Features of alien technology may be how humans first discovered alien life

If aliens observe Earth, many human technologies — from cell phone towers to fluorescent light bulbs — could become beacons of life.

We are two astronomers working on the search for extraterrestrial intelligence or SETI. In our study, we sought to characterize and detect signs of technology originating outside of Earth.

These are called technical signatures. While searching the sky for some televised telecasts of alien Olympics might sound simple, finding signs of distant advanced civilizations is a more delicate and difficult task than it might seem.

Say hello with radio and laser

The modern scientific search for extraterrestrial intelligence began in 1959, when astronomers Giuseppe Cocconi and Philip Morrison showed that radio transmissions from Earth could be picked up by radio at interstellar distances telescope detected.

That same year, Frank Drake launched Ozma, the first SETI search project, to point a large radio telescope at two nearby sun-like stars to see if he could detect any radio signals from them.

With the invention of the laser in 1960, astronomers showed that visible light could also be detected from distant planets.

These first fundamental attempts to detect a radio or laser signal from another civilization are looking for concentrated, powerful signals that are intentionally sent into the solar system and destined to be discovered.

Given the technological limitations of the 1960s, astronomers didn’t give serious thought to finding broadcast signals that would leak into space—such as television and radio broadcasts on Earth.

But a radio signal, with all its energy concentrated on Earth, can be detected farther away – imagine the difference between a laser and a weak light bulb.

Finding intentional radio and laser signals remains one of the most popular SETI strategies today. However, this approach assumes that extraterrestrial civilizations want to communicate with other technologically advanced life.

Humans rarely send targeted signals into space, and some scholars believe that intelligent species may deliberately avoid broadcasting at their location. This search for signals that no one might have sent is known as the SETI paradox.

leaked radio waves

While humans don’t transmit many intentional signals into the universe, many of the technologies people use today produce large amounts of radio transmissions that leak into space. Some of these signals would be detectable if they came from nearby stars.

A global network of TV towers is constantly emitting signals in multiple directions, which leak into space and can accumulate into detectable but relatively weak radio signals.

Research is currently underway on whether the signals emitted by current Earth’s radio towers can be detected using today’s telescopes, but the upcoming Square Kilometre Array radio telescope will be able to detect fainter radio signals with 50 times the sensitivity of current radio telescopes. .

Not all man-made signals are so unfocused, though. Astronomers and space agencies use radio beams to communicate with satellites and spacecraft in the solar system.

Some researchers also use radio waves as radars to study asteroids. In both cases, the radio signal is more concentrated and directed into space.

Any alien civilization that happens to be within the line of sight of these beams could potentially detect these unmistakable man-made signals.

look for megastructures

Aside from the hunt for real alien spaceships, radio waves are the most common feature of technology in sci-fi movies and books. But they are not the only possible signals.

In 1960, astronomer Freeman Dyson speculated that, since stars are by far the most powerful source of energy in any planetary system, technologically advanced civilizations might harvest a significant portion of a star’s light for energy, essentially a giant solar cell. plate.

Many astronomers call these megastructures, and there are several ways to detect them.

After using the energy from the captured light, technology in advanced societies re-releases some of the energy as heat.

Astronomers have shown that this heat can be detected as extra infrared radiation from star systems.

Another possible way to find the megastructure is to measure its dimming effect on the star. Specifically, a large artificial satellite orbiting a star periodically blocks some of its light.

Over time, this will manifest as a decrease in the star’s apparent brightness. Astronomers can detect this effect in the same way that distant planets are discovered today.

a lot of pollution

Another technical feature that astronomers consider is contamination.

Chemical pollutants – like nitrogen dioxide and chlorofluorocarbons on Earth – are produced almost entirely by human industry. These molecules can be detected in the atmospheres of exoplanets using the same methods the James Webb Space Telescope uses to search distant planets for signs of biology.

If astronomers find a planet’s atmosphere filled with chemicals that can only be produced through technology, it could be a sign of life.

Finally, artificial light or heat from cities and industries can also be detected with large optical and infrared telescopes, as can a large number of satellites orbiting the planet.

But a civilization would need to generate more heat, light, and satellites than Earth to be detected in the vast expanses of space using the technology humans currently have.

Which signal is the best?

No astronomers have found a confirmed technical signature, so it’s hard to say what the first signs of an alien civilization might be.

While many astronomers have given a lot of thought about what might produce a good signal, in the end, no one knows what alien technology might look like, and what signals exist in the universe.

Some astronomers support a broad SETI approach, which searches space for anything that current scientific knowledge cannot explain naturally. Some, like us, continue to look for technical signatures, both intentional and unintentional.

On top of that, there are many ways to detect distant life. There is still a lot of exciting work to be done as no one knows which approach might succeed first.

Penn State Massey Houston and Jason Wright (The Conversation)