parallax
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How Far Are the Stars?
Stars don’t look small because they’re really the size of pinholes in a blanket. The smallest are the size of Earth. The largest have 128,865,170 times Earth’s diameter. They look small in the sky because they’re distant. It’s for the same…
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Distances Between Stars
When you look up into the sky on a clear night away from the glare of the city, you see trillions upon trillions of stars. Thousands of years ago, the classical astronomers saw the same thing you do today — except…
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Tycho Brahe, the Observer
It is surprisingly difficult to find a flattering image of Tycho Brahe. Honestly. Do me a favor and do a Google image search for the guy. It’ll come up with all sorts of disfigured images, mostly because his nose got…
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The Ptolemaic Universe
Claudius Ptolemy lived about five centuries after the Greek philosopher Aristotle’s time. Aristotle’s model for the universe — the first geocentric model, with Earth at the center — was still widely accepted, and Ptolemy sought to improve it. Ptolemy was one…
