Discovery

The human gut has around 100 trillion bacterial cells from up to 1,000 different species. Every person's microbiota (the body's bacterial make-up) is different as a result of the effects of diet and lifestyle, and the childhood source of bacteria. What is it about the microbes in our guts that can have such an impact on our lives? Scientists are learning more and more about the importance of these bacteria, as well as the viruses, fungi and other microbes that live in our gastrointestinal tracts. Without them, our digestion, immune system and overall health would be compromised. Adam Hart talks to researchers who are discovering how important a balanced and robust gut microflora is for our health. And he asks how this can be maintained and what happens when things go wrong.(Image: Gut Microbiota Copyright: Getty Images)

Journalist and numbers obsessive Alex Bellos travels around India to explore the fundamental numerical gifts which early Indian mathematicians gave to the world and asks whether the great religions of ancient India - Hinduism, Buddhism and Jainism - had any part in their origins. The number system which the world uses today originated in India in the early centuries of the first millennium AD. It is usually called the Arabic numeral system, but in the Middle East the scheme employing the symbols 0 to 9 is correctly referred to as the Indian system. The designation of zero as a number in its own right by South Asian thinkers was arguably the greatest conceptual leap in the history of mathematics. During his numerical odyssey, Alex visits a temple in Gwalior, containing the earliest zero in India with a known date. He is also granted an audience with one of Hinduism's most revered gurus, who is also an author of books on numbers. His Holiness, the Shankaracharya of Puri tells Alex that the study of mathematics is a path to Nirvana. In conversation with India's most eminent mathematician, Professor SG Dani in Mumbai, Alex hears how early Indian philosophers toyed with numbers far more than the Greeks. Buddhists, for example, mused on a number with 53 zeros and the Jains contemplated various varieties of infinity - something that modern mathematicians do 2000 years later. Alex also dips into the current controvesy surrounding so-called Vedic mathematics. This is a collection of speed arithmetic tricks which a great guru of the early 20th Century claimed to have discovered in the Vedas, Hinduism's most sacred scriptures.(Image: One of the special zeros in its use in '270'. Credit: Andrew Luck Baker)

Australian geneticist Jenny Graves discusses her life pursuing sex genes in her country's weird but wonderful fauna, the end of men and singing to her students in lectures.(Image: Jenny Graves, BBC copyright)

Life on earth has gone through a series of mass extinctions. Mike Benton talks about his fascination with ancient life on the planet and his work on the Bristol Dinosaur Project.Image: Mike Benton BBC Copyright

Joanna Haigh, Professor of Atmospheric Physics at Imperial College, London, studies the influence of the sun on the Earth's climate using data collected by satellites. She talks to Jim al-Khalili about how she got started on her career in climate physics: she can trace her interest in it back to her childhood when she built herself a home weather station. Jo Haigh explains why we need to know how the sun affects the climate: it's so scientists can work out what contribution to warming is the result of greenhouse gases that humans produce, and what is down to changes in the energy coming from the sun. She has sat on the Intergovernmental Panel on Climate Change and discusses with Jim how it delivers its reports. And as a prominent scientist who speaks out about the dangers of increasing man made greenhouse gases in the atmosphere, she explains how she responds to climate change deniers. Image: Joanna Haigh Credit: BBC

Russell Foster, professor of circadian neuroscience at Oxford University, is obsessed with biological clocks. He talks to Jim al-Khalili about how light controls our wellbeing from jet lag to serious mental health problems. Professor Foster explains how he moved from being a poor student at school to the scientist who discovered a new way in which animals detect light. Image: Russell Foster Copyright: BBC

Adam Hart investigates yet another threat to the ash trees of Europe. In the last programme he found out about the latest research developments to save ash trees from ash dieback, a disease that has already devastated trees across Europe, but now it seems that another threat could be on its way from Russia – the emerald ash borer. This beetle already targets ash trees in the USA and kills 99% of the trees it infests. But, what is it, how great is the threat and is there any way to stopping it spreading to Europe?Image: Emerald Ash Borer Traces Credit: Cornelia Schaible

Professor Adam Hart looks at the disease that has devastated ash trees in Europe – ash dieback. Over the last 20 years the fungus that causes ash dieback has been spreading westwards across the continent and last year it was found in the UK for the first time. At the moment there is no cure for the disease and only a tiny fraction of trees seem to be able to survive it. In this programme, he investigates the very latest scientific research into this deadly disease and asks if it will be enough to save this important species.(Image: Professor Adam Hart in Trolleholm seed orchard in Sweden where ash dieback has infected many of the trees. Credit: BBC)

Fracking for gas is highly controversial in the US and the UK as it has been accused of contaminating water courses and causing earthquakes. Yet it provides a cheap source of energy. Beneath England there are thought to be considerable amounts of shale gas and the UK government is considering whether to allow fracking in these areas. Already there is opposition from residents, concerned about pollution and earth tremors. Gaia Vince talks to scientists to find out what fracking involves and what impact it has on the environment, and she discovers what other countries can learn from the pioneers of the technology, the United States.(Image: Views of the Cuadrilla Fracking Site at Balcombe. Credit: WPA Pool, Getty)

We all rely on GPS – the Global Positioning System network of satellites – whether we want to or not. From shipping to taxis to mobile phones, the goods we consume and the technology with which we run our lives depend upon a low-power, weak and vulnerable signal beamed from a few tonnes of electronics orbiting above our heads. This dependence is a new Achilles' heel for the world's financial, commercial and military establishments. From North Korea's concerted disruption of South Korea's maritime and airborne fleet, to white van drivers evading the boss's scrutiny over lunch, this signal is easy to jam - with disastrous consequences. Quentin Cooper meets the scientists and engineers developing alternative, resilient navigation systems.(Image: Captain David Millar, Senior Master, on the bridge of P&O Ferries’ MS Spirit of Britain. BBC copyright)