Liz Bonnin presents a Horizon special about a rare and beautiful event in our solar system, one that we should all be able to see for ourselves - the transit of Venus across the face of the sun. It will start just before midnight of the 5th of June, and won't happen again for more than a century. Liz is joined by Lucie Green and Helen Czerski to show why the transit is such a remarkable event - transforming our understanding of our own solar system as well as helping scientists hunt for alien life on distant planets, hundreds of light years away.

Is there any way to slow or even prevent the ravages of time? Veteran presenter Johnny Ball looks back over the 45 years that Horizon, and he, have been on air to find out what science has learned about how and why we grow old. Charting developments from macabre early claims of rejuvenation to the latest cutting-edge breakthroughs, Johnny discovers the sense of a personal mission that drives many scientists and asks whether we are really any closer to achieving the dream of immortality. (BBC FOUR)