"Oh." She deflates a little. "That's fast." She still hasn't caught a bunny made of cheese.
"Yeah. And once that decoherence has happened, the different branches of the wavefunction can't really interact with each other any more. Which means, essentially, that the different branches become separate universes that are completely inaccessible to one another. Things that happen in these other 'universes' have absolutely no effect on what happens in our universe."
"Why do we only see one branch of the whatchamacallit?"
"Ah, now that's the big question. Nobody knows. A lot of people think this means that quantum mechanics is fundamentally incomplete, and there's a whole community of scientists doing research into the fundamentals of quantum theory, and the various interpretations. Matt Leifer has a whole blog talking about this stuff."
"We don't like him. He said mean things about me."
"It wasn't so much mean, as dismissive. But that's not the point. The point is, there's no way you're going to find steak under my desk, so please get out of there."
"Oh. OK." She mopes out from under the desk, head down and tail drooping.
"Hey, look on the bright side," I say. "In the universe where a version of me dropped a piece of steak on the floor, there's also a version of you."
"Yeah?" Her head picks up.
"Yeah. And you're a mighty hunter, so you probbaly got to the steak before I could pick it up."
"Yeah?" Her tail starts wagging.
"Yeah. So, in the universe where I dropped steak, you got to eat steak."
"Oooh!" The tail wags furiously. "I like steak!"
"I know you do." I save what I was working on. "Tell you what, how about we go for a walk?"
"Ooooh! Good plan!" and she's off, clattering down the stairs for the back door and the leash.
"Oh." She deflates a little. "That's fast." She still hasn't caught a bunny made of cheese.
"Yeah. And once that decoherence has happened, the different branches of the wavefunction can't really interact with each other any more. Which means, essentially, that the different branches become separate universes that are completely inaccessible to one another. Things that happen in these other 'universes' have absolutely no effect on what happens in our universe."
"Why do we only see one branch of the whatchamacallit?"
"Ah, now that's the big question. Nobody knows. A lot of people think this means that quantum mechanics is fundamentally incomplete, and there's a whole community of scientists doing research into the fundamentals of quantum theory, and the various interpretations. Matt Leifer has a whole blog talking about this stuff."
"We don't like him. He said mean things about me."
"It wasn't so much mean, as dismissive. But that's not the point. The point is, there's no way you're going to find steak under my desk, so please get out of there."
"Oh. OK." She mopes out from under the desk, head down and tail drooping.
"Hey, look on the bright side," I say. "In the universe where a version of me dropped a piece of steak on the floor, there's also a version of you."
"Yeah?" Her head picks up.
"Yeah. And you're a mighty hunter, so you probbaly got to the steak before I could pick it up."
"Yeah?" Her tail starts wagging.
"Yeah. So, in the universe where I dropped steak, you got to eat steak."
"Oooh!" The tail wags furiously. "I like steak!"
"I know you do." I save what I was working on. "Tell you what, how about we go for a walk?"
"Ooooh! Good plan!" and she's off, clattering down the stairs for the back door and the leash.
She's really a very silly dog.
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