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Ok, but this (the whole subthread, not just this msg I'm replying to) gets so deep into pedantry that it becomes borderline meaningless. The moon circles the ea

Ok, but this (the whole subthread, not just this msg I'm replying to) gets so deep into pedantry that it becomes borderline meaningless. The moon circles the earth approx every 28 days. When people -- even reasonably well-educated ones like me, with a couple semesters of astronomy from a world-class university -- say "orbit", that is what they mean. I'm deliberately omitting caveats about sidereal month vs synodic period, to avoid the same slippery slope I'm gently criticizing. Given there's no absolute spatial frame of reference, I'd argue that piling such caveats atop each other doesn't "move" us closer to a truer understanding. All that said, it is kind of fun to consider.

pdonis 1y ago
> The moon circles the earth approx every 28 days. In what sense? You state this like it's an obvious fact. It isn't. It contains a number of hidden assumptions, not all of which stand up to close scrutiny. > Given there's no absolute spatial frame of reference, I'd argue that piling such caveats atop each other doesn't "move" us closer to a truer understanding. I disagree, because "there's no absolute frame of reference" is not the same as "all frames of reference are equally useful". The former is true. The latter is not. Once you face up to the fact that different frames are useful for different purposes, you should realize why you can't just state things like "the moon circles the earth" as obvious facts. At the very least, you have to explain why you've picked the frame of reference (centered on the Earth) in which that's (approximately) true. Basically, that would be because you're ignoring the rest of the universe and you only care about the Earth and the Moon. Which is fine for many purposes (it worked for sending humans to the Moon and back), but not for others (like saying "the moon orbits the earth" as opposed to "the moon orbits the sun"--which is simply not true, once we bring the Sun into the picture, you can no longer ignore the Sun's effect on the moon).

pdonis 1y ago

> The moon circles the earth approx every 28 days. In what sense? You state this like it's an obvious fact. It isn't. It contains a number of hidden assumptions, not all of which stand up to close scrutiny. > Given there's no absolute spatial frame of reference, I'd argue that piling such caveats atop each other doesn't "move" us closer to a truer understanding. I disagree, because "there's no absolute frame of reference" is not the same as "all frames of reference are equally useful". The former is true. The latter is not. Once you face up to the fact that different frames are useful for different purposes, you should realize why you can't just state things like "the moon circles the earth" as obvious facts. At the very least, you have to explain why you've picked the frame of reference (centered on the Earth) in which that's (approximately) true. Basically, that would be because you're ignoring the rest of the universe and you only care about the Earth and the Moon. Which is fine for many purposes (it worked for sending humans to the Moon and back), but not for others (like saying "the moon orbits the earth" as opposed to "the moon orbits the sun"--which is simply not true, once we bring the Sun into the picture, you can no longer ignore the Sun's effect on the moon).