Scientists say they have found a method to detect alien civilisations - what do we know?

Of all the unanswered questions in modern science, perhaps the most talked about is whether we are the only ones in the universe. A new study looks at another way we could detect advanced civilisations. At its heart is the need for energy.

Exoplanets discovered boost interest

The search for intelligent life beyond Earth has fascinated scientists, philosophers and even inspired artists for centuries. 

There are hundreds of millions of stars in our galaxy and billions of other galaxies in the Universe. So the odds seem to be on our side to find other civilisations.

The discovery of thousands of exoplanets in recent decades adds to the interest. Scientists are therefore turning their radio telescopes and space probes to the search for extraterrestrial life.

 For example, SETI (Search for Extraterrestrial Intelligence), a programme to search for extraterrestrial intelligent life, scans the skies for unusual signals or messages that could reveal an advanced civilisation. But despite their best efforts, these searches are unsuccessful.

Searching for civilisation by energy

Another way is to search for advanced civilisations based on their energy signatures. This is an innovative idea that seeks to identify civilisations from artificial patterns in the electromagnetic spectrum.

Humanity's energy needs have increased as we have become more advanced, so in theory any more advanced civilisations would need to use much more energy than we do now.

It is possible that civilisations are using giant megastructures such as Dyson spheres to harness energy from the stars. It is the power of these structures, or their effect on starlight, that can be detected.

What the study revealed

A new study published in The Astrophysical Journal suggests that a civilisation could extract energy from a black hole by injecting material into it. Even more interestingly, this process could be detected as far away as 17 000 light years.

The study team ranked civilisations on the Kardashev scale, which measures technological progress by a civilisation's ability to store and use energy. 

An alternative scale has also been proposed, based on the Kardashev scale, which includes a civilisation's ability to explore space at a distance from its home planet.

Based on a theoretical model, the study explores how advanced civilisations could harness energy through Dyson spheres around primordial black holes. 

The team also proposes observational techniques to detect such structures using infrared and submillimeter signals.

The researchers stress that telescopes such as ALMA (Atacama Large Millimetre/submillimetre Array) are suitable for observations and can detect features or even megastructures at distances of up to 5.4 kilo-parsecs.