Entries from October 1, 2008 - October 31, 2008
A Mathematician's Pick-up Line

The winner of the MIT Nerdy Pick-up Line Contest:
Hey, baby, I don’t have a nerdy pickup line, but I can prove that one exists.
Via Quomodocumque.
The Infinite as an Approximation to the Very Large

Many years ago, when I was still at school, I remember one maths lesson in which a pupil had a heated argument with the teacher over the use of infinity in the calculus. The pupil refused to accept that this was valid because infinite sets "did not exist", and the teacher didn't seem to to know how to answer this and instead got rather angry. Well, after reading this post by Alexandre Borovik at A Dialogue on Infinity, I now know what the teacher should have said: that we use the infinite as an approximation to the very large. Hence it does not matter whether infinite sets exist or not. As Borovik explains, calculating with infinities is usually much easier than calculating with the very large.
Oak Gall

A gall on the underside of an oak leaf, probably the result of infestation by the smooth spangle gall wasp (Neuroterus albipes). Each gall contains a developing wasp. In the autumn they fall to the ground with the leaves and stay there until the spring. Then the wasp emerges to mate and the females lay their eggs in new oak buds.