The wrong turns and false dawns in Earth's search for alien life in the universe

The Allen Telescope Array, which will join the search for possible alien radio signals
Image caption The Allen Telescope Array, which has joined the search for possible alien radio signals

There was excitement this week when it emerged a Russian radio telescope had detected a strong signal coming from the direction of a star 95 light years away from Earth.

Could alien life finally have been found?

The signal was detected by the RATAN-600 telescope, in the town of Zelenchukskaya near the Georgian border, last May.

At the time, the telescope was pointed in the direction of a star called HD 164695.

It's a similar size to our sun but is only known to have one gassy, Neptune-like planet orbiting it.

Kepler-186f
Image caption Kepler-186f is an Earth-like planet discovered in April 2014

The Seti Institute, the organisation that coordinates the search for life beyond the earth, was cautious about the report.

For a signal to reach us from 95 light years away it would, they say, need a transmitter that would use an amount of energy comparable to "the total energy consumption of humankind".

But they say the report is "interesting" and other radio telescopes are now joining the search.

Seti is right to be cautious though, because the search for life in the universe has a history of wrong turns and false dawns.

When alien signals turned out to be a microwave oven...

Someone unwittingly hurting the search for extraterrestrial life

Scientists working at the Parkes radio telescope in New South Wales had been detecting unexplained short bursts of radio signals for years.

This was particularly important because the telescope was built to detect short bursts of radio signals from the cosmos, known as "fast radio bursts".

The scientists soon realised that the signals were coming from closer to home but explanations varied from cloud formations to light aircraft.

It was only when they noticed that the signals tended to occur around lunchtime that the real culprits were unmasked.

Impatient scientists in the kitchen opening a microwave door early.

Canals on Mars, but only because of a bad translation...

A canal in Manchester, not Mars
Image caption A canal in Manchester, not Mars

In 1877 Italian astronomer Giovanni Schiaparelli was completing his close observation of the surface of Mars.

Unfortunately, somewhere along the line the Italian word "canali" which he meant as "channels" became "canals" in English.

That led to a frenzy of speculation about the possibility of intelligent life and on Earth's nearest neighbour.

Alien megastructure? Or swarm of comets?

The persid media shower

Tabby's Star, more formally known as KIC 8462852, made headlines around the world last year when astronomers revealed that they had recorded rapid fluctuations in its brightness that couldn't be explained.

Normally a dimming star can be explained by a planet passing in front of it, but Tabby's Star was dimming far more than normal.

One astronomer claimed that it was potentially proof that an alien civilization was building a megastructure around the star to harness its energy, although admitted it was a last resort explanation.

Others suggested a swarm of comets could be responsible.

The wow signal, that was never heard again...

Radio telescopes in New Mexico

In 1977 astronomer Jerry Ehman found something amazing while using Ohio State University's radio telescope.

He was so excited by the 72-second long burst of radio waves from a group of stars in the Sagittarius constellation he wrote the word "wow!" on the computer print out.

Scientists managed to eliminate the dull explanations like aircraft or satellites, but despite multiple attempts the signal has not been heard since.

If it was an alien, they've gone quiet since.

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