There has been a revolution in our understanding over the last forty years, and the gains in knowledge are permanent. But we will never know everything, and that is as it should be. From the obscuring mist of the past, science has ensured that some of the mountains have emerged into clear view, but as soon as that happens the misty shadows of further peaks are glimpsed in the distance, rank upon rank: so many other heights to climb, so many mysteries to investigate. Earth: An Intimate History