Asked by: JAMES DUNCAN, BY EMAILFor many years, astronomers thought the Universe could end in one of three ways. First, the current expansion of the cosmos could slow and then reverse, leading to an eventual ‘Big Crunch’ as it collapses under its own gravity. Alternatively, it could carry on expanding at an ever-slower rate, eventually coming to a grinding halt. Or the expansion could somehow speed up. Since the mid-90s, astronomers have become increasingly convinced that a mysterious force-field, Dark Energy, is propelling the Universe at an ever-accelerating rate. So unless some other effect intervenes, it seems that the Universe faces an endless future in which its contents fades out and disintegrates, and its remnants get ever more separated from one another.