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Find the mistake
See if you can find the mistake in this argument. We know that the sun rises in the east and sets in the west, which means that earth rotates west to east. My textbook (Abell) says that the sun moves eastward on successive days against the stellar background. This means that we are actually the ones moving westward against the stellar background. If the earth rotates eastward but orbits westward, that means our rotation is retrograde to our orbit. They are in opposite directions. Can you find the mistake in that argument? |
#2
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Find the mistake
F/32 Eurydice wrote:
See if you can find the mistake in this argument. We know that the sun rises in the east and sets in the west, which means that earth rotates west to east. Yes. My textbook (Abell) says that the sun moves eastward on successive days against the stellar background. This means that we are actually the ones moving westward against the stellar background. Yes, but see below. If the earth rotates eastward but orbits westward, that means our rotation is retrograde to our orbit. They are in opposite directions. Can you find the mistake in that argument? "Westward" was an unfortunate choice of words to describe the direction of the earth's orbital velocity. If you're standing on the surface of the earth *at noon*, with the sun on your meridian, the earth is indeed moving toward the west. But that's only because our velocity vector points to a spot about 90 degrees west of the sun. At midnight you'd think the earth was moving east. It's a question of perspective. If you look at the Solar System "from above" (that is, from well north of the ecliptic), you'd see that the earth both rotates and revolves counterclockwise. -- Bill Owen |
#3
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Find the mistake
On Mar 30, 9:24*pm, Bill Owen wrote:
F/32 Eurydice wrote: See if you can find the mistake in this argument. *We know that the sun rises in the east and sets in the west, which means that earth rotates west to east. Yes. My textbook (Abell) says that the sun moves eastward on successive days against the stellar background. *This means that we are actually the ones moving westward against the stellar background. Yes, but see below. If the earth rotates eastward but orbits westward, that means our rotation is retrograde to our orbit. *They are in opposite directions.. Can you find the mistake in that argument? "Westward" was an unfortunate choice of words to describe the direction of the earth's orbital velocity. *If you're standing on the surface of the earth *at noon*, with the sun on your meridian, the earth is indeed moving toward the west. *But that's only because our velocity vector points to a spot about 90 degrees west of the sun. *At midnight you'd think the earth was moving east. It's a question of perspective. *If you look at the Solar System "from above" (that is, from well north of the ecliptic), you'd see that the earth both rotates and revolves counterclockwise. The moon, too, right? |
#4
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Find the mistake
F/32 Eurydice wrote:
On Mar 30, 9:24 pm, Bill Owen wrote: F/32 Eurydice wrote: See if you can find the mistake in this argument. We know that the sun rises in the east and sets in the west, which means that earth rotates west to east. Yes. My textbook (Abell) says that the sun moves eastward on successive days against the stellar background. This means that we are actually the ones moving westward against the stellar background. Yes, but see below. If the earth rotates eastward but orbits westward, that means our rotation is retrograde to our orbit. They are in opposite directions. Can you find the mistake in that argument? "Westward" was an unfortunate choice of words to describe the direction of the earth's orbital velocity. If you're standing on the surface of the earth *at noon*, with the sun on your meridian, the earth is indeed moving toward the west. But that's only because our velocity vector points to a spot about 90 degrees west of the sun. At midnight you'd think the earth was moving east. It's a question of perspective. If you look at the Solar System "from above" (that is, from well north of the ecliptic), you'd see that the earth both rotates and revolves counterclockwise. The moon, too, right? Yes, the moon too, all of the planets, and most *but not all* of their satellites. -- Bill |
#5
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Find the mistake
In article ,
Bill Owen wrote: F/32 Eurydice wrote: On Mar 30, 9:24 pm, Bill Owen wrote: snip It's a question of perspective. If you look at the Solar System "from above" (that is, from well north of the ecliptic), you'd see that the earth both rotates and revolves counterclockwise. The moon, too, right? Yes, the moon too, all of the planets, and most *but not all* of their satellites. IIANM Uranus rotates clockwise -- nominally, at least, with an axial inclination of ~98°. -- Odysseus |
#6
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Find the mistake
Odysseus wrote:
In article , Bill Owen wrote: F/32 Eurydice wrote: On Mar 30, 9:24 pm, Bill Owen wrote: snip It's a question of perspective. If you look at the Solar System "from above" (that is, from well north of the ecliptic), you'd see that the earth both rotates and revolves counterclockwise. The moon, too, right? Yes, the moon too, all of the planets, and most *but not all* of their satellites. IIANM Uranus rotates clockwise -- nominally, at least, with an axial inclination of ~98°. Right you are. I was thinking only of orbital motion when I wrote that. Not only Uranus but also Venus and Pluto have retrograde rotation. The "regular" inner satellites of Uranus orbit in the same direction that the planet rotates. -- Bill |
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