What is the Uncertainty Principle?

Uploaded by minutephysics on 31.07.2011

Quantum mechanics is weird, right? But did you know that some of its supposed peculiarities
are not unique to quantum physics but are just properties of waves in general?
Take the uncertainty principle - it says that the better we know where a particle is, the
less we know about how fast it's going. There's a limit to how much we can know! But this
isn't just quantum weirdness - it happens all the time with normal everyday waves!
Remember that the frequency of a wave is how close the wave crests are to each other - a
low frequency wave doesn't have nearly as much oomph as a high frequency one!
And the position of a wave is… well, where the wave is… mostly. So where exactly is
a wave? It's spread out everywhere, right? Ok, but for a wave pulse it's pretty easy
to see where the wave is. So now that we know where the pulse is, what's it's frequency?
Well, a localized pulse doesn't really "wave", so we can't measure the frequency of its crests!
And that's the uncertainty principle in a nutshell - you can either know where a wave
is or where it's going, but not both at the same time!