1.75 billion years till we’re toast ... maybe

Deborah Netburn / Los Angeles Times /

Published Sep 24, 2013 at 05:00AM

Scientists have done the math, and according to their calculations, life on Earth has 1.75 to 3.25 billion years left to thrive.

And that’s if a giant asteroid or a nuclear war doesn’t finish us off first.

Yes, there is a big difference between 1.75 billion and 3.25 billion years, but predicting the end of life on our planet it is not an exact science, at least not yet.

To arrive at that 1.5-billion-year doomsday spread, graduate student Andrew Rushby of the University of East Anglia in Britain created two slightly different equations that estimate the length of time Earth will remain in the “habitable zone” around the sun.

A planet is considered to be in the habitable zone when liquid water can exist on its surface.

If Earth was too close to the sun, high temperatures would cause our oceans to evaporate; too far away, and we’d be an icy wasteland.

Earth is firmly in the habitable zone of our sun right now (obviously — we’re all here!), but that won’t always be the case, Rushby explains in a new paper published in the journal Astrobiology.

As our sun gets older, it will evolve into a bigger, more luminous star. And sometime between 1.75 billion years and 3.25 billion years from now, Rushby says, the 92.9 million miles between us and our host star will not be enough to keep us comfortable.

Instead of being in the habitable zone, Earth will be in what astronomers call the hot zone. Oceans, liquid water and life will cease to exist on the planet.

Rushby’s equations were really designed to help astronomers determine whether newly discovered planets are in the habitable zone around their host star, and how long they will stay there.

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