When does our future meet our past? How does our scientific knowledge grow and change? A newly recognized type of Earth orbit can travel directly above a great circle formed by some of the oldest and most distinctive ancient human constructions on the surface of the Earth: the Giza pyramids, Machu Picchu, Easter Island, Angkor Wat, Mohenjo-Daro, and many others. But is there any connection to all this? What do we need to learn – scientifically – to gain a greater understanding of the links between these sites, and the great changes that happened on our planet 12,800 years ago. Follow the adventures of a science writer and sceptic as…