Carlo Rovelli on the ‘greatest remaining mystery’: The nature of time • Hacker News Board

Re: Carlo Rovelli on the ‘greatest remaining mystery’: The nature of time

#131

Post by mcbits » Sat, Jun 23, 2018, 3:49 PM UTC

redial wrote: post #127

mcbits wrote: post #100

Earlier quoted context omitted.

There are no blues or reds at all if nobody is watching. Color is a purely perceptual phenomenon relying on properties of the eye and brain.

Not true, what we call the color red is an electromagnetic wave with a wavelength between, according to wikipedia, 625 and 740 nanometers. And if you are looking at a picture on a computer, the computer will call red a pixel with an rgb value of (255, 0, 0) even if nobody is looking at it.

The light coming from the car in that image would be concentrated around 450-500 nm, not 625-740 nm. Viewed in isolation, that's blue, but in the context of the rest of the image, it is red. The "redness" of the car exists only in the brain of the viewer, which has evolved to produce stablility of color in a variety of lighting conditions.

That's also why RGB monitors display more than three distinct colors. The colors are synthesized in the brain. If we were orbiting a brown dwarf, we might talk about colors within the infrared part of the spectrum as if they were intrinsic properties of light.

Re: Carlo Rovelli on the ‘greatest remaining mystery’: The nature of time

#132

Post by dmfdmf » Sat, Jun 23, 2018, 4:34 PM UTC

russellbeattie wrote: post #90

dmfdmf wrote: post #58

Earlier quoted context omitted.

The crisis in physics is due to Kant. As long as physicists are disdainful of philosophy the crisis and deterioration will continue. They are Kantians and don't even know it. Ayn Rand identified Kant's error in his Critique of Pure Reason and destroyed his program, she rejected Hume's rank skepticism (which Kant was answering) and showed Descartes how to validate reason (i.e. to be certain) without being omniscient.…

Ayn Rand? Are you serious? The woman was a demagogue, a hypocrite, and a racist homophobe among her other charming qualities. Her "philosophy" of selfishness and greed was based on a worldview of hatred, suspicion, and class warfare, and even then is self-contradictory in many ways and completely meritless in every way. Rand's legacy is one of rationalization for the misguided, unethical, immoral actions of self-cent…

You should read her book "Philosophy who needs it".

Re: Carlo Rovelli on the ‘greatest remaining mystery’: The nature of time

#133

Post by md224 » Sat, Jun 23, 2018, 5:37 PM UTC

redial wrote: post #72

md224 wrote: post #32

Earlier quoted context omitted.

It says a lot that you felt the need to hedge against the assumption that you were talking about religious beliefs. These days it seems like there’s a materialist mindset that assumes anyone who questions certain assumptions about consciousness (e.g. that it is a creation of the brain that begins and ends when the brain does) has ventured into the terrain of religion, the supernatural, or “magic” (whatever that’s sup…

The problem is one of humility. If you admit that something is at this point inexplicable then that is where you should stop explaining it. Sometimes I don't know is the only real answer. Because if you want to make this statement: > It doesn’t seem to occur to people that consciousness itself is completely inexplicable and therefore all bets are off regarding its true nature. You have to, ahem, explain it.

Sure, but the problem is that many people don’t demonstrate this humility when they act like it’s ridiculous to wonder if consciousness exists prior to conception or after death. Ruling these out requires an unwarranted assumption about the relationship between consciousness and the brain.

I agree that people should show some humility and admit that we have no idea if or when consciousness begins and ends. Anyone who makes definitive claims about the temporal limits of consciousness should, as you said, provide an explanation of how they know this.

Re: Carlo Rovelli on the ‘greatest remaining mystery’: The nature of time

#134

Post by Maro » Sat, Jun 23, 2018, 5:45 PM UTC

rufugee wrote: post #126

Maro wrote: post #101

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 tha…

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

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.

Re: Carlo Rovelli on the ‘greatest remaining mystery’: The nature of time

#135

Post by tim333 » Sat, Jun 23, 2018, 6:00 PM UTC

rufugee wrote: post #126

Maro wrote: post #101

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 tha…

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

QED is kind of fun.

Re: Carlo Rovelli on the ‘greatest remaining mystery’: The nature of time

#136

Post by auxbuss » Sat, Jun 23, 2018, 7:26 PM UTC

resource0x wrote: post #120

GnarfGnarf wrote: post #81

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.

The most surprising fact is that the readings of all these instruments are in sync with each other! We take it for granted, and don't appreciate the mystery. It very well might be that the Universe forms a complex landscape with varying "laws", with the pockets where the notions of space and time become quite fuzzy and inconsistent; we might live in a rare oasis where the things more or less "make sense". Elsewhere,…

But "clocks" can only be in "sync" – i.e. record the same time between each "tick" – when they are in the same inertial frame – from special relativity. In addition, there is gravitational time dilation.

Thus, the "reality" is that no two clocks are in sync. As Rovelli points out in "Reality Is Not What It Seems", with the precise clocks we have today, it's possible to measure this effect for a difference in altitude of a few centimetres.

Re: Carlo Rovelli on the ‘greatest remaining mystery’: The nature of time

#137

Post by yashevde » Sat, Jun 23, 2018, 8:15 PM UTC

smallnamespace wrote: post #85

jerf wrote: post #64

Earlier quoted context omitted.

"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 instanc…

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…

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.

Re: Carlo Rovelli on the ‘greatest remaining mystery’: The nature of time

#138

Post by HopDavid » Sat, Jun 23, 2018, 11:54 PM UTC

jerf wrote: post #64

dyukqu wrote: post #35

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 im…

"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 instanc…

I would call Tyson a good spokesman for science if he had a high regard for rigor and accuracy. But he does not. http://hopsblog-hop.blogspot.com/2016/01/fact-checking-neil-...

Re: Carlo Rovelli on the ‘greatest remaining mystery’: The nature of time

#139

Post by _8j50 » Sun, Jun 24, 2018, 1:01 AM UTC

jerf wrote: post #65

_8j50 wrote: post #54

Earlier quoted context omitted.

I was defining time as the measurement of change. Change does not depend on measurement therefore there is no circular definition. For example, a star is different from star light. When I look at the sky through a telescope I don't see a star,I see star light. Same can be said for any object as well,we see light emanating from an object therefore vision is perception of an object as measured by our optics. Time is ho…

The problem is that if you take the time and carefully consider all of your statements, and carefully lay them all out in a row in the right way, you will find you've got circularity hiding in them. I am confident in this statement because you are walking very well-covered ground, and lots of smart people have examined it all very closely. For instance, "change" intrinsically has a before and after element in it; you…

You've given me a lot to ponder with your insightful comment,thank you.

I wanted to separate our perception of time from time itelf (which I called change). Isn't time something perceived?

Re: Carlo Rovelli on the ‘greatest remaining mystery’: The nature of time

#140

Post by oldandtired » Sun, Jun 24, 2018, 4:26 AM UTC

hansen wrote: post #124

oldandtired wrote: post #119

Earlier quoted context omitted.

The problem with the "well established" or "settled" discoveries is that there is enough experimental evidence that is anomalous to the theories thus presented. This effects everything from the ideas from General Relativity, Special Relativity, Big Bang, Quantum Mechanics, the Standard Model of Particles, etc. I think the biggest problem that is faced today (it hasn't really changed in centuries) is that people do no…

> there is enough experimental evidence that is anomalous to the theories Huh? I have more the impression that Λ-CDM & SM are working just too damn good. I’m not aware of any observation that hints that we need something completely different than GR & local QFT. But “settled” and “well established” doesn’t mean that humans will never find a more fundamental theory. Classical mechanics is settled, well established and…

Don't ever use the word "correct" for any theory we use. If you actually read and understand the basis for any theory or model in use, you will come to see that each is capable of giving "close enough" predictions, but none will give perfect predictions and that there are always anomalous data that these theories and models cannot explain.

Be pragmatic and keep in mind that wonderful phrase - "All theories are wrong, but some are useful."

The problem I see is that it is a common activity to present "settled" and "well established" as fact. Often without ever highlighting the anomalies that have been found and that we only have a "belief" that it is useful.

One of the best examples is the case for "dark matter". It has never been established in any way that such "dark matter" exists. It only arises because the observed motion within galaxies does not accord with "settled" and "well established" theory. So to keep this "settled" and "well established" theory, some additional "theoretical entity" has been added to allow the observations to fit the "settled" and "well established" theory.

Now, that addition of a new "theoretical entity" is, in itself, not a problem. What becomes the problem is when every experiment fails to show that "theoretical entity". At this point, one should be saying that mayhaps the "settled" and "well established" theory is not so settled and not so well established. Mayhaps there is a problem that we then need to be looking at.

My point here is that we do not, in fact, have any real or clear understanding of the universe about us. We have models and theories that work within a limited range but they are not global. The simplest of these is that "chestnut" between general relativity and quantum mechanics (the large and the small). The funny thing here is that we can make devices that are macroscopic which exhibit, under certain circumstances, the effects we see at microscopic levels. Why? What is happening here? What are we missing in this crossover realm? Why do we see things in the laboratory and see similar things at extra-solar distances, yet the explanations of these effects do not accord with the "settled" and "well established" theory we use at those massive sizes?