It’s the year 250,000,000 and Earth is alive and well. Humans have long since perished, but the planet is still home to a bewildering array of life forms. Yet apart from a few mysterious fossils there is no trace that we ever existed.
If we could visit this future Earth we would barely recognise it. The continents have crashed together to form a single gigantic supercontinent, surrounded by a global ocean. Much of the land is inhospitable desert, while the coast is battered by ferocious storms. The oceans are turbulent on the surface, stagnant at depth and starved of oxygen and nutrients. Disease, war, or asteroid collisions have pushed humans and many of the species we know today to extinction and competition has seen off all but the hardiest of the rest.
This supercontinent isn’t the first on Earth, and it won’t be the last. Geologists now suspect that the movements of the Earth’s continents are cyclical, and that every 500 to 700 million years they clump together. Unfolding over a period three times as long as it takes our solar system to orbit the centre of the galaxy, this is one of nature’s grandest patterns. So what drives this cycle, and what will life be like next time the continents meet?