Why does life on Earth exist now, rather than at some point in the distant past or future? Researchers probably have an answer to this now.
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A study by a team, including astrophysicists from University of Oxford raises the possibility that we Earthlings might be the first to arrive at the cosmic party in the universe which is roughly 14 billion years old.
They think that life in the universe is much more likely in the future than it is now.
That's partly because the necessary elements for life "such as carbon and oxygen" took tens of millions of years to develop following the Big Bang, and partly because the lower-mass stars best suited to hosting life can glow for trillions of years -- giving ample time for life to evolve in the future.
“The main result of our research is that life seems to be more likely in the future than it is now. That doesn't necessarily mean we are currently alone, and it is important to note that our numbers are relative: one civilisation now and 1,000 in the future is equivalent to 1,000 now and 1,000,000 in the future,” explained Dr Rafael Alves Batista from Oxford's department of physics.
Given this knowledge, the question is, therefore, why we find ourselves living now rather than in the future.
“Our results depend on the lifetime of stars, which in turn depend on their mass -- the larger the star, the shorter its lifespan," Batista added.
In order to arrive at the probability of finding a habitable planet, the team came up with a master equation involving the number of habitable planets around stars, the number of stars in the universe at a given time (including their lifespan and birth rate, and the typical mass of newly born stars.
“We folded in some extra information such as the time it takes for life to evolve on a planet, and for that, we can only use what we know about life on Earth. That limits the mass of stars that can host life, as high-mass stars don't live long enough for that,” the authors noted.
“Now that we have knowledge of a wide catalogue of exoplanets, the issue of whether or not we are alone becomes ever more pressing,” added study co-author Dr David Sloan from Oxford.
The paper, led by professor Avi Loeb of Harvard University, was published in the Journal of Cosmology and Astroparticle Physics.