Peter Woit vs Sean Carroll: string theory, the multiverse, and Popperazism

The present observable universe is at least 91 billion light years across. The universe may be one million billions light years across. We don’t know. But to consider we should make first wild guesses about other universes, is a bit like imagining unicorns, in another cave, when one does even know how big the cave one inhabits is. Why to make wild, untestable guesses, when more sedate guesses could be experimentally tested, if they were only considered?
As Einstein proposed that a particle “in flight” was localized (he had no proof of this, and there are near-proofs that this is false), it came to be considered that all eigenstates were to receive said localized particle (albeit with varying probabilities). But the reception of one particle per eigenstate is possible only if the universe has split in as many universes as there are eigenstates. Therein the genesis of the Many-World “interpretation” of Quantum Mechanics…which many specialists consider equivalent to the Multiverse.
So what is the scientifically minded to do? Well, make an experiment! In the lab. It’s simple: miniaturize, and find out whether the photon gravitationally spreads (as I believe it does), or whether the photon doesn’t spread (as Einstein believed it didn’t). My assumption is that Quantum spreads corresponds to a gravitational spread. In other words, is the Quantum Collapse real, or not? (If it is, Einstein was wrong in his 1905 paper.)
No need to evoke other universes, and unicorns. One should just reach a higher level of experimental accuracy. Not a fancier level of religious prophecy.
Interestingly, Einstein himself, in his 1935 EPR paper, predicted, or, more exactly observed, that the Quantum Theory implied “Entanglement” (so named by Schrodinger, soon afterwards). Entanglement is experimentally proven, collapse is not… Not yet. But one can’t get entanglement without collapse. Methinks top physicists would be better off thinking about these issues (which lead to lab experiments and the Quantum Computer), rather than to try to imagine other universes…

Footnotes to Plato

Peter Woit vs Sean Carroll Peter Woit (left) vs Sean Carroll (right)

The string and multiverse wars are going strong in fundamental physics! And philosophy of science is very much at the center of the storm. I am no physicist, not even a philosopher of physics, in fact (my specialty is evolutionary biology), so I will not comment on the science itself. I take it that the protagonists of this diatribe are more than competent enough to know what they are talking about. But they keep bringing in Karl Popper and his ideas on the nature of science, as well as invoke — or criticize — Richard Dawid’s concept of non-empirical theory confirmation, so I feel a bit of a modest commentary as a philosopher of science is not entirely out of order.

Let me begin with two caveats: first, there are many people involved in the controversy, including Sean Carroll, Peter Woit,

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2 Responses to “Peter Woit vs Sean Carroll: string theory, the multiverse, and Popperazism”

  1. ianmillerblog Says:

    Hello Patrice. Needless to say, I disagree – you can have entanglement without wave function collapse. All you have to do is entangle them at creation.The problem here is you can’t be sure you have entangled them until you observe them, but if they are entangled at creation, you will get the same results. After all, the entanglement merely arises from the application of some conservation law.


    • Patrice Ayme Says:

      Hi Ian: Sorry if I expressed myself poorly somewhere. I agree that, as long as one has entanglement, one didn’t have wave function collapse. And, as you say, one can only observe what is going on, and thus PROVE ENTANGLEMENT, by wave function collapse (in the act of observing).
      So, in a PHILOSOPHICAL sense entanglement implies collapse (we don’t know when and where). Can’t observe the former without the latter…


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