
Carlo Rovelli on the ‘greatest remaining mystery’: The nature of time - wyndham
https://www.washingtonpost.com/outlook/a-physicist-explains-the-greatest-remaining-mystery-the-nature-of-time/2018/06/22/ff6f84ae-3840-11e8-9c0a-85d477d9a226_story.html
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ballenf
Royal Institute presentation that I really enjoyed. Has some visual aspects,
but can be mostly listened to while driving:

The Physics and Philosophy of Time - with Carlo Rovelli

> From Boltzmann to quantum theory, from Einstein to loop quantum gravity, our
> understanding of time has been undergoing radical transformations. Carlo
> Rovelli brings together physics, philosophy and art to unravel the mystery
> of time.

[https://youtu.be/-6rWqJhDv7M](https://youtu.be/-6rWqJhDv7M)

Posted 13 June 2018, recorded 30 April 2018.

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howard941
C-SPAN videotaped Covelli speaking about his new book at a bookstore. About an
hour long:

[https://www.c-span.org/video/?445419-2/the-order-
time](https://www.c-span.org/video/?445419-2/the-order-time)

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badrabbit
I think I'm a simpleton because I could never imagine time being it's own
thing. I see time as simply the amount of change in reality we can
perceptually sample. Much like how an object in motion will continue in it's
motion until it meets resistance,reality in my opinion is in continuous motion
that has yet to meet resistance. Time (imo)is our measure of this change
divided by our ability to sample it(where this ability could be
second,minute,etc...)

Again,that's my opinion as a layman. I've always wondered why time was the
focus, when I at least have been more curious about universal change. Why is
everything in motion? and how is everything universally connected to where it
changes at the same rate?

Maybe there's already plenty of work on this and I'm being ignorant(apologies
if so).

~~~
gowld
Sounds good. Next, please define "change", and explain why or how "change"
exists and is detectable by humans.

That's what Rovelli is investigating/theorizing about.

~~~
badrabbit
Yes but they are investigating our relative perception of the change. It's
like studying astronomy without considering the fact that the stars we
perceive in the sky is just our perception of how they looked like in the
past. We distinguish how things are now from what we can perceive by measuring
light and EMR. Why can't we at least consider the possibility that our
perception of change might be different from the actual nature and attributes
of this change?

~~~
vermilingua
You don’t need to consider that what you see in the sky is “in the past”. The
light that’s reaching us has been travelling at _c_ , the universal speed
limit. Since we cannot possibly have known about that information sooner, what
we see in the sky is for all intents and purposes, “the present”.

Additionally, the _hidden variables_ of the change are exactly what they’re
talking about when people ask the question “what is time?”.

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dyukqu
Some tangential thoughts: even though I like these popular science (physics,
to be precise) books, I have hard times to imagine their writers as a _real
scientists_. Tyson, Greene, Carroll, Kaku, Rovelli... So many writers author
so many books about these _hey-look!-so-fascinating!_ things. It looks like a
bandwagon and more and more scientists (yes, physicists especially) are
getting on it - like they don't have any important research to do, like they
are so hopeless and desperate about the current state of physics and they
stopped caring about it and found a _proxy_ to monetize their knowledge. But
hey, that's not a secret anymore - everyone knows about the crisis, from the
Queen of England to the hounds of hell. Sabine Hossenfelder is a legend for
me. A few years back, when I was taking a Physics101 class, even the lecturer
almost begged for help after the last lecture at the end of the semester: "my
fellow students, please, please, consider (to continue your career in the
field of) physics. Physics is stuck. It needs new ideas, new theories, new
minds. Please consider this." I was stunned. That was some real thing. I guess
the fast advancement of technology in the late ~100 years made even the most
brilliant minds (relatively) lazy. They gradually stopped thinking, beating
their brains out year after year and here we are. No serious discovery after
the quantum theory. String theory? Yeah, gazillions of dimensions - good luck
with that. Higgs boson, Gravitational waves? Come on, nothing revolutionary -
we're still waiting for the revolution to emerge from (upgraded!) LHC. For me,
they are cleverly and beautifully marketed (minor) findings. (Maybe some of
you have heard of, some (if not many) of the top universities have teams
working hard doing all the "scientific-marketing" for the Nobel Prize - it's a
precious prestige win in this _popular_ world we live in).

Minds get eroded by technology by heavily relying on it. And it's getting
worse and worse by the distraction caused by all the digital "life"
surrounding us, pulling and tightening its ropes every day. I imagine a true
scientist as a monk. S/he doesn't think about writing a pop-sci book,
appearing on TV and s/he got a distantiation even for interviews about her/his
latest important research/discovery. "Monks" are needed more than ever for
science nowadays.

Those were my humble 2 cents.

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jerf
"I have hard times to imagine their writers as a real scientists. Tyson,
Greene, Carroll, Kaku, Rovelli..."

If you mean by "real scientist" that they are doing real work that advances
the field, some of them are and, yes, some of them aren't. I don't mean that
as a criticism, because there is real value in being a PR person for science.
(Some danger if they do it poorly, but a lot of value, too.) Hawking, for
instance, was certainly a real scientist by any measure, right up until his
unfortunate passing, but also did good PR and wrote some very popular books.
And not to pick on him, but according to his CV [1], Neil deGrasse Tyson
hasn't published a paper in a decade, and if you skip three related papers in
2007-2008, hadn't published prior to that since 1998. Doesn't mean he's not
doing useful stuff, or that he wasn't at least a scientist in the past, but
he's certainly not on the same sort of track as Hawking was.

~~~
smallnamespace
I think that science is grossly lacking in good spokespeople who are respected
in the field, and it should be rewarded _more_ within the academy, not less.

When a large fraction of the population has frankly anti-scientific beliefs
and when funding for continued scientific endeavor depends on votes, science
_needs_ to continually justify and promote itself in the public eye.

Are there dangers to that? Yes. But it's worse than holing up in the ivory
tower to only quietly do research.

~~~
yashevde
I agree, but it's unlikely that they will get respect and reward within the
academy. They are just as susceptible to feelings of envy as people outside
the academy. You can see this manifest itself in the academy's treatment of
Carl Sagan, and in the many ramblings of Murray Gell-Mann about Richard
Feynman. Sure, their expositions of the science may not have been rigorous and
they weren't perfect human beings, but maybe that's what it takes to
popularize science and draw people in. I often see the role of science
popularization as that of turned the science illiterate to literate, not the
uneducated to the educated.

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FrozenVoid
Time could be composed of tiny frames(quanta) of time.
[https://en.wikipedia.org/wiki/Chronon](https://en.wikipedia.org/wiki/Chronon)
[https://archive.org/details/arxiv-hep-
th0106273](https://archive.org/details/arxiv-hep-th0106273)

~~~
dschuetz
And what do those "time quanta" represent? "Time of light traversing the
radius of an electron", really? Isn't that just another measurement device
based on light quanta and distance?

~~~
backpropaganda
No. That "time quanta" represents the smallest value Δ such that it doesn't
make sense to take about events which happened between t and t+Δ. Δ may not be
a constant though like Planck's constant.

~~~
dschuetz
The shortest distance between two events in space and time, when there are
time quanta, then there must be space quanta as well.

~~~
backpropaganda
What do you mean? We do already have space quanta: Planck Length.

~~~
dschuetz
Ah, well, I heard Planck _Time_ also already exists. What's the point then re-
inventing time quanta when they already are defined?

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GnarfGnarf
Time does not exist. It is an abstraction based on the movement of matter. We
use time to compare the relative motions of things.

Every instrument we use to "measure" time involves movement: pendulum,
sandglass, rotation of Earth, translation of Earth around the Sun, vibration
of atoms, etc.

~~~
fela
Don't you need time to even define movement? Movement is a change of the
position with respect to time. So without time you can't have movement. But
obviously you are right that the two concepts are strictly related, that
doesn't mean time doesn't "exist" (however you define "exist").

~~~
idunnooo
Forgive me for sounding rhetorical in this question, but I'm genuinely
wondering.. Isn't saying "time doesn't exist" akin to saying "human thoughts
don't exist"?

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mgamache
Paradoxically, thought (human or not) is the only thing we might be certain
exists.

[https://www.the-philosophy.com/solipsism-definition](https://www.the-
philosophy.com/solipsism-definition)

------
pmoriarty
Not to nitpick, but I'm not sure the nature of time is so indisputably the
greatest remaining mystery.

The nature of consciousness, life, and death can all certainly give it a run
for its money.

Incidentally, would anyone happen to have a direct link to a version of this
article that could be read without enabling javascript?

~~~
jfaucett
Yes. For me the greatest remaining mysteries are more in this order.

1\. Nature of Life (we are still nowhere near understanding how it arose or
how living organisms work in all their intricate detail).

2\. Nature of Consciousness - what is consciousness, how can living matter
instantiate it, how can we quantify it, etc?

3\. Origin of the Universe

4\. Why do we seem so alone in the Universe?

5\. Resolving Quantum Mechanics / Gravity

6\. Understanding Time

~~~
whatshisface
I would bump the origin of the universe to the top, because no matter what
universe-generating physics you come up with I can always ask, "but what set
things up to work that way?" I'd also put consciousness up there, because it's
fundamentally distinct from measurable things. Consciousness and the origin of
the universe get place 0, and the others all get place 1 because they're
solvable but we don't know in which order.

~~~
redial
> I'd also put consciousness up there, because it's fundamentally distinct
> from measurable things.

No one knows that it is not measurable. Is love measurable? is hunger?
happiness? they seem to be as measurable as consciousness, that is to say we
can at least measure them in binary as either present or not.

~~~
andrepd
How do you know everyone else is not a "p-zombie", indistinguishable in any
external way from a human such as yourself, but devoid of internal
"consciousness"/"subjective experience". Even the mere logical possibility of
p-zombies indicates that consciousness is unmeasurable.

~~~
redial
Solipsism is basically the only defense against the conclusions from the
evidence of the "real" world. But if you argue for solipsism then I say you
have much bigger problems than consciousness because you basically rejected
everything that has ever been "known" or experienced. If you reject our
"shared reality" then anything is possible, including paradoxically, the
"shared reality".

If you accept the shared reality on the other hand, consciousness is
measurable to some degree. So the real question is do you or do you not accept
we share experiences?

As an addendum, if it is all up to me as you suggested, I just made
consciousness measurable so there is no need to keep arguing about it.

~~~
pmoriarty
_" Solipsism is basically the only defense against the conclusions from the
evidence of the "real" world."_

Far from it. There could very well be an external world, and one populated by
plenty of other and fully real human beings even, but your own personal view
or understanding of it could be distorted or false.

This could be simply because you're hallucinating, or insane, or your brain
could be injured, or could be living in a virtual reality (which itself exists
in some other "real" reality), or you could be the proverbial brain in a vat,
or aliens (or god or a demon/devil) could be deceiving you, etc.

~~~
redial
All those options are the same: they are either part of a shared experience or
they are not. Nothing is preventing a demon from deceiving me right now, in
fact one can come anytime I'd love to meet him, preferably her.

~~~
pmoriarty
If experiencing something that's not shared is the only qualification for
solipsism, then we're all solipsists, as (arguably barring the possibility of
telepathy) our experiences are all private.

But that's not what solipsism typically means. Solipsism usually refers to the
position that only you (or perhaps only your own mind) exist. By that commonly
accepted definition, one could be mistaken or deceived in any of the ways I
laid out earlier without them entailing solipsism.

~~~
redial
I meant to say shared context. Everything you said is part of a shared context
or not, those are the only two options.

~~~
pmoriarty
Even if there is some sort of "shared context" (more commonly known as
"objective reality") your view or understanding of it could still be deceived,
hallucinating, simply mistaken, insane, etc. These are not solipsism. What
they are are possible obstacles to your connection to any shared context or
objective reality.

~~~
redial
Sure, but they don't change the fact those are the only 2 options.

And in the "shared reality" option, consciousness is somewhat measurable.

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Maro
Disclaimer: I'm a physicist who didn't finish the Phd and went to work in the
tech field instead.

I wish physicists would stop writing these bullshitty popular science books. A
lot of the books are popularizing unverified / unverifiable things like String
Theory or Multiverse or Arrow of Time. And when they're talking about more
plain things like Special Relativity, then I still cringe, because it's not
something that's worth explaining to lay people: there is no situation in
which some high-level bullshitty understanding of GR or SR or QM will be
helpful or relevant in life, at best it will confuse you.

It is a good and necessary thing to tell students about this, so some of them
become physicists, but you don't need popular science books for that, it
should happen in schools, for free.

If you're going to speak about Physics to lay people, at least do it it in a
way that's relevant to them, eg. look at how Feynman taught Physics. Explain
how a boomerang works, or how thermodynamics relates to photosynthesis.

~~~
rufugee
I Feynman is the right approach to teaching physics to the lay person...which
book is the place to start?

~~~
Maro
Surely you're joking: not a physics book, it's about Feynman's life, it's a
way to get you inspired and into the mindset.

Feynman Lectures on Physics: freshman level course that Feynman taught at MIT.
Lots of material, will last you year(s).

Six easy pieces: 6 easy lectures from Feynman.

Six not so easy pieces: 6 not-so-easy lectures from Feynman.

Feynman lectures on computation.

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crb002
Planck's constant, speed of light travel when you chain across space which
Planck himself should have understood if he thought about transmissions of
information in series. Curves when gravity pushes/pulls light from straight
paths. What questions are there?

~~~
andrepd
Your comment is gibberish (I've read it 3 times and can't make head nor tails,
but maybe I'm missing something).

