The Physicist Who Says Time Doesn't Exist

Physicist Julian Barbour, working independently outside academia for over 50 years from a farmhouse near Oxford, has developed “shape dynamics” — a theory that challenges the foundations of physics by arguing that time is not fundamental but emergent, that the universe is becoming more ordered (not more disordered), and that reality is best understood as a succession of static shapes rather than evolution through time.

Barbour’s core ontology and motivation

• The simplest possible ontology is point particles in Euclidean space with equal masses; all structure in the universe could in principle arise from such a model.
• Time is not something we measure directly — following Ernst Mach, Barbour insists we can only measure changes in things, and time is an abstraction we deduce from change.
• Leibniz’s philosophy was foundational: “Without variety, there would be nothing.” Barbour wanted a mathematical expression for the variety of the universe, and found it in a quantity closely related to the Newtonian gravitational potential.

Shape dynamics and the “complexity” measure

• Barbour defined a scale-invariant quantity he calls “complexity” (also called the shape potential or normalized Newton potential by n-body specialists): it combines the root-mean-square separation of all particle pairs with the inverse of each pairwise separation, making it extremely sensitive to clustering.
• This complexity is positive-definite, so it has an absolute minimum — a unique shape Barbour calls “alpha” — which is the most uniform shape possible.
• The complexity grows steadily as a Newtonian universe evolves, and this growth defines an arrow of time that is about increasing order, not increasing disorder.

The Janus Point: a Newtonian Big Bang without a box

• Newton’s equations are time-reversible. Work going back to 1907 (Sundman, Bloch) showed that “total collisions” in the n-body problem require very special shapes — equilateral triangles or collinear configurations — and that these same shapes, run backward in time, look like a Newtonian Big Bang of extraordinary uniformity.
• This predates Hubble’s law by about 20 years and comes straight out of Newton’s theory with no need for inflation.
• The most interesting Newtonian Big Bang starts from the alpha shape (maximally uniform) and then develops structure — the exact opposite of the second law of thermodynamics, which says the universe goes from order to uniformity.

Challenging the second law of thermodynamics

• Barbour argues the second law was discovered for systems in a box (steam engines, molecules in a container) and that its derivation requires a finite, bounded system — a length scale.
• Entropy is not scale-invariant; complexity is. If the universe is not in a box (and likely it isn’t), then the framework of applicability for thermodynamics breaks down.
• Within the growing Newtonian universe, subsystems can form and “virialize,” behaving like thermodynamic systems — so the second law can be derived as a special case, not a fundamental law.
• Einstein himself said thermodynamics would “never be overthrown” but qualified this with “within the framework of applicability of its basic concepts” — a qualification Barbour says has been forgotten.

Shape space, probability, and quantum gravity

• By removing scale (dilatations) from configuration space, you get a compact “shape space” — for three equal-mass particles, a sphere with area 4π — on which there is a natural probability measure.
• This allows meaningful probability statements about shapes (e.g., the probability that three random points form an obtuse triangle is 3/4, a result recently confirmed using this measure).
• Barbour and collaborator Tim Koslowski propose that quantum gravity could be reformulated as a theory of probabilities over shapes, with complexity serving as time — potentially eliminating the need for a wave function or Planck’s constant.
• The wave function in such a framework would be constant on iso-complexity surfaces, with all the probabilistic content coming from the geometric measure on shape space (analogous to the Born rule).

Mach’s principle and the definition of mass

• Mach criticized Newton’s definition of mass as circular and gave an operational definition based on the mutual accelerations bodies impart to each other upon collision — a definition Barbour considers still unimproved.
• Mach’s principle says the local inertial frame is determined by the relative positions and motions of all bodies in the universe — a holistic, non-reductionist view of physics.
• Einstein was influenced by Mach but, in Barbour’s view, created confusion about what Mach actually meant; much of Barbour’s career has been spent clarifying this.

Consciousness, shape, and the role of instruments

• Barbour distinguishes structure (the shapes and ratios of distances, which physics can explain) from the “gift of consciousness” — the qualitative experience of color, sound, and sight.
• He speculates that the highly special setups of quantum experiments (like the two-slit experiment) may play a role in creating the interference patterns observed, echoing Eddington’s remark that “we have found a strange footprint… and lo, it is our own.”
• On the question of God, Barbour describes himself as agnostic but expresses a deep sense of wonder at the existence of the universe and consciousness.

Working outside academia

• Barbour funded 28 years of research by translating Russian scientific journals, which left him roughly a quarter to a third of his time for his own work — a model he says is becoming more feasible with online access to libraries and collaborators.