Dark Energy

The mysterious force that makes the universe expand at ever increasing speed.

At the start of the twentieth century, scientists believed that the universe was of a constant size and held in place by gravity. When Albert Einstein formulated the general theory of relativity he acknowledged it as " The cosmological constant" because his other findings contradicted the convention of a static universe.

In the 1920s U.S astronomer Edwin Hubble discovered through observation of the red shift of light from distant galaxies that, far from being static, the universe is expanding. This prompted Einstein to declare the cosmological constant his "greatest blunder". It was then assured that the rate of expansion would be slowing as gravity pulls galaxies towards each other. However, in 1998 three astrophysicists - Americans Adam, Reiss, and Saul Perlmutter and Australian Brian Schmidt - discovered that the expansion was accelerating. This necessitated the reintroduction of the cosmological constant into the theory of relativity : it was not a blunder after all.

U.S cosmologist Michael Turner (b 1949) coined the term " dark energy." Dark energy pushes galaxies apart and accounts for approximately 73 percent of the total mass energy of the universe. The remaining problem is that physicists who have tried to calculate the amount of it in space have come up with an answer that seems excessive by a factor of 10120. An explanation of this anomaly may lie in "inflation theory" which suggests the possibility of more than one universe. The theory of multiple universes is supported by string theory, which has 10,500 possible solutions, one in our universe.