Connecting quantum theory and general relativity | Lee Smolin

Summary

In this thought-provoking talk, the speaker delves into the nature of time, questioning whether it is a fundamental aspect of the universe or an emergent property. Challenging prominent theories, they argue that time is indeed fundamental and explore the relational view of space and time, influenced by philosophers like Leibniz. By discussing quantum mechanics and the distinction between the definite past and the indefinite future, the speaker presents a radical perspective on time that pushes against conventional physics. This discussion is aimed at reshaping our understanding of the universe, blending science with philosophy.

Takeaways

• 🔬 The speaker argues that time is fundamental, contrary to popular theories in physics that view time as emergent or not fundamental.
• 🤔 The concept of time as fundamental means that space and time are relational and depend on relationships between objects and events.
• 🧠 The philosophy of 'identity of indiscernibles' plays a crucial role in the speaker's view, proposing that indistinguishable events or objects are essentially the same.
• 🌌 The universe is described as a collection of 'partial views', where each event or observation represents a unique perspective, rather than one unified wave function that covers all events.
• 🔮 Quantum mechanics can only provide probability distributions for future events, making them indefinite, while past events can be definite and have specific outcomes.
• 🕰 The idea of presentism, which states that only the present 'now' exists, is highlighted as an alternative to conventional physics and philosophical perspectives on time.
• ❓ The speaker challenges the belief that past, present, and future are fundamentally the same, suggesting that the present is unique and has no end.
• ⚖️ The uncertainty principle in quantum mechanics does not conflict with the idea of a definite past; it applies to indefinite future events and measurements.
• 🌌 The speaker's view contrasts with those of prominent physicists like Einstein and Carlo Rovelli, who argue that time may not be fundamental and could emerge from deeper physical principles.
• 🧪 The talk is based on new research developed with a collaborator, Claudio Verde, and builds upon previous work with other thinkers like Julian Barbour and Roberto Mangabeira Unger.

Q & A

What is the main focus of the speaker's work?

The speaker's main focus is on fundamental physics, particularly quantum physics, quantum gravity, cosmology, and the nature of space and time.

What is the speaker's stance on the nature of time?

The speaker believes that time is fundamental, arguing against the view that time is emergent and not part of the real fabric of the universe.

Who are some of the key figures mentioned by the speaker in relation to their views on time?

The speaker mentions notable figures such as Carlo Rovelli, Sean Carroll, and Einstein, who argue that time is not fundamental.

What does the speaker mean by being a 'relationalist'?

As a relationalist, the speaker believes that time and space are not absolute or fixed but depend on relationships between dynamic entities. All properties of things, according to this view, arise from their relationships.

What is the 'identity of indiscernibles' principle mentioned by the speaker?

The identity of indiscernibles, a principle from philosophy, states that if two events or particles have the same relational properties with the rest of the world, they are the same. There cannot be two things that are indistinguishable in every way but are distinct.

How does the speaker describe the universe according to relationalism?

According to relationalism, the universe is a collection of partial views of itself, meaning that each event or observer in the universe has a perspective of the world, and the universe is made up of these different views.

What is the difference between this view and the Everett interpretation of quantum mechanics?

The speaker rejects the Everett interpretation, which posits multiple universes based on one wave function. Instead, the speaker argues that there is only one universe, described by multiple partial views, not many universes.

What does the speaker mean when they say quantum mechanics involves 'indefinite answers'?

In quantum mechanics, many aspects of nature, such as the precise time a particle decays or the direction of a neutrino, are indefinite or probabilistic until they are observed. Quantum mechanics provides probabilities, not certainties.

What is the distinction the speaker makes between questions about the future and the past?

The speaker notes that when dealing with indefinite questions in quantum mechanics, they concern the future. In contrast, questions about the past, such as when something happened or what direction a particle moved, have definite answers.

How does the speaker address the uncertainty principle in relation to the past?

The speaker suggests that the uncertainty principle does not apply to the past. Werner Heisenberg, who formulated the uncertainty principle, acknowledged that it pertains to measurements in the future, not past events, supporting the idea of definite past events.