Life on Earth Limited to Only 1.75 Billion Years

Scientists have calculated that life on Earth has 1.75 to 3.25 billion years left to thrive, according to the LA Times.

This calculation may only hold through if a giant asteroid or a nuclear war does not finish off humans first. Although there is a huge difference between 1.75 and 3.25 billion years, the scientists have confirmed that these figures are not absolute. 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 of Astrobiology. As our sun gets older, it will evolve into a bigger, more luminous star.

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. 

Though it may be interesting to consider the final days of life on planet Earth, 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.