The Double Slit Experiment

Ah...the infamous Double Slit Experiment. For those of you who have heard of it before, it probably gave you a headache. For those of you who have no idea what it is, then prepare to be rocked.

There is no mathematical formula, no fancy theory that needs to be known to fully appreciate it. The experiment in itself is enough to be appreciated by someone who doesn't know a thing about quantum physics...or normal physics, for that matter.

At first glance, this is what you see. No mirrors, no magic -- tiny balls of matter acting more like waves in water, "sentient" electrons (although as we will see, that's a bunch of BS), and objects that are apparently two places at once.

In fact, it can be said that the easiest way to fully grasp what quantum physics truly is is to see this experiment. It's often one's first glimpse into the world of Quanta...and often not the last.

There's a famous video from the movie "What the Bleep do we Know?" that's been circulating the internet. If you watch it, I don't have to go through the process of explaining it. It actually does a pretty good job! I'd recommend anyone to watch it, even if they know nothing about quantum physics.



Anyway, this video can explain it better than I can ever do it without pictures. So until I get around to making pictures, please watch it before you continue.

What actually happens? Why does matter behave like a wave? That question deserves an entire post for itself.

Then video tries something that I think is completely absurd. It puts a little eyeball next to the slit and goes "Okay, which one does it go to? We'll watch with the eyeball." Then they fire another electron...and the result is no longer an interference pattern, but two bands, again.

Woah, did the electron know it was being watched, and decided to act like a particle instead of a wave?

While there are obvious psychedelic properties to that theory, it is unfortunately total sensationalism. The video is just hyping things up.

How do they actually observe the electron? Basically, they do the same thing that we do with our eyes. They bounce things (light light rays/photons) off of the electron and observe how the things bounce back. But Electrons are so small that shining light on it will affect its movement. That is, the strength of the light will actually push the electron, just like a wave of water pushes a bouy.

So the electron doesn't change by "just observing", as if by magic. The electron is changed by the way that we observe, as a side-effect.

This is the basicness of the Heisenberg Uncertainty Principle...which warrants a whole post of its own.

A quick summary - When you fire tiny bits of matter through two slits, it behaves like a wave instead of like matter. Why? It's complicated and I'll demonstrate it in simple terms later. So which slit does it actually go through? When they try to observe exactly which one, the electron appears to "decide to become matter again because it knows it is being watched". This isn't exactly true, but it sounds cool. Freaky. Sentient electrons, particles acting like waves...this isn't the last of the Double Slit experiment for this blog. This is just a basic overview.

Hm...well, this article isn't as great as some of my others. You probably have alot of questions about the video. Please leave them in the comments,a nd I'd be glad to answer. Or if you're just passing by, I'd love to see hear your opinions.