Why is the troy ounce used for measuring gold?

Europe has a new entry/exit system based on biometric data. But what exactly is the science behind biometric data, how can we ensure it’s used responsibly, and can it be cracked?

We also look at how some animals use dung as biometric data with Dr. Adrian Shrader, how your walk can be used to ID you from Professor Mark Nixon, and why gold has its own special measurement. All that plus many more Unexpected Elements.

Presenter: Marnie Chesterton Producers: Margaret Sessa-Hawkins with Lucy Davies and Robbie Wojciechowski