Whether the big rip happens or not depends on the nature of the dark energy that is believed to be pulling the universe apart. One form this energy could take is something called phantom energy, whose density increases continuously and which will eventually accelerate the expansion of the universe so drastically that everything will be destroyed.
"Phantom energy will pull the galaxy apart, and then the solar system, the sun and all the planets, until all that you are left with are quarks and electrons," says Vyachadav Dokuchaev at the Institute for Nuclear Research of the Russian Academy of Sciences. Although observations cannot rule out a future big rip, some physicists have considered it implausible because it wasn't clear how phantom energy could rip apart black holes, from which nothing can escape. Now, Dokuchaev and colleagues say that phantom energy does not rip apart the black holes- rather, it dissolves them.
"Our calculations show that the more phantom energy falls into the black hole, the smaller its mass becomes until, just before the big rip, it will disappear completely," says Dokuchaev. This is because phantom energy behaves like negative energy, cancelling out the mass inside a black hole (www.arXiv.org/astro-ph/0505618).
Still, this is not enough to persuade some scientists, who say the problem is the nature of the phantom energy itself. Roy Maartens of the Institute of Cosmology and Gravitation at the University of Portsmouth in the UK believes that phantom energy could theoretically dissolve black holes but says, "One has to be very careful. Phantom energy is very topical but I'm not sure it is physically realistic." In fact, no one has even produced a complete mathematical description of phantom energy.
Figuring out whether the universe's dark energy is of the phantom variety is now the focus for astronomers. "Within the next 10 years new observations will place strong constraints on the dark energy," says Maartens. If it is phantom energy, Dokuchaev believes the big rip will come sooner rather than later in cosmological terms. "I expect the big rip to happen in about 14 billion years time, so we are about halfway through the universe's life."
Author: Stuart Clark
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THIS ARTICLE APPEARS IN NEW SCIENTIST MAGAZINE ISSUE: 2 JULY 2005.
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