Dark Matter, Mice, Crowd Wisdom - S3.E1

Dark Matter - Turns out most of the universe is held together by a mysterious, invisible substance.

Of Mice and Memory - Mice placed in enriched environments can recover lost memories, giving hope to those who study Alzheimer's.

Profile: Hany Farid - This self-proclaimed "accidental scientist" is a digital detective inventing new ways to tell if photos have been faked.

Wisdom of the Crowds - Ask enough people to estimate something, and their combined guesses will get you surprisingly close to the right answer.