Changes to the bacteria that live inside all of us are responsible for increasing the number of people with allergies, suggests new research. The show investigates this claim by conducting a unique experiment with two allergic families in order to find out just what it is in the modern world that is to blame. With a raft of mini cameras, GPS units and the very latest gene sequencing technology, the show discovers how the western lifestyle is impacting their bacteria. Why are these changes making people allergic? And what can be done to put a stop to the allergy epidemic?

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.

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 travels to the South Pole to tell the inside story of the greatest scientific quest of our time. In March 2014, a team of astronomers stunned the scientific world when they announced that their BICEP2 telescope at the South Pole had possibly detected a signal of “gravitational waves” from the early universe. This is the inside story of the hunt for gravitational waves from the beginning of time. How the BICEP2 team came close to making one of the greatest discoveries of the century – and what happened when it all began to unravel...

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.

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.

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.

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.

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?

Michael Mosley investigates the alleged danger in eating red and processed meat, and does a one month test on himself, doubling his meat intake.

Dr Michael Mosley seeks to establish the truth about meat. Every year, humans raise and eat 65 billion animals - nine animals for every person on the globe. In this eye-opening documentary, Michael examines the impact that this is having on the planet and finds out what meat eco-friendly carnivores should be buying. Is it better to buy free-range organic or factory-farmed meat? The answers are far from obvious.

Twenty-five years after the world wide web was created, it is now caught in the greatest controversy of its existence: surveillance. With many concerned that governments and corporations can monitor our every move, Horizon meets the hackers and scientists whose technology is fighting back. It is a controversial technology, and some law enforcement officers believe it is leading to 'risk-free crime' on the 'dark web' - a place where almost anything can be bought, from guns and drugs to credit card details.

The Ebola virus. No-one knows exactly where it comes from but one thing is certain - it's one of the most virulent infections known to science. This special episode of Horizon meets the scientists and doctors from all around the world looking for the cure and hears first-hand accounts of what it's actually like to catch - and survive - this terrible disease.

Dr Michael Mosley and Professor Alice Roberts investigate if male and female brains really are wired differently.

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.

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.

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.