Dark matter is a mysterious type of matter that no one can see but that makes up about 26% of the content of the Universe. What is it? How do we know it is there? What are experiments at CERN doing to find out about it?
This week's hangout features physicists from LHC, AMS and CAST experiments at CERN to talk about what they are doing to explore the "dark side" of the Universe. Watch the hangout live on YouTube at 5pm CEST.