Epic Search of Millions of Stars Finds No Traces of Intelligent Alien Life

Are there civilizations somewhere else in the universe? Somewhere else in the Milky Way? That’s one of our overarching questions, and an answer in the affirmative would be profound.

Humanity’s pursued the Search for Extraterrestrial Intelligence (SETI) in one form or another since shortly after the advent of radio waves in the early 20th century. Efforts have waxed and waned over the decades, but the search has never been completely abandoned.

The search detected transient hints in the form of unexplained radio waves in the past, but nothing that comprises reliable evidence. Now a new search for technosignatures in the Milky Way’s center has turned up nothing.

If we ever discover or come into contact with another civilization, it’ll be an almost mystical moment for our species. People would divide into different camps and ideologies pretty quickly, and start arguing what to do about it. Many of us would pour out into the streets and look at our brother and sister humans with renewed wonder.

We should probably tap the breaks, though. If humanity ever discovers life elsewhere, it’ll likely be single-celled life somewhere in our Solar System. Maybe one of the Solar System’s moons harbors bacteria in their subsurface oceans.

But when we gaze at the night sky and wonder if we’re alone, most of us are thinking of more complex lifeforms. We wonder if there are other technological civilizations out there, facing the same challenges as us and puzzling over their own origins and fates like we do.

So far, there’s no sign of them, and new research hasn’t uncovered any new evidence.

A new paper titled “A Search for Technosignatures towards the Galactic Center at 150 MHz” is the fourth in a series. Each of the four is a search for low-frequency radio waves using the Murchison Widefield Array (MWA) in Australia.

The lead author is Chenoa Tremblay from the Commonwealth Scientific and Industrial Research Organization (CSIRO). The paper is available on the pre-press site arxiv.org.

The results come from seven hours of observations over two nights with the MWA. The search was aimed at the galactic center, centered on Sagittarius A*, the supermassive black hole at our galaxy’s core. The searchers targeted their search for technosignatures on 144 exoplanetary systems.

The search for life focuses on biosignatures. Biosignatures are things like molecules or isotopes that indicate the presence of life. Technosignatures are different.

Different researchers describe technosignatures differently. But in broad terms, technosignatures are evidence of effects that can only result from the use of technology. Mega-engineering projects like Dyson Spheres can leak radiation that could be detected.

A sufficiently advanced civilization might be able to build them, or even to alter the orbits of stars. Those phenomena would be good evidence for another technological civilization. More mundane things like chlorofluorocarbons in an atmosphere would also be evidence, but maybe harder to detect.

Some researchers don’t consider radio waves to be technosignatures since they can be produced naturally. But in terms of any widespread surveys of large regions of space, radio waves are the most practical thing to search for. The recent observations with the MWA were tuned to 155 MHz.

Radio signals are still the bedrock in SETI. That’s partly because they’re an early indicator of a technological species, most likely, and the ability to produce radio waves and detect them likely comes early. It did in our case.

The authors write that”

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