Pigments and paint evolved over time, and these changes are one focus of the 'Making Colour' exhibition at the National Gallery. Different paints fade and degrade in different ways; often the patina of age is what appeals when looking at art, so how do you decide which hue to use when restoring paintings? Another intriguing issue is how you light a painting. The National Gallery is moving away from tungsten lighting, to more modern, tuneable LED lights. How does this affect the way visitors view the art? An interactive experiment is helping them to unpick light perception.

Hadrian's Wall

A listener asks how did the Romans knew where to build the great defensive wall. We get the answer from Professor Ian Haynes, an archaeologist at Newcastle University, who reveals that the Romans were obsessed with measuring.

Cassini mission to Saturn

Cassini-Huygens is an unmanned spacecraft sent to the planet Saturn. The NASA-ESA-ASI robotic spacecraft has been orbiting and studying the planet and its many natural satellites for 10 years. Adam talks to the mission's leader of the imaging science team, Carolyn Porco, about how successful it's been. And he offers her a blank cheque to choose her next mission.

Producer: Fiona Roberts.