A new theory posits the reasons we can't detect technologically advanced civilizations in the universe is either because they've gone extinct or that the indescribable distances involved preclude them and us from ever communicating with each other.

While the former theory isn't new, it's being backed by a new equation developed by Adam Frank and Woodruff Sullivan, who co-authored the paper published in the journal Astrobiology. Frank is a professor of physics and astronomy at the University of Rochester and is regarded as a leading expert on the final stages of evolution for stars like the sun. Sullivan, a physicist and astronomer, is from the astronomy department at the University of Washington Seattle.

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"The question of whether advanced civilizations exist elsewhere in the universe has always been vexed with three large uncertainties in the Drake equation," said Frank.

"We've known for a long time approximately how many stars exist. We didn't know how many of those stars had planets that could potentially harbor life, how often life might evolve and lead to intelligent beings, and how long any civilizations might last before becoming extinct."

The Frank/Sullivan equation is a modification of the famous Drake equation used since 1961 to determine the number of civilizations with intelligent life in the Milky Way. While popular, the Drake equation has been criticized because the error associated with any derived value is so large the equation can't be used to arrive at solid conclusions.

Dr. Frank Drake, however, said his equation wasn't meant to uncover the number of intelligent civilizations but was intended to stimulate scientific discussion on the search for intelligent extraterrestrial life.

The Frank/Sullivan equation (shown in the illustration above) draws on data not available to Drake in 1961. From observations of exoplanets by the Kepler Space Telescope, astronomers can conclude at least one-fifth of stars have planets in habitable zones.

As to Drake's estimate as to the length of time over which intelligent civilizations release detectable signals, Frank/Sullivan asked the question, "Are we the only technological species that has ever arisen?"

The duo's new equation says the probability there has never been any extra-terrestrial life in space is an infinitesimal one in 10 billion trillion or one part in 10 to the 22^nd power. This is an incredibly small number, said Frank.

They also conclude that over the 14 billion years the universe has been in existence, it's very likely these civilizations have become extinct.

TagsAdam Frank, Woodruff Sullivan, Drake equation, SETI, extraterestrial civilizations, intelligent life, Frank/Sullivan equation