Andrew Graham-Dixon reveals how the Medici family transformed Florence through sculpture, painting and architecture and created a world where masterpieces fetch millions today. Without the money and patronage of the Medici we might never have heard of artists such as Donatello, Michelangelo or Botticelli, and Graham-Dixon examines how a family of shadowy, corrupt businessmen, driven by greed and ambition, became the financial engine behind the Italian Renaissance.

Dark energy - the mysterious force that is unexpectedly causing the universe's expansion to speed up. The effects of dark energy were discovered in 1998 but physicists still don't know what it is. Worse, its very existence calls into question Albert Einstein's general theory of relativity - the cornerstone of modern physics. The hunt for the identity of dark energy is on". Experiments on earth and in space generate data that might provide a clue, but there are also hopes that another Einstein might emerge - someone who can write a new theory explaining the mystery of the dark energy.

Explore the myths, misconceptions, truths & amazing mysteries of our unique universe. Could life exist on Mars? Is time travel possible & does Einstein's theory of relativity support it?

Take an exhilarating, unprecedented exploration of the seven most amazing wonders of our solar system. Our virtual tour begins with a trip to Enceladus, one of Saturn's outer moons, where icy geysers spout from its surface. Then venture to Saturn's famous rings, which contain mountain ranges that rival the Alps. Next dive into the eye of the biggest storm in the solar system--Jupiter's Great Red Spot. Soar through the Asteroid Belt, containing millions of leftover rocks from the formation of the solar system. Trek up Mount Olympus, the largest volcano, located on Mars. Have a close encounter with the searing surface of the Sun, and finish the journey by exploring our home planet Earth.

A look at the practices of certain US states toward juvenile offenders convicted of murder. In the last five years, more juvenile offenders were killed in Texas than in the rest of the world combined. America continues to defend its right to execute children.

In 335 BC Alexander of Macedonia set off on an expedition to conqueror the world. The voyage of Alexander the Great covered more than 22,000 miles in ten years, from Greece to India and back, through some of the most difficult and unforgiving terrain. Michael Wood was hot on his trail, following, as closely as possible, in the footsteps of Alexander and the army that he drove to achieve the impossible. In this programme: the Lebanese city of Tyre, scene of Alexander's most desperate battle; the Palestinian legend of `Two-Horned Alexander'; and the Egyptian oasis of Siwa, where Alexander was proclaimed pharaoh and son of God.