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Why there are two high tides a day: the Moon pulls the near sea harder and the far sea softer The sea rises twice a day, not once, and the second high tide happens on the side of the Earth facing away from the Moon. Why? The Moon pulls the near ocean a… Earth & Space4 min read Why the Moon changes shape: always half lit, and only part of it faces you Ask why the Moon changes shape and most people blame the Earth's shadow. It is a natural guess, and it is wrong: the Moon is half lit by the Sun all the time… Earth & Space4 min read Why the Moon always shows us the same face: tidal locking The Moon does spin. It turns exactly once for every trip around the Earth, so the same face always points our way. Walk around a chair while always facing it… Earth & Space3 min read How a 2,000-year-old bronze machine predicted eclipses with the number 223 In 1901, divers pulled a corroded bronze machine from a shipwreck off the Greek island of Antikythera. One dial ended in the number 223, written in Greek… History4 min read Every eye has a hole in its vision, and your brain paints over it Every one of your eyes has a hole in its vision, about ten Moons wide, and you have never seen it. It is where the optic nerve leaves the retina, a patch with… Mind3 min read Why we only ever see one side of the Moon The Moon always shows us the same face, so it's easy to assume it doesn't spin. It does. It turns exactly once for every orbit, about every 27.3 days, so the… Earth & Space6 min read