While humanity has yet to make first contact with alien life, advanced extraterrestrial civilizations may be able to detect us using our own phones, according to a recent study.
The study in question was carried out by researchers from the University of Manchester and the University of Mauritius, which examined radio signals emanating from the Earth due to the use of mobile phones – signals that could, in theory, be detected by advanced alien life.
The findings of this study were published in the peer-reviewed academic journal Monthly Notices of the Royal Astronomical Society.
ET phone home? How could aliens hear our phone calls?
To understand this, it is important to understand how humans are searching for alien life.
Generally speaking, most search for extraterrestrial intelligence (SETI) efforts are made via detecting technosignatures. These are radio signals found in space that don't have a natural origin. The theory goes that if you find a technosignature without a way of forming naturally, you've likely found aliens.
However, these theories have so far been unsuccessful. Barring some exceptions, such as the famous 1977 WOW! signal, there haven't been many radio signals without a natural explanation.
But a civilization may not just constantly send out radio signals into space. Sometimes, the signals might mainly be used for communication among themselves, which is the case here on Earth.
In that case, could scientists on Earth intercept some mundane, everyday conversation of sorts on an alien world?
In theory, the answer is yes, scientists could carry out a sort of cosmic eavesdropping on exoplanets.
This was determined in a study back in the late 1970s, when researchers used Earth's own communications at the time and subsequent radio leakage – a term referring to the different radio emissions that essentially "leak" off of Earth.
Nowadays, though, Earth's communication landscape has changed. While TV broadband broadcasts used to be a major contributor to radio leakage, the Internet and cable TV have changed that. This is also true with radio broadcasts.
This has resulted in some scientists saying that Earth has become more and more radio-quiet. However, this isn't actually the case. Rather, Earth's radio leakage has simply changed to a new source: Mobile phones.
According to data cited by the study, around 91% of people on Earth have and use mobile phones, which comes out to 7.26 billion people. In fact, there are estimated to be over 3 billion more mobile phone connections worldwide than there are people.
These mobile communications go through radio towers, which help transmit the signals to their destinations.
This doesn't mean that mobile phones are the largest sources of radio leakage. Rather, just as was the case originally, the biggest source remains military radar. However, the sheer amount of mobile phone radio emissions isn't something that can be discounted.
So, what does this mean for our presence in space? Would an alien civilization around as advanced or more so than our own be able to detect our radio signals and essentially eavesdrop on a phone call or two?
To figure this out, the researchers behind the study developed a new, updated model based on crowd-sourced data to simulate the Earth's current level of radio leakage from mobile towers.
Based on this information, it was determined that yes, mobile tower radio signals are indeed detectable in space, contributing significantly to the sheer mass of radio leakage that has turned Earth into a sort of bright radio anomaly.
But not only that – the signals might only get stronger.
As our global communications network continues to get more advanced and utilize better technology, such as 5G networks, then the signals we send will only become more pronounced and even more easily detectable by advanced alien life, if they have any radio telescopes like the ones on Earth.
In other words, putting aside any possible theories about the existence of aliens in relation to us like the Dark Forest Theory, as our communications advance, the more likely it is that alien civilizations will end up accidentally listening in on your phone calls.