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15 November 2021/ Free English translation text of Buchverlagsgesellschaft Naumann & Göbel mbH including Thema media GmbH.
The cosmic background radiation is a remnant of the radiation that was created during the Big Bang. We can see it almost uniformly from all directions.
However, the radiation does not come directly from the Big Bang, but from the time when the universe became transparent. That was about 300,000 years after the Big Bang.
How warm is the universe?
The cosmic background radiation has a temperature of 3 °C above absolute zero. Intergalactic space therefore has a temperature of -270 °C.
How big is the universe?
No one knows exactly. We can only see the part of the universe from which light can reach us. We don't know what is behind it.
If there was a big bang, surely there must be a centre of the universe?
According to current theories, there is no place where the big bang once took place.
To understand how such a thing can be, a comparison helps.
To do this, you have to imagine our universe as two-dimensional, i. e. flat like the skin of a balloon. All the galaxies then sit on the surface of this balloon. If you blow up the balloon, each galaxy moves away from the other. Nevertheless, the centre of this universe is not on the surface of the balloon. For an inhabitant of this balloon universe, the world has no centre, as this remains hidden in the third dimension.