And in central London? Why not feed your brain by going to a free scientific lecture. Two excellent opportunities present themselves today. At Gresham College (1pm, Staple Inn Hall, Holborn) Professor Ian Morison provides an overview of the search for other solar systems. It's only around 15 years since the discovery of the first extrasolar planet, and we now know of around 200, some with Earth-like properties. Prof Morison will speculate on the chances we may one day detect signs of life on one of these worlds. Meanwhile, the UCL lunchtime lecture (1.15, Darwin Lecture Theatre) concerns William Jones, the man who first used the familiar Greek symbol to denote pi. Jones' life, at the centre of an early 18th Century network of mathematicians, philosophers and astronomers, is discussed by UCL's Patricia Rothman. Both events are free and there's no need to book.