# Built on Facts

# Archives for **August, 2008**

We can’t graph here, this is bat country! Complex bat country. …well ok, let’s stop and take a look anyway. But no graph. You’ve seen this jewel of mathematics. It’s Euler’s identity. It comes from the more general expression right below this paragraph, which is today’s Sunday Function. You might wonder where this expression comes…

First, a Public Service Announcement: As a decade-long former south Louisiana resident who was in Baton Rouge for Katrina, I have some advice. If you’re in Louisiana anywhere south of about Alexandria, now’s the time to start packing. You might be ok sticking around till Saturday night or possibly Sunday morning to see if it…

I really loathe politics, and have mostly tried to avoid writing about it. But finally something interesting has happened, and it’s worth a brief comment. In physics we like to talk about symmetry. Conservation laws and symmetry are intimately related, and you can learn a lot about one by studying the other. One of the…

Top 10 lists are silly. But they’re fun, which is why there’s so many of them. In a week or two, I’m going to start a brief biographical series with a little bit of information on the lives and works of the great physicists. The top 3 are obvious (Well, to me anyway). The top…

Nine dayes they fell; confounded Chaos roard,And felt tenfold confusion in thir fallThrough his wilde Anarchie, so huge a routIncumberd him with ruin: Hell at lastYawning receavd them whole, and on them clos’d,Hell thir fit habitation fraught with fireUnquenchable, the house of woe and paine.– Milton, Paradise Lost The biblical description of Satan’s fall is…

Physics professors have this annoying habit. They’ll present a problem to be solved, figure out how to describe it in mathematical terms, and declare that the physics is done and the rest is just math. Well yeah, but that’s kind of like drawing a blueprint for a house and then declaring to your trainee workers…

We all know what the formula for kinetic energy is. Take the mass, multiply by the velocity squared, divide by two. In 1905, Einstein raised his hand and said that we’re not quite right. In fact the actual expression for kinetic energy is where c is the speed of light and That doesn’t look much…

This is one of those times when being a non-anonymous blogger is a little inconvenient. Nonetheless, I think I can make things a little vague and change a few names and I’ll be ok. As I mentioned a couple of days ago, I’m taking two classes. I thought nothing of it when I signed up…

If you’re a regular reader of this site, you might remember a post about this fascinating specimen from the collection of unusual functions. I’m only showing it on the interval [-1,1] for reasons that will become apparent, but outside that region the growth tapers off rapidly and the function approaches 1 for large negative and…

Don’t think I’ve forgotten about the falling electron question from a while back. Short version: an accelerating charge radiates. So if you let an electron fall in a gravitational field, it should radiate. But a person (or detector) falling along beside it does not perceive the electron as accelerating and so the electron shouldn’t radiate…