Which of the Basic Assumptions of
Modern Physics are Wrong?
There’s
something unnerving about unifying physics. The two theories that need to be
unified, quantum field theory and Einstein’s general theory of relativity, are
both highly successful. Both make predictions good to as many decimal
places as experimentalists can manage. Both are grounded in compelling
principles. Both do have flaws — including an unfortunate tendency to produce
the number ∞ — but those flaws remain safely behind the scenes, never
undermining the theories’ empirical successes.
And
yet, if the theories are incompatible, something has to give. That is what
makes unification so hard. In conferences, I see physicists go down the list of
assumptions that underpin their theories. Each, it seems, is rock solid. But
they can’t all be right. Maybe one will, on closer inspection, prove to be not
like the others. Or maybe physicists have left the culprit off their list
because it is so deeply embedded in their way of thinking that they don’t even
recognize as an assumption. As economist John Maynard Keynes wrote, “The
difficulty lies, not in the new ideas, but in escaping from the old ones, which
ramify… into every corner of our minds.”
So,
for its latest essay contest, the Foundational Questions Institutee is asking
entrants to ferret out these mental interlopers”Which of Our Basic Physical
Assumptions Are Wrong?”. Scientific
American is a co-sponsor of the contest, which, in practical
terms, means that I’ll serve as one of the judges and my colleagues and I will
consider the top-placed winners for publication. The previous contest, on the
question of”Is Reality Digital or Analog?”, drew lots of mind-opening,
Zeitgeist-challenging entries.I summarized my favorities here, and one will
appear in the magazine this fall.
The
contest will remain open through August 31st. The fun part is that you don’t
need to submit an essay to participate. All the essays are available for reading,
remarking, and rating. The community rankings factor into the judging decision,
which we’ll announce in early December.
( George Musser, blogs.scientificamerican.com, May 24, 2012 )
Is Reality Digital or Analog?
Last
week, the Foundation Questions Institute announced the winners of its third
essay contest, which Scientific
American co-sponsored. (I helped to decide on the question, judge
the essays and hand out the awards at the World Science Festival in New York City.)
The essay question was, "Is Reality Digital or Analog?" Is nature, at
root, continuous or discretized? You can make a powerful case for either
option. Or both options. Or neither. A venerable tradition in essay-writing is
to question the question.
In
fact, whenever I tell people about the contest, many object to the word
"reality." What does it even mean? Will we humans ever be able to
grasp it? The deeper that physicists dive, the more the concept of reality
keeps swimming away from them. Leonard Susskind suggests in an interview in our
August issue that reality is inherently slithery. Black holes, in particular, introduce
an unavoidable ambiguity into our description of nature. That said, we have no
choice but to keep swimming after it. I personally am optimistic that one day
we’ll succeed. (I wrote a whole book on that premise.) The progress physics has
made over the centuries makes a strong case that the amazing complexity of the
natural world arises from the repeated application of a few simple rules that
are within our power to apprehend.
Essay
contests have a distinguished history in physics to gain traction on slippery
problems, outside the strictures of the standard journal paper. They also
broaden the pool of intellectual talent. A total of 161 people from 30
countries entered this contest, and 70 percent of them were not academic
physicists or philosophers. The awards reflected a combination of public
ratings and judge deliberations. I would say that all the essays that placed deserve
reading. They don’t provide watertight arguments—I daresay I found something to
object to in nearly all of them—but do get you thinking. Let me offer a sense
of the range of ideas.
Living
in the age of bits and bytes, we tend to think reality must be digital, so some
of my favorite essays were ones that took the contrary point of view that the
world is really analog.
David
Tong of the University of Cambridge and Ken Wharton of San Jose State
University did just that. Quantum theory is usually thought of as discrete;
after all, that’s what the word "quantum" connotes. But its equations
are actually formulated in terms of continuous quantities. Discrete quantities
appear only when a system is constrained in some way, just as a guitar string
produces certain tones because it is pinned down at both ends. For instance,
the stair-step energy levels of atoms reflect the fact that atoms are held
together by a balance of forces.
Partisans
of the digital view argue that even the continuous quantities are, on closer
inspection, discrete: they lie on a grid whose elements are spaced so tightly
together that they give the illusion of a continuum, like the pixels on an
iPhone 4 screen. But Tong observed that at least one feature of nature really
does seem to require a true continuum: the fact that elementary particles of
matter come in distinct left- and right-handed versions. And Wharton, by
considering the varieties of constraints we can impose on continuous quantum
systems, offered a provocative interpretation of one of the most important
concepts in physics, the principle of least action.
That said, the digital view has strong appeal. The main evidence is that quantum mechanics, when applied to gravity, implies that distance and duration come in smallest possible units. Susskind’s work on black holes showed that quantities such as energy and entropy are discretized, too. True, space and time can’t be anything so straightforward as a grid of pixels, because such a grid would spoil the symmetries we observe in nature. Instead, discreteness suggests to many physicists that space and time are derivative concepts that emerge from some deeper level of reality. A number of essays reviewed the solutions proposed by mainstream schools of thought, including string theory (Moshe Rozali of the University of British Columbia and Philip Gibbs, who was trained as a physicist and now works as a software engineer) and loop quantum gravity (Daniele Oriti of the Max Planck Institute for Gravitational Physics), as well as dark-horse candidates for a deep theory of nature, such as Stephen Adler’s noncommutative matrix model (Tejinder Singh of the Tata Institute of Fundamental Research in Mumbai) and the proposition that the world is a big computer (Giacomo Mauro D’Ariano of the University of Pavia, among other entrants).
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Finally, some of the best essays approached the discrete-vs.-analog dilemma in a fresh way. Jarmo Makela of Vaasa University in Finland imagined a dialogue with Isaac Newton in which he described how to count the possible discrete internal states of a black hole—a quantity known as the partition function, which in turn defines the hole’s thermodynamic properties. Tobias Fritz of the Institute of Photonic Sciences in Barcelona proposed studying graphene as an analogue to quantum gravity. Dean Rickles of the University of Sydney and Thomas McFarlane, a mathematician-turned-patent-agent, suggested that our conceptual and experimental tools bias us toward discrete models of reality.
After
you’ve had a chance to read some of the essays, cast your vote in our online
poll below!
( George
Musser, blogs.scientificamerican.com, June 14, 2011 )
About the Author: is a contributing editor at Scientific American. He focuses on space science and fundamental physics, ranging from particles to planets to parallel universes. He is the author of The Complete Idiot's Guide to String Theory. Musser has won numerous awards in his career, including the 2011 American Institute of Physics's Science Writing Award. Follow on Twitter @gmusser.
About the Author: is a contributing editor at Scientific American. He focuses on space science and fundamental physics, ranging from particles to planets to parallel universes. He is the author of The Complete Idiot's Guide to String Theory. Musser has won numerous awards in his career, including the 2011 American Institute of Physics's Science Writing Award. Follow on Twitter @gmusser.
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