MIAMI An astronaut is planning a unique test of Sir Isaac Newton's theory of gravity - by taking an original piece of the scientist's famous apple tree on a 5m-mile journey into space.British-born Piers Sellers plans to release the 10cm fragment in zero gravity during his 12-day mission to the international space station, as a tribute to Newton's discovery of gravity in 1666, when he watched an apple fall to the ground in his garden.

“I'll take it up and let it float around for a bit, which will confuse Isaac,” said the 55-year-old Nasa spaceman, a veteran of two previous shuttle missions and a graduate of the University of Edinburgh.

“While it's up there, it will be experiencing no gravity, so if it had an apple on it, the apple wouldn't fall.

“I'm pretty sure that Sir Isaac would have loved to see this, assuming he wasn't space sick, as it would have proved his first law of motion to be correct.”The tree fragment, engraved with the scientist's name, is stowed aboard the shuttle Atlantis at Cape Canaveral, Florida, awaiting Friday's blast-off.

The stunt is part of the 350th anniversary celebrations of the Royal Society, of which Newton, who died in 1727, was a president. The society hopes to display the fragment at its 10-day festival of science and arts at London's Southbank Centre next month, and later at its HQ in Carlton House Terrace, London, where it will join exhibits including Newton's first telescope and his death mask.

Several sections stripped from the tree, which still stands at Woolsthorpe Manor, the physicist's former home in Lincolnshire, are stored in the society's vaults as part of a huge collection of Newton memorabilia donated by the antiquarian Sir Charles Turner in the 1700s.

Sellers, who was born in Crowborough, Sussex, but assumed dual UK-US nationality in 1991 to join Nasa, invited the society to send an item to go into space. On a previous spaceflight, he took a commemorative medallion that the group presented to the physicist Stephen Hawking.—Dawn/The Guardian News Service