Big Rip

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This article is about a physics concept. For the Massively Multiplayer Online (MMO) Game Network, see The Big Rip.

The Big Rip is a cosmological hypothesis first published in 2003, about the ultimate fate of the universe, in which the matter of the universe, from stars and galaxies to atoms and subatomic particles, is progressively torn apart by the expansion of the universe at a certain time in the future. Theoretically, the scale factor of the universe becomes infinite at a finite time in the future. The Big Rip should not be confused with exponential expansion due to a cosmological constant, which would not rip individual galaxies apart.

The hypothesis relies crucially on the type of dark energy in the universe. The key value is the equation of state w, the ratio between the dark energy pressure and its energy density. If w < −1, the universe will eventually be pulled apart. Dark energy with this property is sometimes called phantom energy. If w = −1 then the dark energy behaves like a cosmological constant and the universe expands exponentially. Current observations are consistent with w = −1, meaning that the Big Rip hypothesis cannot be ruled out.

In a phantom energy dominated universe the distance to the cosmological event horizon decreases over time. When the size of the horizon is smaller than any particular structure, then no interaction between the farthest parts of the structure can occur, neither gravitational nor electromagnetic (nor weak or strong), and they will be ripped apart.

First, the galaxies would be separated from each other. About 60 million years before the end, gravity would be too weak to hold the Milky Way and other individual galaxies together. Approximately three months before the end, the Solar system would be gravitationally unbound. In the last minutes, stars and planets would be torn apart, and an instant before the end, atoms would be destroyed.

The authors of this hypothesis, led by Robert Caldwell of Dartmouth College, calculate that the end of the universe as we now know it would be in approximately 50 billion years.

The idea of the Big Rip was used by Arthur C. Clarke and Stephen Baxter in their novel Firstborn (novel), the third and last part of their A Time Odyssey trilogy.