Dr Tim Gregory is a nuclear chemist at the United Kingdom National Nuclear Laboratory at Sellafield, public speaker, broadcaster and author of Meteorite- How Stones from Outer Space Made our World. In 2017, he was a finalist in BBC2's Astronauts- Do You Have What it Takes and has also presented on BBC's The Sky at Night and Channel 4's Steph's Packed Lunch. He has a PhD from the University of Bristol and lives in the North of England. His website is www.tim-gregory.co.uk.