ASTR 101 Chapter Notes -Aberration Of Light, Inverse-Square Law, Diurnal Motion
1 Feb 2014
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The moving earth: to understand how the earth moves, we have to compensate for diurnal motion by observing the stars at the same time each day, month, or year. Would appear as if stars shift very slowly with the sun drifting in from the west, slowly moving east (left) across the stars in a counter-clockwise direction (in the northern hemisphere) Various changes in star brightness as we move around. Brightness over distance follows the inverse square law, where standing twice as far away from an object looks 1/4 as bright (since 2 --> 1/22 = The minute changes will be so insignificant that it is not feasible with modern technology to measure. Measure speed similar to how cops measure traffic speeds. Practical by measuring the doppler effect in the light of the stars, which shows earth clearly is orbiting in a way such that we move towards some stars while moving away from others.
