Many argue that flying saucers and other extra-terrestrial space ships continuously visit the earth. If that were true, what kinds of technologies would such alien spacecraft require? And do eyewitness reports of UFO sightings jibe with modern theories of how interstellar travel might be possible? Authors, astronomers and theoretical physicists weigh in with the blueprints for inertia-canceling devices, nuclear-powered craft, antimatter propulsion systems and even warp drives. Based on Einstein's theories and countless scientific studies, we'll find out how these visitors might bridge the vast distances between the stars. And if they could survive such hazardous journeys, are they flesh and blood or intelligent machines?

The second part, Nothing, explores science at the very limits of human perception, where we now understand the deepest mysteries of the universe lie. Professor Jim Al-Khalili sets out to answer one very simple question - what is nothing? His journey ends with perhaps the most profound insight about reality that humanity has ever made. Everything came from nothing. The quantum world of the super small shaped the vast universe we inhabit today, and Jim can prove it.

A look at the probes which explored our Solar System, laying the groundwork for a future spacecraft to search for life on a second Earth. That space craft must communicate, it must navigate, it must have power, it must have propulsion. We will have to give it all the intelligence necessary to make its own decisions. In 'The Explorers' the spacecraft Artemis initiates launch sequence and begins its 4.7 light year journey to Minerva B - an Earth-like exoplanet.