Week 3: Quantum physics
Introduction
This week, you will learn about some of the more mysterious physical discoveries of the 20th century, as you enter the world of quantum physics. You will learn how quantum theory helps explain experimental observations that are not predicted by classical physics, such as how light behaves simultaneously as both a particle and a wave. You will see how quantum theory is fundamentally probabilistic in nature and how this explains radioactive decay. And you’ll find out how a famous thought experiment involving cats and deadly poison can help us understand quantum superposition.
Here’s Marcus to introduce this week’s topic.
Download this video clip.Video player: Video 1
Transcript: Video 1 Introduction
MARCUS DU SAUTOY
I’m holding a pot of uranium. When will it spit out its next bit of radiation? Quantum physics posits that we can never know. Our third week reveals that at the small scale, unknowability might be an integral part of the way we must do science. At its heart is the tension between whether things like electrons or photons are best described as particles or waves.
It turns out that quantum physics puts inbuilt limitations on what we can know about the behaviour of the very small particles we met last week. Embodied in something called ‘Heisenberg’s Uncertainty Principle’, current theories of physics say that there’s no mechanism that will tell us when a pot of uranium is going to radiate, or where we’ll find an electron when you next look for it. Instead there seems to be a quantum dice deciding the future of the universe, whose dynamics will remain always hidden
Video 1 Introduction
Interactive feature not available in single page view (see it in standard view).
By the end of this week, you should be able to:
- understand the basic notion of wave motion
- understand the notion of wave-particle duality
- appreciate the consequences of Heisenberg’s uncertainty principle
- demonstrate a general level knowledge of quantum theory.