The last episode in the series examines how humans perceive and experience time, investigating the internal body clock which tells people when to eat, drink, sleep and relax. The importance of accurately measuring time is explored in relation to human evolution, and there's a debate about whether mankind will ever be able to travel between past, present and future.
In this episode of NOVA scienceNOW, journey back in time to the birth of our solar system to examine whether the key to our planet's existence might have been the explosive shockwave of an ancient supernova. Meet a chemist who has yielded a new kind of "recipe" for natural processes to assemble and create the building blocks of life. And see how the head louse, a creepy critter that's been sucking our blood for millions of years, is offering clues about our evolution. Finally, meet neuroscientist André Fenton, who is looking into erasing painful memories with an injection.
Comedian Jimmy Carr takes over Horizon for this one-off special programme, produced as part of BBC2's sitcom season. Jimmy turns venerable documentary strand Horizon into a chat show, with eminent laughter scientists as guests and a studio audience to use as guinea pigs. Jimmy and his guests try to get to the bottom of what laughter is, why we enjoy it so much and what, if anything, it has to do with comedy. Between them, and with the help of contributions from other scientists on film, Jimmy and guests discover that laughter is much older than our species, and may well have contributed to making us human. With professors Sophie Scott, Robin Dunbar and Peter McGraw.