David Wallace

speaker

1,940 appearances 2 recordings 1 series first heard May 2025 last heard 20 Jul

David Wallace’s voice in public audio — every appearance, attributed to the second.

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Recordings per month over the last 12 months — 1 in all, peaking in Jul 2026 with 1.

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Theories of Everything with Curt Jaimungal · Emily Adlam & David Wallace: The Quantum Interpretation That Divides Physicists · 20 Jul 2026 podcast

I mean, I think collapse theories are good science.

And one of the ways to tell they're good science is that I think they're within 10 or 20 years of being completely ruled out experimentally.

Well, only if it's true, Everett's false.

If on Oppenheimer's approach, then effectively you have a wave function collapse.

So if I can have a superposition of the matter, the idea of the Oppenheimer approach, and it has a long pedigree, is that the gravitational force isn't sourced

by the matter distribution, it's sourced by the sort of smeared matter distribution of all the terms in the quantum superpositions.

If the quantum superpositions evolve unilaterally and don't collapse, that will rapidly and radically violate experiment.

So those theories are only viable in the context of some kind of collapse mechanism.

which is normally tied to gravity itself.

So the idea is if I have a sufficiently spread out mass distribution in a superposition, then the dynamics will somehow have to select one of those.

And so the gravitational field can still carry on being sourced by the smeared mass distribution because it's not really that smeared anymore.

So obviously, if that's right, then these macroscopic superpositions, whichever it's committed to, don't exist.

I mean, I'd say I think the technical problems of having superpositions of geometry are massively overstated.

I think the technical problems of not having them are much more severe.

I think we have a mathematically fairly satisfactory theory of quantum gravity at energies below the Planck scale.

Well, below the Planck scale.

Yes.

It has a whole bunch of interpretational questions.

Some of which are just the measurement problem, but bracket that.

So, I mean, I hesitate to disagree with Sir Roger Penrose, but it's worth saying Penrose very much has a minority view here.

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