At this moment, two Voyager probes are speeding out into the unknown each carrying a "golden record" with information about our planet, our many different languages, our sciences and arts. The thinking was that those records could tell other civilizations in the cosmos about ourselves when they encounter the probes. But if a new theory about life in the universe is correct, those records may never find an audience.
The new theoretical study comes from scientists from Oxford and Harvard and suggests that life on Earth may have arrived early cosmically speaking, so the advanced civilization we're always combing the galaxy for might actually be us.
The general assumption that other civilizations older than our own exist in the universe seems well-founded. After all, the logic goes, the universe is 13.8 billion years old, while the Earth is a relative spring chicken of only 4.5 billion years young. Therefore there's been plenty of time for life on other planets to outstrip us.
But the new research study, led by Professor Avi Loeb of Harvard University, suggests that life in the universe is statistically much more likely in the future than it is now.
That's partly down to the preponderance of red dwarves.
Although medium-mass stars like our sun seem to offer the best conditions for orbiting planets to host life, lower-mass stars such as red dwarfs are almost as adequate; their "goldilocks zone" is narrower, but not by that much.
And the good news for red dwarf fans is that lower-mass stars have a much longer lifespan than medium-mass stars – in fact, they can glow for trillions of years longer. This means that ultimately, these long-lived, lower-mass stars offer much more time for life to evolve in the eons to come as the universe matures and our Sun eventually burns out.
The master equation that the team came up with factored in 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.
Dr Rafael Alves Batista of Oxford's Department of Physics, one of the study's authors, says the main result of the research is that life seems more likely to evolve in the future than it does now. That doesn't necessarily mean we're currently all alone in the universe. But if there were 1,000 planets with life on them today, there's likely to be 1,000,000 in the future he says.
"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," says Dr Batista. "That limits the mass of stars that can host life, as high-mass stars don't live long enough for that. So unless there are hazards associated with low-mass red dwarf stars that prevent life springing up around them – such as high levels of radiation – then a typical civilization would likely find itself living at some point in the future. We may be too early."
It's an interesting idea to ponder. It's pretty clear that a lot of us hope to make contact with civilizations beyond our planet. If we discover that we're living in an era when life is emerging, but still relatively rare, will it change the way we approach this theoretical contact?
The research has been published in the Journal of Cosmology and Astroparticle Physics.
Source: University of Oxford