The Physicist Who Says Time Doesn't Exist

Episode Overview

• This episode features physicist Julian Barbour, who presents his controversial, decades-long work challenging the foundational belief that time's direction is governed by increasing entropy (disorder).
• Barbour argues that the universe is fundamentally becoming more ordered and complex, proposing "shape complexity" as the true driver of the arrow of time, a concept derived from Newtonian gravity and Leibniz's philosophy.
• The discussion critiques the second law of thermodynamics, arguing its laws are only valid for contained systems ("in a box") and do not apply to the unbounded universe as a whole.
• The conversation explores the concept of "shape space" as a mathematical framework to resolve problems of infinity in physics, and speculates on its profound implications for reformulating quantum mechanics.

Key Concepts

• Shape Dynamics: A theory positing that time is not a fundamental dimension but an illusion. What we perceive as the flow of time is our interpretation of the universe transitioning between different static, unchanging "shapes" or configurations.
• The Arrow of Time vs. Complexity: A direct challenge to the second law of thermodynamics. Instead of the arrow of time being driven by increasing entropy (disorder), it is driven by the universe's evolution from a state of maximum uniformity toward ever-increasing order and "shape complexity."
• Leibniz's Principle of Variety: The philosophical idea that the universe is the "most varied" possible, governed by the simplest rules. Barbour reinterprets this dynamically, suggesting the universe is constantly "striving to become ever more varied."
• Relational Physics & Mach's Principle: The concept that physical properties like inertia and mass are not intrinsic to an object but are defined by its relationship and interactions with all other matter in the universe.
• The Problem of "The Box": The argument that the laws of thermodynamics are fundamentally limited because their formulation requires a contained system with an artificial scale. Since the universe is not in a box, a scale-invariant law is needed.
• Shape Space: A compact, finite mathematical arena where all possible shapes of a system (like a three-body problem) can be represented. This solves the problem of unboundedness in traditional configuration space and allows for a well-defined probability measure.
• Critique of Quantum Mechanics: The speculative idea that quantum phenomena (like wave functions or interference patterns) might not be inherent properties of an external reality, but rather artifacts created by the highly structured nature of the experiments themselves.

Quotes

• At 0:00 - "We are challenging the belief which is now held for 170 years... that the only way to explain our sense of the direction of time, the arrow of time, is that... entropy is increasing, that disorder is increasing." - Julian Barbour explains the conventional view of time's direction that his work seeks to overturn.
• At 0:15 - "But we're finding strong evidence in Newton's theory that it's the exact opposite." - Barbour states that his findings directly contradict the idea that the universe is moving toward greater disorder.
• At 1:02 - "It's utterly impossible to measure the changes of things by time. Quite the contrary, time is an abstraction that we deduce from change." - Barbour inverts the common understanding of time, arguing that change is fundamental and time is a concept derived from it.
• At 1:48 - "The exact opposite of the second law of thermodynamics, which says that the universe goes from being ordered to being uniform and uninteresting. And we've got exactly the opposite behavior coming out of Newton." - Barbour directly contrasts his model's prediction of increasing order with the principle of increasing entropy.
• At 22:57 - "When you take them far away from it, they will go much faster... the effective inertia that they have, their resistance to motion is much less." - The speaker explains a key consequence of a relational model of inertia, where inertia is not constant but depends on the distribution of other masses.
• At 23:46 - "But you still need to specify a mass within any of these things, you still need Mach's definition through the mutual accelerations that bodies impart to each other." - He reiterates that mass is not an inherent property but must be defined through the interactions between objects, a core tenet of Mach's principle.
• At 51:58 - "We live in the universe which is more varied than any other possible universe, but subject to the simplest possible rules." - Julian Barbour quoting Leibniz's core philosophical principle that drives his work.
• At 52:49 - "It's not so much that the universe is eternally maximally varied... but that it's striving to become ever more varied." - Barbour explaining his refined understanding of Leibniz's philosophy, emphasizing dynamism over a static state.
• At 54:58 - "That complexity is extremely sensitive to clustering." - Barbour highlighting the key property of his complexity measure: it naturally increases as structure and order emerge in the universe.
• At 55:45 - "The Newtonian N-body problem... it's all about how those two numbers [size and complexity/potential] change." - Barbour revealing the profound connection between his complexity measure and the fundamental components of Newtonian dynamics.
• At 1:14:57 - "It is the only physical theory of universal content which I am convinced that within the framework of applicability of its basic concepts will never be overthrown." - Barbour quoting Albert Einstein's profound respect for thermodynamics.
• At 1:15:14 - "Einstein did not say what is the framework of applicability of its basic concepts... It's that the system cannot be distributed in unlimited space." - Barbour identifying the crucial, often-overlooked limitation of thermodynamics: its reliance on a bounded system.
• At 1:16:08 - "A steam engine stops working if the steam escapes from the cylinder. The steam has to be in a box!" - Barbour using a simple, powerful analogy to illustrate that thermodynamics was developed for and requires contained systems.
• At 1:16:53 - "And amazingly, people haven't thought about that. And nobody, as far as I'm aware... has seriously asked, 'What happens if the box is not there?' This is what the main message of The Janus Point is." - Barbour summarizing the core, overlooked question that his book and theory attempt to answer.
• At 80:06 - "He says that there are circumstances in which the coefficient of probability vanishes and the... law of distribution becomes illusory." - The speaker explains Gibbs's caveat that the laws of probability in statistical mechanics do not apply to systems with infinite extension or energy.
• At 82:39 - "The great thing about the three-body problem... is that two angles determine the shape of the triangle. So you can represent... all possible shapes when you've got three particles as points on the surface of a sphere." - Introducing the concept of "shape space" to solve the problem of unboundedness.
• At 91:41 - "What was the evidence that the founding fathers of quantum mechanics used to arrive at the idea of a wave function? ...It's essentially in structures that we see in non-quantum terms." - The speaker begins to question the foundations of quantum mechanics, suggesting its evidence is based on macroscopic, classical records.
• At 98:33 - "We have found a strange footprint on the shores of the unknown... And lo, it is our own." - Quoting Arthur Eddington, the speaker introduces the idea that the fundamental laws of nature we discover might be reflections of our own methods of inquiry.
• At 99:08 - "Maybe the human experimentalists who set up an incredibly special situation were actually what created those interference fringes by doing that." - The speaker speculates that quantum phenomena are created by the specific, structured nature of experiments themselves.

Takeaways

• View time not as a fundamental dimension, but as an emergent concept we deduce from observing change and the growth of complexity.
• Critically examine the foundational assumptions of long-held scientific laws, such as whether the conditions they require (like a closed system) apply to the subject of study (like the universe).
• Consider that the universe's ultimate trajectory may be toward greater structure and order, rather than the "heat death" of uniform disorder predicted by thermodynamics.
• Adopt relational thinking, where physical properties are seen not as intrinsic but as emerging from the interplay of a system with its environment.
• Prioritize the search for scale-invariant laws to describe the cosmos, as theories dependent on an imposed scale may not be truly fundamental.
• The formation of structure and patterns in the universe can be seen as a primary, law-driven process, not just a random event.
• When theories break down due to infinities, seek a different mathematical representation of the problem space (like shape space) to find a more coherent framework.
• The objective reality we observe may be inextricably linked to our methods of observation; the "footprints" we find in nature may be our own.
• Don't be afraid to challenge scientific orthodoxy, even if it has been entrenched for centuries, as fundamental misunderstandings can persist.
• Use philosophical principles as a guide and inspiration for developing new and testable scientific theories.
• Recognize that revolutionary ideas in science often require decades of dedicated work, frequently outside of mainstream academic channels.