By Ron Cowen
BALTIMORE — Let ’er rip!
![](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2008/05/7739.jpg?resize=300%2C199&ssl=1)
If cosmologist Will Percival of the University of Portsmouth in England is right, the universe will end about 60 billion years from now, when every molecule and atom will be torn asunder by a mysterious entity that opposes gravity’s pull and turns it into a cosmic push.
The cosmic killer is a runaway version of what astronomers call dark energy, an unidentified substance that pervades all of space. Dark energy appears to cause the universe to expand at an accelerated rate. Many studies have found hints that the density of dark energy is constant over time and that it therefore exerts a constant repulsive force.