
A Different Kind of Theory of Everything - evanb
https://www.newyorker.com/science/elements/a-different-kind-of-theory-of-everything
======
mindgam3
This article introduces a geometric structure known as an "amplituhedron" as a
way to understand reality.

"Some researchers are attempting to wean physics off of space-time in order to
pave the way toward this deeper theory. Currently, to predict how particles
morph and scatter when they collide in space-time, physicists use a
complicated diagrammatic scheme invented by Richard Feynman. The so-called
Feynman diagrams indicate the probabilities, or “scattering amplitudes,” of
different particle-collision outcomes. In 2013, Nima Arkani-Hamed and Jaroslav
Trnka discovered a reformulation of scattering amplitudes that makes reference
to neither space nor time. They found that the amplitudes of certain particle
collisions are encoded in the volume of a jewel-like geometric object, which
they dubbed the amplituhedron. Ever since, they and dozens of other
researchers have been exploring this new geometric formulation of particle-
scattering amplitudes, hoping that it will lead away from our everyday, space-
time-bound conception to some grander explanatory structure."

The wikipedia page for amplituhedron provides some kind of simulated
visualization but doesn't clarify in layman's terms how reality fits into this
particular structure. It seems like an interesting concept, I wish I
understood it better.

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

~~~
phkahler
I am not a physicist, but when I first read about the amplituhedron whatever
article it was seemed to indicate it was an interesting way to do computation.
It was also simpler and quicker than the usual way. They never indicated any
reason for it, or model of reality, just that computing volumes produced the
same results as some other method used by physicists. I don't even recall if
they proved it to be equivalent or just showed that in every case they tried
it produced the correct result.

I suspect the folks reformulating QM in Clifford Algebras may have (or find) a
way to explain why a geometric interpretation works the way it does.

------
apo
The article uses the term "Rashomon effect" without defining it. I hadn't
heard of it before, and here's what I found:

 _The Rashomon effect occurs when an event is given contradictory
interpretations by the individuals involved. The effect is named after Akira
Kurosawa 's 1950 film Rashomon, in which a murder is described in four
contradictory ways by four witnesses.[1] The term addresses the motives,
mechanism and occurrences of the reporting on the circumstance and addresses
contested interpretations of events, the existence of disagreements regarding
the evidence of events and subjectivity versus objectivity in human
perception, memory and reporting._

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

And here's a short video summary of the film:

[https://www.youtube.com/watch?v=BP2MhghDal4](https://www.youtube.com/watch?v=BP2MhghDal4)

~~~
blacksqr
The so-called "Rashomon effect" is mis-named. The point of the film was not
that everyone has a different perception of the truth. It was that everybody
lies to preserve their sense of self-righteousness, no matter who else it
damns, even when they have nothing left to lose.

It was a depiction of Hell.

~~~
throwaway2048
I think the point of the story is subtler than that, its not so much that
people consciously lie, its that their recollections are shaped by their own
desire to be in the right.

------
naasking
> And the Rashomon effect also suggests that reality isn’t structured in such
> a reductive, bottom-up way.

Does it? I don't see why. If there are numerous equivalent ways of describing
a phenomenon, that seems to suggest that most structures have inherent
isomorphisms. I don't think anyone would find this is particularly surprising.

------
ymolodtsov
Each more complex theory turns into its simpler predecessors jn certain cases.
There’s no magic in that, it’s simple math: if v << c, then the equations of
special reativity become much easier and we get Newton mechanics. The same
applies to the rest. If you want to discuss why does our world have to obey
the math — that’s a whole another story.

------
calebm
This reminds me of this article (mostly focused on John Wheeler):
[https://blogs.scientificamerican.com/cross-check/do-our-
ques...](https://blogs.scientificamerican.com/cross-check/do-our-questions-
create-the-world/)

------
rwallace
“I always found that mysterious, and I do not know the reason why it is that
the correct laws of physics are expressible in such a tremendous variety of
ways. They seem to be able to get through several wickets at the same time.”

Conjecture: because this conversation is necessarily taking place in a
universe where a certain level of intellectual and technological development
was able to happen, which means one in which there is an evolutionary path to
attaining such, which means one in which you can build a series of models of
the universe, each progressively more accurate, but the early ones still give
usefully accurate predictions.

------
DoctorOetker
I spent a week or so (in 2013 or so) trying to understand the notes and I
believe also a youtube lecture. Novel named concepts were simply used without
any introduction, now I don't mind naming some new mathematical object with a
relevant name (used to calculate amplitudes), but only after rereading the
notes and rewatching the lecture did it eventually click: the diagrams
depicting schematically the amplituhedron with a bunch of points ... it's a
convex hull. Any sane person would introduce each new concept - and I really
don't mind giving it a pet name - as long as it is defined in terms of well
known objects or concepts. If one can't bring up the effort to just write:
"the amplituhedron is defined as the convex hull of a set of points" how can
you expect your audience to put in the effort to understand what you are
trying to say? Also define what the points represent, give concrete examples,
what are the coordinates of these points? etc... After multiple times finally
realizing what the author was referring to with a new concept or procedure or
so, and then always realizing he could have said the very same in much simpler
terms I just gave up _trying_ to decode the rest. Now we are about 6 years
later, and there is a wikipedia page, but unless there is a clearly written
text that starts from well known concepts, and introduces new ones _in terms
of known ones_ instead of using them without introduction and assuming the
reader can read your mind... unless there is a clear text I see no point in
even trying. If anyone knows if the situation has changed please point me to
some clear explanations, otherwise I have no choice but file it under the
"suspiciously obfuscated: either malicious or inept" category...

------
subjoriented
Not that I have any real answers here (re: theories of everything), but I do
have something to add regarding "laws".

Charle's Law states that Pressure * Volume = Temperature.

That's true and you can do a million experiments with a million balloons and
liquids/gases to validate it - until you find a non-newtonian substance, try
to apply it to a solid, introduce moving fluids, etc.

Charle's Law isn't a fundamental law of physics, but a consequence of the
material properties and statistical outcomes of a large number of interacting
molecules. Before atoms and molecules are characterized, it _does_ look like a
fundamental law to an experimenter.

It doesn't seem to me that looking for "lower layers" of theoretical physics
(holographics, quantum foam, strings, whathaveyou) is an infinite regress and
doomed to never be a completed project. I do think that the project may reach
some point where the theories fail to be scientific (read: falsifiable)
because it could be possible that reaching deep enough through layers of
physical abstraction can not be achieved / no physical instrument can provably
be built to look deeper (as an analogy, no instrument can be built to probe
the full amplitude space of a quantum state).

------
bubble-07
We tend to prefer simpler theories that still manage to make good predictions.
Is it really a surprise that our best theories are simple in light of our
aesthetic preferences? The "true laws of physics" could be god-awful, and we
could find ourselves in a universe where we're literally incapable of knowing
that due to practical constraints. It's also not surprising at all that
theories that are aesthetically-pleasing to us manage to have multiple
different mathematical formulations -- if we're assuming from the outset that
they're not very arbitrarily-defined theories, it seems perfectly natural that
multiple interpretations would exist. Nature could be more horrifyingly
complex than we could ever imagine, and even if that were the case, it's
conceivable that all of the laws "good enough" to make testable predictions
would have a nice mathematical structure. Even then, we're nowhere near the
"end of physics" \-- how are we supposed to know that we've not just been
wading around in the shallow part of the pool, only to find a bottomless pit
waiting for us just a few meters away?

------
nabla9
Same writer, longer articles:

Visions of Future Physics [https://www.quantamagazine.org/nima-arkani-hamed-
and-the-fut...](https://www.quantamagazine.org/nima-arkani-hamed-and-the-
future-of-physics-20150922/)

A Jewel at the Heart of Quantum Physics
[https://www.quantamagazine.org/physicists-discover-
geometry-...](https://www.quantamagazine.org/physicists-discover-geometry-
underlying-particle-physics-20130917/)

Nima Arkani-Hameds Lecture: The Doom of Space Time: Why It Must Dissolve Into
More Fundamental Structures
[https://www.youtube.com/watch?v=qTx98PUW6lE&t=860s](https://www.youtube.com/watch?v=qTx98PUW6lE&t=860s)

------
empath75
I do wonder if we're just a bunch of drunks looking under a lamppost for our
keys because that's where the light is.

We've discovered a bunch of phenomena that happen to be able to be described
by the mathematical tools we have because those are the only way we can
understand them.

There's no reason to believe that any of them are fundamental to nature. There
may be an uncountably infinite number of phenomena out there which are
fundamentally unable to be formulated in any way which we can understand or
predict them.

Our minds aren't constructed to understand reality, they're constructed to
help our bodies survive in a savannah a few hundreds of thousands of years
ago.

~~~
helen___keller
>Our minds aren't constructed to understand reality, they're constructed to
help our bodies survive in a savannah a few hundreds of thousands of years
ago.

I agree with your main point, however I don't find this a compelling argument.
Regardless of what our brains are constructed for, with pen and paper and a
set of rules we can roughly approximate a turing machine. Everything we as
humanity know about computation suggests that at minimum this is equivalent to
any computation possible using all known physical properties & interactions
with some amount of overhead (even quantum can be simulated classically).

Thus, while it's possible there is an unknown kind of interaction that we
cannot understand or simulate classically, the fact that our brain is more or
less designed around survival and reproduction is irrelevant; change or
optimize our DNA and the new super-human will still be at best roughly
equivalent to a turing machine in terms of computation.

~~~
AstralStorm
There are computation devices more powerful than the Turing machine, which is
why we have complexity classes. (P, #P, #BQP are some examples described by
different kinds of Turing-like machines.)

So calling humans equivalent to standard Turing machine is ultimately wrong if
you even start to assume quantum processes are important in our thinking.
(which is actually unproven as of yet)

Then you need to start with a more intricate parallel quantum Turing machine,
high end mathematics required already. It is already non-deterministic.

And no, quantum effects cannot be simulated efficiently classically. That is
the difference between P and #P complexity classes. Add parallelism, you get
#BQP. You would be able to tell something about the nature of reality by
building physical instances of those problems and timing them. Timing attack
on the structure of reality, structure of time itself, anyone? (Of course the
required energies would be ridiculous.)

To falsify any Turing model, you need to answer the question: what cannot be
done by any given machine? Or by any machine? It is possible that there's a
Goedel trap in this question.

A parallel would be to find and answer to what cannot be computed efficiently
by best human geniuses ever. Hard introspective question might I add. Answer
probably requires building or finding something more than human.

~~~
helen___keller
>There are computation devices more powerful than the Turing machine, which is
why we have complexity classes

Equivalent meaning computability, not complexity. The two machines can
simulate each other (even w/ exponential slowdown) then it's equivalent.

> cannot be simulated efficiently classically

Efficiency isn't really the point. The OP is suggesting there's a literal wall
which makes something impossible to understand. This would require a
computational behavior that _cannot_ be programmed as a turing machine.

> To falsify any Turing model, you need to answer the question: what cannot be
> done by any given machine?

Correct. The answer is that a turing machine can't decide a turing-complete
decision problem, so hypercomputation is achieved by equipping a turing
machine with an oracle for a turing-complete problem. This actually leads to a
hierarchy that is each strictly more powerful than the previous ones by using
oracles for problems that are "more undecidable" so to speak (see
[https://en.wikipedia.org/wiki/Arithmetical_hierarchy](https://en.wikipedia.org/wiki/Arithmetical_hierarchy)
)

Either way, we have no evidence that suggests theres a natural process that
lives higher up on the arithmetical hierarchy. An example of a physical
process that would fulfill this criteria: suppose there were a type of
particle that only sometimes collide with each other, and it turns out that
they only collide not just by running into each other but also when the sum of
their velocities encode halting turing machines, otherwise the particles pass
right through each other. A classical turing machine cannot decide the halting
problem, so it's impossible to simulate a system with these particles because
you never know if they will collide or not.

------
unparagoned
This should be an article about mathematics not physics.

------
jonsen
“What if that’s not the point?”

Euclid will turn in his grave.

~~~
will_brown
Euclid’s lost 6th Postulate:

“To draw a line from any point to any non point”

------
lostmsu
TL;DR; anyone?

~~~
earthicus
It's (sort of) discussing the work of Nima Arkani-Hamed and his Colleagues,
and their attempt to reformulate quantum field theory so that it doesn't refer
explicitely to space-time, in analogy to how the principle of least action of
Lagrangian mechanics doesn't refer explicitly to the causality/determinism of
Newton's formulation (modulo some subtitles). Here's a bit more about their
technical work.

The motivation for doing this is as follows. When the principle of least
action was discovered, it was philosophically very puzzling: why should this
equivalent, non-causal formulation of newton exist? The reason of course
turned out to be quantum mechanics! (it's a kind of stationary phase
approximation to the path integral formulation of quantum theory, roughly
speaking). Now in the early 21st century, there is a whole bunch of hints that
space and possibly time are not truly fundamental quantities (in analogy to
how newtonian causality was not fundamental). So how do you proceed?

Method 1: make random guesses.

Method 2: attempt to extend existing physics in non-random ways (e.g. string
theory)

Method 3: take a lesson from history

Method 1 never works, method 2 is apparently too hard this time, so they are
attempting method 3: if you need to get rid of space-time, don't MODIFY
existing physics, but REFORMULATE it so that it doesn't depend explicitly on
that concept, in analogy to how lagrangian mechanics reformulates newtownian
mechanics to not depend explicitly on causality ( & quantum theory is then a
simple deformation away). And if you can reformulate state of the art quantum
field theories so they don't depend on _space-time_ explicitly, perhaps a
deeper theory will just be a simpler deformation away as well.

~~~
lostmsu
Wow, that's not as short, as I expected, but nailed it.

A TL;DR; of TL;DR; : they are talking about reformulating laws of physics, so
that formulas would not be dependent on space and time.

------
mihaifm
I wish physics would explore the theory of a simulated universe a bit more.
What if these incomplete laws of physics are flaws with the simulation, maybe
dark matter is just a hardcoded variable or a hotfix to an existing problem.
Is this something physics can tackle or does it lie more in the philosophy
realm?

~~~
ymolodtsov
I don't think the simulation theory is falsifiable therefore there's no
practical reason to dig into that. You can explain almost anything with it,
it's very close to religion and creationism in that sense.

And although we still haven't found the dark matter directly, we notice its
effect in the stars motion, galaxies' gravitational lenses, large-scale
structure of the Universe and even notice the coinciding data in the cosmic
background radiation. Sounds like too much for a "hotfix".

