Built on Facts

Archives for October, 2010

You’re taking your morning shower and a thought occurs to you. “In classical electrodynamics, an accelerating charge radiates. In general relativity, acceleration is equivalent to a gravitational field. Therefore a stationary charge should radiate simply by virtue of being in a gravitational field. What’s up with that?” You wonder about what the radiated power would…

Sunday Function

Here’s a straightforward function of two variables, x and y: Its domain is all real x and y, with the single exception of x = y = 0, which would make the denominator 0. But we have experience with functions such as sin(x)/x, where we can find the limiting value as x approaches 0 and…

Time-Reversal

Generally speaking, if you play a movie backwards everything that happens is still physically possible. If I throw you a baseball and you catch it, reversing the video is just the equally plausible situation of you throwing the baseball followed by my catching it. If entropy is changing in the video – e.g., breaking an…