
What If Time Really Exists? (2008) - privong
https://arxiv.org/abs/0811.3772
======
monktastic1
Between modern physics suggesting time and space may be illusions, leading
technologists agreeing that we're almost certainly in a simulated reality, and
many ancient traditions being certain that this is all an illusion, I may have
to have to go ahead and take this seriously....

~~~
stale2002
The simulation argument comes from the fact that there a quite a lot of
physics effects that are both surprising, and look an awful lot like dirty
hacks that a programmer might put it.

Quantum physics looks a lot like lazy evaluation (State doesn't exist until
"observed").

The speed of light seems like a hack to prevent an n squared problem of
everything in the universe effecting everything at the same time.

~~~
gus_massa
> _Quantum physics looks a lot like lazy evaluation (State doesn 't exist
> until "observed")._

This is a common misconception (¿among programmers?).

Let's think about the double slit experiment.
[https://en.wikipedia.org/wiki/Double-
slit_experiment](https://en.wikipedia.org/wiki/Double-slit_experiment)

In a classical word, you must simulate only one path. In a quantum word, you
must simulate both. You don´t need some magical conscious observer to force
the collapse of the wave function. A CCD detector of a camera or a simple wall
is enough to force that the "wave" collapse into a "particle" and the detector
or wall gets a small spot where the "particle" hits it.

A similar experiment is possible with spin, and you can use that to get a
qbit. In a classical word, a qbit is simply a bit and you only have to chose
between the 0 or 1 state and simulate it. In a quantum word, you must simulate
both.

But it's worst with many qbits. Let's say you have a 10 qbits computer. In a
classical word you pick a value for each of them and simulate each one, so the
total computation is ~10. In a quantum word, you can combine any of the states
of the 10 qbits and you must simulate the 1024 states.

So the idea that a quantum computers is better than the classical computer is
opposed to the idea that quantum physics is some hack to reduce computational
resources.

I think that the main problem is the quantum mechanics is weird, use a lot of
linear algebra, but the calculations are somewhat straightforward and well
defined. But the popularization explanations try to avoid the algebra and make
some simplifications, so the explanation only keeps the weird part.

~~~
lohankin
> In a classical word, you must simulate only one path. In a quantum word, you
> must simulate both. You don´t need some magical conscious observer to force
> the collapse of the wave function. A CCD detector of a camera or a simple
> wall is enough to force that the "wave" collapse into a "particle" and the
> detector or wall gets a small spot where the "particle" hits it.

This is a common misconception (among programmers). There's zero experimental
evidence for the effect you mention, and zero theoretical derivation.
Circumstances under which wave function collapses is the greatest mystery of
QM.

~~~
ikeboy
[https://en.wikipedia.org/wiki/Bell's_theorem#Practical_exper...](https://en.wikipedia.org/wiki/Bell's_theorem#Practical_experiments_testing_Bell.27s_theorem)

~~~
alphydan
That is not an answer to his objection.

If you follow the equations of the wave packet of the particle arriving to the
wall (or CCD) detector, you then need to solve the equation of the interaction
of the particle + all the particles in the wall or the CCD. The challenge of
the collapse is that simulating anything beyond a few dozen quantum particles
is too demanding. Mathematical models that simulate millions of particles need
to make assumptions (typically they are too hot, too cold, too strongly bound,
so you can ignore most effects - think 1D Ising model, Bose-Einstein
Condensates, Photon gases, etc). But the full description of a particle + all
particles in a detector still escapes us.

Therefore the transition between: superposition of paths -> particle lands at
specific points has never been truly explored. The best description currently
involves decoherence. Many theorems have been proven (and experiments done) in
that area. The gist is that as you add particles to a system (2, 3, 4, 5, 10,
...) the superposition effects slowly cancel each other out. Another angle is
the monogamy of entanglement (the more particles are entangled, the weaker the
entanglement between any 2 particles). The idea of decoherence is that as
things get larger, the weird effects of quantum physics become more "dilute".
However, going from double slit to macroscopic reading still has many
assumptions along the way.

Take the above explanation with a grain of salt (as I have tried to make it
accessible).

------
mindcrime
What do we want? Time Travel.

When do we want it? Doesn't matter.

------
dirkg
Science is by definition incomplete. It only provides a means for proposing
theories to test observed phenomenon, test them, and use them to extrapolate
and make future predictions, which can invalidate or strengthen the theory.

e.g. we don't even know if the physics we have is universal or local to our
observable corner, the only evidence we have is we haven't seen any evidence
to disprove it, but that's not proof.

String theory could be considered dogma. But it at least provides means to
test its predictions, its just that we are very very far off from ever getting
close to that capability.

If we live in an illusion, its entirely possible and in fact likely that it is
beyond our ability to even detect that. In fact that would be one of the first
requirements of such a 'program'. You can should 'computer, end program!' all
you like but the holodeck will just ignore you :)

There really is no point to wondering about the reality of time if it doesn't
lead to anything we can test/influence or use to advance our understanding and
so far there is none.

You could just say the entire universe is but one of infinite multiverses
which are being continuously spawned in the cosmic sea, but that doesn't
change anything.

~~~
bnegreve
> There really is no point to wondering about the reality of time if it
> doesn't lead to anything we can test/influence or use to advance our
> understanding and so far there is none.

I think this is wrong. There are some (possibly many) such apparently
pointless questions that eventually lead to actual experiments. I remember
that Einstein's book's about relativity theory starts with such questions. Off
the top of my head, questions such as "how could you prove that two events in
different places have happened at the same time."

I'd also argue that the whole concept of science came from the Philosophers
from ancient Greece trying to answer such unanswerable questions. But this may
require a longer dissertation :).

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thinkloop
Seems like a lot of the problem with "time" is semantic. Do things change?
Yes, and if that's the definition then it certainly exists.

But people don't generally see time like that, they think of it as some
medium, or 4th dimension, that can possibly be traveled through. This kind of
time does not exist (as much as anything can't exist). There are only
particles and their positions. Traveling back in time would require moving
every particle in the universe back to the state you want to experience. But
this is not "traditional" time travel, just god-like influence over particles.
Traveling back in time, in how people fantasize about it, would require copies
of the universe being made every plank-time, that you can visit. And even that
is just another 3d space that happens to look like one you saw before.

Time is chemical and physical reactions. The minimum amount of time (sorry) a
reaction can take to happen is possibly plank-time. Nothing can "happen"
faster than plank time. So time is possibly granular. If reactions stopped
happening, time would stop.

That's one set of views.

~~~
timcederman
Time is very much a dimension. You should read up on relativity.

~~~
semi-extrinsic
In relativity we can model time as a dimension, with great success. But even
there it is always evident that the time dimension is very different from the
spatial ones; for one, we cannot travel in it. I believe GP is only saying
this is the problem, ignoring that the time dimension is very special.

~~~
witty_username
We can travel in it. We all are travelling in time and at different rates
depending on our speed and gravity.

~~~
thinkloop
That's the sci-fi terminology and view that complicates and confuses the
issue. Can reactions happen faster or slower, yes. No need to say "travel",
that word has distinct meaning and connotations that lead to incorrect
possibilities.

~~~
baytrailcat
You have unknowingly stumbled into the heart of Special Relativity :) "travel"
is the same all dimensions. If you think you are moving from (x1,y1,z1) to
(x2,y2,z2) you are actually moving from (x1,y1,z1,t1) to (x2,y2,z2,t2). If you
think you are staying put at (x1,y1,z1), then you are continuously moving from
(x1,y1,z1,t1) to (x1,y1,z1,t2) to (x1,y1,z1,t3) and so on. The more you move
in space, the less you move in time.

Also, when you put General Relativity in the picture, any sort of movement
within this 4D space is possible (because the geometry of this space is
wrapped) go to past, future, anything.

~~~
thinkloop
Your comment perfectly crystalizes everything I'm trying to say. You explain
the relationship of time to space very nicely and succinctly and correctly,
however you decided to use the word "move", which comes with a lot of 3d
baggage, which leads you to start thinking that "any sort of movement within
this 4D space is possible". Nothing in relativity shows that freely moving
back and forward in the time dimension is possible. The closest semblance is
slowing your own time relative to other things you care about, so that, for
example, you can have the body of a 30yr-old while earth is at 3000AD, but
again that's not "traveling" around time, it's closer to putting food in the
fridge so it spoils slower.

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MrQuincle
To me it wasn't completely clear.

\+ A discrete, infinite Hilbert space, with (wave) functions defined at each
point. Why discrete?

\+ An operator across this Hilbert space that describes the evoltion of the
universe.

\+ A non-recurring property of the overall system that depends on the infinity
of the system.

\- Question. If the system is really big, can we see if it is recurrent or
not?

\- Question. Deviations from equilibrium should be "minor". However, minor
deviations on a very fundamental level (of quantumgravity) might perhaps
result in genesis/destruction of complete universes. If there is some kind of
process that goes to low entropy can it be self-inforcing till it big bangs?

\- Question. If time is a parameter for the universe's walk in Hilbert space,
why is it real?

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crb002
I take the endofunction view. plank :: u -> u

Assume u is finite. Then we are either losing information or stuck in an
infinite loop.

------
zamalek
Another interesting thought experiment: what if time (rather entropy) is the
_only_ thing that exists? While highly likely to be untrue, it's an
interesting mode of thought: as matter dominated beings we naturally approach
conclusions from the perspective of matter.

~~~
johndoez
You could also ask, what if time is the primary thing that exists? That is, it
has authority over everything else that exists. This would mean that the laws
of physics, for example, could change over time.

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nobrains
Those who say we live in simulation, are they saying that there is a
creator(s)?

~~~
Noughmad
Yes. Except that we're probably not their chosen people, just one of the
experiments.

~~~
psyc
One of my pet hypotheses is that the universe is so vast, that god doesn't
have the slightest clue that we're here.

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tomelders
Time exists. It's the observed difference between two states.

Also, i am not a physicist.

~~~
ChristianGeek
Exactly; it's the measurement of change. As long as things are changing, time
exists. (The fact that this discussion is taking place proves it's existence!)

~~~
ImTalking
> As long as things are changing, time exists.

Except at the speed of light.

~~~
dirkg
Which by definition is impossible to reach.

~~~
alansammarone
Photons reach it all the time. Therefore, time does not exist for photons.

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lngnmn
Then conservation laws would not hold.)

~~~
mlechha
Exactly!!! To me this is the obvious consequence. Another thing is Fermat's
principle, if time doesn't exist then what is light minimizing as it moves
through space?

~~~
state_less
Aren't you showing necessity? If you transition from state A -> B , then X
must hold. Where X is conservation of energy, charge, etc... It doesn't say
anything about how long it takes to get from state A to state B. Or time
existing per se, rather some relations that must hold between states. They
don't actually have to hold, but you don't live in those invalid states.
Similar to constructive light perhaps.

I remember the old boost mode on PCs where you could run your game 2x as fast
by increasing the CPU clock speed (increasing game transitions relative to
brain transitions), and yet the rules of the game still hold despite the game
transitioning faster. Also making very hard to see/play (No turbo boost for
the brain :)

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zosegal
Any recommended books on this topic?

~~~
jesuslop
Chemistry nobel Ilya Prigogine has defended the idea beautifully in his books
embedding the hard science in a wider humanistic context, including biology,
ecology, urbanism, societal, entomology and other examples. He kindled my
interest in dynamics and makes a huge effort to be understandable.

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johndoez
Check out Henri Bergson. The first person to argue that Time is Real.

~~~
nabla9
He had a public debate with Albert Einstein about the nature of time and lost
badly. Never fully recovered.

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Radio2034
Title needs a (2008).

~~~
bobbyi_settv
Or does it?

~~~
quickben
It depends on the arrow of time.

~~~
ktRolster
Title needs a (2028)?

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digitalshankar
I'll leave it here:

[https://youtu.be/v99-S4_IvVg](https://youtu.be/v99-S4_IvVg)

~~~
libraryatnight
Save me some Googling and time, is this a documentary with information or is
it a bunch of people with doctorates in angel therapy like What the bleep do
we know?

~~~
baytrailcat
It is part of an excellent PBS documentary by Brian Greene - the Fabric of
Cosmos. It discusses Newtonian View, Relativity revolution, etc. Though it
doesn't go to the depth of quantum cosmology levels as in the parent post.

