When astronomy is faced with the unexplained, ET is sometimes invoked until we know better. There were the “canals” of Mars in 1877. And the idea of “little green men” was raised when Jocelyn Bell Burnell detected the regular “beep-beep-beep” of pulsar stars 50 years ago. Soon after, the discovery of the vast explosions of gamma ray bursts led to speculation of intergalactic war.
Last year the media was abuzz with talk of Tabby’s star, a pretty unremarkable F-type star in the constellation of Cygnus in our galaxy. NASA’s Kepler satellite found its light varied in a complex and unexpected way. Natural explanations were proposed, including a lumpy disc of orbiting material, the chaotic break-up of a planet, or clouds of comets. But the media latched on to one idea in particular, that the dimming could be due to “alien megastructures”.
So it was not a huge surprise when the headline “Harvard Scientists Theorize That Fast Radio Bursts Come From Alien Space Travel” appeared last week.
First seen in 2007, these intense and mysterious flashes of radio waves come from the depths of space and last milliseconds. Their brevity means they must originate in cosmically tiny regions, some 100 kilometres across. Astronomers have suggested natural events that could fit the bill, such as neutron stars and black holes colliding or potent flares from extraordinary stars.
But the Harvard idea proposes that we might be catching a glimpse of beams produced by advanced civilisations to propel spaceships with immense light sails between the stars.
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