Is there an edge of the universe

Free University of Berlin

Readers ask, experts answer

Raul Schneeberg from Pankow would like to know whether the universe is actually infinite. From the Institute for Theoretical Physics, Prof. Dr. Robert Schrader.

Modern research on the structure of the universe began in 1917 with Albert Einstein. He postulated what is now called the cosmological principle: On average, the universe looks the same everywhere and in all directions. According to this postulate, the universe has no edge, i.e. no end.

This assumption of homogeneity was confirmed in 1926 by the American astronomer Edwin Hubble. In his observations of how galaxies are distributed in space, he found no evidence of an edge of the universe. It was also he who discovered that galaxies move away faster the further away they are from us. Modern studies of light signals that have traveled through space for over 13 billion years have confirmed this. The Belgian priest and physicist Georges LemaƮtre, who is considered to be the founder of the Big Bang theory, interpreted this phenomenon in 1927 using the general theory of relativity as an expansion of a finite universe. The general theory of relativity by and large predicts that the masses present in space bend it because of their mutual attraction. Finiteness can therefore be understood in such a way that the galaxies, so to speak, bend the universe inward until it closes itself.

One can visualize the universe like the surface of a balloon. Astrophysicists interpret the expansion as the result of an explosive "birth" (big bang) of the universe 13 billion years ago and corresponds to the inflation of the balloon.

The latest astronomical measurements indicate that this expansion is currently even accelerating. It is probably caused by a so-called "dark energy" that has a repulsive effect. However, their origin and thus other physical properties are not yet understood.

It competes with the usual masses as well as with the equally attractive, invisible but nonetheless proven "dark matter". If the latter prevail, this could lead to the universe collapsing at one point ("big crunch").