The Meaning of Quantum Mechanics (and Physical Reality)

The quantum world is different from the world you intuitively (and intellectually) understand. Very, very different. We know that the quantum physics (QP) works, in the sense that it can explain and predict observable phenomena, and in that sense it is certainly a good description of the physical reality. We know how to -compute- things using its mathematical apparatus, but no one really understands it at the same intuitive level as, say, classical physics, or even relativity. Feynman himself said so, so it must be right ;)

To many people this is profoundly troubling. We map physical systems, the whole universe included, into mathematical descriptions,and that works within some degree of accuracy, and then a deeper theory does it better, and so on. But mathematics is not physics, and mathematical concepts are not the same as the physical objects they describe.

This matters, not only because we want to understand the world, but also because QP is inherently probabilistic, and implies both some profound limitations of what can be known (e.g., via the Heisenberg's uncertainty principle), and possibly even that the world (not just the theory) is inherently probabilistic.

The debate has been going on from the very start, with people like Einstein, Bohr, etc. deeply involved, and it is still going on. For a recent dustup, see, e.g., this blog and follow the links.

To learn more, start with the Wikipedia article and follow the links therein. Also, look for the EPR pradox, Bell's theorem, and Bell test experiments.

Then let's talk about it.

How Science Works

You all probably have a pretty good intuitive idea how science works, but it would be good to articulate this more clearly. For example, why is astronomy better than astrology? Why is medicine better than a "healing witchcraft"? Why is science so successful? You get the idea. How would you explain it to your grandma? How would you argue with a creationist who is saying that "science is just another religion?"

Well, there have been some good philosophers of science who thought a lot about this. (Stay with me, this is actually interesting.) Research on the web on your own: Karl Popper, Thomas Kuhn; Gödel's theorem. Think about this: what are the roles and the limitations of logic (or deduction) and induction? Given the relativity and the quantum physics, is the Newtonian physics still valid or true in some sense?

Or to put it in another way: why are you here at Caltech, rather than, say, at Maharishi Institute?

Keep thinking.

Class time

Please don't forget, the class time is now at 1 pm, Tue & Fri

The Fermi Paradox

Google it and read about it.

Pick your favorite explanation or two - or better yet, come up with your own.

Then we'll analyze them in the class.

FS3 assignment: How is computing changing the way you think?

And now for something completely different:

Watch my TEDx video.

Now think: how is the information and computing technology changing the way you think and learn? What do you take for granted? What do you wish you could do? Where do you think this is going? And what questions would you ask on this theme?

Let's start here and continue the discussion in class.

An interesting video that dealt with lots of what we've talked about.

I thought this was fun.

http://apod.nasa.gov/apod/ap020702.html