When you look up at the night sky, you see countless stars.
Is there any intelligent life among them, staring into space like we are?
If they exist, how far away would they be able to detect Earth’s civilization?
A recent paper published in February 2025 by a joint research team from the SETI (Search for Extraterrestrial Intelligence) Institute and the University of California, Berkeley, provided a scientific answer to this question.
They calculated how far a “technosignature” from Earth could be detected and came to some surprising conclusions.
The results showed that an extraterrestrial civilization with advanced observation technology could potentially detect Earth from up to 12,000 light years away .
Since the solar system to which Earth belongs is located approximately 27,000 light years from the center of the Milky Way , this fact covers a significant area of the Milky Way galaxy, meaning that human technological activities have already “leaked out into space.”
This research can be considered a historic step in clarifying the scope of the Earth’s unconscious “self-introduction to the universe.”
“Are we being watched?” How far is the signal of Earth’s civilization?
Some signals from the Earth cannot be explained by mere natural phenomena.
This is a technological imprint called a “technosignature . ”
The research team analyzed various signals emitted from Earth and calculated how far into space the most potent ones could be detected .
For example, television and radio waves are part of our everyday lives.
In fact, these leak out into space and may be subject to observation from outside.
When the study did some calculations on these issues, some interesting facts emerged.
First, there are about 50 star systems that can be considered Earth’s neighbors, including Proxima Centauri (4.24 light years away), and detectable traces from these systems are evidence of “atmospheric pollutants.”
For example, chlorofluorocarbons (CFCs) are substances that do not exist in nature, and if they are detected through remote spectroscopic observations, they could be evidence of the existence of an industrial civilization on Earth .
It turns out that these gases can be detected from as far away as 4.36 light years away , which includes Proxima Centauri.
We also cannot overlook the presence of high-powered lasers used for space communications and scientific observation. The Earth is surrounded by more than 3,000 artificial satellites, and it has been calculated that the X-band radio waves used for communication with NASA’s Deep Space Network (DSN) and planetary probes can reach up to 65 light years away .
If these lights were by chance detected by another civilization, they could alert us to Earth’s existence.
The signal that has been calculated to reach the furthest is a radio signal intentionally sent as a message to extraterrestrial civilizations.
The most famous of these is the “Arecibo Message” sent from the Arecibo Observatory in 1974.
The message is believed to reach up to 12,000 light years , extending all the way to the center of the galaxy .
Naturally, the direction of the galactic center is where many star systems are concentrated, so this area contains billions of star systems and is therefore an area where intelligent life is likely to exist.
So if there is intelligent life out there, it could potentially find Earth from quite far away.
But is that really a good thing?
Innocently leaking signals into space may be dangerous
The biggest takeaway from this research is that Earth is already shining its light into the galaxy as a technological lighthouse .
But that’s not always a good thing.
Theoretical physicist Stephen Hawking once warned about these problems.
According to him, the reason we cannot find traces of intelligent life in other universes from Earth is because they remain silent as a survival strategy, and the reason for this is that sending out signals indiscriminately would run the risk of being detected by hostile civilizations.
This idea is also known as the ” Dark Forest Hypothesis.”
The idea is that shining a light in the forest is tantamount to signaling your location to potential predators.
Many viewers have probably seen a character in a horror movie waving a light around, asking, “Hey, is anyone there?” and thought, “You idiot, stay quiet.”
Humanity continues to scream out loud into the dark universe, not knowing what lurks there. Perhaps this is the behavior of a silly horror movie protagonist.
Dr. Sophia Sheikh of the SETI Institute also points out, “We are constantly unconsciously introducing ourselves to the universe. How we handle this information will be a scientific and ethical challenge for the future.”
The day when Earth’s signal reaches someone 12,000 light years away
This research quantitatively shows the extent to which human civilization is supported by distant sources in space.
However, it will take 12,000 years for a signal from Earth to reach that distance of 12,000 light years.
Even if someone in space were to discover Earth and respond, it would take an incredibly long time for that response to arrive.
This research stimulates the imagination and stimulates intellectual curiosity in many ways.
If an alien civilization were to find us, what should we tell them?
Perhaps one day, alien intelligence will be able to detect humanity’s “technological traces” floating in space.
And that moment may be the day when we are freed from the “loneliness of space.”