and here we are the granddaddy of all quantum weirdness the infamous double slit experiment to understand this experiment we first need to see how particles or little balls of matter act if we randomly shoot a small object say a marble at the screen we see a pattern on the back wall where they went through the slit and hit now if we add a second slit we would expect to see a second band duplicated to the right now let's look at waves the waves hit the slit and radiate out striking the back wall with the most intensity directly in line with the slit the line of brightness on the back screen shows that intensity this is similar to the line the marbles make but when we add the second slit something different happens if the top of one wave meets the bottom of another wave they cancel each other out so now there is an interference pattern on the back wall places where the two tops meet are the highest intensity the bright lines and where they cancel there is nothing so when we throw things that is matter through two slits we get this two vans of hits and with waves we get an interference pattern of many bands good so far now let's go quantum an electron is a tiny tiny bit of matter like a tiny marble let's fire a stream through one slit it behaves just like the marbles a single band so if we shoot these tiny bits through two slits we should get like the marbles two bands what an interference pattern we fired electrons tiny bits of matter through but we get a pattern like waves not like little marbles how how could pieces of matter create an interference pattern like a wave it doesn't make sense but physicists are clever they thought maybe those little balls are bouncing off each other and creating that pattern so they decide to shoot electrons through one at a time there is no way they could interfere with each other but after an hour of this the same interference pattern is seen to emerge the conclusion is inescapable the single electron leaves as a particle becomes a wave of potentials goes through both slits and interferes with itself to hit the wall like a particle but mathematically it's even stranger it goes through both slits and it goes through neither and it goes through just one and it goes through just the other all of these possibilities are in superposition with each other but physicists were completely baffled by this so they decided to pee and see which slit actually goes through they put a measuring device by one slit to see which one it went through and let it fly but the quantum world is far more mysterious than they could have imagined when they observed the electron went back to behaving like a little marble it produced a pattern of two bands not an interference pattern of many the very act of measuring or observing which slit it went through meant it only went through one not both the electron decided to act differently as though it was aware it was being watched it was here that physicists stepped forever into the strange never world of quantum events what is matter marbles or waves and waves of what and what does an observer have to do with any of this the observer collapsed the wavefunction simply by observing