
Information Is Physics - mana99
https://cacm.acm.org/magazines/2019/11/240356-information-is-physics/
======
mjfl
Landauer's principle intuitively: the laws of physics are reversible, and
therefore two distinct states (1 or 0) always map to two distinct states (1 or
0, evolved). So how can you erase a bit - take a 1 or 0 and map them to a 0?
The answer is that you have to send the 0 or 1 to the environment i.e. map 1
or 0 to (system,environment) = (0,1) or (0,0) , which manifests as the
dissipation of heat.

~~~
derefr
So where does the information go upon the final heath death of the universe?
Does it become encoded by, say, the final diameter of the post-expansion
universe (i.e. by some "environmental" property at the sub-quantum field
level)?

~~~
akvadrako
There is no environment when you are considering the entire universe. This
means it evolves unitarily and no information is ever erased.

~~~
kgwgk
> evolves unitarily and no information is ever erased.

Nor created.

------
juretriglav
Fascinating! Thank you for sharing, OP! Having recently gone down a similar
rabbit hole [1], having references and starting points is incredibly useful
for further exploration, as this stuff is very hard to search for. There does
seem to be a direct computational link between information and the universe -
and the way we’re using this link now , with classical computers, is highly
abstracted and inefficient (the article also compares current energy cost of
computing vs the much much lower theoretical limit). Quantum computers come
closer to the nature of that link, but still require many abstractions.

I wonder if it will be possible to eventually compute without abstractions,
directly on the substrate of the universe. Though that might be equivalent to
real magic ;)

1\. [https://juretriglav.si/computing-with-
nature/](https://juretriglav.si/computing-with-nature/)

~~~
hos234
I don't think you need to bring quantum computing into the picture. For
example "naturally" 3D printing a Mango takes a few years. Just drop a seed in
the right place on earth and wait. Isn't that computing on the substrate of
the universe?

Are you asking if nature can be coaxed into doing it in a few seconds or a
day? Or maybe you are not bothered about time and want to drop in that seed
and grow a chair? The answer is probably yes to both. It will just take some
time to get there. I don't think quantum computing will be required but who
knows...

~~~
juretriglav
Yeah, dropping a seed in and growing a chair very quickly sounds like it is in
the same ballpark, or at least further along the spectrum of efficient
computation. That seed (program) would very tricky to produce, though.
Contrary to the current practice of writing programs relatively easily, but
the machines to run them are incredibly complex, both to run and to
manufacture. With the seed, though, the machine would be nature, 1=1.

I agree that there is no need to bring quantum computing into the discussions,
but it is higher on the efficient computing scale. It also requires a lot of
effort to come up with programs that make sense, and they use more of natural
phenomena (superposition, entanglement, etc) compared to classical computers.
It’s something to look at for inspiration, at least?

~~~
hos234
Definitely. You might like - [https://www.edge.org/conversation/seth_lloyd-
seth-lloyd%E2%8...](https://www.edge.org/conversation/seth_lloyd-seth-
lloyd%E2%80%94life-what-a-concept)

------
deepnotderp
For anyone interested in this, the Landauer limit now has experimental
evidence.

Also, it is now believed that the Margolus-Levitin theorem puts a lower bound
on energy even on reversible computations.

~~~
ci5er
Weird. It's new to me that we _didn 't_ have experimental evidence before, but
I guess it would have to be pretty subtle equipment.

I wish I knew how to catalog/index my assumption/belief set, so I could scrub
it down for unverified sub-assumptions from time-to-time. I'm happy to update
them, when they are proven wrong, but I don't know how to do this methodically
and as a result, my brain fills up with crap. And then I can't trust my own
glib reasoning, and then I have to be methodical for anything I need to think
through, and that slows me down. And I hate that.

~~~
bcaa7f3a8bbc
There are quite a few things in physics which didn't have direct experimental
evidence, while most are convinced because the theoretical results and
incomplete evidence are persuasive enough. If this Science article is
accurate, there was no direct experimental evidence that proved the majority
energy of the Sun comes from the fusion of protons into helium, until the
neutrino experiment in 2014.

[https://www.sciencemag.org/news/2014/08/underground-
experime...](https://www.sciencemag.org/news/2014/08/underground-experiment-
confirms-what-powers-sun)

~~~
dredmorbius
"They did a stellar job..."

Well ... yes, yes they did.

Pretty fascinating, if light, overview of what's involved in neutron
detection. A case of understanding theoretical models (causal knowledge),
materials, purity and processing, conversion processes (neutrino interaction
-> light -> photodetector), statistics, and ultimately, a view of what was
happenning inside the solar core _eight minutes ago_ , events which won't
manifest on the solar _surface_ for another 100,000 years.

------
csomar
I think the next step for physics could be potentially in establishing the
link between abstract information and what is perceived as "real matter".

~~~
fixf
Self squared dragons and monstrous moonshine.

~~~
fixf
I find it amusing that I didn't say anything for _OR_ against, just mentioned
them and that apparently someone 'disagrees.' With what, an inaccuracy? Then
post a reply. Just voting says: I don't get it.

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ppod
This reminds me a bit of David Deutsch's Constructor Theory. What's the
mainstream acceptance of that like at the moment?

[https://en.wikipedia.org/wiki/Constructor_theory](https://en.wikipedia.org/wiki/Constructor_theory)

~~~
knzhou
I'm always ticked off when I hear the hype around constructor theory. While
information theory has had profound impacts in physics, constructor theory has
always seemed to me to accomplish nothing but add fancy words. Yet it has done
very well trading on the past prestige of its proponents, and promoting itself
through popular talks where no real scientists are present to question them.

For example, constructor theory "explains" why life exists. Their argument is
as follows (condensing 20 pages of vague equation-free words into a few
sentences): first assume that there exists a constructor for life. Such a
constructor is defined to be an object that can create new life. This leads to
the creation of more life. Therefore life exists.

I was so shocked by this that I reread their paper three times before
concluding their argument really was that vacuous. Their physics-related stuff
is similar: assume the desired conclusion, then pretend you've derived it by
adding the vague term "constructor" everywhere. (To derive F = ma... assume F
is a constructor for ma!) It's so content-free I literally can't find anything
specific to criticize. But they keep getting press by making more and more
outrageous claims.

The fact that tens of thousands of curious people around the world have been
duped into thinking that it is on par with ideas that actually have content
proves the absolute bankruptcy of science communication. It is also a warning
to avoid blind trust in past credentials.

~~~
perl4ever
The first sentence of the Wikipedia article is "Constructor theory is a
proposal for a new mode of explanation in fundamental physics".

Well, if it's a "new mode of explanation", then the baseline expectation is
that it doesn't add anything to all existing explanations of physics. The
point of it would be to somehow allow explanations of things that were
unexplainable before...

I mean, if you have a new way of explaining things, you _have_ to derive all
of the things we already know are true.

Edit:

The "Outline" at the bottom of the page doesn't _sound_ like a profound new
way of understanding the universe; it makes my bs meter twitch, but I don't
see anything that provides a definitive reason to consider it all null.

~~~
knzhou
You’re completely correct: new modes of explanation can be extremely useful,
and you can’t judge from the Wikipedia article alone because it can’t get to
the meat! That’s why I had to read the papers. Turns out, the meat just isn’t
there, it doesn’t exist. There aren’t any ideas beyond the vague popsci
outline, which by itself does no good.

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java-man
"settled into something that many people agree is a problem."

love this phrase.

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pier25
Can someone ELI5 the general concept?

~~~
rzzzt
A contest near the end of this chart:
[https://xkcd.com/435/](https://xkcd.com/435/)

~~~
guramarx11
where are the philosophers with applied consciousness to imagination?

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foobar_
Does this relate to entropy (information theory) by any chance ?

Information Theory part 12: Information Entropy (Claude Shannon's formula)
[https://www.youtube.com/watch?v=R4OlXb9aTvQ](https://www.youtube.com/watch?v=R4OlXb9aTvQ)

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rooundio
[https://web.stanford.edu/~montanar/RESEARCH/book.html](https://web.stanford.edu/~montanar/RESEARCH/book.html)

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kgwgk
ENERGY AND INFORMATION:
[https://www.jstor.org/stable/24923125](https://www.jstor.org/stable/24923125)

------
ngcc_hk
Feed sad. It is really one of the few area has long term impact. Sadly my
young fellow hkust student cannot have a chance to explore and see it. Even
get a funeral house to refuse to burial him. Rip. Just not sure what to say.

------
macawfish
It was only a matter of time

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davidivadavid
What else could it be? Everything is physics.

~~~
goatlover
This is the same sort of claim as everything is water, the four elements,
matter, mind, math, or according to this article, information. The difficulty
as always is showing how everything is actually X. It started with Thales or
Parmenides, and the allure of reducing everything to one substance remains
with us to this day.

~~~
davidivadavid
Except physics is precisely _not_ a substance. So let me ask that again, what
_else_ could information be? _Even_ dualistic philosophies are conceptually
reducible to "physics" because physics is _all there is_ , _by definition_. To
paraphrase George Carlin about the Earth and plastic, even if you think
"minds" or "information" are not "physical" (by which people usually mean
material, which is yet again something else), then redefine physics to be "old
physics"+"that new arbitrary thing you named" and you'd still have physics.

Those discussions might involve interesting physics, but it's certainly
clouded in very poorly chosen and confusion-inducing terminology.

~~~
goatlover
Physicists certainly don't concern themselves with the study of everything.
Take sociology or art, for example. At best you can you say everything is made
up of physical stuff.

But even then, there are questions. Are math and logic made of physical stuff?
What about causality or laws of nature? And what of universals or possible
worlds or counterfactuals? If those exist, are they physical?

And then there's consciousness, and the ideas we have about the world, of
which the study of physics is but one domain (containing concepts of energy,
mass, fields, laws, information). Are these ideas physical?

What about the debate over the proper interpretation of quantum mechanics? Is
that physical or philosophical? Is philosophy physics?

You quickly run into problems when you say that everything is domain X,
because then you have to justify lumping everything into that category.

And the idea that everything is physics is open for debate, so clearly not
everyone agrees that it is true by definition. Most things in philosophy don't
get a free pass by virtue of definition, because people aren't going to
usually agree to go along with said definition. Instead, they will want to ask
what it means for everything to be physical.

~~~
davidivadavid
That the _discipline_ of physics doesn't _study_ everything doesn't entail
that _everything_ isn't _physics_. The title of the OP doesn't refer to the
discipline.

As for your other points, I'm familiar with the debates on physicalism in
their various forms. I just believe most of them are elaborate semantic games
with very little actual content.

That people will ask what it means for everything (or anything) to be physical
is precisely my point — stating that "information is physics" is a vague and
(in my view) probably empty/tautological statement if you don't explain what
you mean by that more precisely.

------
Agebor
Theories are now emerging that Universe is running one large bayesian learning
algorithm (bayesian inference itself is proven to be an optimal knowledge
creation method)

See e.g. Bayesian Brain and Universal Darwinism

~~~
alexpetralia
See also: brain as hydraulics, brain as a system of cogs, brain as a
computer.[1]

[1] [https://aeon.co/essays/your-brain-does-not-process-
informati...](https://aeon.co/essays/your-brain-does-not-process-information-
and-it-is-not-a-computer)

~~~
salty_biscuits
Argh, that article! Those are metaphors at some level of representation!!! You
could argue in the same specious way that a computer is not a computer because
it is really a bunch of atoms interacting via non deterministic quantum
mechanical rules so it can't really implement deterministic algorithms and
error free information storage. The three conditions stated in the article
basically are the set up for reinforcement learning, (which can be implemented
at some level of abstraction on a computer) and the question about if a
representation is required or not is a mathematical one. For linear systems
with gaussian noise the optimal control this is an answered question, yes you
optimally estimate the state, then you base your controller off the optimal
estimate. For more complicated systems it is unclear if the representation is
required or not, but it sure seems reasonable that some level of
representation is required. In the baseball example they are still talking
about keeping a constant optical line, not what happens to raw optic nerve
inputs. It has a reduced dimensionality representation!

~~~
goatlover
> You could argue in the same specious way that a computer is not a computer
> because it is really a bunch of atoms interacting via non deterministic
> quantum mechanical rules so it can't really implement deterministic
> algorithms and error free information storage.

Jaron Lanier argues that computers and computation are cultural. Why give them
a special ontological status? Yeah, we can think of the universe as
computational or informational. We can also think of it as mathematical,
mental or just whatever physics posits (fields, strings, higher dimensions,
etc). Whatever the case, when someone like the article in the OP states that
reality is X, then an ontological claim is being made. Its metaphysics.

One could instead argue that the world just is itself, and anything we say
about it is our human model or best approximation. Which would be a
combination of realism (the world itself) and idealism (how we make sense of
it). Then it's just a matter of not mistaking the map for the territory.
Instead of saying that the brain or the universe is X, we say that X is our
best current map for Y. We don't say that London is a map. That would be
making a category error.

