The Royal Institution
5 HN recommenders · recommended in 9 months, 2018–2022
54:54 · 1.4M views · Jun 13, 2018
Physicist Carlo Rovelli gives a public lecture at the Royal Institution on how our understanding of time has changed, from Boltzmann and Einstein to quantum theory and loop quantum gravity. He blends physics, philosophy and art to argue that time is stranger than everyday intuition suggests.
HN commenters point to it as a lucid, general-audience lecture that shows how wrong common conceptions of time are, often in threads on entropy and the arrow of time.
9 comments from Hacker News
Our conception of time is just totally wrong, or at least this is true for 99.9 % of all humans and that is certainly an underestimate. Something like THE time does not exist, we are just all living together in a small bubble in the universe, all of us experiencing more or less the same gravitational field, all of us moving together at more or less the same speed as Earth moves through space, and that is what makes it look like there is THE time. But actually time is more like counting the calories you burn as you walk through the world, it is specific to you and the path you take. There is a great lecture »The Physics and Philosophy of Time« by Carlo Rovelli [1] aimed at the general public that does a good job pointing out how wrong we are. [1] this video
Rovelli is an astounding communicator. Here's a wonderful lecture he did for the Royal Institute on the nature of Time: this video His communication style is a model of lucidity and kindness that more specialists should emulate when talking or writing to general audiences.
There is a very good introduction - 20 lectures of 45 minutes - to loop quantum gravity by Carlo Rovelli [1] who worked together with Lee Smolin on that topic. In a nutshell loop quantum gravity is about triangulating space with tetrahedra, then representing this triangulation as a graph - one vertex per tetrahedron, one edge between every two tetrahedra sharing a face - with the edges labeled with SU(2) transformations describing the change in orientation due to spacetime curvature as one moves from one tetrahedron to a neighboring one, and of course the dynamics of this description. I hope I got this right, I am totally not a physicist. There is also a very good talk for the general public focusing on the nature of time by Rovelli [2] in case the lecture series is to long or technical. Well, I initially started writing this comment because of the quote »Leibniz argued (against Newton) that there’s no fixed backdrop to the universe, no “stuff” of space; space is just a handy way of describing relationships.«. According to Rovelli - he talks about this in the lecture series mentioned above - Newton was fully aware [3] that his notion of space and time are just abstract notions and that space and time are fundamentally relational. But due to the success of using abstract space and time in science and engineering this got somewhat forgotten and those abstract notions were and are considered much more fundamental than they are. This in lectures two (space) and ten (time) which b
Watch this video: this video I myself lean to the Aristotelian definition: count of change. After all, all our clocks are built on this definition. If there were a lone particle traveling in an infinite universe, it'd be nonsensical to talk about its speed because there'd be nothing to relate the distance traveled to (and no observer). Indeed, whenever we talk about "time" and related quantities like "speed", we always compare the observed object to some other, existing reference. So I think of the interaction of particles/matter as being something fundamental, whereas "time" is a synthetic human notion.
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. this video Posted 13 June 2018, recorded 30 April 2018.