Quantum Physicist 1: Did you hear about the quantum cowboy?
Quantum Physicist 2: No, do tell.
QP1: There was this cowboy who was in a quantum superposition of states between reaching into his back pocket for a little round can of snuff or not reaching into his back pocket for a little round can of snuff, all the while waiting for an observer to collapse the wave function.
QP2: Yeah?
QP1: Yeah, it seems the cowboy subscribed to the “Copenhagen interpretation.” Ha ha ha ha!
QP2: I don’t get it.
QP1: Don’t you see? The joke plays on a pun between the “Copenhagen interpretation” of quantum mechanics and the brand of snuff called “Copenhagen.” It also plays on the irony of a cowboy involved in a joke about quantum mechanics.
QP2: Oh, I get it now. It’s just not funny.
QP1: Of course it’s funny.
QP2: What if the cowboy subscribed to the “many worlds” interpretation? Then it wouldn’t make any sense at all. As a matter of fact, if I were a cowboy jonesing for snuff, I would surely hope the many worlds interpretation is correct. That way in at least one universe I would be sure to get my nicotine fix.
QP1: Hoo Hoo. Look who is “Mr. glass half full.” You didn’t stop to think that in the next universe over from that he would be certain NOT to get his nicotine fix.
QP2: Oh yeah. In the universe three doors down he meets that universe’s version of Scarlett Johansson, and for reasons that are explicable only if one invokes infinite universes, she overcomes her revulsion to his nasty snuff habit and falls in love with him and together they make beautiful blonde babies.
QP1: Hoo Hoo, Mr. smarty pants. In the universe two doors further down he gets mouth cancer and half his face rots off before he dies an excruciatingly painful death.
QP2: Oh. That would be bad. But you have to admit that the Copenhagen interpretation sets up an infinite regress. While the cowboy is waiting for his observer to collapse the wave function; that observer is waiting for an observer more remote still to collapse his wave function and so on.
QP1: Yes, I suppose that’s right unless we posit a primordial unobserved observer whom we shall call “God.”
QP2: Oh my dear boy, since Leplace we have had no need of that hypothesis
QP1: I will choose that hypothesis, because while I cannot explain it at least it is rational. Many worlds is irrational at a fundamental level.
QP2: Au contraire, many worlds is all the rage. It is the “multiverse” we have heard so much about.
QP1: I agree it is all the rage but irrational nevertheless as I can show with one simple equation.
QP2: This I have to see.
QP1: OK, as we have just demonstrated, many worlds is able to account for the instantiation of any possibility like our cowboy getting his snuff. True?
QP2: Of course.
QP1: But many worlds is also able to account for the negation of any possibility, like our cowboy not getting snuff.
QP2: That seems to be true as well.
QP1: Then let the set “the instantiation of all conceivable possibilities” be “A” and let the set “the negation of all conceivable possibilities” be “B.” Is it not true that A plus B equals zero?
QP2: It seems it is.
QP1: Indeed. So don’t you see that the many worlds hypothesis that explains everything and its negation in sum explains nothing, and therefore pointing to it as an explanation of anything is irrational?
QP2: I’m tired of that subject. Let’s talk about a universe where Scarlett Johansson falls madly in love with a quantum physicist and together they make beautiful nerdy babies . . .