Monday, March 14, 2016

Review: Mysteries of Modern Physics - Time

I started auditing the Great Courses Physics series on Time by Sean Carroll on a whim. Carroll is a physics professor at Caltech, and a great lecturer even for those of us who had a liberal arts education. For one thing, the topic is a great motivator: understanding the mysteries behind Time and the Arrow of Time, it turns out drives you wanting a better understanding of philosophy, psychology, neurobiology, cosmology, ideal gas laws, the second law of thermodynamics, Newtonian mechanics, quantum mechanics, relativity, and touches on high energy physics and of course string theory.

What astonished me was that Carroll successfully did this using minimal mathematics: he didn't even get around to PV=nRT, but still managed to explain the combinatorial expansion that drives the scientific understanding of entropy and what it means. I think it was Richard Feynman who said that "If you can't teach it to a smart undergraduate, then you don't really understand it," and Carroll's understanding and explanation more than passes the bar.

The mystery behind time, it turns out, isn't that it exists, but that there's a directionality to it. Since physics equations don't actually manifest an arrow of time, we're left with trying to explain it, but Carroll points out that ultimately, the question isn't "why is entropy going to go up tomorrow?", but "why was the entropy lower yesterday, and even lower the day before that", and so forth all the way until the moment of the Big Bang.

Along the way, Carroll takes us through a grand tour of modern physics, touching from gas laws, Boltzman's equation, and quantum mechanics as well as modern cosmology. It's a lot of fun. If physics had been taught with as much energy, literacy, and fun at my high school, I might have been a more interested and motivated student of the subject. And yes, he'll also address questions like: "Why am I always late?", and "Does time really start flowing faster as you get older?"

So yes, watch the series, or forget the video and just listen to it as you drive/hike/run errands. If you've been exposed to the material before, it'll be a great refresher, but if not, I can assure you that the presentation is much lighter and less intimidating than say, Lisa Randall's book. Recommended!
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