PureInsight | January 2, 2001
Since the 1920s, scientists have known that the universe is expanding. Most believe that this expansion has been going on since the Big Bang, estimated to be 12 billion to 15 billion years ago.
But one of the most pressing questions in cosmology (the study of the structure and history of the universe) is whether this expansion will continue forever, or whether gravity will take over, reverse the course, and pull all of the galaxies back together into a Big Crunch, which would signify the end of time as we know it.
Suddenly, in the past two years, something weird has made the question loom even larger: The expansion of the universe, according to two independent studies, seems actually to be accelerating.
'This is completely unexpected,' says Morris Aizenman, senior science associate in the National Science Foundation's Mathematical and Physical Science Directorate. 'What force is causing that acceleration? We have no answer.'
Researchers speculate that the acceleration might be caused by some strange and unknown matter or energy whose force of gravity repels, rather than attracts, over long distances.
(IMAGE: Cosmologists ponder whether our expanding universe is closed, open or flat.)