Canberra, Oct 26 : Scientists have come up with an answer to the puzzling question of why life on Earth coincides with a momentous shift in the makeup of the universe.
According to a report by ABC News, research into finding an answer to this mystery was done by Ph.D. student Chas Egan and Charley Lineweaver from Australian National University.
The conundrum has its roots in the way the universe changes as it expands, explained Egan.
Soon after the Big Bang, some 14 billion years ago, most of the energy in the universe was in the form of heat. Later, as the universe cooled and expanded, matter, such as stars and planets, became dominant.
As the expansion continues, it is expected that "dark energy" - a mysterious force that causes the expansion of the universe to accelerate - will become most important.
Over the past 10 years, observations of the universe have shown that the expansion is accelerating, suggesting that the gradual transition from the current matter-dominated phase to the dark-energy era is underway.
"We're right on the cusp between the matter-dominated and dark energy-dominated epochs," said Egan.
Astronomers have been puzzled why this shift is happening right now, just when humans are here to observe it.
"When theorists see something like that, that indicates something suspicious. It looks like a coincidence," said Egan.
Various efforts have been made to explain this coincidence problem over the years, but none of the ideas raised have gained widespread acceptance.
Now, Egan and Lineweaver have taken a pragmatic approach, reasoning that the only time in the history of the universe that it would be possible for us to exist is around now - when stars have been formed, galaxies coalesced and planets have evolved for us to live on.
"It struck us that it's kind of silly to think that observers could have occurred anywhere during the whole history of the universe," said Egan.
"If we are tied to terrestrial planets, then we could not possibly have observed the radiation era, and when the universe gets large and diffuse and so on then we could not possible observe that late future either," he added.
"The results are important for the direction of dark energy research," Egan said.
"It means we can focus on other problematic aspects of dark energy with some confidence that there is a reasonable explanation for the coincidence problem, regardless of what dark energy turns out to be," he added.