Our Place in the Cosmos Our Place in the Cosmos The Ancient Greeks - - PDF document
Our Place in the Cosmos Our Place in the Cosmos The Ancient Greeks and and By far the most famous early astronomers are the ancient Introduction to Introduction to Greeks. Between about 500BC and 100BC, they built a picture of the Universe
By far the most famous early astronomers are the ancient
picture of the Universe which dominated for over 1000 years.
He created the first heliocentric cosmology; that is, he was the first to propose that the Earth, and the other planets, went around the Sun. 1,750 years later Copernicus will claim the credit. Aristarchus is also famous for devising a way of measuring the size of the moon in terms of the size of the Earth. Hipparchus later used this to conclude that the moon had about
its distance was about 60 Earth radii away (modern value 60.4). However, his calculations did not give absolute values; only those relative to the unknown radius of the Earth. Aristarchus also measured the relative distances of the Sun and
Sun was bigger than the Earth.
Measured the circumference of the Earth with amazing accuracy. He did so with a particularly powerful piece of observational technology, namely a long stick.
Powerful insights into many aspects of
worked out the size of the moon, developed star and eclipse catalogues. Perfected the geocentric model with epicycles. It will go unchallenged for 1300 years.
Ptolomey’s revised epicycle mode See also http://astro.unl.edu/naap/ssm/animation s/ptolemaic.swf
Credited with the heliocentric model of the Solar System. He divided the planets into the `inferior’ ones closer to the Sun than the Earth, and the `superior’
Only planets out to Saturn were known at that time. The orbits were all taken as circular.
Finally we shall place the Sun himself at the centre of the Universe. All this is suggested by the systematic procession of events and the harmony of the whole Universe, if only we face the facts, as they say, `with both eyes open'.
Nicolaus Copernicus
Almost as famous for his silver nose (he lost the original in a duel) as for his observations. With the support of the King of Denmark, he developed instruments of unprecedented quality, capable of positional accuracies of
He is less remembered for his cosmological model, an attempted compromise in which the Sun goes round the Earth but the planets round the Sun.
Painstaking studies of Tycho’s
accepted conclusion that planets moved not on circles but on ellipses. He went on to formulate his three laws of planetary motion, which we will be studying in a later lecture.
(and might well not have dropped cannonballs off the leaning tower of Pisa either).
inventor of the modern scientific method, with its emphasis on experimental verification of theoretical models. Galileo was the first to properly exploit the telescope for astronomical purposes. Considering that his original telescope had a magnification power
large moons of Jupiter, sunspots, and the rings of Saturn. His belief in Copernicus’s heliocentric Universe nearly led him to a nasty end. GALILEO NOW
Widely acknowledged as one of the greatest scientific geniuses of all
founder of the modern theories of dynamics and optics, he also developed a theory of gravity. His theory explains Kepler’s Laws, and shows that the gravity we feel
that governs planetary orbits. Despite the development of the telescope, it would be many years before the remaining planets of the solar system were discovered. Uranus was discovered in 1781 by William Herschel.
Neptune was first observed in 1846, after its position was predicted by Adams and Leverrier by analysing perturbations to the motion of Uranus... … while Pluto was not discovered until 1930, and its moon Charon
WMAP (2003) COBE (1989)