Seth Lloyd is an MIT professor of mechanical engineering who wrote a book called Programming the Cosmos. Some of the ideas in this book have been stated in a recent scientific paper he wrote entitled The Universe as Quantum Computer. In this paper Lloyd deals with some fascinating ideas, and flirts with some promising lines of thought. But does he come up with a workable conclusion?
will skip over the first seven sections of this paper, which mainly
deal with a discussion of exotic issues in computer science such as
universal Turing machines and cellular automata. In section 8 “The
Universe as Quantum Computer,” Lloyd leaps to the conclusion that
the universe is “observationally indistinguishable from a giant
quantum computer,” but does not justify this assertion. For
one thing, no one has built a giant quantum computer. For another
thing, if we were to build a giant quantum computer, there is no
reason to think that it would look anything like our universe of
galaxies, stars, and planets.
then asserts, “The ordinary laws of physics tell us nothing about
why the universe is so
complex.” This is a very serious misstatement which is easy to
disprove. In fact, the ordinary laws of physics tell us a great deal
about why the universe is so complex. We have large complex objects
such as galaxies, stars, and planets largely because of the law of
gravitation. We have 100 different types of atoms (and many complex
molecules) largely because of the laws of electromagnetism, and the
laws of nuclear physics involving the strong nuclear force. We have a
stable planet partially because of conservation laws that maintain
various types of balances such as the balance between positive
charges and negative charges. We have complex life partially because
of various complicated laws that allow stable sun-like stars to
produce thermonuclear fusion at a slow, steady pace. I could list
numerous other examples of laws of physics that help to assure that
we have a universe as complicated as ours rather than merely an
unordered lifeless soup of particles.
then asserts that the known laws of physics can be written on the
back of a tee shirt, something that will come as quite the surprise
to anyone studying physics in graduate school, who has to lug around
600-page books filled with the complex mathematics and equations of
general relatively, nuclear physics, electromagnetism, and quantum
mechanics. This page lists or gives links to more than a hundred laws of physics, a much
larger list than can be written on the back of a tee shirt.
then wonders how the universe got so complicated after the simplicity
of the Big Bang, when everything was presumably packed into a simple
incredibly hot and incredibly tiny superdense ball. To explain the rise of complexity in
the universe (things such as galaxies, planets, and life), Lloyd
offers his “quantum computational model of the universe,” which
he attempts to explain in terms of typing monkeys.
story of the typing monkeys is well-known to anyone who has read
books on the origin of order in the universe. The idea is that if you
have a sufficient number of monkeys typing for a sufficient length of
time, they will eventually produce any imaginable literary work.
Lloyd imagines monkeys typing text that will be fed into a computer.
Purely by chance, Lloyd infers, some of this output would produce a
working computer program. Lloyd suggests such a randomly produced
program might somehow be responsible for order in our universe.
where is this computer, and where are the monkeys? Lloyd gives this
answer: “In addition, quantum fluctuations – e.g., primordial
fluctuations in energy density – automatically provide the random
bits that are necessary to seed the quantum computer with a random
program. That is, quantum fluctuations are the 14 monkeys that
program the quantum computer that is the universe. Such a quantum
computing universe necessarily generates complex, ordered structures
with high probability.”
literally, this thesis is quite nonsensical.
let's look at the primordial quantum density fluctuations mentioned
by Lloyd – not his speculations about them, but the basic concept
of primordial quantum density fluctuations.
imagine these as incredibly tiny random variations in density that
occurred in the early universe. Cosmologists say that such
fluctuations would have occurred in the early universe because of
Heisenberg's Uncertainty Principle. But that law of nature (and its
associated physical constant, Planck's constant) set a very specific
limit on these fluctuations. According to Heisenberg's Uncertainty
Principle, a quantum fluctuation cannot be greater than about a billionth
of a trillionth of a trillionth of a joule during any second. A joule
is about the energy needed to slide a brick a distance of one meter.
So the maximum allowed quantum fluctuation in a second is an amount of energy
billions of times smaller than the energy used in a single one-second
flash of a firefly.
that limit, it is quite nonsensical to imagine quantum fluctuations
literally being the source of some randomly produced program that might help to
produce order in the universe. Even with random fluctuations
occurring all over the universe, nowhere in the universe would we
have for even one second some program that might be used later in
producing order in the universe. If such a program were to somehow
permanently pop into existence (contrary to the limitations of
Heisenberg's Uncertainty Principle), there is no reason to think that
it would then somehow be applied generally as the universe's computer
program. Since quantum fluctuations would be occurring all over the
universe, any random process producing one computer program would
also produce trillions of other computer programs. If those programs
were then somehow used by the universe, what we would see is not the
universe we see (one in which there are physical laws the same
everywhere), but some totally different hodgepodge smorgasboard
patchwork-quilt universe in which every little patch of space had its
own laws of nature. Our universe is totally different, and scientists
have done observations tending to confirm that laws of nature behave the same at opposite ends
of the universe, indicating a great uniformity of law throughout the observable universe.
may also note that there is absolutely no reason for thinking that a
particular part of space would start to use a random program that
happened to pop into existence due to a quantum fluctuation. Just
because a computer program pops into existence doesn't mean that a
nearby computer will start using that program as its operating
system. Also, if we are to explain the order needed for life by
postulating something like a computer program, we need not a random
computer program created by quantum fluctuations, but a highly
optimized, fine-tuned program (given the huge number of anthropic
requirements for observers like us, discussed here).
perhaps Lloyd is just speaking in metaphorical terms (despite making
such statements in a scientific paper). Given his completely
incorrect statement that “the ordinary laws of physics tell us
nothing about why the universe is so complex,” perhaps Lloyd thinks
that most of the universe's order is because of some lucky quantum
density fluctuations in the early universe, and perhaps he is
poetically or metaphorically referring to these as a computer
program. In reality, only a small fraction of the universe's order
(less than 10%) is due to such quantum density fluctuations, with
most of it (much more than 50%) being due to the universe's seemingly optimized
laws of nature and physical constants.
his credit, Lloyd seems to have some general idea or suspicion that
programming and computation play an important part in the universe.
But he's taken this promising idea, and failed to create a workable
thesis from it. The truth is that the universe's order is mainly
caused by a series of highly favorable laws and fine-tuned physical constants that seem to have existed from the very beginning, a
seemingly goal-oriented set of laws and constants that can only be
described as programmatic and conceptual. Our universe seems to have
been programmed for success from the very beginning, as I discuss
here and here. We understand only a small part of this programming
(that part which we call the known laws of nature), Far from being
some simple thing that can be written on the back of a tee shirt,
there is every reason to suspect that the programming that allows a
life-containing universe to evolve from the super-dense state of the Big
Bang is some programming vastly more complicated and proficient than any software
man has ever created. We cannot plausibly explain that cosmic
programming either through a theory of typing monkeys or through a
theory of quantum fluctuations occurring after the origin of the