I have a degree in theoretical physics and a gold medal, which is to say I have endured the requisite intellectual beatings. Often the best interpretations of physical theory are unpalatable to the average person. The idea that there is in fact no objective physical reality is the most egregious offender in this regard. However, it is nonetheless the best conclusion that one can draw given strict adherence to what the mathematical formalism of QM provides. There is simply no physical machinery to support an objective reality, period.

Now, that being said, the remarkable part is that the forgoing conclusion does us zero harm. We can still have the logical predictive fiction that an objective reality exists. What staggers the mind is the corollary that no human has ever erected a truth. Moreover, every intelligent species that ever endeavors to ask these questions will find the same non-answer.

This is not radical. His thought is clearly in line with a very old and very mainstream philosophical tradition called "idealism," and I was surprised to see this go unmentioned in the article. See: https://plato.stanford.edu/entries/idealism/

> Within modern philosophy there are sometimes taken to be two fundamental conceptions of idealism:

> 1. Something mental (the mind, spirit, reason, will) is the ultimate foundation of all reality, or even exhaustive of reality, and

> 2. although the existence of something independent of the mind is conceded, everything that we can know about this mind-independent “reality” is held to be so permeated by the creative, formative, or constructive activities of the mind (of some kind or other) that all claims to knowledge must be considered, in some sense, to be a form of self-knowledge.

Among mainstream philosophical traditions, idealism is IMO the weakest, as it's inevitably solipsistic. Physicalism has become strongest.

I am puzzled that Carlo Rovelli associates the perception of time flow with entropy increase. Entropy increase allows to define the direction of time, but it cannot explain why we perceive the time flow.

Time is not an illusion. It can be experimentally verified. There is a flow in a certain direction. Carlo is saying that time is not absolute, every point on the space is a clock, essentially trying to convey the core concepts of special relativity with engaging interaction.

People interested in this subject might enjoy this interview with David Albert [1], as well as this interview with Tim Maudlin [2], who offers a different perspective from Albert. They are both philosophers of physics, or in other words physicists working on the foundations of physics.

[1] https://www.youtube.com/watch?v=JR2sMeXLuLw [2] https://www.youtube.com/watch?v=3riyyEmWwoY

I think the idea of an "external reality that follows certain rules and humans operate in" could itself be a kind of evolutionarily-advantageous belief, even if it's not actually true in a quantum physics sense. In other words, we become capable of science and technology only after assuming there are scientific rules to be found.

There are many concepts like this throughout human history - another one I'm thinking of is the (in the West) monotheistic idea of narrative history/time. By framing time as something that can have a beginning and end, you enable or at least incentivize "progress", and mentally unlock the ability to work toward some idealized future, rather than accepting that time is cyclical and/or without some notion of moving forward.

I must admit the foundation of the argument presented punches well above my understanding, but I recently read Carlo Rovelli's short work "The Order of Time" and found it wonderfully engaging and relatable.

I like the article. And I applaud any physicist trying to come to grips with our conceptions of reality AND reading up on philosophy. That being said, he's neither the first nor will he be the last, nor is "perpectivism" in epistomology a new thing. I like, however, how he is throwing in several streams (I saw James, Nietzsche, Kuhn, and even Rorty and Wittgenstein II) of thought, centered on Kant's ideas of the noumenon and its inaccessibility. I don't think I agree with him, though ;)

If I had to label him, I'd say he is mostly an anti-realist.

> There is no objective reality, according to Rovelli — only perspectives. “This is very radical, because you can no longer say, ‘This is a list of things in the world, and this is how they are.’"

Perfectly in line with his political views, when he's a guest on the Italian TV's, or on social media he spend so much time defending the reasons of the Russian in the Ukrainian invasion. With hosts that often asks physics and political questions in the same set, as if his way of looking at reality gives him any ground truth. I'm wondering how much his physics and political views overlap. Such a delusion for me as Italian, I stopped reading his books for this reason and because at some point, after the wonder effect of reading about quantum worlds, I was left with the sensation that I read a lot and nothing at the same time

Another Ph.D. physicist here. Any popularization of quantum mechanics (or quantum gravity in this case) can quickly degenerate into potentially foolish, or even harmful, metaphysical speculation. Physicists are in the business of finding the best set of mathematical rules that describe "If the conditions A exist, then B happens [with a certain probability]." The frustrating part is that about 100 years ago, quantum mechanics provided a set of rules that didn't have an easy intuitive interpretation (i.e. that quantum mechanics is not both a "real and local" theory.) Yet it is wildly successful for what it does, and the mathematics is crystal clear. (By the way, regular non-relativistic quantum mechanics can be interpreted as having "no reality", no fancy quantum loop gravity needed; see e.g.https://arxiv.org/abs/quant-ph/9609013 - more precisely, only correlations exist.)

Taken to its metaphysical conclusion, though, "there is no objective reality" can lead to harm. So, I guess morality is all a matter of perspective? That can be used to justify anything. We do seem to have an emergent reality (at least the one I am experiencing at the moment) that is held in common - just because the underlying mathematics is hard to interpret doesn't justify "anything goes", or my crazy belief is just as good as your crazy belief.

So although it is fun to think about, don't take "there is no objective reality" too seriously - you still have to go to work, you still have to pay your taxes.

Carlo Rovelli: 'Time Is an Illusion' - https://www.youtube.com/watch?v=PuLaUYQFIwg

Related. Others?

Carlo Rovelli on challenging our common-sense notion of time - https://news.ycombinator.com/item?id=17893865 - Sept 2018 (74 comments)

Carlo Rovelli on the ‘greatest remaining mystery’: The nature of time - https://news.ycombinator.com/item?id=17376437 - June 2018 (143 comments)

A person proposing to stop or limit military aid to Ukraine "for peace" has decidedly radical view on reality, that's for sure.

Seriously, it would interest me when they enable the creation of something akin to a warp drive.

- First, because it would be a way to test these hypotheses

- Second, because it would dramatically expand humanity's playground, even if it's only in the solar system in the first step.

- Third, because building a Warp drive would be good for the economy. Currently, we have no equivalent to the space race. We have AI, but there are doubts that it will enable more than incremental steps.

Baader-Meinhof complex in action: I have _just_ ordered a book of Rovelli's (Reality is Not What It Seems - https://en.wikipedia.org/wiki/Reality_Is_Not_What_It_Seems), it should be in my hands by the end of the week. I am fascinated by the ongoing work in quantum gravity, it's tantalising by its nature.

This is a great interview and I must say I like the man a lot more than I did before. He has articulated something here that I have long felt: that it is as important in politics as it is in philosophy or theoretical physics to be able to state one's assumptions, to suspend one's assumptions for the sake of argument and to drop/change one's assumptions in the face of evidence.

I feel like this is a vital skill that we, as a society, need now maybe more than ever, in literally any field in which there is any meaningful concept of "correct" (which I think is most fields). I also think it's a skill you basically learn at university - and that that is a problem. I don't know what an approach to cultivating it more widely would look like.

The core idea of relational quantum mechanics is that when we talk about an object — be it an atom, a person or a galaxy — we are never just referring to the system alone. Rather, we are always referring to the interactions between this system and something else. We can only describe — and in fact understand — a thing as it relates to ourselves, or to our measuring devices.

Lee Smolin has gone down a different track but with similar spirit of sorts. Carlo poked fun at Lee for all the work they've done together despite disagreeing on so much in his recent talk[1] at Lee's Fest[2].

Smolin has named his approach the Causal Theory of Views, in which he postulates that spacetime emerges from events, ie relational interactions. This[3] interview, which is a few years old now, contains a decent high-level explanation. The idea that kinda overlaps with Rovelli he explains like this:

The theory that I've been looking for would take advantage of the fact that the notion of locality and nonlocality is key to understanding quantum mechanics, and then try to understand that with the lens of the unification of quantum physics with space and time, which is quantum gravity.

In both approaches, there's a principle, which is the idea of relational physics—that the degrees of freedom, the properties of whatever it is that's dynamical that you're studying, arises from dynamical relationships with other degrees of freedom.

In other words, you don't have absolute space, you don't have particles that occupy points or follow paths or trajectories in absolute space. You have many particles which, between them, allow you to define relative motion.

Lee has given several talks[4] at PIRSA since that interview with more details as he's developed his idea.

So while both go hard on the relational aspect, they disagree on some fundamental things. Rovelli thinks time is an illusion, but in Lee's CTV time is real and space is the illusion (emergent).

Who knows if it'll pan out or be a dead end, but since the quantum physics community has been headbutting the fundamental issues with little progress for so many decades, it seems prudent to try some bold approaches.

[1]: https://pirsa.org/25060030

[2]: https://pirsa.org/c25023

[3]: https://www.edge.org/conversation/lee_smolin-the-causal-theo...

[4]: https://pirsa.org/speaker/lee-smolin

How do these quantum + gravity loops/patches evolve continuously w/o time? The more I learn about theoretical physics & physicists the more I'm convinced these people are basically idiot savants.

> My intuition is that the overall flow of time really could be like the rotation of the sky every day. It’s a majestic, immense phenomenon, but it’s actually an illusion. This is a totally perspectival understanding of the second law of thermodynamics. It’s real in the same sense that the rotating sky is real, but it’s real only with respect to us.

And later:

> Our community has wasted a lot of time searching after speculative ideas. What we need instead is to digest the knowledge we already have. And to do that, we need philosophy. Philosophers help us not to find the right answers to given questions, but to find the right questions to better conceptualize reality.

I think it’s odd that a physicists proposes a new theory without suggesting experiments that could falsify the theory.

I love Rovelli, but to me he’s just another proof that if you look for too long into the quantum abyss, the abyss is gonna eventually look back at you…

Most folks don't understand what Physicists mean when they say "Reality doesn't exist at the Quantum level". Words like "Reality", "Illusion" etc. mean quite different things when applied at quantum level vs. classical-macro level.

The best book to get a grasp on the above is Werner Heisenberg's classic Physics and Philosophy: The Revolution in Modern Science. The introduction by Paul Davies itself is worth the price of the book since it highlights the main issues quite clearly.

At the fundamental level quantum systems have an inherent indeterminism (as a consequence of the famous uncertainty principle) which is what we find hard to grasp. It does not mean total anarchy but that you can only calculate relative probabilities of the alternatives in the answer set i.e. it is a statistical theory. Thus it can make definite predictions about sets of identical systems but generally cannot say anything definite about a specific individual system.

For example, an electron doesn't exist as a single thing occupying a specific trajectory around the nucleus. It only exists as a set of potentialities occupying an area of space viz. the so called electron shell. Only when a measurement is made does a electron-with-position or electron-with-momentum can be said to come into existence (since before the measurement there are only probabilities and you cannot measure both position and momentum sharply simultaneously). It is in this sense that the Reality of an electron is said to only exist in the Measurement/Observation and cannot be said to exist otherwise.

The other side of the coin is that, Modern Neuroscience tells us that the Brain itself is wired to Construct Reality from incomplete data and we seek/construct patterns where there are none. See for example Cordelia Fine's A Mind of Its Own: How Your Brain Distorts and Deceives and watch this Ted talk by Susana Martinez-Conde Reality is made of illusions—and we need them - https://www.youtube.com/watch?v=FzDw07RqCSs