Regular readers will have guessed from my blog and Twitter feed that I really enjoyed the 40th anniversary celebrations surrounding Apollo 11 last month. Whilst delving into the multifarious space websites and blog posts, I came across a description of the Apollo 10 capsule that is currently housed at the Science Museum in London.

The Science Museum website states that "North American Aviation, the contractors for the capsule, estimated that some 20 percent of the 500 million person hours in the project were contributed as free overtime by staff."

This astounding fact reminded me of Google, which encourages its engineers to spend 20 percent of their paid time working on their own projects. Among the Google products and initiatives that began life as 20 percent projects are Gmail, Google News and the internet-equipped biodiesel shuttle buses that take employees to the Googleplex from San Francisco.

It seems to me that there's something magic about 20 percent. What would happen if we spent 20 percent of our working hours pursuing projects that we are passionate about? Or gave 20 percent of our services away for free to good causes? Or spent 20 percent of our spare time pursuing an otherwise neglected idea? 20 percent is not so much: it could be one evening a week and one weekend a month.