Talks

A discussion of the surprising results of the single slit and double slit experiments.
Learning Outcomes:
• How the single slit experiment suggests that chance is at the heart of nature, and that the behaviour of particles might need to be described by something different from Newton’s laws.
• How the double slit experiment suggests that understanding the behaviour of particles will require a radically new way of thinking about how nature works at a fundamental level.
• A video of an actual double slit experiment done with a beam of electrons (in case you don’t believe it).

Making the connection between particle probability patterns and wave intensity patterns, leading to the famous de Broglie relationship.
Learning Outcomes:
• Repeating the single slit experiment with waves instead of particles. Seeing that the particle probability pattern is the same as the wave intensity pattern.
• Same as above, but for the double slit experiment.
• Putting it all together to derive the de Broglie relationship between the momentum of a particle and the wavelength of a corresponding wave.

An introduction to spacetime diagrams – a first step towards understanding Einstein’s special theory of relativity.
Learning Outcomes:
• Newton’s absolute space and time vs. Einstein’s relative space and time.
• Bodies move through both space and time – spacetime diagram “worldlines” show both motions.
• Drawing worldlines for bodies in various states of motion: at rest, moving with various constant velocities, and accelerating.

Continuation of a thought experiment from SR-2 leading up to a derivation of the familiar Doppler shift for sound in air. Learning Outcomes: The real meaning of Newton’s assumption of absolute (or universal) time; Understanding the Doppler shift for sound in terms of a spacetime diagram; How to derive the (non-relativistic) Doppler shift formula for sound as a consequence of assuming Newton’s universal time.

Drawing spacetime diagrams of simple thought experiments involving sound in air as a warm up exercise for light in vacuum.
Learning Outcomes:
• Deepening our understanding of how to draw and interpret spacetime diagrams.
• Measuring space and time in the same units – a first step towards unifying space and time into “spacetime.”
• Why, for an observer at rest with respect to still air, the speed of sound is independent of the motion of the source of sound.

An experimental introduction to electron spin.
Learning Outcomes:
• To develop the classical understanding of a spinning bar magnet, and how we would expect it to be affected on passing through a Stern-Gerlach apparatus.
• How actual experiments with silver atoms (containing an electron that acts like a tiny spinning bar magnet) give results that are completely different from the above classical expectations.
• How a variety of different experiments lead to two main conclusions: (1) the spin of an electron is quantized (“spin up” or “spin down”), and (2) probability plays a fundamental role in the spin direction selected by the Stern-Gerlach apparatus.

In the first part of the talk, a brief introduction to general relativity and quantum theory is given. Their independent successes are discussed, as well as the desire and difficulty in merging them, to obtain a unique language to describe the universe. Then I focus on Loop quantum gravity, a particular approach towards this objective, in which a discrete microscopic structure of spacetime is envisaged.