The search for alien Earth rages on, with hopes ignited as NASA telescope Kepler recently spotted 1,284 new exoplanets. But why does any habitable planet out there remain undiscovered – if there is indeed one – and what does its existence mean to us?

Until recently, exoplanets were purely science fiction. As Carl Sagan was introducing his masterpiece Cosmos to the public back in the 1980s, astronomers were not yet acquainted with any single planet orbiting an alien star.

Today, they have examined nearly 5,000 planet candidates, confirming more than 3,200 alien worlds. Life-hunting Kepler, launched into deep space in 2009, remains faithful to its task of seeking exoplanets that orbit alien suns, with the new study boasting of the largest exoplanet find ever made.

None of the 2,325 confirmed alien worlds so far, however, appears to be like Earth, according to the mission scientists who announced Kepler’s latest accomplishment.

“We don’t necessarily have an exact dead ringer for a planet like Earth, in terms of its orbit and size,” scientist Natalie Batalha said at a news conference on May 10, citing exoplanets Kepler-1638b and Kepler-1229b as among the most Earth-like to date.

These examples orbit the “habitable zone” – the ideal range of distances where liquid water could probably exist on the planetary surface – of their host stars. But they’re not exactly Earth-like for a variety of reasons, such as Kepler-1229b orbiting a red dwarf, which is dramatically smaller and cooler than our own sun.

But there’s no quitting this mission. An Earth 2.0 is hoped to spur space travel that could move faster than currently available methods. This is despite the considerable distance of those exoplanets from Earth.

“Imagine looking through a telescope to see another world with life just a few million miles from your own. Or, having the capability to travel between them on a regular basis,” said Dimitar Sasselov of Harvard University. “I can’t think of a more powerful motivation to become a space-faring society.”

Perhaps another reason why humans are obsessing over the possibility of having a twin, according to science writer Sarah Scoles back in 2014, is that without one, Earth appears special – a philosophical position she said is stuck in the last century.

Scoles cited the Mediocrity Principle, which holds that nothing about human position in or experience of the universe is special, and that the cosmos behaves the same no matter where Earth’s telescopes are pointed.

And there’s been a cultural shift, Scones explained, that has led us from seeking to occupy the center of the universe to “wanting so badly not to be anomalous and alone.”

“We seek Earth analogs because maybe someday we can rocket toward them,” she wrote in Slate. “We seek them because Manifest Destiny, because curiosity, because science.”

The ultimate discovery of these Earth-like worlds, NASA echoed, will close the book on humanity’s long-standing cosmic solitude. The question is whether humans can actually arrive at that point and stare at a galaxy filled with “pale blue dots.”

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