Time travelers have been invited to attend the memorial service for Professor Stephen Hawking. The legendary physicist, cosmologist and author died on March 14. Thousands of fans and well-wishers lined the streets in Cambridge, England for his funeral two weeks later. His family has now arranged a special ceremony to allow people to remember and celebrate his life, and time travelers have been invited. Hawking famously wrote in his book "A Brief History of Time" that: "If time travel is possible, where are the tourists from the future?" Now they have the opportunity to travel back in time. The online entry form for the memorial allows people with birth dates up to December 31, 2038 to take part.

The concept of time travel had fascinated and intrigued Professor Hawking over the decades. In 2009, he staged a glitzy party for time travelers at Cambridge University. He arranged champagne and snacks, and a banner saying: "Welcome time travelers". No one from the future attended that particular event. A spokesman for the Stephen Hawking Foundation, which is organizing the memorial service, said he had yet to receive a response from any time travelers to attend the memorial service. The deadline to reserve a place at the June 15 event at London's Westminster Abbey is today. The spokesman said it was still possible. He said: "We cannot exclude the possibility of time travel as it has not been disproven to our satisfaction."