Carlo Rovelli: Loop Quantum Gravity, 7 Brief Lessons on Physics & The Order of Time (122)

The speaker expresses admiration for Carlo Rovelli, comparing him to Stephen Hawking and Albert Einstein. They discuss Rovelli's ability to engage in high-level conversations about experimentalism, philosophy, and poetry. The speaker teases Rovelli's new perspectives on quantum gravity, his collaboration with Benedict Cumberbatch, and his fearless approach to controversy. They also mention an upcoming project involving Galileo.

The speaker proposes a project to Rovelli to help translate Galileo Galilei's 'Dialogue Concerning the Two Chief World Systems' into an audiobook. They discuss the importance of Galileo as an influential writer and scientist, and the concept of the Dunning-Kruger effect. The speaker also shares insights on science writing and the different audiences who appreciate it.

Rovelli's book 'The Order of Time' is discussed, which explores the concept of time beyond the common understanding. The speaker highlights Rovelli's ability to disentangle various aspects of time, including its experience, direction, memory, and measurement. They also touch on the influence of thermodynamics, Newtonian physics, quantum gravity, and the human brain's role in perceiving time.

The conversation delves into the origins of time, touching on the Big Bang, quantum gravity, and the no-boundary proposal by Hawking and Hartle. Rovelli shares his views on the possibility of a previous phase before the Big Bang and the concept of time beginning at the event. They also discuss the separation of science and religion, with Rovelli emphasizing that they are distinct but not mutually exclusive.

The speaker and Rovelli debate the relationship between religious texts, such as the Torah, and scientific understanding. They argue that while wisdom and knowledge are different, they should not be separated. The speaker criticizes the overemphasis on the Nobel Prize and the misconception that old books hold great wisdom. Rovelli champions the idea that science can inform our worldview and deepen our understanding of ourselves.

The discussion highlights Einstein's impact on physics, acknowledging both his significant contributions and his mistakes. Rovelli emphasizes the importance of being open to changing one's mind, which he sees as a sign of intelligence. They also discuss the public's fascination with Einstein and the tendency to focus on individuals rather than their ideas.

The speaker and Rovelli talk about the importance of experimental evidence in validating scientific theories. They discuss a claim related to loop quantum gravity and the speed of light, which was later disproven, leading to further astrophysical research. Rovelli emphasizes that quantum gravity theories must be testable and that nature seems to respect Lorentz invariance.

The conversation explores the potential for cosmic parity violation and its implications for our understanding of the universe. They discuss a recent claim using Planck 2018 data and the possibility of observing parity-violating signatures. Rovelli suggests that loop quantum gravity could offer new insights into chirality and its effects in nature.

Rovelli explains loop quantum gravity's predictions about black holes, suggesting that they could transform into white holes and that the information paradox might be resolved through quantum phases. The speaker questions the observability of quantum gravitational effects and the necessity of a quantum theory of gravity. Rovelli counters that black holes provide a clear example where quantum gravity is both necessary and observable.

The discussion addresses the information loss paradox associated with black holes. Rovelli argues against the idea that information is lost and criticizes the reliance on the holographic principle. He asserts that loop quantum gravity provides a consistent picture where information is retained and that the theory allows for calculations within the quantum gravity regime.

Rovelli delves into the quantum nature of space-time, explaining that space-time is quantized and not continuous. He discusses the concept of spin networks and foams, which are key to understanding the quantum states of space-time. The speaker and Rovelli explore the philosophical implications of quantum mechanics and the importance of updating our intuition to align with quantum theory.

The conversation touches on the concept of a theory of everything and Rovelli's perspective on loop quantum gravity. While he acknowledges that loop quantum gravity is not a theory of everything, he believes it provides a solid foundation for understanding quantum space and its implications. They also discuss the importance of testable predictions and the limitations of current theories.

The speaker proposes the idea of revisiting existing data to find evidence for theories like loop quantum gravity or string theory. They discuss the potential for overlooked information in past experiments to provide insights into these theories. Rovelli agrees with the idea but admits that identifying such data is challenging.

The speaker introduces a project inspired by Galileo Galilei, called 'Il Sagittore' or 'The Assayer'. They discuss Galileo's contributions to science and his ability to make conjectures about the nature of reality. The speaker expresses a desire to re-examine Galileo's work and its implications for modern physics.

The conversation concludes with a discussion on the future of physics and the hope for experimental confirmation of quantum gravity. Rovelli expresses optimism about the potential for discoveries in the field and the importance of continued exploration. The speaker thanks Rovelli for his insights and looks forward to future discussions.