Astronomers may have unwittingly hastened the end of the Universe by simply looking at it, according to a theory reported in next Saturday's New Scientist magazine.

The novel idea is being aired by two US physicists, who attack the notion that the Universe, believed to have been created in the "Big Bang" some 13.7 billion years ago, will go on, well, forever.

In fact, the poor old cosmos is in a rather delicate state, they say.

Until recently, a common idea was that the energy unleashed in the Big Bang happened when a "false vacuum" - a bubble of high energy with repulsive gravity - broke down into a safe, zero-energy "ordinary" vacuum.

But recent evidence has emerged that places a cosmic question-mark over this cosy thought.

For one thing, cosmologists have discovered that the Universe is still expanding.