Particle physicist Prof. Brian Cox asks, 'What time is it?' It's a simple question and it sounds like it has a simple answer. But do we really know what it is that we're asking? Brian visits the ancient Mayan pyramids in Mexico where the Maya built temples to time. He finds out that a day is never 24 hours and meets Earth's very own Director of Time. He journeys to the beginning of time, and goes beyond within the realms of string theory, and explores the very limit of time. He discovers that we not only travel through time at the speed of light, but the experience we feel as the passing of time could be an illusion.

The drug policies have remained unchanged over the last 40 years so should they be reformed in the light of new research? Recent research has analysed the link between the harmful effects of drugs relative to their current classification by law with some startling conclusions. Perhaps most startling of all is that alcohol, solvents and tobacco (all unclassified drugs) are rated more dangerous than ecstasy, 4-MTA and LSD (all class A drugs).

Professor Brian Cox visits Geneva to take a look around Cern's Large Hadron Collider before this vast, 27km long machine is sealed-off and the experiment to create the simulation of a black hole begins. When it's up and running, it will be capable of creating the conditions that existed just a billionth of a second after the Big Bang. Brian joins the scientists who hope that the LHC will change our understanding of the early universe and solve some of its mysteries.

We are in the grip of an allergy epidemic. 50 years ago one in 30 were affected, but in Britain today it is closer to one in three. Why this should be is one of modern medicine's greatest puzzles. In search of answers, Horizon travels round the globe, from the remotest inhabited island to the polluted centres of California and the UK. We meet sufferers and the scientists who have dedicated their lives trying to answer the mystery of why we are becoming allergic to our world.

Scientists have no idea what it is, but Dark Matter and Dark Energy make up 96% of the Universe. Dark Matter is everywhere. It passes through everything we know on earth at billions of particles every second, yet no one has ever gotten a direct detection of this mysterious dark substance. An even more bewildering force is Dark Energy, which is rapidly pushing apart our Universe. Discovered only ten years ago, scientists are struggling to comprehend its unusual characteristics and answer the ultimate question; what is the fate of our Universe? Using cutting-edge computer graphics watch as the universe is brought down to earth.

Does life exist on other planets? Astrobiology is a visionary new science that searches for life in space by combining the disciplines of astronomy, biology and geology. How did life evolve on Earth? What will life look like on other planets? These and other pertinent questions will be answered by a diverse group of scientists. Viewers will visit the Pilbara region of West Australia where the oldest evidence of life on Earth has been discovered. Travel to the moons of Jupiter and Saturn to test a theory that life could exist in the clouds of Venus. Finally, watch as experiments are done to see if life exists on exoplanets, earth-like planets beyond our solar system.