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.

We love talking about the weather - is it too hot or too cold, too wet or too windy? It's a national obsession. Now scientists have started looking to the heavens and wondering what the weather might be like on other planets. Today, we are witnessing the birth of extra-terrestrial meteorology, as technology is allowing astronomers to study other planets like never before. They began with our solar system, sending spacecraft to explore its furthest reaches, and now the latest telescopes are enabling astronomers to study planets beyond our solar system.

Our exploration of the universe is revealing alien worlds with weather stranger than anyone could ever have imagined - we've discovered gigantic storm systems that can encircle entire planets, supersonic winds, extreme temperatures and bizarre forms of rain. On some planets, the temperatures are so hot that the clouds and rain are believed to be made of liquid lava droplets, and on other planets it is thought to rain precious stones like diamonds and rubies.

We thought we had extreme weather on Earth, but it turns out that it is nothing compared to what's out there. The search for the weirdest weather in the universe is only just beginning.