20 years ago, two astronomers made a remarkable discovery, one which would change the way we view the universe for ever. A planet outside our solar system, orbiting a distant star - an exoplanet. Since then, we have found worlds where it rains diamonds, ones that boil at 3,000 degrees centigrade and even a world with four suns in its sky. But the big question is - will we ever find another Earth? As we close in on the discovery of the 2,000th planet outside our solar system, or exoplanet, we investigates the techniques that are revealing so much about these alien worlds. The documentary asks if we are really any closer to finding another world like our own - a second Earth.

Visit the planet most like Earth. There is a discussion of what life on Mars would be like and about the life forms that could've evolved there

The first second of the Universe, the creation of everything when space, time, matter and energy burst into existence. It is the most important second in history, which seals the Universe's fate and defines everything that comes after - including us.

Where did everything in our universe come from? How did it all begin? For nearly a hundred years, we thought we had the answer: a big bang some 14 billion years ago. But now some scientists believe that was not really the beginning; our universe may have had a life before this violent moment of creation. Take the ultimate trip into the unknown, to explore a dizzying world of cosmic bounces, rips and multiple universes, and finds out what happened before the big bang. Horizon takes the ultimate trip into the unknown, to explore a dizzying world of cosmic bounces, rips and multiple universes, and finds out what happened before the big bang.

On a trip to the fortified Moroccan village of Ait-Ben-Haddou in the Atlas Mountains, Professor Brian Cox reveals how by watching the stars' motion across the night sky, it is quite natural for man to think he is at the centre of everything. That view was held for many ages, but innate human curiosity has eventually led to an understanding of mankind's true place in space and time, and an appreciation that Earth is not a focal point but a mere particle of rock in a possibly infinite expanse of space, 13.8 billion years from the beginning of the universe.

Learn about what the moon is made and its formation; how it played a role in the evolution of life on Earth; and the future plans of NASA to establish a permanent base on the surface. Know more about moons on other planets.