The question of whether intelligent life exists elsewhere in the universe is one that continues to occupy astronomers and science-fiction movies alike. And, while the idea of aliens descending on Earth in spaceships may be far-fetched, scientists may also be looking for alien life in all the wrong ways.

That’s the contention of astrophysicist and author Ethan Siegel, who argues that searching for electromagnetic signals may no longer be the smart way to truly discover if we have company in the universe. Humanity has been sending these signals beyond Earth’s atmosphere since shortly after the advent of radio at the start of the 20th century. It was then in 1960 that the Search for Extraterrestrial Intelligent Life (SETI) began to look for similar signals sent back from beyond our borders.

As Siegel argues, the speed of light means that at this point we could only have received a signal back from a star 40 light years away. That encompasses less than 1,000 stars, an infinitesimal number given that astronomers reported last week that they now estimate there are 2 trillion galaxies in the universe. What's more, electromagnetic signals could soon be largely confined to the past with broadcasting increasingly done through cable and satellite.

“Perhaps an alien civilization, making note of these observations when the signals do arrive, would draw the conclusion that this blue, watery planet orbiting our star in the great distance actually achieved intelligent, technologically advance life for a short while, and then wiped ourselves out as the signals gradually stopped,” Siegel wrote for Forbes Friday. “With SETI focusing solely on electromagnetic signatures, we may, at present, be looking for the cosmic equivalent of smoke signals in a cellphone-filled world.” 

In a paper published earlier this year, two Canadian researchers argued that the best way to discover alien life was through observing “Transit Zones.” These are the shadows planets make as they pass in front of their host star, or sun.

“It’s impossible to predict whether extraterrestrials use the same observational techniques as we do," said one of the study’s authors, astrophysicist Rene Heller. "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."

However, Sigel predicts that an advanced civilization is most likely to be using nuclear fusion power, an energy source that scientists on Earth have been trying to harness for decades. If we could discover what signature is being emitted by this power, Siegel says, we could finally have an affirmative answer to the question of whether anybody is truly out there.

“If we can predict what that signature is, understand it, build a detector for it and measure it, we can find a fusion-powered civilization anywhere, and not have to worry about whether they’re broadcasting or not,” Siegel concludes. “So long as they’re making power, we can find them.”