# Physics Beyond the Edge (audio)

An interesting follow up to what I remember from high school & first year physics. My guess is that the subject of the class is too basic for those with a degree in physics, but this is something I should ask Alex! I really liked how all of the topics flowed into each other. I found this to be somewhat surprising given Einstein's failed struggle to find some unified theory of everything. This is probably credit to the lecturer, who, in addition to being a great instructor, also coined the term qubit.

The structure of the class follows Arthur C. Clark's second law:

The only way of discovering the limits of the possible is to venture a little way past them into the impossible.

The lecturer, Benjamin Schumacher, is quite engaging, and starts by breaking impossibility down in terms of logical, physical and statistical terms. He then goes into thermodynamics, framing the first and second laws in terms of perpetual motion machines.

I enjoyed the various Demons that show up in this lecture. Maxwell's demon can control a flap between two chambers to make sure that eventually all of the molecules end up in one of the chambers (thus decreasing entropy). Laplace's demon is able to, from knowing the current state of the world, predict the future perfectly. Both of these thought experiments are forays into the impossible that, when disproven, set the stage for the third law of thermodynamics and chaos / quantum mechanics.

The section on space-time was fascinating, and served as a good introduction to space-time diagrams (aka Minkowski diagrams), which I really liked. Although, one thing that was missing is the visual element. Although very lightweight in mathematical treatment, there were clearly some materials that supplemented the lectures, which would have made learning easier. The whole discussion on faster-than-light travel, time travel, and quantum cloning was tied together nicely through the lens of the impossible. By the way, space-time diagrams seem to be the reason for this observable universe thing.

Which brings us to Quantum. I've been interested in being interested in the topic for a while because it's so unintuitive and strange. Schumacher's overview is good, but I'm obviously still very confused. He outlines basics of Quantum Mechanics:

- Wave-particle duality: light has both wave and particle like behaviors.
- Uncertainty: position and momentum of a quantum particle cannot both be known.
- Tunneling: because of this uncertainty, quantum particles can tunnel through what in newtonian mechanics are inpenetrable barriers.

There seem to be some fundamental truths about symmetry as pertaining to conservation laws. Noether's theorem seems remarkably deep but way over my head, which states that every symmetry in physics has some associated conservation law.

I was also somewhat lost in the information theory asides (the lecturer's specialty is information theory). That information theory is a branch of physics at all is mysterious to me. Probably worth learning more about, though, given my information-related profession.