VII

Kosmisch

Anaxagoras (499 - 428)To every great there exists a greater.

Empedokle (483 - 425)The universe is three times as large as the system earth-moon.

Demokrit (460 - 375)Milky way consists of many stars. The universe has no center

Aristotele (384 - 322)The earth is tiny compared to the universe.The earth is in the center of the universe.The earth is a sphere. When sailing to south always new stars appear.

Aristarch of Samos (310 - 230)

First proponent of the heliocentric system

Determined the ratio of distances to moon and sun.Angle measured: 87° cos 87° = 1 : 19Improved by Kepler: 89°51' 1 : 380

Eratosthenes (276 - 194)

Born in Cyrene (today Schahhat, Libyen)240: third chairman of the MuseionEducator of the crown prince

Very universal scholar.Invented the leap day.Produced the first astronomical maps with over 600 stars.

Sieve of Eratosthenes

Determined the circumference of earth

Alexandria (31°)Well diggers in Syene (= Assuan, 24°)

Result: 41000 km improved in 1670: 39800 kmcorrect: 40009 km (over the poles)

Claudius Ptolemaios (85 - 165)Worked in AlexandriaFair skin, small feet, red birtmarkAt chin, black beard ???

Geocentric system

Nicole d‘Oresme (1320 -1382)Heliocentric system

Jean Buridan (1295 - 1358)Prof. at Univ. ParisThought like OresmeBuridan‘s donkey, two heaps of hay.

Nicolaus Copernikus (1473 - 1543)

1510: The foundations of his heliocentric system. 1543: De revolutionibus orbium coelestium

Thomas Digges (1546 - 1595)1576: Infinite WorldBut there can be no movement of infinity and of an infinite body, and therefore no diurnal revolution of that vastest Primum mobile.

William Gilbert (1544 - 1603)De mundo nostro sublunari (1651)

Heinrich Olbers (1758 - 1840)

Astronomer and physician at Bremen

Olbers‘ paradox: Why is heaven dark at night?

Solid angle of a star ~ A/r2

Number of stars in spherical shell ~ r2rSolid angle covered by stars of a shell ~ Ar

r

Expansion of the universe started 13,7 109 years agoage = 4,3 1017 s

Vesto Slipher (1875 - 1969) 36 of 41 galaxies move off of us.

Edwin Hubble (1889 - 1953)

1929: Expansion of the universe: Hubble-constant

Finite universe with Doppler-redshift

George Gamow (1904 - 1968) 1949: predicted cosmic background radiationleft over from the big bang

Arno Penzias (1933) Robert Woodrow Wilson (1936)

1965: Discovery of cosmic background radiation

2,7 KMaximum has = 1,1 mm375 photons / cm3

Radius of the universum = 46.5109 lightyears

Volume of the universum = 1080 m3

1080 atoms

1088 photons

1080 m3 / (10-95 m)3

less than 10365 elementary cells