The depth of the heavens: Belief and knowledge during 2500 years

摘要

We see the Sun, Moon, and stars in the heavens as if placed on the inside of a sphere. But even early man had ideas about the distances to these heavenly objects. The Greek philosopher Anaxagoras living in Athens 2500 years ago claimed that the Sun is a fiery rock larger than the whole Peloponnesian peninsula. This implies a distance to the Sun larger than 20,000 km. Anaxagoras, however, was accused of blasphemy and had to leave Athens for that reason. His contemporaries believed that the sun god Helios drove his fiery wagon with the Sun across the sky in the day and returned at night sleeping on his ship. Do we perhaps see this empty golden ship of Helios on the 'Disc of Heavens' from Nebra? This gold plated bronze disc (Figure 1) from 1600 B.C. would then be the first known image of cosmos in the history of mankind. What is in the heavens? Men at all times have seen the Moon, Sun, planets, and stars. Christians in Antiquity and Middle Ages have believed that also God, angels, and saints live in the heavens. Astronomers today do of course find the Moon, Sun, planets, and stars in the heavens, but also star clusters, galaxies, dust, gas, white dwarfs, neutron stars, black holes, and quasars, and furthermore invisible dark matter whose true physical nature is a great mystery of astronomy today, since it is not made of atoms or the like. But we shall be mostly concerned with the belief of mankind over times about the size of the universe with respect to distances to the Moon, Sun, planets, and stars. The recent 100 years with galaxies and the Big Bang shall however be mentioned at last.