Why Branching Spacetime Is a Bad Idea
John Earman (Department of History and Philosophy of Science, University of Pittsburgh)
A number of philosophers have opted for branching spacetime as
a way to model indeterminism and the openness of the future
(e.g. Belnap (1992), McCall (1994, 1995), Müller (2004), Placek (2000)).
Attempting to implement this idea in the context of relativistic spacetimes
runs up against “no-go” results on topology change. I examine the various
ways to circumvent these results and argue that each of them comes with
a high cost. I also argue that the motivation for branching in individual
spacetimes is defective and that indeterminism is better represented
in terms of metaphorical branching—i.e. the branching behavior refers
not to individual spacetimes but to the ensemble of physically possible
spacetime models; it means that two (or more) members of the ensemble
can agree for all past times but disagree for future times.
References:
Belnap, N. (1992) “Branching Space-Time,” Synthese 92: 385-434.
McCall, S. (1994) A Model of the Universe. Oxford: Clarendon Press.
McCall, S. (1995) “Time flow, non-locality, and measurement in quantum mechanics,”
in S. Savitt (ed), Time's Arrow Today, pp. 155-172. Cambridge: Cambridge University Press.
Müller, T. (2004) “Probability theory and causation: A branching spacetime analysis,”
http://philsci-archive.pitt.edu.
Placek, T. (2000) “Stochastic Outcomes in Branching Space-Time: Analysis of
Bell's Theorems,” British Journal for the Philosophy of Science 51: 445-475.