Is there anyone out there? Astronomers have been pointing their radio telescopes at the skies for decades trying to pick up alien signals, so far without success. But now there's a new way of looking for aliens. Hitch a ride with Dr Graham Philips as he joins astronomers trawling through the galaxy looking for signs of extra-terrestrial intelligence.

Stephen Hawking, the world's most famous living scientist explores the greatest mysteries of the cosmos. In three landmark instalments he reveals the wonders of the universe as never seen before. Definitive, provocative, surprising, and beautiful, Into the Universe with Stephen Hawking is a fascinating look through the mind's eye of one of the finest brains on the planet. In 'Aliens' Hawking considers one of the most important mysteries facing humankind - the possibility of alien, intelligent life. He leads us on a journey rendered in eye-popping detail, from the moons of Jupiter to a galaxy maybe not so far, far away. We will meet possible aliens and wonder at their form, we will delve into the very principles of what it is to call something alive, and we will calculate the likelihood of 'contact' being made.

Brian Cox looks at our attempts to answer one of the most profound questions we can ask – are we alone in the universe? With scientists sending space probes to the furthest reaches of our solar system and beyond, the scientific search for alien life has begun. Inspired by a childhood love of science fiction, Brian still hopes to hear from ET. In this film, he explains why this search deserves to be taken seriously, and he explores the chances of it happening.

The hunt for aliens is on! After a distinguished career in cosmology Professor Martin Rees, the astronomer royal, has taken up the search for extra-terrestrials. Looking for aliens is no longer science fiction - it is a question that's engaging some of the greatest minds in science." As our knowledge of the universe has increased, we're getting closer to answers. Many scientists now think we live in galaxy with a billion Earth-like planets, many of which may be teeming with life. But what kind of life? Has anything evolved into beings we could communicate with? This film gets inside the minds of the scientists considering one of the most exciting and profound questions we can ask - are we alone in the universe? Professor Rees thinks we may have our idea of what an alien is like all wrong. If he's right, it's not organic extra-terrestrials we should look for, it's machines.

Odds are excellent that extraterrestrial life exists. So why haven’t we found aliens out in the galaxy? Are we looking in the wrong places? New research shows we should look closer to home, even inside our bodies. It turns out that a lot of our DNA is from a mysterious, nonhuman source. Theoretically, alien microbial life can make the journey to Earth from distant worlds, and scientists are finding some unearthly microbes in our upper atmosphere. Could it be from outer space? Could we be part alien? It’s even possible alien life is already here as digital life forms, hiding inside our technology.

Is mankind alone, or are there aliens out there, either waiting to be discovered, or on their way to find Earth? Professor Brian Cox spends this episode asking such questions, and what he discovers may raise a few eyebrows. He begins by exploring the human race's efforts to find neighbours in outer space, including the launch of two golden discs containing a greeting from Earth in the 1970s; they are still travelling and are now the most distant man-made objects from the planet. Brian also meets members of the Search for Extra-Terrestrial Intelligence, who have been monitoring radio signals for 50 years without success, before discussing the ingredients needed to make an intelligent civilisation with astrophysicist Dr Frank Drake.