Calling all scientists! How do you explain the concept of time to an 11-year-old?
Rick Bates, of Penn State University, shares handy tips for how to care for your Christmas tree.
The film tells the stories of a soldier addicted to painkillers, and a doctor with no time for her patients.
Bacteria locked under Antarctic lake ice may shed light on life's limits, and the possibility of life on other worlds.
Two astronauts answer your questions and discuss the many curiosities of living in space.