We have thus far discovered that time can flow very differently. The river of time has estuaries and sinks. However, does it have a source?

Now that it is clear that the properties of time are a function of the physical processes that go on in nature, this question no longer seems to be so absurd. Philosophers pondered this problem for quite a long time. However, the striking successes of Newtonian mechanics and, as a result, the universally accepted Newtonian concept of eternal and unchanged time accustomed them to thinking that the source of time was in the infinite past.

Time was thought of as a uniform river or a never changing road which stretched from the past to the future. In fact, scientists had to face the problem of the beginning of time again, and quite dramatically, in the 20th century. This happened after the discovery of the expansion of the Universe. A detailed description of this achievement is given in the book Edwin Hubble: the Discoverer of the Big Bang Universe, that A. Sharov and I wrote in 1989. (An expanded version in English translation was published in 1993 by Cambridge University Press.) Here I will only trace the main points on this road.

It all began at the end of the 19th century. A rich American astronomer Percival Lowell had a private observatory built for him in the Arizona desert.