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Comment by loup-vaillant | Hacker News Reader

I must say, I'm not sure what he even means by this "zero universe" business. Sure, the classical illusion is bust, but the wave function itself, as far as we know, is real, is it not?

While we're at throwing quantum explanation links, here is the Quantum Physics Sequence on Lesswrong: http://lesswrong.com/lw/r5/the_quantum_physics_sequence/ I'd say the math is even simpler there, yet the explanation go deeper. It's a long read however.

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Whether the wave function is real depends on your answer to the question: is momentum real? You can't directly measure or observe momentum, you can't point to it in the world, but you can definitely feel its impact and it's a convenient measure for certain properties of objects. In that sense the wave function is just as real.

But you can argue both those things are not as real as e.g. extension, force and energy, which are much more readily available to our senses.

Can't I just weigh Galileo's cannon ball, then based on T from when I dropped it know its momentum?

I think the difference comes on moving past the macroscopic world: say I drop a uranium atom into Shroedinger's box - I can't calculate at time T whether the cat is alive.

Yes, you can calculate the momentum it had anywhere along the path while it dropped. Does being able to calculate some property make it real? If I take the square root of the momentum and call it the 'squish' of an object, is my 'squish' property then real?

Doesn't it depend on what it means for a theoretical construct to be "real" or not? Isn't "does it work" a better question?

Don't get confused by simple words such as "real". It means what it obviously mean in everyday life.

For instance, apples are real, and gravity is real. So when you drop an apple, what happens? It falls. Now what really, ultimately happens? It falls.

Once in Hawaii, at a meeting of philosophers sitting around a table discussing reality, several days passed and Suzuki said nothing. And finally the chairman said, "You've been silent all this time. Would you say something about reality." And Suzuki didn't say anything. I think he may have looked up. Finally the man said, "Well, is this table real?" And Suzuki said, "Yes." And then the man said, "In what sense is it real?" And Suzuki said, "In every sense."

Recently, there was a paper talking about this aspect of quantum theory - http://xxx.lanl.gov/abs/1111.3328 ... well, it was "recently" and fresh in my mind, but it appears to be back in 2011 :)

If readers want to dive in and get to the point where "entanglement = time's arrow" becomes evident, the post would be that on "decoherence" [1]

[1] http://lesswrong.com/lw/pp/decoherence/

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