On the 50th anniversary of the invention of the laser, Jem Stansfield explains how they work and builds himself a homemade one. Dallas Campbell looks at the rise of Citizen Science and takes part in the research projects that need people power. And Dr Yan recreates a demonstration to calculate the speed of light. The programme is co-produced with the Open University. For more ways to put science to the test, go to www.bbc.co.uk/bang and follow the links to The Open University. Show less