the shadowy green valley
Some interesting math
Road to Reality answers . Roger Penrose wrote a wonderful book which (tries) to take you from high school math to twistor theory, with exercises along the way. But he didn't provide the answers. So here are some.
my amazing adventures in biological self-help
"Fracking" - unconventional shale gas drilling - has run into a lot of opposition here in New York State. Here's the larger picture, and how and why fracking is being demonized.
Why are so many people so fat?
The unridable bicycle. David Jones made a lot of URB's based on common ideas about what makes a bicycle stable. But they turned out to be ridable. Finally he came up with his own theory and really made an unridable bicycle.