Which of us was not immersed in our youth in Herbert Wells' famous short novel The Time Machine? The protagonist of this story uses a device that can travel in time to visit a very remote future of the Earth. Wells also imparted to this device the property of reverse motion into the past.

A large number of books have been written which fantasized about the possibility of freely visiting the past and the future. In all likelihood, their authors were never in doubt that their inventions belonged to pure imagination and treated this as nothing more than a literary stratagem.

The entire experience of mankind and scientific knowledge have made inevitable the conclusion that travel in time is impossible. Space is where motion is allowed. Say, travel on the Earth is possible in different directions and one can also return to the starting point. On the contrary, we are seemingly unable to choose the direction of motion in time, we are bound to ‘float’ passively in this flow. It was assumed that here lies the dramatic difference between time and space.

Einstein's discovery of the surprising properties of time in 1905 demonstrated the fallacy of the view that we are ‘captives’ of the river of time and thus cannot ‘steer’ on it; it was seen as a fruit of not knowing, as a consequence of the limited possibilities that mankind had during its preceding history. But does this mean that we are free to roam in time?