Leading article: The not-so-brief history of Hawking

We are all living longer; but a 70th birthday is still a cause for celebration. Even more so, when the party is for one of the world's greatest physicists, a scientist who has dominated his field for nearly 40 years.

When that man is Professor Stephen Hawking – who was diagnosed with motor neurone disease at the age of 21 and given only two years to live – it is nothing short of inspirational.

Professor Hawking's intelligence, academic rigour and unswerving search for the origins of the universe are remarkable enough. He has both an unusually brilliant intellect and an unusual gift for communication, creating a whole genre of science writing with his best-selling A Brief History of Time. To have achieved so much with his mind while managing the decline of his body can only be wondered at.

Doctors point to any number of reasons for Professor Hawking's triumph over his gloomy prognosis, suggesting everything from chance, to genetics, to a misdiagnosis of his condition. Perhaps. But it is hard not to think that his evident force of character was not also a factor.

Like any new septuagenarian, Professor Hawking deserves congratulations on reaching a landmark birthday. But he has also earned our gratitude: for his contribution to the sum of human knowledge, and also for the encouraging example of a person who refused to give in.