If you have $19.99 and an interest in astrophysics, here's some good news. Errol Morris's documentary "A Brief History of Time," a profile of the brilliant scientist Stephen Hawking and his struggle with the degenerative disease that paralyzed him, is now available on iTunes. The film, named after Hawking's book, was critically acclaimed for its ability to break down some of his theories into layman's terms. However, it was not widely available until now. Super fans can also preorder the Criterion Collection Blu-ray edition on Amazon.