Dallas Campbell looks back through almost 50 years of the Horizon archives to chart the scientific breakthroughs that have transformed our understanding of the universe. From Einstein's concept of spacetime to alien planets and extra dimensions, science has revealed a cosmos that is more bizarre and more spectacular than could have ever been imagined. But with every breakthrough, even more intriguing mysteries that lie beyond are found. This great journey of discovery is only just beginning.

It was the world's last Islamic empire - a super-power of a million square miles. From its capital in Istanbul it matched the glories of Ancient Rome. And after six centuries in power it collapsed less than a hundred years ago.