Quantum Weirdness 103: How Many Worlds?// Summer Rerun

“He who laughs has not yet heard the bad news.”–Bertold Brecht

The good news is, this is the last of the current series of summer reruns.  The bad news is, that means vacation is over and I have to go back to work.  Grumble.

“There is no question that there is an unseen world. The problem is, how far is it from midtown and how late is it open?” –Woody Allen

For the quantum physics-uninitiated, get ready for the weirdest of the weird: the many worlds interpretation of quantum mechanics.

In Quantum Weirdness 101, we talked about the wave-particle duality of sub-atomic quanta, and how they appear to be in a superposition of every possible trajectory and location until an observer measures them.

In Quantum Weirdness 102, we discussed The Copenhagen Interpretation, which basically states that reality is just fuzzy on that level.  They are only potential trajectories–probabilities–interfering with each other, and this doesn’t have a measurable effect on our everyday macro world.   But we also visited Schrödinger’s infamous cat–the mind experiment that poked a colossal hole in  Copenhagen.

Image Credit: University of Oregon, 21st Century Science

The Copenhagen interpretation remained the most popular explanation for decades, in spite of Schrödinger.   But in 1957 cosmologist Hugh Everett made an astonishing proposal.  He suggested that the particles themselves–not merely their probabilities–interfere with one-another.  In this interpretation, they actually take every possible trajectory, each in an alternate universe.  Effectively every physically possible history exists in a huge–possibly infinite–number of alternate universes. So when we look in the box containing that possibly dead or alive cat it is actually in two universes: alive in one, dead in the other.   We just see it in the one we are in.   Taken to the extreme, every one of us would exist in a countless number of alternate universes.   Some would be imperceptibly different from ours, in others we might not even recognize ourselves or the the world around us.  And while Everett was mostly ignored or derided in his day, his many worlds interpretation has become a leading explanation of quantum weirdness, rivaling even Copenhagen.

So where do I stand?  Agnostic.  It is a rather optimistic world view.  I hope it’s true; I’m afraid it isn’t.  But many of the world’s top physicists now lean towards many worlds, and David Deutsch, among others, makes some very convincing arguments using deductive reasoning if not direct evidence.  I will leave it at this: it is a strong possibility that greatly influences my millennium conjectures. For more detailed background, check out the Wikipedia articles on The Many Worlds interpretation,  as well as general overview of quantum mechanics interpretations.   Or if you prefer, here is an entertaining video, shamelessly lifted from YouTube.


  1. Of course you could also send people my way!

  2. Uncertain which self is clikcing “liked”; perhaps from another universe, there is another liked me!

    • I am trying not to look in the box to see which universe this is, though. I am in an appropriate-for-this blog state of super-position, simultaneously believing and disbelieving the MW theory. What really worries me is landing in a universe where I believe strongly one way or the other–but it’s the wrong way.

  3. In some worlds, Everett’s son made some geat records too

  4. ok I guess I can live with MWI if it means we are immortal afterall. But will I know I am alive when I die? From a social standpoint does this mean there are no good or bad people?

  5. I don’t know a me who wouldn’t like this post; but what about the me’s who, for whatever reason, are not aware of it?

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