Researchers from the University of East Anglia's School of Environmental Sciences analysed other planets outside our galaxy in an attempt to work out how long it will be before our planet becomes uninhabitable.

The study, published on Thursday in the journal Astrobiology, examined seven planets, including Earth, to determine how their "habitable zones" will change as their stars get hotter and brighter over time.

The key factors in determining a planet's habitability are whether it is the correct distance from its star to have liquid surface water and a temperature less than 50C.

"Within around 1.75 billion years, conditions for human life will become impossible as the sun grows in size, temperatures soar and the world's oceans evaporate," Andrew Rushby, who led the study, told The Independent.

The research didn't specifically account for man-made climate change or the "possibility that we'll all be wiped out by an asteroid or a nuclear war", he said. Climate change may well decimate humanity before the concept of habitable zones become relevant.

"Of course, conditions for humans and other complex life will become impossible much sooner - and this is being accelerated by anthropogenic climate change," he said.

"Humans would be in trouble with even a small increase in temperature, and near the end only microbes in niche environments would be able to endure the heat."

Even if some humans did manage to survive for another 1.75 billion years, the end would not come instantly. "Even if you were alive at 99.9% of the way through our habitable zone, you still wouldn't have to worry about it," Rushby said. "Life isn't going to be extinguished at the flick of a switch."

Instead, as the sun gets older, it will get hotter and temperatures on Earth will soar over the course of "perhaps one million years" as we enter a "hot zone" and seas evaporate, leaving the planet lifeless except for some forms of microscopic life. "The optimist in me hopes we'll still be around to see this," said Rushby. "Or that we'll have migrated to Mars or developed the technology to spread out across the galaxy. But that's getting into the realms of science fiction."

The study has also allowed Rushby and his team to make predictions about what stage life might be at in other parts of the galaxy: "There's no point in studying a planet for signs of life if it's only been habitable for a million years. That sounds like a long time, but in terms of geology and biology it isn't. The most interesting planets in the search for alien life are ones that have been habitable for billions of years.

"Anatomically, modern humans have only been around for the last 200,000 years - so you can see it takes a really long time for intelligent life to develop.