Fourth episode examines how plants either share environments harmoniously or compete for dominance within them. Attenborough highlights the 1987 hurricane and the devastation it caused. However, for some species, it was that opportunity for which they had lain dormant for many years. The space left by uprooted trees is soon filled by others who move relatively swiftly towards the light. The oak is one of the strongest and longest-lived, and other, lesser plants nearby must wait until the spring to flourish before the light above is extinguished by leaves. Tropical forests are green throughout the year, so brute force is needed for a successful climb to the top of the canopy: the rattan is an example that has the longest stem of any plant. As its name suggests, the strangler fig 'throttles' its host by growing around it and cutting off essential water and light. Some can take advantage of a fallen tree by setting down roots on the now horizontal trunk and getting nutriment from the surrounding moss and the fungi on the dead bark. The mountain ash (eucalyptus regnans) grows so tall, that regeneration becomes a considerable problem. It is easily flammable, so its solution is to shed its seeds during a forest fire and sacrifice itself. It therefore relies on the periodic near-destruction of its surroundings in order to survive. Attenborough observes that catastrophes such as fire and drought, while initially detrimental to wildlife, eventually allow for deserted habitats to be reborn.

We are in the grip of an allergy epidemic. 50 years ago one in 30 were affected, but in Britain today it is closer to one in three. Why this should be is one of modern medicine's greatest puzzles. In search of answers, Horizon travels round the globe, from the remotest inhabited island to the polluted centres of California and the UK. We meet sufferers and the scientists who have dedicated their lives trying to answer the mystery of why we are becoming allergic to our world.

New technologies are making rockets cheaper and more powerful than ever before. As companies like SpaceX and Virgin Galactic make space more accessible, and NASA returns to crewed spaceflight, a new era of space exploration may be on the horizon.

Join top scientists at the Johns Hopkins Applied Physics Laboratory in conjunction with NASA on a historic mission to the edge of our solar system with the goal of capturing the first clear images and data ever recorded of Pluto. Small, cold, and absurdly far away, Pluto has always been selfish with its secrets". Since its discovery in 1930, the dwarf planet has revolved beyond reach, its frosty surface a blurred mystery that even the most powerful telescopes can’t bring into focus. We know about Pluto. But we don’t really know it. That will change on July 14, when NASA’s New Horizons spacecraft is scheduled to fly within 8,000 miles of the frozen dwarf. It’s a risky maneuver, but if all goes well, the fleeting close encounter will unveil the last of the classical solar system’s unexplored worlds. We’ll finally get to meet the former ninth planet face-to-face—to really see its surface and that of its largest moon, Charon. Scientists have some guesses about what they might find, but the only thing they can say for sure is that Pluto promises to be a surprise.

Recently, the Event Horizon Telescope project captured the first image ever of a black hole. Now, new discoveries might finally reveal how supermassive black holes are made, and using the latest technology, experts are on the verge of understanding how these monsters grow and how they affect life on our planet.
Supermassive black holes: Gargantuan monsters that lurk at the center of galaxies. Right now you are travelling at half a million miles an hour around a giant black hole four million times the mass of the sun. But there's a mystery about these colossal beasts. We have no idea where they came from. How did they get so big so quickly?

Professor Jim Al Khalili from the University of Surrey 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 remarkable idea that our universe simply began from nothing has not always been accepted with the conviction it is today and, from fiercely disputed leftfield beginnings, took the best part of the 20th century to emerge as the triumphant explanation of how the universe began. Using curious horn-shaped antennas, U-2 spy planes, satellites and particle accelerators, scientists have slowly pieced together the cosmological jigsaw, and this documentary charts the overwhelming evidence for a universe created by a Big Bang.