Julian Barbour: What Happens When Physics Abandons Time Entirely
episodePreviously titled “When Physics Gets Rid of Time and Quantum Theory | Julian Barbour” — renamed by the publisher on Aug 3, 2026
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What is the central premise of Julian Barbour’s discussion on abandoning time?
I think it's just possible that there really isn't any quantum mechanics at all. It's just a manifestation of classical physics that has not been recognized. This is a major discovery in Newton's theory of gravity, only four years old. This is probably the most important symmetry in physics. This is why I think we may have stumbled on the nature of creation.
Physics traditionally builds from notions of time and scale. However, today we have a treat with British physicist Julian Barbour, who argues that the universe is grounded fundamentally in relationships between particles, and this upends even the primacy of wave functions.
All the evidence can in principle be explained without any wave function.
Discarding external clocks and rulers, Julian develops something called shape dynamics. This is where instantaneous configurations or snapshots are primary.
My conjecture now is that the whole story is incredibly much simpler than anybody else.
thinks ordinarily we rely on concepts like entropy increase and the past hypothesis to explain time's arrow. However, the second law applies to systems in a box. If the universe is not in a box, all bets are off. This relational view implies that quantum mechanics comes from the statistics of the ratios of the shapes between particles.
Nothing but ratios.
You said that you have some radical ideas that you've developed recently with your main collaborator about the structure of creation. You're gonna speak about what that means. You also have some ideas on consciousness and some new ideas about how quantum theory needs to be interpreted without reference to wave functions or Planck's constant. Please explain what all of that means.
Right. Well leaving actually uh well just about quantum mechanics. I think I think it's it's just possible that there really isn't any quantum mechanics at all. It's just a manifestation of classical physics that uh has not been recognized. But we can we let's come to that because we need to build up to it step by step. Um and um all of this has come from In fact it came from a very um standard idea um that's been doing the rounds in attempts to create quantum gravity for sixty years because well nearly sixty years when uh the famous Wheeler de Witt equation suggested that the quantum universe was completely static. There were just probabilities for different configurations. If you had the simplest model
Yeah. uh according to the Wheeler DeWitt equation, you would just have probabilities for those triangles and nothing less. Now I've been thinking for a long time. It's nonsense to say if there's just three particles that they have a triangle which has both a shape and a size, because a size assumes that you've got a ruler in addition to the universe. If the three particles are the whole universe, it's ridiculous to say that there's a ruler in addition, uh t to measure its size. So you must think just purely in terms of its size. Sorry, its shape. So my idea was to So i in this idea with the Wheel of DeWitt equation, people had been thinking that Uh
How does Barbour redefine the concept of time and change without a universal clock?
There's no sort of change overall, but what happens is part of the universe looks n i i is I if you look what Uh well i you can see as I move my head, my head is moving relative to the background. Uh-huh. Uh so but you could have lots of snapshots where my head is in different positions relative to the background. So you you would have a heap of snapshots. My head is there in different positions relative to the background. And then they would say that my head is the hand of the moving clock, and that tells you what uh what the rest of the universe. So it yeah, the you'd have to have pictures with the rest of my uh room looking rather different than it is with just that beam above behind me. So this was called the sort of the internal time idea.
And it's people have been putting it forward different versions of what they would propose. Now none of them had chosen something which was scale invariant and it was always a bit sort of Um Invidious, they were choosing out one part of the universe to be the clock and the rest to be the the rest of the universe.
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Chapters
8 chapters
1
What is the central premise of Julian Barbour’s discussion on abandoning time?
0:00–3:33
2
How does Barbour redefine the concept of time and change without a universal clock?
3:33–9:01
3
What is Barbour’s alternative explanation of entropy and temperature?
9:01–38:38
4
Why does Barbour claim the second law of thermodynamics fails for the whole universe?
38:38–1:01:15
5
How does the idea of ‘variety’ replace entropy as the driver of cosmic structure?
1:01:15–1:25:35
6
What does an ‘open’ universe of ratios imply for cosmic expansion?
1:25:35–1:51:06
7
In what way does consciousness shape our perception of structure and motion?
1:51:06–2:06:07
8
What are the broader implications of shape dynamics for physics and consciousness?
2:06:07–2:15:46
Speakers
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