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Malcolm Ocean in Berlin (37/100 vids)
@Malcolm_Ocean
TIL that in addition to the moon's gravity creating the tides by pulling water up about 1m (=~3ft) it ALSO stretches the solid Earth by 30cm=1ft Which means "water is sloshy" is… only part of an explanation for how gravity's so strong at such a distance:
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Malcolm Ocean in Berlin (37/100 vids)
@Malcolm_Ocean
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Replying to @sokindling
Haha I mean it's rly big, and water is rly sloshy. But yeah it's also rly far. Beyond the above, I don't have an intuition for why the moon should do that from how far it is.
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Malcolm Ocean in Berlin (37/100 vids)
@Malcolm_Ocean
The other half of the explanation, I think, is that earth is actually quite smooth! Not smoother than a billiard ball (as is sometimes claimed) but more "grippy" than "bumpy".
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Dr. James O'Donoghue
@physicsJ
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How smooth is Earth? Earth's highest/lowest points are the 8.9km/-11km, but let's assume a local variability of 1km for now If Earth were shrunk to bowling-ball width (21.6cm), then 1km bumps represents 0.017mm: about the particle size of P1000 Super fine sandpaper! (1/3)
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Mark Moon
@eka_mark_moon
The high tide closest to the moon is due to the moon pulling (up) on the water more than on the earth beneath it (the water is closer). The high tide farthest from the moon is due to the moon pulling (down) on the earth more than on the water above it (the water is farther).
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QC (in Berlin 7/29-??? w/ COVID 😷)
@QiaochuYuan
Replying to
@Malcolm_Ocean
and
@eka_mark_moon
yeah i tweeted about it yesterday!
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QC (in Berlin 7/29-??? w/ COVID 😷)
@QiaochuYuan
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Replying to @Malcolm_Ocean
okay this video was cooler than i expected. i also found a physics.SE answer that looks like it gives an explanation of why the tidal forcing function has period ~12 hrs and not ~24 hrs: physics.stackexchange.com/questions/1184
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3:03 AM · Sep 29, 2020Twitter Web App
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