In the days of the Mayas, cenotes – deep, natural pits on the Yucatan peninsula - provided the only means of obtaining drinking water. But in the mythology of this advanced civilisation, these waterholes and caves were also the entrance to Xibalba – the underworld. All deceased were obliged to pass through Xibalba and wait there until they were called into heaven. It was a place in which one made sacrifices to the gods – objects of daily life, as well as bloody, human sacrifices. To this day, the relics of these acts are still in place preserved underwater for more than a thousand years. The entrance to the underworld begins at a dirty waterhole in the middle of the Mexican jungle overgrown and barely recognisable. But immediately after entry, a hall of breath-taking dimensions and beauty is revealed. As if they were sculptures, stalactites and stalagmites lend the underwater cave an almost sacred ambience. By now, one has succumbed to the fascination emanated by the world’s largest underwater cave system. We accompany four professional research divers to Yucatan – a team of specialists, able to squeeze their bodies through crevices and holes, barely larger than their bodies and who master dives that would push even the most experienced divers to their limits. With them, we penetrate worlds only a few people have ever ventured into. We encounter the remains of human victims, prehistoric fireplaces and primeval animal skeletons and undertake a dive, which takes us from the primeval forest to the open sea. We then enter Xibalba – the place of myths and the dead. In the days of the Mayas - a voyage of no return. Today, this is one of the greatest challenges one can face as a diver – the hidden world of the underwater caves of Yucatan – all filmed in 3D.

This episode explores the wave theory of light as studied by mankind, noting that light has played an important role in scientific progress, with such early experiments from over 2000 years ago involving the camera obscura by the Chinese philosopher Mozi. Tyson describes the work of the 11th century Arabic scientist Ibn al-Haytham, considered to be one of the first to postulate on the nature of light and optics leading to the concept of the telescope, as well as one of the first researchers to use the scientific method. Tyson proceeds to discuss the nature of light as discovered by mankind. Work by Isaac Newton using diffraction through prisms demonstrated that light was composed of the visible spectrum, while findings of William Herschel in the 19th century showed that light also consisted of infrared rays. Joseph von Fraunhofer would later come to discover that by magnifying the spectrum of visible light, gaps in the spectrum would be observed. These Fraunhofer lines would later be determined to be caused by the absorption of light by electrons in moving between atomic orbitals when it passed through atoms, with each atom having a characteristic signature due to the quantum nature of these orbitals. This since has led to the core of astronomical spectroscopy, allowing astronomers to make observations about the composition of stars, planets, and other stellar features through the spectral lines, as well as observing the motion and expansion of the universe, and the existence of dark matter.

The 1980s was an era in which a fusillade of new genres emerged, and many are still with us today, such as hip-hop and house. Dylan Jones has mined the archives to select some of the most crucial tracks in the rise of these two genres.
From a young Kurtis Blow making his Top of the Pops debut to the sonic bombardment of Public Enemy and the sampling skills of Bomb the Bass, this episode showcases the evolution in rap and house music across the decade. There are rare archival interviews and stellar performances from Run-DMC, Salt 'N' Pepa, S'Express, Cookie Crew and Neneh Cherry, as well as iconic videos from Herbie Hancock, The Beastie Boys, M/A/R/R/S, Grandmaster Flash and the Furious Five, and many more.

Did you know that 1% of the white noise you see on old televisions is background radiation from The Big Bang? That the gold on a wedding ring comes from a star that exploded 5 billion years ago? And, that we're connected to the salt water of the first oceans through the water in our bodies? Our human story is actually 14 billion years old and the clues are all around us. This CGI-driven special will tell the history of our world in two hours, an ambitious story that will give surprising connections to our daily lives. From the formation of the earth and the emergence of life, to the advance of man and the growth of civilization, it’s a rapid-fire view of our unforgettable story.

The film tells the story of the ill-fated Nazi Land Speed record attempts. This is a story of engineering excellence, Grand Prix racing, Nazi propaganda, celebrity, and an intense rivalry which would leave a speed record unbroken for 79 years and one of Nazi Germany's best racing drivers dead. During the rise of the Third Reich two German car manufacturers were ordered to build the most high performance vehicles the world had ever seen. What followed was a rivalry that would reap Grand Prix victories, international domination that was a propaganda coup, and provide world fame to its drivers who risked their lives smashing speed records that would stand for 79 years. All under the direct orders of the Fuhrer himself.
Bugatti and Alfa Romeo dominated racing before 1934. But the years from 1934 to 1939 were six tumultuous years in which Grand Prix racing was dominated by the German Auto Union, the arranged marriage of Audi, Horch, Wanderer, and DKW, and Mercedes-Benz teams and provided a spectacle of speed, sound and fury never previously attained and never since matched. There are few periods of racing that have excited as much interest, event attendance and sophistication of equipment as the era of the Silver Cars. They were so far ahead of their time that many of their accomplishments were not duplicated until Mercedes went racing again in the early 1950s. There is also something about men who faced the challenges of staying in a cockpit of a highly sophisticated machine capable of 200 mph with no safety systems. They were giants and among them were Italian Tazio Nuvolari and two greatest German pilots of the thirties, Rudolf Caracciola of Mercedes and Auto Union's Bernd Rosemeyer who duelled with faster, more innovative and sleeker machines, developed in wind tunnels.
This special documentary charts the rise of Nazi Germany's dominate 'Silver Arrow' Grand Prix and Speed Record cars of the 1930's. Leading motor racing and World War 2 experts James Holland, Richard Williams, Eberhard Reuss and Chris Routledge tell the story of the Nazi funded Auto Union and Mercedes Benz 'National Racing Cars'. Hitler's Supercars interweaves the rise of the Third Reich with the racing exploits it funded and what propaganda messages these racing cars where sending.

On a dusty highway between Australia's most isolated city and its largest gold pit lies Coolgardie - where the arrival every three months of a new pair of foreign backpackers to work the only bar in town is a keenly anticipated event. Fresh off the plane and lured by the promise of an authentic outback experience, Finnish travellers Lina and Steph find themselves en route to a dot on the map - to pour beers, replenish depleted travel funds, and live amongst the locals. But their working holiday quickly deteriorates into a baptism of fire.
Harangued by their new boss, relentlessly pursued by booze-addled patrons, and prey to the madness and malaise of an environment as claustrophobic as it is isolated - the girls soon realise that to meet expectations out here, they'll need to do more than just serve drinks.