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Chapter 2

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CHEM 222
Karine Auclair

2. The Size and Age of Our Universe - We know the solar system condensed as long as 4.54 x 10 years ago. 9 - We also know that the solar system is comprised of materials that must have been formed in earlier phases of stellar evolution. Measuring Astronomical Distances and Time The Ancients Greeks and Astronomy - Western astronomical science is based in the early Greek civilization • Thales – promoted the understanding of nature • Anaximander – universe as consequent of the basic element, water • Pythagoras – planet was a sphere, heavenly bodies moved in circles • Anaxagoras – moon’s light was reflected from the Sun • Eudoxus – mathematical-geometrical cosmology • Aristotle – proof that Earth was a sphere • Aristarchus – Sun as the centre of the universe - Ptolemaic theory of an Earth-centred universe = the Almagest - Two thousand years ago, we knew the Earth was round. We knew its size. We have measured the relative distances to the Moon and the Sun. We had discovered the heliocentric reference frame Scales in the Solar System - Copernicus – heliocentric view - Brahe – made important measurements - Kepler – used Brahe’s measurements to discover the laws of planetary motion. - Galileo – provided supporting evidence for Kepler’s work. Parallax Triangulation - For nearby stars, we can use parallax measurement to determine their distance - For the most distant objects that we can observe, the most distant quasars, we need to use other methods • Quasars = sources of electromagnetic radiation – high energy output - The Earth orbits the Sun in an orbital diameter of 2 AU (300 x 10 km) - By observing the same star 6 months apart, we see it from a different perspective (across a distance of 2 AU) - Parallax second (parsec) – The distance corresponding to a parallax angle of 1 arcsec (1”) - 1 pc = 3.08 x 10 km - 1 pc = 3.26 light years Distance (parsec) = 1/ Where  = the parallax angle (arcsec) - Using the Hipparcos telescope, we can now determi
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