Thursday, June 25, 2015

Slices of Time

Brian Greene monostich

(Not quite a monostich,
nor a haiku neither.
It is  what it is.)

Every moment is illuminated,
and every moment    remains illuminated.
Every moment  is.
-- Brian Greene, The Fabric of the Cosmos (2004), p. 141


I have  on occasion  fulminated against “Physics porn” -- the tawdry down-dumbing of physics for a popular audience -- not so much a matter of (necessary) simplification, as of appealing to their baser, sensationalistic instincts.
Brian Greene does not practice that. The books of his that I have read (The Elegant Universe, The Fabric of the Cosmos) -- with titles like the Parthenon, elegant but restrained -- are worthy examples of haute vulgarisation.   The matters he treats of  are difficult to explain, even to fellow-physicists (if they work in a different lab, and thus subscribe to a different groupthink); he does a laudable job of trying.  Moreover, the fellow writes really, really well -- at times even poetically (witness the above).

Nor is the cited haikustich  poetry merely.  The idea behind it, appears in the next paragraph  in plain prose:

Einstein said that the problem of The Now  worried him seriously.  He explained that the experience of the Now  means something special for man, something essentially different from the past and the future, but that this important difference  does not  and cannot occur within physics.

Albert Einstein,  worrying about The Now

That is not to suggest that the Now at all resembles a mathematical instant, as in the calculus and thus in classical physics.  Each perceived ‘moment’ of consciousness presumably corresponds to an integral over some interval.   The ‘density’ being integrated need have no determinate evaluation at a single point of the continuum, any more than does the Dirac delta.  The psychological present is more of a Nowabouts.

The same point, with a different metaphor:

The practically cognized present is no knife-edge, but a saddle-back, with a certain breadth of its own  on which we sit perched.
-- William James, The Principles of Psychology (1890), vol. I, p. 609

The present is simply the past’s ever-moving outer edge.
-- Hendrik Hertzberg in The New Yorker, 18 Dec 2006, p. 33


That the “now”, as such, has no special status in physics, is unsurprising, since it is relative to each observer.  That simultaneity (implicitly dependent thereon:  “Both A and B are happening now”) turns out to be untenable, was a shock introduced by Einstein; eventually you sort of learn to live with it.   The real scandal is that physics is likewise agnostic as to any distinction in principle between the future and the past.   And that thesis is cognitively and theologically abhorrent.
Feynman among others calmly accepted solutions to equations, whereby certain particles ran backwards in time.  At its grandest, as a prominent mathmatician-cosmologist writes, “the time-reverse of the universe  is just as much a solution of the dynamical equations” as the one we thought we lived in (Roger Penrose,  The Road to Reality (2004), p. 729).

For humans, the unidirectionality of time’s arrow  is as fundamental as the privileged status of the Now.  America’s premier 19th-century psychologist, on remembering:

However the associationist may represent the present ideas as throning and arranging themselves, still, the spiritualist insists, he has in the end to admit that something, be it brain, be it ‘ideas’, be it ‘association’, knows past time as past, and fills it out with this or that event.
-- William James, The Principles of Psychology (1890), vol. I, p. 2

eppur’ si muove …


James crops up in the first paragraph of a New York Times op-ed concerning durée (subjective time) from 10 May 2015, by Gregory Hickok, a professor of cognitive science:

In 1890, the American psychologist William James  famously likened our conscious experience to the flow of a stream … the stream … of consciousness.

The professor then puts his predecessor in his place:

Recent research has shown that the ‘stream’ of consciousness  is, in fact, an illusion.  We actually perceive the world in rhythmic pulses rather than as continuous flow.

The cognitive scientist then climbs down a bit from the claim that this insight is “recent” -- “Some of the first hints of this new understanding came as early as the 1920s, when physiologists discovered brain waves.”

One suspects, however, that James would not slap his forehead upon being apprized of this newly-minted insight, since he cites “the Humian doctrine that our thought is composed of separate independent parts, and is not a sensibly continuous stream”.  (Hume wrote in the eighteenth century.)

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