Cyclic creation and destruction of the universe could explain a mystery that has had physicists puzzling for decades; why the "cosmological constant" – related to the energy in the vacuum of space and contributing to the expansion of the universe – has a value that is "improbably perfectly" suitable for the formation of stars and planets.
Paul Steinhardt of Princeton University in the USA and Neil Turok of Cambridge University in the UK think the "cyclical universe" theory might explain the mystery.
Einstein first introduced the cosmological constant in his theory of general relativity in the 1920s as a way to mathematically explain why the universe didn't contract under the force of gravity.
He later discarded the idea as his "biggest blunder" when Hubble redshift was discovered. Redshift showed that stars were receding in all directions, so the universe was expanding and not static as Einstein had believed.
However, scientists recently became interested in the cosmological constant again when it was discovered that the universe is not only expanding, but at an increasing rate. Einstein's cosmological constant formula models this observation well.
The mystery to physicists is, if the cosmological constant is used to approximate the expansion of the universe, why is its value a googol (1 followed by 100 zeroes) times smaller than would be expected if the universe had formed under the standard "big bang theory"?
Scientists have tried various mechanisms to solve this question, but for the cosmological constant to reach the present estimated value it would take far longer than the 14 billion years our universe is said to have been in existence for – so long that all matter in the universe would dissipate in the meantime.
But, say Drs Steinhardt and Turok in the recent edition of Science , if time existed before the "big bang", and if matter was recreated every trillion years or so, the cosmological constant would have plenty of time to decline to the level observed today.
In their "cyclic universe" theory, the universe spends most of its time with a small cosmological constant, and the repeated creation of matter means that each expansion cycle would include a significant amount of matter, as we see today.
Other theories attempting to explain the mystery include the "anthropic principle" which says that the cosmological constant has different values in different parts of the universe. This theory proposes that we live in a rare region of space where the cosmological constant happens to have a low value, suitable for the formation of stars, planets and life.
Another popular idea is "string theory", which suggests that there are billions of different universes, each with different cosmological constants and even different laws of physics.
"With an infinite number of universes, there is bound to be one with a cosmological constant like ours" said the founder of string theory, Dr Leonard Susskind in an interview with New Scientist last year.
Although new to science, the theories of multiple and cyclic universes have featured in the beliefs of ancient cultures such as the South American Mayans and various religions since ancient times.
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