the information puzzle

In The Truth is Still Out There, the argument between general relativists and quantum theorists about whether or not information can escape or survive the collapse of a black hole is spelled out in terms even I can understand. 🙂
NYTimes Op-Ed author, physicist, and social-cyber-scientist (?!!), Paul Ginsparg, challenges the absence of calculations supporting Stephen Hawking’s change of mind, suggesting that historical trends show brilliant scientists becoming more speculative as they age, casting doubt on this new theory as the final answer. But what Hawking says is interesting and seems to shift the grounds of debate from either/or to some kind of mutually-compatible middle ground. I think there are potential parallels to group dynamics/discourses. To wit:
“If you jump into a black hole, your mass energy will be returned to our universe, but in a mangled form, which contains the information about what you were like, but in an unrecognizable state.
“The black hole only appears to form but later opens up and releases information about what fell in, so we can be sure of the past and we can predict the future.”

Of course, Hawking is talking about the past and future in cosmic terms, as macro as one can get. But, as the BBC reports, “Whether information is or is not lost has practical and philosophical consequences.”
A quantum concept I hadn’t come across before is unitarity. This may (in my imagination, at least!) have some parallel (?) to the maintenance of some kind of stable discursive foundation….such that shifts in discourse (from one to another) must occur along a kind of continuum in which the transition points (PMs) don’t alter the underlying stable state of, shall we call it, “groupness”…?

The Truth Is Still Out There
August 3, 2004
Ithaca, N.Y.
Stephen Hawking’s recent concession that black holes do not
irretrievably eradicate information after all has garnered
much attention. It is refreshing to see the public focused,
if just for a moment, on an important conundrum that has
fascinated theoretical physicists for three decades, and
prompted much conceptual progress. The scientific issues,
however, remain much less settled than Dr. Hawking’s
celebrated wager on the question. He most recently
pronounced: “If you jump into a black hole, your mass
energy will be returned to our universe, but in a mangled
form, which contains information about what you were like
but in an unrecognizable state.”
To appreciate why this is different from awakening after
any night’s sleep requires a brief reprise of 20th century
physics. Einstein’s theory of general relativity in 1915
was the culmination of centuries of classical physics, and
Einstein and others soon found solutions to his
gravitational field equations. One of these solutions was
later termed a “black hole” in the 1960’s, since it
describes the gravitational field produced by an object so
dense that nothing can escape, not even light. Indeed, the
existence of black holes is inferred only through their
gravitational effects on other astronomical bodies. Stars
recently detected orbiting very close to the center of our
own Milky Way galaxy, for example, suggest the existence of
a supermassive black hole at the center, almost three
million times the mass of our sun and about five million
miles in radius. If the mass of the entire Earth were
compressed into a black hole, it would be a little ball
only a third of an inch in radius. Fortunately, the Earth
is in no imminent danger of collapse because of the
electrostatic repulsion of its constituent atoms.
Quantum mechanics, which describes the behavior of very
small objects like atoms, blossomed a decade after general
relativity, and the two are notoriously difficult to
reconcile. Thirty years ago, Dr. Hawking published a
calculation incorporating some quantum mechanical effects
into black hole physics, and showed that matter or energy
could leak from a black hole. While surprising, this was
not paradoxical since there are examples of processes
forbidden by classical physics but allowed by quantum
mechanics. Shortly afterward, however, Dr. Hawking
articulated a more shocking consequence of his calculation.
One of the central tenets of relativity theory, termed
causality, is that nothing, not even information, can
travel faster than the speed of light. This means that as
long as a black hole exists, no information about objects
that had fallen into it can ever emerge. Therefore,
according to Dr. Hawking’s original calculation, the
radiation emitted quantum mechanically from a black hole is
generic, in the sense that it conveys no information.
Further, if a black hole were permitted to evaporate
entirely, then the information content of any objects
previously ingested by it would vanish from the universe,
without a trace. By contrast, if you throw your diary into
a fireplace, then the information contained therein could
be reconstructed, at least in principle, from subtle
properties of the resulting smoke and flames. A permanent
loss of information because of black hole evaporation, on
the other hand, is in contradiction with one of the central
tenets of quantum mechanics, termed unitarity, which
permits tracking information flow in all such processes and
forbids its disappearance.
In the early 1980’s, I was fortunate to attend some of Dr.
Hawking’s lectures in which he speculated on ways to modify
quantum mechanics to accommodate this potential loss of
information. He stimulated much debate among quantum field
theorists, who in turn enjoyed working to rebut his
arguments. The black hole information paradox thereby
emerged as an important catalyst toward further theoretical
progress in reconciling gravitational and quantum effects.
Despite many new ideas and progress on other fronts, no
definitive resolution emerged.
Near the end of a small meeting I attended in 1993, the
question of “What happens to information that falls into a
black hole?” arose, and a democratic method was chosen to
address it. The vote proceeded more or less along party
lines, with the general relativists firm in their adherence
to causality, and the quantum field theorists equally
adamant in their faith in unitarity. Of the 77
participants, 25 voted for the category “It’s lost;” and
39, a slight majority, voted for “It comes out,” (that it
re-emerges). Seven voted that the black hole would not
evaporate entirely, and the remaining six voted for an
unspecified “Something else.” I voted with the majority,
anticipating progress and hoping that one of us would soon
perform a calculation to help Dr. Hawking and the
relativists see the light. But with the question still
unresolved four years later, three of the protagonists
eschewed the old political duel-to-the-death methodology
for a variety of practical reasons, settling instead on a
simple wager whose unsatisfying outcome was announced last
It once was that important scientific results were
presented to the general public only after they were
subjected to peer review and accepted for publication in an
edited journal. Some professional journals, particularly in
medicine, still refuse to publish results that have already
been announced via press release. Since the early 1990’s,
articles in many fields have nonetheless been publicly
available in “prepublication” form through organized
Internet repositories, a type of instant communication
frequently concurrent with peer review.
The recent “resolution” of the information puzzle, however,
has neither supporting publication nor calculation,
peer-reviewed or otherwise. While a press release may be
sufficient in some realms of human endeavor, one of the
joys of scientific research is that it is subject to more
objective measures of progress. It is possible that some
new revolutionary mechanism to avoid information loss will
yet emerge from the latest spectacle. But without even a
hint yet as to what might have been missing from Dr.
Hawking’s original calculation, it is more likely that
theoretical physicists will continue to view the
information paradox as a profound puzzle whose resolution
will provide clues to understanding the basic laws of
String theory, a parallel quantum gravitational effort over
the past 30 years, offers many tantalizing hints toward
possible resolution of the puzzle. Perhaps some of its
ideas have subconsciously persuaded Dr. Hawking to join the
quantum conservation of information camp. But should we
ultimately be more inclined to trust Dr. Hawking’s past
youthful intuition? Physicists, particularly eminent
British ones, have a historical tendency to stray in
excessively speculative directions in their later years. A
bigger surprise may yet await us, and those who voted for
“Something else” may prove the most prescient. Perhaps the
real winners of this bet will be some middle-school
students who, inspired by the current hoopla, will help
provide a more substantive answer a decade from now.
Paul Ginsparg, professor of physics and information science
at Cornell University, was named aMacArthur fellow in 2002.
Copyright 2004 The New York Times Company

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