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

#101

Post by Maro » Sat, Jun 23, 2018, 9:24 AM UTC

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.

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

#102

Post by catamorphismic » Sat, Jun 23, 2018, 9:30 AM UTC

jerf wrote: post #68

mongol wrote: post #33

Earlier quoted context omitted.

I would add Free will to it. Does it exist?

Also, what exactly is it that we mean by "free will"? Even just that question can get ugly, fast. I think I've only ever heard one definition of the concept sufficiently precise to even have a meaningful answer. (In short, it was this: If we our model of the material universe is essentially correct, and if we assume that it is closed and that the material that we see is all there is, or at least all that can ever inf…

> In that case, it can be mathematically shown that you are simply too complicated to be fully correctly simulated by any system that attempts to build a model of your actions simply by external observation of you; you do not produce enough bits in your external actions to uniquely identify the state space of the inside of your head, not even if you turn the entire rest of the universe to the task (literally!).

Really? Which mathematical result is this?

Do scanning techniques such as fMRI and EEG count as external?

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

#103

Post by jpmoral » Sat, Jun 23, 2018, 9:34 AM UTC

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…

> 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.

If I only learned and experienced things that would be 'helpful' or 'relevant' it would be a very dull life.

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

#104

Post by fantispug » Sat, Jun 23, 2018, 9:39 AM UTC

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.

By similar logic you could argue all physical units are abstractions, which I guess they are. They are very useful in creating a simple accurate predictive model of things we observe on many scales. What's the utility of a distinction between existence and abstraction?

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

#105

Post by idunnooo » Sat, Jun 23, 2018, 9:41 AM UTC

fela wrote: post #89

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.

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").

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"?

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

#106

Post by backpropaganda » Sat, Jun 23, 2018, 9:42 AM UTC

dschuetz wrote: post #99

backpropaganda wrote: post #98

Earlier quoted context omitted.

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.

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

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

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

#107

Post by ekianjo » Sat, Jun 23, 2018, 9:57 AM UTC

fantispug wrote: post #104

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.

By similar logic you could argue all physical units are abstractions, which I guess they are. They are very useful in creating a simple accurate predictive model of things we observe on many scales. What's the utility of a distinction between existence and abstraction?

If you know the distinction you dont ask yourself why the abstraction exists. Researching the nature of time is a waste of... time, I guess, because you should know time is an abstract concept, a proxy for something else.

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

#108

Post by hansen » Sat, Jun 23, 2018, 10:05 AM UTC

jpmoral wrote: post #103

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…

> 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. If I only learned and experienced things that would be 'helpful' or 'relevant' it would be a very dull life.

Yeah, science isn’t about being useful and relevant in day to day life. It’s an important part of human culture and scientist should at least try to communicate their findings to general public (which is paying for it!).

I partially agree with the first comment that it isn’t really helpful to popularize highly speculative – and thus probably false – ideas. But well established but still “weird” discoveries like GR & QM are interesting on their own and have huge implications on our understanding of nature. You don’t need a science degree to be fascinated by black holes, the big bang and quantum weirdness.

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

#109

Post by mgamache » Sat, Jun 23, 2018, 10:07 AM UTC

idunnooo wrote: post #105

fela wrote: post #89

Earlier quoted context omitted.

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").

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"?

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

https://www.the-philosophy.com/solipsism-definition

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

#110

Post by hansen » Sat, Jun 23, 2018, 10:18 AM UTC

fela wrote: post #89

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.

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").

All our accepted model of nature assume that in some sense time exists. But in general relativity it doesn’t make much sense to speak of a single event. In the same way it doesn’t make much sense to speak of a single point in the euclidean plane (you can only localize one point relative to another one).

So some people (like Rovelli) think one should try to formulate relativity only in terms relations of events. This might be relevant in a more fundamental theory of spacetime but on a classical level it’s irrelevant. You can measure the geometry of spacetime in our solar system w/o disturbing it. The gravitational field of e.g. some satellite is negligible to the gravitational field of planets and the sun.