PSYC 2500 Lecture Notes - Lecture 5: Angular Diameter, Astronomy Class, Copernican Revolution
1 Jun 2020
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Triangulation: measures angles at a and b and the baseline length to calculate distance, longer baseline make measurement accurate and easier. Apparent motion of object against distant background from 2 vantage points. Object near your nose has larger parallax than object held at arms length. Measure distance to object in space using parallax. Measure distance beyond solar system need larger baseline. Baseline/ circumference of circle (2n x distance) = parallax/ 360. If parallax measured solve distance: distance = (360/2n) x baseline/parallax. Parsec: pc distance to an object that gives a parallax of 1 arc second with baseline of 1 au. Nearest star is 1. 3pc = 4. 3 ly away. If we know angular diameter and distance to object we calculate diameter. Suns rays strike different parts of earths surface at different angles. Sun directly overhead in one city at an angle in another: measuring that angle and distance between cities gives radius, earth"s circumference = 40,000km.
