Science-fiction is filled with technologically advanced species that could easily overwhelm us - but it may be that we are going to be that first interstellar traveler, and we may discover other life before it even knows it is being discovered.
The universe is 13.8 billion years old, while our planet formed just 4.5 billion years ago. That large time gap may mean that life on other planets, should it already exist, could be billions of years older than ours. Or it could be that present-day life is actually premature from a cosmic perspective and we have the huge head start by even being able to ask those questions.
Red stars may be why. If so, 'now' is when life is most likely to emerge, and those chances grow more likely in the future. That we are already here may be the anomaly.
Yes, life as we know it first became possible about 30 million years after the Big Bang, when the first stars seeded the cosmos with the necessary elements like carbon and oxygen. But possibility is not likely. We also assume life will end 10 trillion years from now when the last existing stars fade away and die. The relative likelihood of life between those two boundaries is what lead author Avi Loeb of the Harvard-Smithsonian Center for Astrophysics and colleagues speculate about.
The dominant factor is the lifetimes of stars. The higher a star's mass, the shorter its lifetime. Stars larger than about three times the sun's mass will expire before life has a chance to evolve. Conversely, the smallest stars weigh less than 10 percent as much as the Sun. They will glow for 10 trillion years, giving life ample time to emerge on any planets they host. As a result, the probability of life grows over time. In fact, chances of life are 1000 times higher in the distant future than now.
"So then you may ask, why aren't we living in the future next to a low-mass star?" says Loeb. "One possibility is we're premature. Another possibility is that the environment around a low-mass star is hazardous to life."
Although low-mass, red dwarf stars live for a long time, they also pose unique threats. In their youth they emit strong flares and ultraviolet radiation that could strip the atmosphere from any rocky world in the habitable zone.
Obviously our premature existence or the hazard of low-mass stars remains more philosophy than science. The only way to know is to study nearby red dwarf stars and their planets for signs of habitability. Which we can't do yet. What we know probably will never work is listening for radio waves sent by alien species that would have been sent 400 years before we ever had radios. We may have to stop waiting and start seeking.
