Aliens spying on us from across interstellar space is a classic trope of science fiction. But working out what those extraterrestrials might see if they pointed their telescopes at us could help in our quest for finding life on distant Earth-like planets, as James Romero explains
“No-one would have believed in the last years of the 19th century that this world was being watched keenly and closely by intelligences greater than man’s.”
So begins H G Wells’ classic 1897 novel The War of the Worlds, in which terrifying Martians invade our planet. Although the creatures die after being exposed to pathogens to which they have no defence, the notion of aliens eyeing the Earth is a common plot in science fiction. In Childhood’s End, for example, Arthur C Clarke describes extraterrestrials who had secretly watched Earth’s evolution for millions of years from across interstellar space – before invading and becoming our overlords.
In reality, it is we humans who have been looking for distant worlds. Over the past few decades, astronomers have discovered almost 5000 planets circling stars other than our own. And the nature of our interstellar voyeurism is evolving. Not just content with finding and cataloguing these alien exoplanets, we want to characterize them too. Accompanied by artists’ impressions of volcanic landscapes or storms raging above shimmering oceans, such work makes distant planets feel somehow more real.
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