Seeing the Light - S2.E4

Reflect on the speed of light and the colour of space. Why Father Christmas is never seen. See what your screen looks like in black and white, red, blue and green. A solar plane that could reach new heights and how you could ride on a sun-beam for free... So if you don't want to be in the dark switch on to see the light - from infra red to ultra violet. Meanwhile - Think of a Number - it's all relative! If 2 is company and 3 is a crowd, what are 4 and 5?