The truth of the hypothesis relies on the type of dark energy present in our universe. The type that could prove this hypothesis is a constantly increasing form of dark energy. If the dark energy in the universe increases without limit, it could overcome all forces that hold the universe together. The key value is the equation of state parameter w, the ratio between the dark energy pressure and its energy density. If w < −1, this dynamical vacuum energy is known as phantom energy, an extreme form of quintessence.
Expansion
A universe dominated by phantom energy is an accelerating universe, expanding at an ever-increasing rate. However, this implies that the size of the observable universe is continually shrinking; the distance to the edge of the observable universe which is moving away at the speed of light from any point moves ever closer. When the size of the observable universe becomes smaller than any particular structure, no interaction by any of the fundamental forces can occur between the most remote parts of the structure. When these interactions become impossible, the structure is "ripped apart". The model implies that after a finite time there will be a final singularity, called the "Big Rip", in which all distances diverge to infinite values. The authors of this hypothesis, led by Robert R. Caldwell of Dartmouth College, calculate the time from the present to the end of the universe as we know it for this form of energy to be where w is defined above, H0 is Hubble's constant and Ωm is the present value of the density of all the matter in the universe.
Authors' example
In their paper, the authors consider a hypothetical example with w = −1.5, H0 = 70 km/s/Mpc, and Ωm = 0.3, in which case the Big Rip would happen approximately 22 billion years from the present. For w = −1.5, the galaxies would first be separated from each other. About 60 million years before the Big Rip, gravity would be too weak to hold the Milky Way and other individual galaxies together. Galaxies would be destroyed as stars separate from the main black hole. Approximately three months before the Big Rip, the Solar System would be gravitationally unbound. Planets would be detached from the star's orbit. In the last minutes, stars and planets would be torn apart, and 10−19 seconds before the Big Rip, atoms would be destroyed. At the time the Big Rip occurs, even spacetime itself would be ripped apart and the scale factor would be infinity.
Observed universe
Evidence indicates w to be very close to −1 in our universe, which makes w the dominating term in the equation. The closer that w is to −1, the closer the denominator is to zero and the further the Big Rip is in the future. If w were exactly equal to −1, the Big Rip could not happen, regardless of the values of H0 or Ωm. According to the latest cosmological data available, the uncertainties are still too large to discriminate among the three cases w < −1, w = −1, and w > −1.
