Astronaut Tim Peake: We're not alone in the universe

British astronaut Tim Peake is certain that alien life must exist among the billions of galaxies in the universe.

Speaking to De-Graft, Major Tim explained the science that has inspired him to write a fictional book about extra-terrestrials visiting Earth.

In 2016 he spent six months in orbit around the planet as part of the crew aboard the International Space Station (ISS).