Astronomy Picture of the Day

Today's Astronomy Picture of the Day is striking. However, should I be concerned that I spotted which of the two pictures was Earth without a moment of hesitation? It does make the point quite nicely that Earth is a varied planet and that it is unreasonable to categorise any other planet from one or two shots (Ice Planet Hoth or Forest Moon of Endor, anyone?).

Stargate SG1 once showed this very well by having Carter and O'Neill wind up in Antarctica, and Carter reports back 'Colonel? It's an ice planet. That's all there is as far as the eye can see. No chance.'. (Season 9 of SG1 is now filming).

The Calendar

At the moment I am reading The Calendar by David Ewing Duncan. This is a nice little book which covers the history of the calendar. Its brief takes us from carving notches on bones to count the days between full moons to trying to establish a true length for the year (and prevent the calendar drifting compared to the seasons).

The book encompasses science (astronomical measures), maths (being able to specify fractions of a day), religion (the date of easter) and history. It seamlessly takes us on a chronological journey through the ages.

I like cross-curricular books, my favourite books tend to be those which span subjects, as there is something familiar to take us on into the unknown. Also one can spot how one discipline feeds off another, other books of this ilk include Dava Sobel's "Longitude" and William Poundstone's "The Prisoner's Dilemma".

The closest I can find for users is a similar book by the same author. "Longitude" and "The Prisoner's Dilemma" are available in the US.