It really is the end of the world

STICK it in your diary: AD 1,000,002,008. March 16. Noon. World ends.

Scientists have produced the most detailed ever prediction of the ultimate fate of our planet and readers of a nervous disposition would be well advised to look away now.

In a billion years, they calculate, the Sun will have become 10% brighter than it is now, boiling away the oceans and making life as we know it impossible. About six billion years after that, a massively expanded Sun will pull the scorched Earth out of its orbit and drag it to a fiery death and total oblivion.

It has long been predicted that the Sun, at the end of its life cycle, will become a red giant and roast the inner planets.

But the work of astronomers Klaus-Peter Schroeder, of the University of Guanajuato in Mexico, and Robert Connon Smith, of the University of Sussex, sets out the most detailed timescale yet, gives new details of the mechanics of destruction, and predicts our planet will be totally destroyed.

Their report, to be published in the Monthly Notices of the Royal Astronomical Society, is the latest instalment in a long-running debate about the fate of the Earth.

Only last year, the discovery of a giant planet orbiting the faint, burnt-out cinder of a star in Pegasus had suggested that the Earth could survive the Sun's death.

Smith called the new forecast "a touch depressing," but "looked at another way, it is an incentive to do something about finding ways to leave our planet and colonise other areas in the galaxy."

If anything, he added, in the new calculations, he and Schroeder had underestimated the forces that would be dragging Earth down toward the Sun. "So I would be surprised if anyone were able to rescue the Earth again in a future paper," Smith said.

The good news is that planetary life has around a billion years to prepare for the new Armageddon. After that, it will be just 6.59 billion years before the planet itself disappears. There won't even be any fragments.

Earth's basic problem is that the Sun will gradually become larger and more luminous, according to widely held theories of stellar evolution. In its first 4.5 billion years, according to the models, the Sun has already grown about 40% brighter.

"Even if the Earth were to marginally escape being engulfed, it would still be scorched, and life on Earth would be destroyed," said Mario Livio, an astronomer at the Space Telescope Science Institute.

That is forecast a billion years in the future and it's all downhill for the planet from there. The Sun will run out of hydrogen fuel in its core about 5.5 billion years from now and start burning hydrogen in the surrounding layers. As a result, the core will shrink and the outer layers will rapidly expand as the Sun transforms itself into a red giant.

The heat will transform the solar system. It will briefly be springtime in the Kuiper Belt out beyond Neptune, while Mercury and Venus will be swallowed whole.

Earth's orbit will wind up about where Mars is now because the Sun will exert less gravitational pull as a result of blowing off outer layers.

According to Smith and Schroeder, the chances of the Earth surviving are nil because the red-giant version of the Sun will expand so much – 256 times as big across as the star is today and 2,730 times as luminous.

One way of rescuing Earth's inhabitants would be to leave for another planet or another star system. Another, Smith said, would be to engage in some high-stakes engineering. In the same way that space probes can get a trajectory boost by playing gravitational billiards with Venus or Jupiter to gain speed and get farther out in space, Earth could engineer regular encounters with a comet or asteroid, thus raising its orbit and moving farther from the Sun, according to a paper in 2001 by three US scientists.

Gregory Laughlin, of the University of California, in Santa Cruz, said they were not actually advocating the orbit-shifting project.

"There are profound ethical issues involved," he wrote. "And the cost of failure is unacceptably high."

Anyway, such a manoeuvre would prolong the viability of the Earth for only a few billion years. After that, the planet would be stranded in the cold and dark.

On thin ice

Glaciers are shrinking at record rates and many could disappear within decades, the UN Environment Programme has found.

Scientists measuring the health of 30 glaciers around the world found that ice loss reached record levels in 2006.

The agency said millions of people depend on glaciers for drinking water, irrigation and power generation.

The most severe loss in 2006 was at Norway's Breidalblikkbrea, which shrank 10.2ft, while Chile's Echaurren Norte was the only one to grow slightly thicker.

On average, glaciers shrank by 4.9ft in 2006, the most recent year for which data are available.