Rachel Riley rides across a steel cable 60ft in the air on a bike like no other, while Romesh Ranganathan discovers how science is muscling in on the dating scene and conducts a special experiment of his own. Plus, Ben Miller travels to Germany to witness the groundbreaking moment when a new fusion reactor is turned on. Last in the series (but not until they've also tested the flammable properties of hydrogen).

• Romesh Ranganathan
• Kevin Fong
• Rachel Riley