The Loop Quantum Gravity Debacle: Carlo Rovelli Strikes Back

Carlo Rovelli is a renowned theoretical physicist and author, best known for his work on loop quantum gravity, a leading candidate for a theory of quantum gravity. Carlo explores the intersection of physics and philosophy, delving into the nature of time, reality, and the fundamental structure of the universe.

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TIMESTAMPS:
00:00 - Introduction
00:36 - China’s Recent Physics Results
06:04 - Lee Smolin Contributions
18:46 - Distance in Quantum Field Theory
22:50 - Quantum Fields
25:33 - Curvature, Torsion, and Gravity
32:10 - Interpretations of Quantum Mechanics
41:49 - Quantum Gravity
49:11 - Lorentz Invariance
01:02:48 - The Black Hole Information Paradox
01:15:02 - Dark Matter and Testing Quantum Gravity
01:20:01 - Relational Quantum Mechanics and Category Theory

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#science #physics #sciencepodcast #theoreticalphysics #podcast #stringtheory

[johncouture]

I am constantly amazed/impressed at how conversant you are on all of the various theories and your ability to ask such relevant and insightful questions. Thanks for providing such fantastic content.

[Achrononmaster]

@11:30 I think you should fact-check Rovelli here. Angular momentum is not quantized at all. If anything variables are more continuous in QM not less (due to superposition allowing continuous state transitions). For *_bound states_* there are quantized eigenvalues, but they arise from steady state solutions, an equilibrium _resonance_ phenomenon. The only other type of discrete angular momentum numbers are in Stern Gerlach type experiments, but that is a filter effect, not a quantized _L_ effect, and this is obvious to anyone who has numerically solved the Dirac equation and examined the streamlines for all solutions, they "split" smoothly into two streams, depending on the imposed magnetic field orientation — a filter effect, not a discrete spin-current (magnetic dipole) effect.

[NoahWolfe]

Thank you Curt for these incredible discussions with our greatest minds. I could listen to Carlo read a dictionary and somehow come away feeling enlightened. What a treasure.

[monty]

He seems like such a gentle man. He's really a burning furnace of ambition who will bite the head off of anyone who stands in his way.

[jacksourlis]

Always enjoyable to watch a gentleman such as Carlo

[johnnyliminal]

Good two hours. C-Rov, Sir, you have been my favourite theoretical physicist for years. Glad to see you, and thank you for your time.

OP (C-Jai?), I’m impressed that you paced and got good answers out of Carlo.

[freedomeppo]

Hey Curt, your channel is unmatched. Very much appreciate what you do.

I wonder if Gerard 't Hooft would be willing to do an episode

[ARJ-Richard-Arendsen]

Carlo Rovelli argues that we use vague words when it comes to consciousness. I think most physicists use vague words when they talk about information in physics, especially in combination with black holes. Information is a construction of human intelligence and has no meaning without human consciousness and no human will ever experience the sensations of a black hole. I argue that physicists are not the most qualified scientists to advance our understanding of consciousness.

[VictorArdemagni]

Dr Rovelli doing what Dr Rovelli does best: mumbling vague platitudes, skirting around questions, dodging the point entirely, and topping it all off with sycophantic chuckles and shallow rhetoric.

If you contradict him, he’ll claim he never said that in the first place. Occasionally, he’ll throw in random, invented claims, too used as he is to monologues rather than engaging in real dialogue (for instance, angular momentum—no, it’s absolutely untrue that it’s quantised). When you back him into a corner, he pivots to philosophy, epistemology, and pseudo-intellectual ramblings, with an amateurish dialectic style that might have passed 40 years ago, but certainly doesn’t hold up now.

On one level, it’s always a shame to watch a man struggle. But then I remind myself of that unique charm shared exclusively by Dr Rovelli and ingrown toenails, and all sympathy vanishes.

Guys, I envy those of you spared the misfortune of hearing him play the guru on the Italian scene. A first-class bluffer, long before the Chinese experiment.

[williamjmccartan]

Its cool when your guests show their appreciation for your questions, Curt

[Achrononmaster]

Can I disagree with your genius friend? Or is that risking ridicule? @3:00 I'd say most "quantum gravity" theories predict there is a minimal length _which can be measured._ But not all predict there is a minimal length in nature. Just because a thing cannot be measured does not mean it does not exist. In a CPT symmetric Big Bang the evolution goes through a conformal zero, and there no good reason to suppose the Weyl invariance cannot hold indefinitely to absolute zero conformal time. Remember, at the Big Bang the conformal time is not physical time, physically the universe just keeps going down in scale forever (by "clock" time that is). Personally, just for the aesthetics alone, I rather like this view as opposed to clunkiness and discrete metrics. It is still discrete in the sense the massless particles still imply nontrivial spacetime topology.

[Khashayarissi-obyj]

👏👏👏
So beautiful video.
Thank you professor revolli. May god bless your life.
Thank you Doctor.
Hoping for more videos.
Dear doctor, I would be greatful if you would make great videos in the fields of philosophy of science, scientific philosophy, Logic, Mathematics and computer science with the same seriousness as the great physics videos. I wish you success.
With thanks.

[pokerandphilosophy]

What a fantastic interview! When I saw this video in my feed, I looked at the time stamps and jumped straight to the "Lorentz invariance" topic. I'm so glad Curt chose to quote Sabine's argument about the expected value of the area operator in LQG. It should be noted that a couple days after posting her video, Sabine edited it and removed this part of her argument. It's possible that she has had an epiphany and doesn't stand by it anymore (as she indeed shouldn't). But it would have been better if she had issued a correction, of course.

[hanochlivneh]

Rovelli appears (at times) to make up his answers as he goes along. It is obvious that he was struggling with defending his positions in more than one instance and tried to change the topic to fit his "needs".

[RWin-fpjn]

Of all philosophers Forrest Gump understood the Nature of gravity best: '..Gravity is as gravity does..' We shouldn't think too complex when dealing with fundamentals. To understand, we should just notice what gravity does. Curt shortly mentioned the crux; It is BOTH the static contraction of spacetime AND the effect of an accelerated contraction of spacetime and anything in it. This dual working is crucial. It forms a contradiction; How can something that is contracTED also be contracTING? Moreover; each effect of gravity separately violates what we call 'conservation of energy'. Because a continuous contraction of spacetime is a perpetual effort to counter re-normalising of spacetime towards its un-contracted state. Likewise, the force aspect, causing a perpetual acceleration of spacetime and all in it, likewise suggest a source of unlimited energy over time. We can unify both effects back into accepted conservation of energy when we suggest that the one effect is the (inverse) compensating effect of the other. We kind of know a similar concept in math; complex numbers. So the contracTED spacetime is the real effect of gravity (actually a result of Einstein's Special Relativity) whilst the contracTING effect is its inverse 'imaginary' effect. These are the 'loops' in which spaceyime is wound up in like a standing wave around the speeding objects (or 'restmass' which is made of countless speeding subatomic speeds) . And in these quantized loops, the grid is defined by energy and clock by mass and as a result speed is defined by -J/kg there. -J/kg to be translated back into [-Nm/kg=-m2/s2] in spatial terms, . This is our virtual accelerating effect as per each loop, mach like a crowd surfing over an audience....

[gteichrow]

So funny to hear Carlo mention that maybe Sabine “didn’t read the paper” and just yesterday I streamed a “debate” between Sabine and a philosopher (can’t recall his name) where the the philosopher is basing his position on likely the wrong paper.

It’s all wonderful of course to simply listen to either of these great minds and have fabulous moderation like you provide Curt ❤

[isedairi]

Seems next in line is Lee again to give his perspective on this

[isatousarr]

The exploration of hidden laws of gravity and theories like loop quantum gravity offers intriguing possibilities for understanding the fundamental nature of black holes, including the concept of anti-gravity. Loop quantum gravity, which attempts to reconcile general relativity with quantum mechanics, suggests that spacetime has a discrete, granular structure at the Planck scale. This could potentially alter the way gravity behaves in extreme environments, like the intense gravitational fields around black holes. Some theorists speculate that these quantum effects might create conditions where gravity could be counterbalanced or even reversed, leading to the concept of anti-gravity. Understanding these dynamics could reshape our knowledge of black holes' inner workings and the nature of spacetime itself.

[charlottesimonin]

facinating discussion. His verbal presentation is similar to his books.

[Clayn]

20:05 ❤
potential/kenetic = energy
*entanglement = space/time 21:10
*actuation 23:27