Moving with the Tides

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Have you ever been to the beach?

If you’re from California like me, then I’m betting you have. If you’re from a place that’s not near an ocean and you’ve never been near the water all your life, then I’ll tell you a little bit about the tides.

They happen every day, twice a day. If you find yourself a nice comfortable spot overlooking the beach, you can see the waves come into the shore and then gently roll out again. If you stay for hours on end, you’ll see the water level eventually rise a bit.

And if you stay even longer, you’ll see the water level lower back down. When it’s high, it’s called high tide, and when it’s low, it’s called low tide.

The tides are partially responsible for the myth that the moon’s gravity affects you in some kind of metaphysical way. But this isn’t true at all.

So why do the tides happen? Continue reading

How Orbits Work

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Since Aristotle’s time over 2000 years ago, we have accepted that the moon orbits the Earth. We didn’t always know why, and we didn’t always accept this for the right reasons.

We used to assume that it happened just because we saw the moon move across the sky, and we believed the Earth to be the center of all motion in the solar system. But even when we realized—in the 1540s CE—that the sun was in fact the center of the solar system, the moon kept its place around the Earth.

And rightfully so. Astronomers now know that the moon orbits the Earth based on scientific observation, rather than the “logical” guesses of Aristotle’s time. And we even know why it orbits—gravity, the one force in all the universe we can’t escape.

But I can tell you, the moon’s orbit isn’t a perfect circle, and if gravity were the only reason it orbited, it would crash straight into the Earth. After all, people stay grounded on Earth’s surface because of gravity, and we don’t orbit our planet, do we?

So how does the moon orbit the Earth? For that matter, how does any satellite? Continue reading