A transcription of physicist Stephen Hawking's audio message to Newsnight in which he explains why he is standing down from the prestigious academic title of Lucasian Professor of Mathematics at Cambridge University. Previous holders of the position include Sir Isaac Newton and Charles Babbage.

I will carry on with my scientific work, and my efforts to explain it to other people. I'm currently working on the quantum creation of the universe, and the rapid inflation in size that followed.

Despite having been unfortunate enough to get motor neurone disease at the age of 21, I have had a full and satisfying life. I have three wonderful children, and have been able to add to our understanding of the universe.

It has been a glorious time to be alive, and doing research in theoretical physics. Our picture of the universe, has changed a great deal in the last 40 years, and I'm happy if I have made a small contribution.

I want to share my excitement and enthusiasm. There's nothing like the Eureka moment, of discovering something that no-one knew before. I won't compare it to sex, but it lasts longer.