 When we first started talking about two slit interference, we were trying to figure out where the light was a wave or a particle. Well it turns out that if you turn down a light beam when you're making this beautiful two slit interference pattern, you also see these blobs appear one by one. And so quantum mechanics doesn't just describe electrons, it also describes light and those little blobs are called photons. And in fact, absolutely everything in the universe seems to obey the laws of quantum mechanics. So everything, all kinds of matter, all kinds of light, everything appears to travel as waves and when you look at them it jumps. So quantum mechanics is the model for all stuff in the universe. And in fact, two slit interference has been performed on molecules containing almost a thousand atoms. So if quantum mechanics really applies to everything, big and small, then the real question shouldn't be, well in that case, why is the theory so weird? The real question should be, so why are things so simple? Why haven't I seen this strange behavior before? If I'm actually a wave and I can walk through two doors at once, then I ought to have noticed that by now.