Heads or Tails

It’s the fiftieth anniversary of Hugh Everett’s ‘many worlds’ interpretation of quantum mechanics, which attempted to apply quantum mechanical equations to both the subatomic world and the macroscopic world we ordinarily inhabit. It’s long been accepted that subatomic particles like electrons or photons exist as both wave and particle until collapsed when an observer makes a measurement; Everett’s proposal that hawks, handsaws, and human beings also exist in a multitude of simultaneous states - parallel worlds - has been much more contentious. But now, at a meeting at Oxford University, reported in the latest issue of New Scientist (you need to be a subscriber to read the full report, but Peter Byrne has blogged the meeting for Scientific American), David Deutsch and his colleagues claim that ‘key equations of quantum mechanics arise from the mathematics of parallel worlds’. Or to put it another way, if they’re right - and it’s an extraordinary claim that requires extraordinary evidence - every time we make a decision, the universe really does split into two parallel branches. Coin-tossing may never be the same again.