The best chance of finding alien life is to assume "extraterrestrial observers" are also looking for us in the same way we're looking for them, experts have said.
Two astrophysicists believe these observers may have already made contact with us based on the fact that they have to "deal with the same physical principles as we do" when searching for alien life.
Part of the Milky Way galaxy as seen from Australia
René Heller and Ralph Pudritz published a paper looking at the question what if aliens discover the Earth as it transits the sun?
Their conclusions are based on the techniques we traditionally use on earth to spot other planets.
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For example, NASA's Kepler has spotted "more than 1,000 worlds," according to Nature, by observing how light dims as planets orbit their stars.
Intelligent aliens could spot Earth if they can see Earth passing in front of the sun, the researchers suggested.
"It's impossible to predict whether extraterrestrials use the same observational techniques as we do," Heller said in a statement.
"But they will have to deal with the same physical principles as we do, and Earth's solar transits are an obvious method to detect us."
In order to increase our chances of finding alien civilisations, if they exist, we need to focus on exoplanets from which Earth can be seen to be passing the sun.
Heller and Pudritz have helpfully suggested a few stars that could help kickstart our search.
"If any of these planets host intelligent observers, they could have identified Earth as a habitable, even as a living world long ago and we could be receiving their broadcasts today," wrote Heller and Pudritz.
Their research has been published in the journal Astrobiology.