on the temporal axis. Hence has arisen the concept of the "block universe," a world in which there is no future and no past, but where everything conceived to be past, present or future has always existed, and always will exist, in all its exquisite detail.

Perhaps this view is correct, but if so, it contradicts Ocham's razor, the principle that, among alternatives, the simplest theory is the one that should be preferred. And it does not merely contradict Ocham's razor, it makes an utter mockery of it, for what it asserts is that for everything that ever happened, that is, for every microscopic event, and every nanoscopic, or picoscopic event that has ever occurred, or will ever occur, there exists a complete copy of the entire universe, to which a time traveler could transport himself. Worse still, time travelers, by showing up in the past or the future, would necessitate countless more copies of the world: giving rise to an infinity of infinitely many worlds.

Something else the theory of the block universe implies is that the creator is a practical joker, for whereas the universe has every appearance, from the microwave background radiation to the fossil record, of being a system in continual transformation, everything in a block universe, from the big bang to the evolution of the big brain and onward to eternity, has always existed and always will exist in a world where absolutely nothing has happened or ever will.

The evidence for evolution, according to this view, whether cosmic or organic, is a matter of appearance created by the juxtaposition of events preserved eternally in aspic but seemingly related to one another as cause and effect in accordance with temporal scientific laws. Morally, this notion seems odious. It means that for all that a person may strive, he will achieve nothing, good or bad, that is not  already cut in stone.

Contrary to the view presented here, Isaac Newton held time to be
absolute, true, and mathematical ... in and of itself and of its own nature, without reference to anything external, flows uniformly... 
Newton's great contemporary Gottfried Leibniz, on the contrary, held time to be, not the reason for, but a consequence of, the linkage of events in accordance with strict laws of cause and effect, a view also held by Einstein's mentor, Ernst Mach,* who wrote.
Time is an abstraction, at which we arrive by means of changes of things. 
Clockwork Time by Fractamonium
Taking the Newtonian view, Julian Barbour has argued that the structure of the universe is such that events are interconnected as if driven by gears in a gigantic clockwork mechanism.*

There is, however, a serious problem with the Newton–Barbour view of time, which is that time is not, as Newton believed, "absolute, true and mathematical," or uniformly flowing as would be required within Barbour's clockwork cosmology. Rather, time, as measured by the best clocks known, the oscillations of a photonic wave, or the vibrations of a quartz crystal, flows at different rates according to circumstance, as observation of clocks moving relative to one another or subject to a difference in gravitational field reveals.

Thus, although Einstein's Theory of Relativity is widely believed to prove the existence of a space-time continuum underlying physical reality, Einstein was not without doubts, remarking that:*
Perhaps, ... we must also give up, by principle, the space-time continuum. It is not unimaginable that human ingenuity will some day find methods which will make it possible to proceed along such a path."
With that intuition, Einstein seems to have come down on the side of Leibniz and Shakespeare, seeing time as a record of the succession of events in an evolving universe. On that view, the universe exists only in the present, not in any past or future states, which means that time travel is impossible since there is no past or future world existent to which one might travel.

* Quoted by George Musser in "Spooky Action at a Distance." Scientific American/Farrar, Straus and Giroux, New York, 2015.

CanSpeccy: The Nature of Physical Reality, Part II: Space
CanSpeccy: More about time
Thibault Damour: Time and Relativity

First published November 26, 2015