Kepler’s third law
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How Massive are Galaxies?
If you needed to measure the mass of, say, a brick — or some other Earthly object — you could just set it on a scale. (Yes, scales measure mass, not weight.) With galaxies, it’s not so easy! I don’t…
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How Massive is the Milky Way?
Over centuries of philosophy and research, through the times of the classical astronomers to Galileo’s observations of the Milky Way, humanity’s understanding of our universe has evolved from a simple model of the sun and planets to a vast wheel…
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Johannes Kepler and Planetary Motion
Thales and Pythagoras suggested that the natural world could be understood. Aristotle dared to imagine what was beyond the Earth. Plato encouraged thought about the universe, even if he did take astronomy one step forward and two steps backward. Copernicus…
