25th August

On this day in 1664 Robert Hooke wrote to Robert Boyle about new experiments he was performing in the damaged steeple of Old St Pauls.  One involved a 180 foot long pendulum with a four pound weight that swung with a 12 second period.

On this day in 2009 Google released a Galileo telescope doodle.

The postage stamp of one of today's mathematicians at THIS LINK was issued in 1990.