Many excellent books have been written about the past history of the universe and of the various objects—galaxies, stars, planets— to be found in it. All the exciting events from the original Big Bang to the appearance of human beings have been carefully recorded. Much less has been written about what comes next. What will happen to all these galaxies, stars, and planets in the future? And what will happen to us, and to any other intelligent life in the u- verse? It is obviously more dif?cult to examine the future than the past, but there are ways of doing it. Not everything in the universe is the same age; so a study of the older objects gives us some idea of what will happen to the younger objects. Some things vary in a fairly regular way, so you can guess what will happen next. For example, the number of spots visible on the Sun’s surface increases and then decreases again every eleven years on average. These ups and downs can be expected to continue for a considerable time in the future. Finally, theoretical explanations of how things work at present often give some hint of how they will develop in the future. One rule-of-thumb in astronomy—though there are plenty of exceptions—is that the further away objects are, the less we know about them. This means that it is often more dif?cult to forecast the future for distant objects than for ones nearby.
