S4, E2: Hunt for Alien Earths: NOVA scienceNOW visits astronomers on the brink of finding another Earth in our galaxy with a new planet-hunting machine that will soon be operational: the Kepler telescope. This and other ingenious new techniques could finally answer the age-old question: Are we alone? / Art Authentication: Try once more to spot the fake in NOVA scienceNOW's classic challenge to three different computer teams: find the meticulously forged van Gogh in a group that includes five genuine works by the artist. Can computers really be used to identify which works are really his? / Profile-Maydianne Andrade: Some arachnophobes might see Maydianne Andrade's career as a horror film (her favorite kind), but Andrade can't imagine how she would spend her days and nights if not studying the cannibalistic behavior of the Australian redback spider. And she believes the redback can teach us about how sexual selection, social interactions, and ecological conditions interact to affect the evolution of mating systems. / Autism Genes: Rudy Tanzi, a pioneer in discovering genes for Alzheimer's disease, is turning his attention to autism. Using gene chips that can scan up to a million genetic markers across the entire human genome, Tanzi and others are on the hunt for the genetic key to a heartbreaking disease that seems to come out of nowhere, and yet affects millions of children and their families.