Re: The Whole Universe as a Finite Binary String?

On Mon, 12 Nov 2007 17:29:05 -0000, richardalanforrest@xxxxxxxxxxxxxx
wrote:

On Nov 11, 9:15 pm, r norman <r_s_norman@xxxxxxxxxxxx> wrote:
On Sun, 11 Nov 2007 10:34:20 -0800, Seanpit



<seanpitnos...@xxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
On Nov 11, 4:58 am, richardalanforr...@xxxxxxxxxxxxxx wrote:
On Nov 10, 4:31 pm, Seanpit <seanpitnos...@naturalselection.

0catch.com> wrote:
SETH LLOYD is Professor of Mechanical Engineering at MIT and a
principal investigator at the Research Laboratory of Electronics. He
is also adjunct assistant professor at the Santa Fe Institute. He
works on problems having to do with information and complex systems
from the very small-how do atoms process information, how can you make
them compute, to the very large - how does society process
information?

http://www.edge.org/3rd_culture/lloyd2/lloyd2_index.html

One of the things we do with our quantum computers is to use them as
analog computers to simulate other physical systems. They're very good
at simulating other quantum systems, at simulating quantum field
theories, at simulating all sort of effects, down to the quantum
mechanical scale that is hard to understand and hard to simulate
classically. These numbers are a lower limit to the size of a computer
that could simulate the whole universe, because to simulate something
you need at least as much stuff as is there. You need as many bits in
your simulator as there are bits registered in the system if you are
going to simulate it accurately. And if you're going to follow it step
by step throughout its evolution, you need at least as many steps in
your simulator as the number of steps that occur in the system itself.
So these numbers, 10[120] (10 to the 120) ops, 10[90] (10 to the 90)
bits of matter -10[120] if you believe in something like holography ­
also form a lower bound on the size of a computer you would need to
simulate the universe as a whole, accurately and exactly. That's also
uncontroversial. . .

From my perspective, it's also uncontroversial that the universe

registers 10[90] bits of information, transforms and processes that
information at a rate which is determined by its energy divided by
Planck's constant. All physical systems can be thought of as
registering and processing information, and how one wishes to define
computation will determine your view of what computation consists
of. . .

If you look at a quantum computer you don't see anything, because
these molecules are too small. But if you look at what's happening in
a quantum computer, it's actually attaining these limits that I
described before, these fundamental limits of computation. I have a
little molecule, and each atom in the molecule registers a bit of
information, because spin up is zero, spin down is one. I flip this
bit, by putting it in an NMR spectrometer, zapping it with microwaves
and making the bit flip. I ask, how fast does that bit flip, given the
energy of interaction between the electromagnetic field I'm putting on
that spin and the amount of time it takes to flip? You find out that
the bit flips in exactly this time that's given by this ultimate limit
to computation. . . It goes exactly at the speed that it's allowed to
go and no faster. It's saturating its bound for how fast you can
perform a computation. . .

The other neat thing about these quantum computers is that they're
also storing a bit of information on every available degree of
freedom. Every nuclear spin in the molecules stores exactly one bit of
information. We have examples of computers that saturate these
ultimate limits of computation, and they look like actual physical
systems. They look like alanine molecules, or amino acids, or like
chloroform. Similarly, when we do quantum computation using photons,
etc. we also perform computation at this limit. . .

http://www.edge.org/3rd_culture/lloyd2/lloyd2_p4.html
________________

Just a few interesting if not controversial thoughts . . .

The idea of quantum computers has been around for a while, and there
has been some progress in developing the technology which will make
them practical devices rather than theoretical concepts. When a
theoretical model has developed to the extent that it is being funded
by industry it's no longer controversial, but part of mainstream
science.

What none of this supports is your assertion that "all information in
the whole universe over all
time could be represented by a single binary string of digits", of
course.

That is indeed what Lloyd is saying. Try actually reading the
article. Lloyd is actually saying that the entire information
produced and represented by the universe from its origin until now is
finite and can indeed be represented by a finite computer or binary
string.

Just another example of Pitman obfustication in the pretence of
scientific competence in fields about which you know little.

You honestly think Lloyd is not trying to promote the idea of a finite
amount of information representing and produced by the universe? Why
on Earth do you think there is so much controversy surrounding his
ideas?

Given that the universe occupies a finite volume and contains a finite
number of particles and has existed for a finite time and that
theoretically neither space nor time are infinitely divisible
(continuous) but are quantized, everything about the universe is
finite and hence can be described by a finite length binary string.
That is not so controversial. That the universe is purely
informational might be.

There's not controversy there.
However, Sean's assertion was that "all information in the whole
universe *over all time* could be represented by a single binary
string of digits".

As we cannot predict the quantum state of elementary particles, such a
string can only describe the state of the universe up to the present.
It cannot predict the states of the universe in the future, and can
therefore only be completed after the end of the universe, which puts
it outside the frame of reference of the universe. If the universe is
is all that every was or will be, this is a bit of a problem.

There is also the problem that such a string would have to be encoded
as part of itself if it existed inside the universe. The part of the
string which encodes itself would have to include the encoded part
which encodes itself within the encoded part of the string which
encodes itself and so on. As the string cannot have zero length, and
is repeated a infinite number of times, the string has to be
infinitely long.


I missed the reference to "all" time and only meant to say that the
history of the universe from the big bang to the present is finite.
And you can get around the self-reference paradox by the mathematical
trick of simply asserting that such a string 'exists' without having
to produce it in physical form. The real problem with actually
writing out the string is that it would contain far more bits than
there are particles in the universe.

I seem to recall a sophomoric computation (literally, it probably
happened my sophomore year in college) that although the game of chess
is a finite game and you can simply work out all the possibilities so
it is no more complex (in a mathematical sense) than tic-tac-toe, a
computer with every particle in the known universe operating at a
clock speed of visible light computing for the entire history of the
universe still couldn't compute all the possibilities. There are some
'finites' that are so big as to be, for all practical purposes,
infinite.

.

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