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.

Horizon travels to the South Pole to tell the inside story of one of the greatest scientific quests of our time. In March 2014, a discovery there made headlines around the world, with evidence from the Big Bang itself - ripples in space and time called 'gravitational waves'. In the world of theoretical physics, this was a bombshell. For some it meant Nobel Prizes, while for others, their ideas were in shreds. This is the story of this extraordinary discovery, and what happened when it all began to unravel...

Scientists genuinely don't know what most of our universe is made of. The atoms we're made from only make up four per cent. The rest is dark matter and dark energy (for 'dark', read 'don't know'). The Large Hadron Collider at CERN has been upgraded. When it's switched on in March 2015, its collisions will have twice the energy they did before. The hope is that scientists will discover the identity of dark matter in the debris. The stakes are high - because if dark matter fails to show itself, it might mean that physics itself needs a rethink.

The team investigate the use of modern medical technology to scan Egyptian animal mummies from museums across the world. By creating 3-D images of their content, experts are discovering the truth about the strange role animals played in ancient Egyptian belief. This episode of Horizon meets the scientists working in Egypt who are exploring the ancient underground catacombs where mummies were originally buried to reveal why the ancient Egyptians mummified millions and millions of animals.

How bad can our drinking pattern be for our health? Doctors and genetically identical twins Chris and Xand van Tulleken want to find out. With the current drinking guidelines under review, the twins embark on self-experimentation to see the effects of different drinking patterns on their health. With Chris drinking 21 units spread evenly across the week and Xand having his 21 in single weekly binges, how will their bodies differ after a month? Catching up with the latest research into alcohol drinking patterns, we ask if moderate drinking is genuinely good for us - and whether binge drinking is really that bad.

In 2014, the International Space Station had to move three times to avoid lethal chunks of space debris and there is an increasing problem of satellites mysteriously breaking down. With first-hand accounts from astronauts and experts, Horizon reveals the scale of the problem of space junk. Our planet is surrounded by hundreds of millions of pieces of junk moving at 17,000 miles per hour. Now the US government is investing a billion dollars to track them, and companies around the world are developing ways to clear up their mess - from robot arms to nets and harpoons. Horizon investigates the science behind the hit film Gravity and discovers the reality is far more worrying than the Hollywood fiction.

Michael Mosley puts himself through a battery of health tests available to people who feel perfectly well. From an expensive heart scan to a new national screening procedure to detect the earliest signs of bowel cancer, Mosley sets out to discover which if any of the tests are worth doing.

Horizon reveals how new archaeological discoveries are painting a different picture of the very first native Britons. For centuries it's been thought that these hunter-gatherers lived a brutal, hand-to-mouth existence. But extraordinary new evidence has forced scientists to rethink who these people were, where they came from and what impact they had on our early history. Now, our impression is of a hardy, sophisticated people who withstood centuries of extreme climate change and a devastating tsunami that was to give birth to the island nation of Britain. Their way of life may even have survived beyond its greatest ever threat - the farming revolution.

Most of us think that Obsessive Compulsive Disorder (OCD) is just over fussy tidying. But it's actually much more serious. Sophie has to check that she hasn't killed people, looking for dead bodies wherever she goes, Richard is terrified of touching the bin, and Nanda is about to have pioneering brain surgery to stop her worrying about components on her body - that her eyebrow might not be aligned or that she has bad breath. Professor Uta Frith meets the people living with OCD, looks at the therapy available and asks what neuroscience can offer by way of a cure.

Imagine a world where dinosaurs still walk the earth. A world where the Germans won World War II and you are President of the United States. Imagine a world where the laws of physics no longer apply and where infinite copies of you are playing out every storyline of your life. It sounds like a plot stolen straight from Hollywood, but far from it. This is the multiverse Until very recently the whole idea of the multiverse was dismissed as a fantasy, but now this strangest of ideas is at the cutting edge of science.And for a growing number of scientists, the multiverse is the only way we will ever truly make sense of the world we are in. Horizon asks the question: Do multiple universes exist? And if so, which one are we actually in?

Forget the big bang. The real moment of creation was the Cosmic Dawn - the moment of first light. This is the scientific version of the story of Genesis. The big bang gets all the credit for creating our universe. But in fact, the universe it gave was dark and boring. There were no stars, no galaxies, just a vast, black fog of gas - the cosmic dark ages. But, after a hundred million years of nothing, came a dramatic moment of transformation - the Cosmic Dawn. It's the moment the first stars were born, the moment that lit up the Universe, and made the first structure and the first ingredients of life. This was the real moment of creation. Astronomers are now trying to witness the cosmic dawn. For the first time they have the tools to explore the very first stars of the universe and to tell the scientific story of our creation.

The video game industry is a global phenomenon. There are over 1.2 billion gamers across the planet, with sales projected soon to pass $100 billion per year. But their very popularity fuels the controversy that surrounds them. They frequently stand accused of corrupting the young - of causing violence and addiction. But is this true? Horizon reveals a scientific community deeply divided. Some are convinced that video games incite aggression. Others insist they have no effect whatsoever on real-world violence. But away from the controversy, there is a growing body of evidence that suggests video games may help keep the brain sharp, and could soon revolutionize how we combat mental decline as we age.