In a scenario dubbed the "big trip", so-called phantom energy trickling into a wormhole will cause it to swell up so much that it eventually engulfs the entire universe, says cosmologist Pedro Gonzalez-Diaz at the Institute of Mathematics and Fundamental Physics in Madrid, Spain.

IT COULD go rip, it could go crunch. Or, according to the latest theory on how our universe will end, it could be swallowed by a giant wormhole.

In a scenario dubbed the "big trip", so-called phantom energy trickling into a wormhole will cause it to swell up so much that it eventually engulfs the entire universe, says cosmologist Pedro Gonzalez-Diaz at the Institute of Mathematics and Fundamental Physics in Madrid, Spain.

Phantom energy is a form of the dark energy that could be responsible for the puzzling accelerated expansion of the universe. Its defining property is that its energy density increases with time. "Phantom energy is precisely the form of energy one needs to create a wormhole," says Diaz. "Wormholes, therefore, would actually be expected components of the space-time foam if dark energy is actually phantom energy. It is natural to study both at the same time."

Wormholes are theoretical structures connecting two regions of space, or even two parallel universes. In Diaz's scenario, phantom energy enters the wormhole through one end, making it grow. Eventually, the wormhole will grow so large and so quickly that the whole universe will be swallowed by it (Physics Letters B, www.arxiv.org/astro-ph/0510771).

"The paper deals with a remarkable combination," says Christian Armendariz-Picon at Syracuse University, New York. "However, wormholes have two entries. What happens at the second one?"