Physics and Philosophy for a Phriday

*   I quite like Philip Ball's explanation of the Many Worlds Interpretation of quantum physics in his article at Quanta.   He makes some points I do not recall having read before, such as this one (about the nature of the "splitting"):

For starters, about this business of bifurcating worlds. How does a split actually happen?

That is now seen to hinge on the issue of how a microscopic quantum event gives rise to macroscopic, classical behavior through a process called “decoherence,” in which the wavelike states of a quantum system become uncoordinated and scrambled by their interactions with their environment. Parallel quantum worlds have split once they have decohered, for by definition decohered wave functions can have no direct, causal influence on one another. For this reason, the theory of decoherence developed in the 1970s and ’80s helped to revitalize the MWI by supplying a clear rationale for what previously seemed a rather vague contingency.

In this view, splitting is not an abrupt event. It evolves through decoherence and is only complete when decoherence has removed all possibility of interference between universes. While it’s popular to regard the appearance of distinct worlds as akin to the bifurcation of futures in Jorge Luis Borges’ story “The Garden of Forking Paths,” a better analogy might therefore be something like the gradual separation of shaken salad dressing into layers of oil and vinegar. It’s then meaningless to ask how many worlds there are — as the philosopher of physics David Wallace aptly puts it, the question is rather like asking, “How many experiences did you have yesterday?” You can identify some of them, but you can’t enumerate them.

Interesting.

I must say, however, that I feel a little less convinced by the article as it goes on with his explanation of his problems with the theory.   There's a heavy concentration on it attacking the concept of self;  but in these days where Buddhist ideas of there being no core self anyway have gained quite a bit of intellectual traction, it feels a little odd to be going after a theory on that basis.   (Not that I am a fan of the Buddhist idea - I think it's a worry for quite a few reasons.)

*  Now for philosophy:  if you want a dose of the most headache inducing philosophical question - the matter of free will, its existence, and whether a belief in its absence makes a nonsense of making moral judgement about human behaviour, you could do much worse than read this back and forth between Daniel Dennett and Gregg Caruso at Aeon.   In fact, I have not read all of it carefully yet - but at first glance, Daniel Dennett is making quite a lot of sense.

Great links, hey?