# There is Certainty in Uncertainty: Brian Schmidt at TEDxCanberra (Full Transcript)

Brian Schmidt – TRANSCRIPT:

Last December, me and my fellow Nobel Laureates were asked by a journalist if there was one thing that we could teach the world, what would it be? And to my surprise, two economists, two biologists, a chemist, and three physicists gave the same answer. And that answer was about uncertainty. So I’m going to talk to you today about uncertainty.

To understand anything, you must understand its uncertainty. Uncertainty is at the heart of the fabric of the Universe. I’m going to illustrate this with a laser. A laser puts out a small, but not infinitesimally small point of light. You might think that if I go through and I try to make that point of light smaller by, for example, bringing two jars of a slit together, that I could make that point as small as I want. I just want to make those slits closer and closer.

So let’s see what happens when I do this for real. My friends at Mount Stromlo gave a call and made up a nice little invent, a little here. By essentially adjusting the laser, the slit – we’re going to go through and we are going to see what happens when I close the jaws of the slit. The more I close it, instead of getting smaller, the laser gets spread out. So it works exactly the opposite of what I was expecting. And that’s due to something known as Heisenberg’s Uncertainty Principle.

Heisenberg’s Uncertainty Principle states that you can’t know exactly where something is and know its momentum at the same time. Light’s momentum is really its direction. So, as I bring those slits closer and closer together, I actually constrain where the light is. But the quantum world says you can’t do that. The light then has an uncertain direction.

So instead of being a smaller point, the light has a randomness put out to it, which is that pattern that we saw. Many things in life you can think of as a series of little decisions. For example, if I start at a point, and I can go left or right, well, I do it, let’s say, 50% of the time I can go left or right.