It is one of the most baffling questions that scientists can ask: how big is the universe that we live in?

Horizon plunges down the biggest rabbit-hole in history in search of the smallest thing in the universe.

Dark flow is the latest in a long line of phenomena that have threatened to re-write the textbooks. Does it herald a new era of understanding, or does it simply mean that everything we know about the universe is wrong?

'To send a spacecraft there is a little bit insane,' says Scott Bolton when talking about Jupiter, the largest planet in the solar system. But that is exactly what he has done, because Scott is head of Juno, the Nasa mission designed to peer through Jupiter's swirling clouds and reveal the wonders within.

Horizon goes behind the scenes at Nasa to discover how it is preparing for its most ambitious and daring mission: to land men - and possibly women - on the surface of Mars.

With the dream of sending humans to Mars closer than ever before, Horizon asks the world's leading experts on Mars where they would go and what they would need to survive.

The intriguing possibility of life on Mars has fuelled man's quest to visit the Red Planet. Drawing on 45 years of Horizon archive, space expert Dr Kevin Fong presents a documentary on Earth's near neighbour.

The oceans define the earth. They are crucial to life and we used to think that they were unique to our blue planet. But we were wrong.

Around the world, a new generation of astronomers are hunting for the most mysterious objects in the universe. Young stars, black holes, even other forms of life.

Scientists are expecting a fit of violent activity on the sun which will propel billions of tonnes of superheated gas and pulses of energy towards our planet.

A gas cloud three times the size of our planet has strayed within the gravitational reach of our nearest supermassive black hole. And across the globe, telescopes are being trained on the heart of our Milky Way galaxy, some 27,000 light years from Earth, in the expectation of observing this unique cosmic spectacle.

This is the story of how our solar system will be transformed by the aging sun before coming to a spectacular end in about eight billion years. Astronomers can peer into the far future to predict how it will happen by analysing distant galaxies, stars and even planets in their final moments.

Horizon looks at dark energy - the mysterious force that is unexpectedly causing the universe's expansion to speed up.

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.

Presented by Professor Iain Stewart, this film explores what meteorites and asteroids are, where they come from, the danger they pose, and the role they have played in Earth's history.

On the 15th December, Tim Peake will launch into space to be Britain's first astronaut on board the International Space Station. For the past two years, Tim has been filming a video diary for Horizon showing the risks, pressures and rigorous training required to launch into space. Horizon also talks exclusively to his wife and two children as they prepare to wave him goodbye on his voyage to space.

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.

There is a strange and mysterious world that surrounds us, a world largely hidden from our senses. The quest to explain the true nature of reality is one of the great scientific detective stories.

Until very recently the whole idea of the multiverse was dismissed as fantasy. Horizon asks whether multiple universes exist and, if so, which one we are actually in.

Black holes are one of the most destructive forces in the universe, capable of tearing a planet apart and swallowing an entire star. Yet scientists now believe they could hold the key to answering the ultimate question - what was there before the Big Bang?

Famed for their ability to inflict Armageddon from outer space, asteroids are now revealing the secrets of how they are responsible for both life and death on our planet.

New planets are now being discovered outside our Solar System on a regular basis, and these strange new worlds are forcing scientists to rewrite the history of our own Solar System. Far from a simple story of stable orbits, the creation of our Solar System is a tale of hellfire, chaos and planetary pinball. It’s a miracle our Earth is here at all.

Professor Jim Al Khalili delves into over 50 years of the BBC science archive to tell the story behind the emergence of one of the greatest theories of modern science, the Big Bang.

The definitive story of going to the moon, told by those who went. Between 1969 and 1972 an elite group of men achieved an incredible dream. They were, and remain, the only human beings to set foot on a planet other than our own.

Using cutting edge visual effects and CGI, this scientific visual extravaganza creates the first accurate non-stop journey from here to the edge of the universe

Two-part series in which Professor Jim Al-Khalili shows how, by uncovering its secrets, scientists have used light to reveal almost everything we know about the universe.

Professor Jim Al-Khalili tells the story of how we went from thinking we were close to a complete understanding of the universe to realising we had seen almost none of it. Today, our best estimate is that more than 99 per cent of the cosmos is hidden in the dark, invisible to our telescopes and beyond our comprehension.

In 2009, NASA celebrated the 40th anniversary of the first moon landing. This documentary series offers audiences a unique chance to glimpse an astronaut\'s view of spaceflight.

Right now you're hurtling around the Sun at a hundred thousand kilometres an hour. Join Kate Humble and Dr Helen Czerski as they explore the relationship between the Earth's orbit and the weather

Right now you're hurtling around the sun at 64,000 miles an hour (100,000 kms an hour). In the next year you'll travel 584 million miles, to end up back where you started. Presenters Kate Humble and Dr Helen Czerski follow the Earth's voyage around the sun for one complete orbit, to witness the astonishing consequences this journey has for us all. In this first episode they travel from July to the December solstice, experiencing spectacular weather and the largest tides on Earth. To show how the Earth's orbit affects our lives, Helen jumps out of an aeroplane and Kate briefly becomes the fastest driver on Earth.