Legend has it that an apple which fell from its branches was the inspiration for Sir Isaac Newton's discovery of gravity . But now history's famous fruit tree is paying the price of fame. The thousands of visitors drawn to Sir Isaac's childhood home each year could be damaging the tree. A willow barrier has been put around the tree. It means visitors to the 17thcentury Woolsthorpe Manor, near Grantham, Lincolnshire, will no longer be able to sit under its branches as Newton was said to have been doing in 1665 when "the notion of gravitation came to mind." The National Trust, which owns the small manor where Newton was born in 1642, said the 2ft-high barrier was designed to _ the tree. Official Ann Moynihan said there had been no damage so far but warned that there could soon be a problem."Visitor numbers have gone up by around 50 percent, to 33,000 a year in three years. The more people who visit, the more the earth will become compacted  around the tree and over the roots. We just want to _ the tree for another 400 years if we can."She said visitors will still be able to take apples from the tree. Visitor Chris Gwyther,37,said,"I suppose it is a pity that you can't sit under the tree like Newton. But you can still see it and the tree is 400 years old, it needs saving for the future." Newton left no information saying he had been inspired by a falling apple. The story appeared in a book by French philosopher Voltaire published in 1727, the year Newton died at the age of 84. When did Newton have the inspiration for the discovery of gravity?
In 1642. In 1665. In 1820. In 1727.