Our radio transmissions "would definitely show up as artificial."

Hide and Seek

Despite our best efforts at scanning the skies for signs of extraterrestrial life, we've come up short.

Scientists have offered up several theories as to why that is. In 1950, Italian-American physicist Enrico Fermi famously pointed out the discrepancy between the fact that we have yet to stumble upon life and the apparent likelihood of it existing somewhere in the staggeringly expansive universe.

But here's an idea that turns the paradox on its head: maybe we're looking at the problem in the wrong way, with some astronomers now suggesting that aliens may have already spotted us, even though we remain ignorant of them.

Ground Control

For one, if intelligent extraterrestrial life does exist, it wouldn't have a particularly hard time spotting us.

For well over a century, humanity has made its existence known by broadcasting radio signals into space with abandon. As the BBC reports, that's especially true for the period between 1900 and World War 2, when radio transmitters had to blast out powerful signals to make up for relatively primitive receivers.

Then there are the numerous spacecraft we've sent hurling across the solar system — and beyond, in the case of NASA's Voyager 1 and 2 probes — each outfitted with their own transmitters. Earlier this year, Howard Isaacson, an astronomer at the University of California, Berkeley, found that the Voyager probes' journeys will have technically alerted more than 1,000 stars of our existence by the year 2300.

"The signal would definitely show up as artificial," he told the BBC, adding that in just eight years from now, the closest star to us would've had sufficient time to both receive our signals and return a message.

Telltale Signs

Beyond radio transmissions, alien astronomers may have also spotted us by using similar techniques human as astronomers use to spot exoplanets orbiting nearby stars. Or they could've analyzed the Earth's atmosphere, discovering signs of liquid oceans that could harbor life.

Other experts suggest aliens could spot us from the wealth of sodium-emitting city lights, a telltale sign of an advanced civilization, or our pollution, a preoccupation of our own SETI scientists.

Science fiction has long explored the possibility of alien life visiting us with oftentimes catastrophic results. Scientists have hotly debated whether we should even make an active effort to make ourselves known to possible alien life, given the inherent risks.

Maybe it's too late, with aliens having already spotted us — but choosing not to make their existence known.

More on aliens: James Webb Spots Possible Signs of Life on Distant Planet

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