EARTHSC 1121 Lecture Notes - Lecture 3: 30 Foot Fall, Observable Universe, Magnesium
9 Feb 2017
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Document Summary
First measurement came from the egyptians: eratosthenes calculated the circumference. He measured shadows in deep wells 800 km apart. Measurements were taken at noon on the same day. He calculated that 800 km was 1/50th of earth"s circumference. For anybody who sailed ships on the sea etc. , it was already pretty obvious that the. Earth spins rapidly on an axis of rotation. A time-lapse photo of stars shows this rotation. One spin ~40,000 km per day or ~1,700 kph (1,040 mph). Rotation centered on polaris, the north star. Pendulum swings back and forth in the same plane (as the earth rotates. Because it has a large mass and little friction, it will tend to stay in motion, Earth"s rotation moves the ground beneath the pendulum. swaying back and forth without rotating. underneath it). Visual observation + telescopes reveal seven other planets in our solar system. Is a large solid body orbiting a star (the sun).
