Further more! A little about the universe. The universe is infinite? But what, then, for its edge? Albert Einstein found a way out of this logical impasse. The universe, although finite, but boundless! C It just all right. The trouble is in ourselves - in our blind adherence to the geometry of Euclid. We believe that parallel lines do not intersect, that the shortest distance between two points - a straight line. But no one ever not proved. Besides, we all know that this is not the case.
To shorten the way from Moscow to Vladivostok, the pilot will guide the aircraft was not in a straight line, and the great circle of the Earth - the so-called geodesic line. If draw on a vast range of Earth's surface, the ratio of its diameter to circumference is less than Pi. All this is due to the curvature of the planet, due to the fact that it is not flat. Parallel lines - great circle - intersect. And we learned about this long before space travel, people do not have to look at our planet from the outside to see what it forms. And Einstein, pondering the known astronomical facts have come to the conclusion that our universe is curved and in the mathematical sense equivalent to the four-dimensional sphere Here is a complete analogy with Ploskatiey, located on the surface of a large ball, which is also curved in space, but higher (Three-dimensional) than what they can understand the flat "dvumertsy." Flat "dvumertsy" living in the area, would be able to discover that their universe is curved, if of steel, for example, to build fences around some of his palace (instead of fences can be any of concentric circles) - one after another, each longer than the previous one. At one point, they would find that the new fence is less material.