One of the most poetic descriptions of time travel occurs in a popular medieval legend describing a monk entranced for a minute by the song of a magical bird. When the bird stops singing, the monk discovers that several hundred years have passed. Another example is the Moslem legend of Mohamad carried by a mare into heaven. After a long visit, the prophet returns to Earth just in time to catch a jar of water the horse had kicked over before starting its ascent. Today, we know that time travel need not be confined to myths, science fiction, Hollywood movies, or even speculation by theoretical physicists.
Time travel is possible.
This means that if you were to travel into outer space and return, moving close to light-speed, you could travel thousands of years into the Earth's future. In addition to high-speed travel, researchers have proposed numerous ways in which time machines can be built that do not seem to violate any known laws of physics. These methods allow you to travel to any point in the world's past or future and are discussed towards the end of this book. He showed the force causing apples to fall is same as the force that drives planetary motions and produces tides. However, Newton was puzzled by the fact that gravity seemed to operate instantaneously at a distance.