
A realist takes on quantum mechanics - jonbaer
https://www.nature.com/articles/d41586-019-01101-0
======
gus_massa
> _Smolin concludes with the implications of all this for our understanding of
> space and time. He suggests that time is irreversible and fundamental, in
> the sense that the processes by which future events are produced from
> present ones are truly basic: they do not need to be explained in terms of
> more basic ideas. Space, however, is different. He argues that it emerges
> from something deeper._

In Special Relativity space and time can be mixed (almost interchangeable),
like the x, y and z usual coordinates.

If your coordinates and x and t, in a moving system the coordinates x' and t'
are

    
    
      x' = something1 * x + something2 * t
    
      t' = something3 * x + something4 * t
     

The coordinates in the other system are just linar combinations of your
coordinates. So how can be time and space have a different nature?

~~~
jerf
Your equations are for Galilean space, in which your objection is correct;
there _is_ no way of distinguishing time from space, making the distinction
arbitrary. This was not noticed for a long time. It was hard to tell until we
had Einsteinian relativity to compare to. (Galilean space is actually broken
in a lot of ways.)

In relativity, those are not the correct equations; the correct equations
observe the Minkowski [1] invariant -t^2 + x^2 + y^2 + z^2 staying invariant
under all Lorentz transformations, and it's that negative sign before the t^2
that separates time in relativity. Time and space can be mixed in relativity,
but they do still retain a distinctiveness; even when they get turned entirely
"on their side" as inside a blackhole, time and space are still distinct, just
very very twisted relative to the rest of the universe.

[1]: [https://en.wikipedia.org/wiki/Minkowski_space#Four-
dimension...](https://en.wikipedia.org/wiki/Minkowski_space#Four-
dimensional_Euclidean_spacetime)

~~~
lisper
Another interesting thing to note: because of the negative sign, Minkowski
space obeys an _inverse_ triangle law: a straight line is the _longest_ route
between two points (in terms of the relativistic interval) rather than the
shortest. That is the reason for "time dilation". Clocks don't actually
measure "time", they measure the relativistic interval, which just happens to
be what we call "time" in our own reference frame.

This insight makes it easier to understand the "twin paradox". If a clock
takes any non-inertial trajectory between two events, its path through
Minkowski space is _shorter_ than it would be on an inertial (straight-line)
trajectory, so the reading on the clock is lower than a clock that travelled
on an inertial trajectory (straight line) between the same two events.

------
empath75
I feel like when people say ‘realist’ in this context, they mean someone who
believes that ordinary intuitions about the way the world works are how the
world must work at all levels. And there is no reason to believe that our
minds were evolved to understand reality at anything but the macro level.

I’ve long thought that the study of physics at the extremes is as much a study
of the human mind and what we’re capable of comprehending as it is a probe of
fundamental reality. Which is to say that experiments are essentially a chain
of processes by which we translate information from whatever we’re studying
into a form capable of being understood by our mind — often translating it
into something visual so our visual cortex can process it and store it.

But I wonder how much is out there that is simply impossible to transform in
such a way.

~~~
FakeComments
> I feel like when people say ‘realist’ in this context, they mean someone who
> believes that ordinary intuitions about the way the world works are how the
> world must work at all levels.

From the article:

> Like Einstein, Smolin is a philosophical ‘realist’ — someone who thinks that
> the real world exists independently of our minds and can be described by
> deterministic laws.

So no, they don’t.

Also, realism is consistent with quantum experiment — non-realism is merely an
interpretation that’s had more developers work on it, not somehow a proven
component of reality. (Commonly called Copenhagen interpretation; MWI and
Bohmian are other interpretations; arguably loop quantum gravity too.)

I agree with Smolin: non-realism is an extraneous assumption meant to preserve
locality, but reality is empirically non-local.

Ironically, it’s actually the non-realists who are guilty of what you say —
they can’t let go of their Euclidean intuitions, and so come up with nonsense
like denying realism. Their entire model is fundamentally predicated on things
looking like a smooth Euclidean space at all scales below some threshold —
that is, that reality _all the way down_ looks like what we see when we look
around.

Non-realists insist on a Euclidean world despite contrary experimental
evidence.

If you view energy as distributed across the topology of your space, which
often is radically non-Euclidean, you immediately have realism back — the
world just is nothing like what’s in front of your eyes. (Enter loop quantum
gravity.)

~~~
TelmoMenezes
> non-realism is an extraneous assumption

Realism is as much an assumption as non-realism. It doesn't feel that way,
because realism fits the common sense of some evolved monkeys. Common sense
sometimes is correct, sometimes is not. It doesn't really mean anything when
we deal with these matters.

In fact, I would argue that Occam's Razor advises us to prefer non-realism.
With non-realism, we are restricted to something we know to exist, by virtue
of our human experience: our first-person perception of things. The
independent reality, or third-person perspective, is undoubtedly a useful
model, but we have no empirical data to suggest it is real. In fact, I would
argue that quantum mechanic does raise some serious issues w.r.t. the this
model.

Btw, this debate is almost as old as human culture. It was already present in
Aristotle (materalism) vs. Plato (idealism). You can also find many traces of
it in Eastern thought, e.g. the idea of Maya, or the question of: how can you
really know if you are dreaming right now?

> not somehow a proven component of reality

There are no proven components of reality. Proof is something possible in the
domain of mathematics, if one accepts certain axioms. Science is not in the
business of proving things, it is an empirical endeavor. It gives us theories
that resist falsification (until seen) + eternal doubt. Once you abandon
doubt, you abandon science.

~~~
v_lisivka
> In fact, I would argue that Occam's Razor advises us to prefer non-realism.

Can you list these arguments, please? IMHO, Occam's Razor is at side of
realism: our Universe has no bounds in space, in time, and in scale. So, we
can predict future of any particle if we will have enough information about
it, but we cannot do that with 100% confidence, because Universe is endlessly
deep. We can only collect information about particles at our "layer" of
Universe only (or "dimension" in terms of String theory). The deeper we will
go, the more uncertainty we will have, because particles will be influenced by
"layer(s)" ("dimensions") below our.

~~~
TelmoMenezes
> Can you list these arguments, please?

I can give you mine... Realism argues that we (as minds, let's say) exist
within a reality that keeps existing when we are not looking, i.e. that is
independent of our own existence. These are two types of entities, mind-body
beings such as you and me + the external, persistent material world. If
there's just entities like you and me (whatever we are) sharing a collective
dream, that is one less type of entity. Occam's Razor advises against the
unnecessary propagation of entities in explanatory endeavors.

This of course does not falsify realism, but it demands that it is there only
if to explain something that could not be explained otherwise.

> our Universe has no bounds in space, in time, and in scale

Perhaps I don't understand what you mean. I would say that our universe
(forgetting MWI stuff) is bounded in time (Big Bang was 13.7 billion years
ago), in space (expanding but finite) and in scale (there is such a thing as
the fundamental building blocks of matter, maybe they have internal structure,
but they seem to be below the level where the concept of "structure" even
makes sense -- they are phenomena more than "things").

> So, we can predict future of any particle if we will have enough information
> about it,

Not really.
[https://en.wikipedia.org/wiki/Quantum_indeterminacy](https://en.wikipedia.org/wiki/Quantum_indeterminacy)

> but we cannot do that with 100% confidence, because Universe is endlessly
> deep.

You are alluding to chaos theory, but quantum indeterminacy is more
fundamental than that. Also, nobody knows if the Universe is "endlessly deep",
and current empirical evidence points to "it's not".

~~~
FakeComments
The very notion of “you and me” is an appeal to realism: without an external
world, there is only me — “you” become a figment of my imagination.

Realism explains why my paper a) arrives while I’m asleep and b) sometimes
surprises me with the content or by not arriving.

I’ve yet to see a non-realist explanation of my paper that doesn’t seem deeply
more convoluted than “someone like me, but not me dropped it off independent
of my awareness”.

I’m not saying you can’t make a model out of that, but you quickly arrive at
the equivalent of epicycles to explain even basic things like my newspaper
arriving (or not).

Also, “quantum indeterminacy” is an assumption, not a proven fact supported by
evidence. That’s the exact thing under discussion now: it’s justification as
an interpretative assumption.

------
arbitrage
From the article:

> The book is, however, upbeat and, finally, optimistic. Unapologetically
> drawing on historical tradition and even modern philosophy, Smolin proposes
> a new set of principles that applies to both quantum mechanics and space-
> time. He then explores how these principles might be realized as part of a
> fundamental theory of nature, although he stops short of supplying details
> of the implementation.

That's nice. Too bad QM doesn't care about tradition, philosophy, or your
feelings.

> Smolin concludes with the implications of all this for our understanding of
> space and time. He suggests that time is irreversible and fundamental, in
> the sense that the processes by which future events are produced from
> present ones are truly basic: they do not need to be explained in terms of
> more basic ideas. Space, however, is different. He argues that it emerges
> from something deeper.

Smolin routinely bullshits, and does not back up much with rigorous theory. He
attempts to make a name for himself in a publish-or-perish field by getting
his ridiculously unsupported and contrarian ideas traction in the press.

In short, he's all talk, with no substance to back it up.

~~~
BenMorganIO
Having read Three Roads to Quantum Gravity, I think there's a lot of substance
there. It's a book made to even include high schoolers, so you have to give it
some benefit of the doubt.

As per the philosophy question, neither classical mechanics, relativity, or
even death cares about what we think. What matters here is how we perceive and
understand a concept.

