Does the many worlds interpretation of quantum physics apply only to the future, or does it apply equally to the past?

Rather than a cat in a box, imagine a dinosaur in a box 65 million years ago. In one past the dinosaur is alive and in the other past the dinosaur is dead. In both pasts, each dinosaur is smashed by an asteroid. Do both pasts exist under the many worlds interpretation?

  • $\begingroup$ But wouldn't one dead dinosaur be inside the box while the other does something else until it dies? $\endgroup$ – JMac Mar 1 '18 at 3:37
  • $\begingroup$ @JMac Perhaps, for a millisecond. But the point is that whatever happens just before the asteroid strikes will be "wiped out" causally speaking as an influence on the future so that you have more than one possible past leading to the same present. So, according to the many worlds interpretation, did both pasts exist? $\endgroup$ – John Wayland Bales Mar 1 '18 at 3:47
  • $\begingroup$ What does "exist" mean, precisely? $\endgroup$ – probably_someone Mar 1 '18 at 4:27
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    $\begingroup$ Yes, I think they have to. After all, I haven't heard any MWI proponents saying that there is a collapse of the wave-function before the dinosaurs went extinct, and unitary evolution with MWI thereafter. $\endgroup$ – innisfree Mar 1 '18 at 4:28

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