Jim Al-Khalili investigates the amazing science of gravity, recreating groundbreaking experiments, including the moment when Galileo first worked out how to measure it. He investigates gravity waves, finds out from astronauts what it's like to live without gravity, sets out to find where in Britain gravity is weakest and so where we weigh the least, and helps design a smartphone app that volunteers use to demonstrate how gravity affects time and makes us age at slightly different rates.
It's called the speed limit of the universe. Einstein blew all of our minds when he worked out the Theory of Relativity, and showed that space and time were malleable substances. He also theorized that we as humans can never travel faster than the speed of light, which leaves the stars and other galaxies almost impossibly out of our reach. But the dreams of Star Wars and Star Trek are not dead. In fact, there could be ways to travel faster than the speed of light - and some of them are already being tested in labs around the world.
Meet Nikola Tesla, the genius engineer and tireless inventor whose technology revolutionized the electrical age of the 20th century. Although eclipsed in fame by Edison and Marconi, it was Tesla's vision that paved the way for today's wireless world. His fertile but undisciplined imagination was the source of his genius but also his downfall, as the image of Tesla as a "mad scientist" came to overshadow his reputation as a brilliant innovator.