The last episode explores Mescaline, the psychoactive molecule in San Pedro and peyote cacti, a sacred medicine that Native Americans have had to fight for the right to use. At the Indigenous practices there's always an elder, someone who knows the territory very well, who's presiding. There's usually a group, a community is involved, There's always an intention, a purpose to what you're doing, and you're treating it as sacred, in order to achieve altered states of consciousness, which contribute to worship in various ways, or celebration or healing.
But maybe all this is not so new to Western culture after all. In the old Greek histories of Eleusis, people who were initiated there got the drink, the kykeon, and then they had the illumination. The precise recipe is a mystery, but we know that the kykeon was a psychoactive brew that was used at the Eleusinian mysteries, a sacred annual ritual of enlightenment practiced by some of the world's greatest minds including Socrates, Plato, and Aristotle. So why did this ritual come to an end more than 1,000 years ago? Was the possibility of illumination or achieving a higher consciousness considered threatening to the powers that be? Have the drug wars been merely an extension of that fear?
Psychedelics has a major part in how we can heal as a community, how we can heal as a city, and how we can heal as a country. The current renaissance of psychedelics could not come at a better time as the world confronts a crisis in mental health. But psychedelics have much to offer. The psychedelic experience changes the mind in ways that will help scientists better understand how it works. All these altered states allow us to probe what is the greatest mystery in all of nature. The emergence from mere matter of something as miraculous as consciousness. But an even bigger question is whether psychedelics might help us address the environmental crisis of how we think about our place in nature. One of the greatest gifts of psychedelics is how they reanimate the natural world, allowing us to perceive the subject, the spirit of all species, not just our own. And to feel a deeper sense of interconnectedness with nature.

Mathematician Dr Hannah Fry explores the mystery of maths. It underpins so much of our modern world that it's hard to imagine life without its technological advances, but where exactly does maths come from? Is it invented like a language or is it something discovered and part of the fabric of the universe? It's a question that some of the most eminent mathematical minds have been wrestling with. To investigate this question, Hannah goes head first down the fastest zip wire in the world to learn more about Newton's law of gravity, she paraglides to understand where the theory of maths and its practice application collide, and she travels to infinity and beyond to discover that some infinities are bigger than others.
In this episode, Hannah goes back to the time of the ancient Greeks to find out why they were so fascinated by the connection between beautiful music and maths. The patterns our ancestors found in music are all around us, from the way a sunflower stores its seeds to the number of petals in a flower. Even the shapes of some of the smallest structures in nature, such as viruses, seem to follow the rules of maths. All strong evidence for maths being discovered. But there are those who claim maths is all in our heads and something we invented. To find out if this is true, Hannah has her brain scanned. It turns out there is a place in all our brains where we do maths, but that doesn't prove its invented.
Experiments with infants, who have never had a maths lesson in their lives, suggests we all come hardwired to do maths. Far from being a creation of the human mind, this is evidence for maths being something we discover. Then along comes the invention of zero to help make counting more convenient and the creation of imaginary numbers, and the balance is tilted in the direction of maths being something we invented. The question of whether maths is invented or discovered just got a whole lot more difficult to answer

This documentary attempts to make history by finding the lost city of Atlantis once and for all. Adventurer-geologist Dr. Martin Pepper sets out to prove his theory – that the true Atlantis existed on the Greek island of Santorini, and was destroyed in the biggest volcanic eruption in human history". In order to achieve his goal, Pepper will use new scientific evidence gathered using state-of-the-art sonar scans of the sea bed and microscopic analysis of the ancient landscape. One of the challenges he faces is that he must also match Santorini to a series of key clues embedded in the first ever description of Atlantis by the Greek philosopher Plato – from the lost city’s strange ring-shaped design, to the role Egyptian priests played in recording the legend in the first place. His journey will take him across the Mediterranean and out into the Atlantic Ocean. By the end of the program, he reveals the stunning findings which may pinpoint the city and show exactly what it looked like.

The Pythagorian philosopher Plato hinted enigmatically that there was a golden key that unified all of the mysteries of the universe. It is this golden key that we will return to time and again throughout our exploration. The golden key is the intelligence of the logos, the source of the primordial om. One could say that it is the mind of God. With our limited senses we are observing only the outer manifestation of the hidden mechanics of self similarity. The source of this divine symmetry is the greatest mystery of our existence.

Could the fabled lost city of Atlantis have been located? Professor Freund explained how he led a pursuit to find the lost civilisation, believed by many to be an ancient Greek myth, by using deep-ground radar, digital mapping and satellite imagery. He contends that Atlantis, described by Plato in 360BC, in Spain's Donaña National Park, north of Cadiz, and was wiped out by a giant tsunami. Plato wrote it had been destroyed by a natural disaster in 9,000BC. Experts are now surveying marshlands in Spain to look for proof of the ancient city.

It is fairly extraordinary that this film exists. The level of access attained by Tim Hetherington and Sebastian Junger over their 15-month period embedded with the Second Platoon, Battle Company, 173rd Airborne Brigade allows for an incredibly unvarnished account -- including footage of deaths both civilian and military. It's perhaps the most intimate and unflinching examination yet of the processes of modern warfare -- and an exhilarating, heartrending, profoundly moving film in its own right.