
In the fundamental physics of the world, there is neither space nor time - dnetesn
http://nautil.us/issue/64/the-unseen/the-end-of-time
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honorious
I just finished reading Rovelli's book "The Order of Time." The article is the
last chapter, where the author summarizes the results of the "journey" of the
book.

I recommend the book, it was an enjoyable read. The author is able to explain
clearly concepts that I had struggled to understand before.

Throughout the book there are a many references to philosophical ideas and to
the history of science, in some cases quite emotional. This being the last
chapter, is quite heavy on them. However, I found them quite useful and
interesting as a tool to break from preconceived notions of time.

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combatentropy
> we have imagined the existence of "eternity," a strange world outside of
> time that we would like to be inhabited by gods, by a God, or by immortal
> souls

If fundamentally there is no time, then fundamentally there is only eternity.

~~~
stareatgoats
Yes, I suspect (without further proof ATM) that this is the main reason for
this quest for timelessness which Sean Carrol (cited in another comment) finds
so perplexing [0]. Eternity has traditionally and in various ways been
associated with (especially) monotheism. Same with infinity (of which eternity
is a sort of subset).

A much simpler but perhaps more tedious way out of this apparent rational
loophole for religions would be accept it. Religion may keep this final straw
of rationality: we don't and can't know everything given a (probably) infinite
universe. Religion is not best understood as a theory of physics anyway, but
rather as a study of history, society and mind.

[0]
[http://www.preposterousuniverse.com/blog/2009/06/17/timeless...](http://www.preposterousuniverse.com/blog/2009/06/17/timelessness/)

~~~
AltruisticGap
The universe IS completely unknown, and forever will be. It is like a sandbox.

As Alan Watts put it with his mischievous sense of humor:

"Science is the art of prediction"

Talking about religion, Christianity used to refer to this, then it lost its
way. See eg.

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

~~~
paganel
> Talking about religion, Christianity used to refer to this, then it lost its
> way.

This is still true, to an extent, in the Christian Orthodox world, Pseudo-
Dionysius the Areopagite is still reguarded as one of the main “intellectual
stars” (so to speak) of the Christian Orthodox thought. As for the “lost way”
that you mention, I think that that change started in the West once the
Reformartion took off and people wanted to “be sure” that they’ll get to live
the eternal life. Here in Eastern Europe people do not think in absolute terms
about life after death, as in nobody actually believes you can “earn” your way
into Heaven, it all resides in God’s Will which is not possible for us to
know. There’s also that New Testament parable of a guy asking Jesus at some
point with whom of his wives will he be married in Heaven (the guy had been
previously married to a different woman) and Jesus basically answered that
that is a stupid question as nobody knows anything about Heaven.

~~~
combatentropy
Just a nitpick, but the example the man gives is of a hypothetical woman who
over time had seven husbands --- just one at a time of course, but one husband
would die and then she would get married again. The question was, which one
will be her eternal husband?

> Jesus basically answered that that is a stupid question as nobody knows
> anything about Heaven.

Jesus said it was an ignorant question, yes, "You are in error because you do
not know the Scriptures or the power of God." But he didn't say nobody knows.
He said that she won't be married: "At the resurrection people will neither
marry nor be given in marriage; they will be like the angels in heaven"
(Matthew 22:29).

~~~
paganel
Thanks for the correction, I had last read that almost 20 years ago :)

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Koshkin
I think Sean Carroll has a point:

[http://www.preposterousuniverse.com/blog/2009/06/17/timeless...](http://www.preposterousuniverse.com/blog/2009/06/17/timelessness/)

~~~
honorious
It might not be clear from the last chapter, but the book doesn't claim that
time doesn't exist.

To paraphrase (but use the same example because it is funny): time doesn't
appear at the fundamental concepts in physics. Cats also don't appear at the
fundamental level of physics. But cats exist. Time (and our perception of it)
must appear somewhere as a emergent feature.

~~~
foxes
Time does appear in fundamental concepts in physics?

In relativity it is particularly important. Timelike dimensions are treated
differently in the metric, with a +1 or -1 depending on taste, ie

ds^2 = c dt^2 - dx_1^2 - dx_2^2 - dx_3^2,

so I don't think its quite fair to say that it doesn't "appear". In quantum
physics unitary evolution is invertible. Decoherence is not reversible (I mean
interaction - loss of entanglement).

Maybe these theories have been biased by our perception, but they are good
(but incomplete) models.

~~~
TomMckenny
Time in relativity bears almost no resemblance to the common definition of
time.

1) There is no such thing as simultaneous. There is no universal now. 2) Time
does not proceed at a constant rate 3) Time proceeds at different speeds for
different observers.

So time as relativity defines it is certainly true. But time as people
conceive it is fundamentally different. At best, common sense time is a
profoundly special case that can't imagine the general case. And at worst, a
nonsensical concept evolution gave us. Perhaps so erroneous it might be valid
to say it does not exist.

~~~
FreeFull
Humans never travel at significant fractions of the speed of light with
regards to other nearby things, so relativistic effects are rather hard to
observe in person.

It's the same how Newtonian Mechanics is a really good approximation (and
still widely used, too), and because everything around us happens to obey it
very closely, it is more intuitive. The difference between what Newton's
equations and Einstein's equations predict for most planetary orbits is very
slight.

~~~
goldfeld
If time is a dimension not constraining to fundamental physics, there could be
higher dimensions where more fundamental things manifest, as a way to explain
it, as does string theory. If there are higher dimensions, what's to say we
can't actually experience more fundamental realities through consciousness
traveling. If time passes slow by in an emergency or a profoundly concentrated
moment, humans if definable as the human consciousness could be traveling at
relativistic speeds and not knowing. Elegantly, it's not matter doing that
since matter wouldn't survive the trip.

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empath75
I'm starting to think that there's a point where physics becomes almost as
much a study of our own mind as it is of the external world.

~~~
bodi
Much of the ancient esoteric wisdom taught that we were all of one, a mind, a
singularity if you will.

I think this bit of truth was purposely hidden, as Einstein himself alluded
to, by a dark cabal, and has coincidentally been rediscovered albeit as a
secular institution primarily through a diefication of the scientific process.

Some of our still very early study of Quantum Mechanics points right to this
matrix reality we experience.

However uncomfortable that may be.

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dschuetz
It's rare to read from such a sober-minded yet deeply philosophical world
view. He basically outlines to most essential things in the universe - gravity
and uncertainty. Everything else is a means to quantify the world to make it
more understandable to us. At least quantum mechanics show that uncertainty is
quantifiable to an extent with the means we already have. I'm not even sure
whether gravity is as un-quantifiable as it seems to be. That's what
scientific minds ought to figure out.

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stephengillie
> _Perhaps, ultimately, the emotional dimension of time is not the film of
> mist that prevents us from apprehending the nature of time objectively.

Perhaps the emotion of time is precisely what time is for us._

The application of sufficient Time and Space can solve almost any problem. If
2 groups are in conflict, putting 10 light years and 100 million calendar
years between them often removes the ability to conflict.

------
kr4
We do have an easy way of doubting space/time real existence in form of
dreams. In dream we feel sensation, experience space and time and it feels so
real till the dream last. You can experience long hours or someone can
experience years [0] within few seconds/minutes of a dream.

Hence to take a next big leap in understanding the cosmos we as a society will
eventually need to be bold enough and open for other ideas regarding the truth
of objective reality we experience in waking state. Could it be just like a
dream, though a grand one, being projected by some cosmic consciousness of
which we are inseparable part? Not some divine form I'm proposing here, but a
formless pure consciousness awareness that each of us possess and experience
it in silence. Eastern mystical traditions have long been investigating these
alternative ideas and countless individuals have testified experiencing such
super conscious state confirming the idea.

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mirimir
Maybe so, but he also says ...

> To this blurring is added quantum indeterminacy. The ignorance that follows
> from this determines the existence of a particular variable—thermal time—and
> of an entropy that quantifies our uncertainty.

... and ...

> The variable “time” is one of many variables that describe the world. It is
> one of the variables of the gravitational field: At our scale, we do not
> register quantum fluctuations, hence it is possible to think of spacetime as
> determined. Hence we can think of spacetime as being as rigid as a table.
> This table has dimensions: the one that we call space, and the one along
> which entropy grows, called time. In our everyday life we move at low speeds
> in relation to the speed of light and so we do not perceive the
> discrepancies between the different proper times of different clocks, and
> the differences in speed at which time passes at different distances from a
> mass are too small for us to distinguish.

But whatever, I am moved to read his book :)

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incompatible
I'm not sure about entropy arguments for explaining the direction of time. On
Earth, the entropy doesn't change much over time, thanks to a constant stream
of low-entropy in the form of radiation from the Sun. Overall, the system is
increasing in entropy. But why do we, on Earth, need to care what happens in
the Sun? We could just as well go backwards in time as forwards, but
influencing the past seems to be extremely difficult (just try kicking a
football backwards in time).

~~~
dwaltrip
I believe the same reasoning applies here on Earth. Imagine a pile of ash
(high entropy) assembling into a copy of Shakespeare (low entropy), compared
with the reverse.

You can get isolated pockets of low entropy that appear (e.g. the human
brain), but I think I've heard it described that there has to be thermodynamic
pathways leading to such states. We understand parts of these pathways, but
there are important aspects still left to figure out.

And of course, as you mentioned, the system as a whole is still increasing in
entropy the entire time.

Imagine a mountain where height inversely correlates with entropy. The summit
represents the very low entropy state of the big bang, and the second law of
thermodynamics is an enormous steam-roller that is currently in the process of
flattening the entire mountain. Then, us humans are simply pebbles that have
been shaken loose and are dancing in the foothills. In a few billion or
trillion or quadrillion years, all the dancing pebbles will have been crushed
into a fine dust and spread across a perfectly flat, unchanging plane.

But they will have danced beautifully in the many years before.

~~~
TomMckenny
> very low entropy state of the big bang

This always confuses me a bit, why do we consider the first instants of the
universe maximally ordered? A near homogeneous sea of per-subatomic particles
seems less ordered than the later universe of galaxies and stars and hydrogen
atoms with cold areas in between.

~~~
sgt101
I tried to understand Roger Penrose's arguments about this in his book "Cycles
of Time". I admit that I really struggled! But the idea seems to be that the
initial state of the universe is very unusual compared with the rest of
eternity and is essentially 1 vs nothing - and then differentiation
instantaneously occurs through some physical process and immediately the
universe can only be described in a complex way. The universe moved from
undifferentiated high energy to and extremely complex high energy and then
falls down from there back to flat.

One point that seems not to feature in these debates is that this is all
(physics) fundamentally subject to the constraints of language (maths) and
cognition (human), we choose to describe things in a way that appears useful
to us, but these judgements and perceptions are filtered by how we understand
things. We are squashy and small and it is quite silly to imagine we really
are thinking about these processes in an objectively meaningful way.

------
zyxzevn
Our physical world is space and time, but in the maths of physics we lose
track of it. ;-)

~~~
v_lisivka
Some books about QM include big warning about "Mathematics is not Physics!" at
very beginning, but nobody reads it.

Chapter 2

The Formulation of Quantum Mechanics

2.1

Basic Theoretical Concepts

Every physical theory involves some basic physical concepts, a mathemati- cal
formalism, and set of correspondence rules which map the physical concepts
onto the mathematical objects that represent them. The correspondence rules
are first used to express a physical problem in mathematical terms. Once the
mathematical version of the problem is formulated, it may be solved by purely
mathematical techniques that need not have any physical interpretation. The
formal solution is then translated back into the physical world by means of
the correspondence rules.

Sometimes this mapping between physical and mathematical objects is so obvious
that we need not think about it. In classical mechanics the position of a
particle (physical concept) is mapped onto a real number or a set of real
numbers (mathematical concept). Although the notion of a real number in pure
mathematics is not trivial, this correspondence rule can be grasped
intuitively by most people, without any risk of confusion. The mathematical
formalism of quantum mechanics is much more abstract and less intuitive than
that of classical mechanics. The world does not appear to be made up of Hermi-
tian operators and infinite-dimensional state vectors, and we must give
careful and explicit attention to the correspondence rules that relate the
abstract mathematical formalism to observable reality.

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neuralzen
Certainly makes sense if the holographic principle is correct, and our
universe of experience is encoded in the entropic 2D planar surface of a
blackhole.

~~~
xaedes
What I don't understand about this idea: What is with all the other black
holes? Are the holographic universes of each black hole the same? Do they
encode the other black holes in their surface?

~~~
jakeinspace
The idea is that we are inside (or on the surface of, same thing) a black hole
whose event horizon encompasses the entire universe (observed and unobserved).
The black holes we can see in our universe would then be children black holes
(or great-great-grandchildren, who knows how far down the holographic rabbit
hole we are).

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mannykannot
There was a time when it seemed that science worked within the constraints of
epistemology, but now it seems to be radically reshaping that domain.

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yters
Makes sense. Everything can be encoded in a bitstring, which is a single
number, and a single number has no sense of space and time.

~~~
pbhjpbhj
Not everything, but perhaps a description of most things.

~~~
yters
If reality is finite and discrete, then it is everything.

On the other hand, if there are non computable processes at work in reality,
then not everything.

------
ASipos
Strangely, Julian Barbour is never mentioned.

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sunstone
In which case it's obviously broken from the get go.

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xvedejas
Article: Spacetime is an illusion! Time isn't real! Reality: The details of
time diverge a bit from common understanding. The author has an emotional
reaction to this.

Who else dislikes this sort of pop-science writing? It seems to care more
about evoking some mystical and philosophical idea of the universe than
effectively communicating the science.

~~~
sixstringbudha
>It seems to care more about evoking some mystical and philosophical idea of
the universe

What is wrong about mystical, philosophical idea of the universe? I like
mystical, philosophical idea of the universe.

~~~
dgut
Nothing wrong about it per se. Just don't try to mask it as or "soften" the
principles of science.

~~~
sixstringbudha
> "soften" the principles of science.

How can it soften the principles of science, if it does not masquerade as
science. Can you point me in the article where it tries to pass some mysticism
or philosophy as science?

~~~
m4r35n357
"Carlo Rovelli is a theoretical physicist and writer"

------
blueprint
> The difference between past and future does not exist in the elementary
> equations that govern events in the world.

Such bullshit. QM does not govern events. The probability function encodes
everything about how it's governed. QM does not speak to that at all.
Unitarity assumes the probability function remains correct. That doesn't mean
the probability function does not have any inputs which can be influenced by
change. Dumb article

~~~
blueprint
Lol downvoters don't even know the Copenhagen interpretation is deeply flawed
and never learned to use their words

