Doomsday predictions about the end of the world will have to be rewritten, according to a Sussex scientist.

Researchers at Sussex University in Brighton claim to have proved the sun will not one day engulf the earth, as previously thought.

In a ray of hope for mankind's future, the team of astrophysicists now believe our planet will survive - after a fashion.

For decades, scientists have insisted the Earth would ultimately be sucked into a fiery inferno when the Sun runs out of fuel and expands across the solar system.

The earth, it was thought, would disappear into oblivion.

However, the scientists, led by Dr Robert Smith, say they've showed the earth will survive to see another day.

According to their calculations, published in the current issue of the journal Astronomy And Geophysics, the planet will escape total destruction by a hair's breadth.

However, as the crucial moment takes place 5.7 billion years from now, Dr Smith, 60, of the university's department of physics and astronomy, admits he will not be around to test his theories.

He said: "It's been known for some time the sun is going to expand and become a red super-giant star.

"When it does, it will become something like 200 times its current size, about the size of the Earth's orbit, with the result that we should be swallowed up.

"But, because the Sun is getting larger, it will lose mass, with the gravitational pull at its surface becoming smaller.

"That means the Earth will move further away and escape being engulfed."

However, mankind cannot breathe easily yet.

The Sun's intense heat will ensure the Earth is burnt to a crisp in temperatures of 1,800C (3,272F), hotter than a blast furnace.

Dr Smith believes our only hope is to leave Earth for another planet.

He said: "I'm sure we're going to develop the sort of technology that would allow us to construct space stations."

As the Sun expands, the solar system's so-called habitable zone, in which planets can sustain life, will move outward.

Unfortunately, because of the solar system's huge distances, there will be periods when there is no habitable planet.

Dr Smith said: "There is a sort of doomsday scenario here in that mankind cannot survive forever on the Earth, even if we succeed in curing all the political and social problems.

"But it may be a matter of academic interest in the sense that mankind may manage to destroy itself long before this happens. But one hopes not."