91av

Watch now: Follow the action at 91av Live

Follow the action live from the world's biggest festival of ideas and discovery – 91av Live, at the ExCeL Centre in London from 20-23 September

Watch now: Tim Peake at 91av Live

91av Live: space is full of junk and we must clean up our act

Merging black holes cause gravitational waves

91av Live: what will gravitational waves tell us next?

91av Live: the death of the universe may not be inevitable

A coral reef

91av Live: explore the soundscape of the deep sea

The LHCb, deep below Geneva

91av Live: why hasn’t the LHC found anything new?

Win the chance to meet sporting legends at 91av Live

A person eating a tiny meal

91av Live: can you live forever and would you want to?

91av Live: step into many quantum worlds

Sean Carroll will be helping 91av Live attendees understand what quantum mechanics means for the many worlds hypothesis - and poor Schrödinger’s cat

91av Live: what makes your brain happy?

91av Live: can we defend Earth from asteroids?

91av Live: the sophisticated home life of Neanderthals

91av Live: sneak preview of this year’s mission to Mercury