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BBC News - Earth may once have had two moons
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BBC News - Earth may once have had two moons
On 8/3/11 7:27 PM, Yousuf Khan wrote:
BBC News - Earth may once have had two moons http://www.bbc.co.uk/news/science-environment-14391929 Pretty hard to prove that the Earth didn't have tens of thousands of moons... 4, 3, 2, and finally one, given the current theory of the formation of the moon from an impact! |
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BBC News - Earth may once have had two moons
On 03/08/2011 8:45 PM, Sam Wormley wrote:
On 8/3/11 7:27 PM, Yousuf Khan wrote: BBC News - Earth may once have had two moons http://www.bbc.co.uk/news/science-environment-14391929 Pretty hard to prove that the Earth didn't have tens of thousands of moons... 4, 3, 2, and finally one, given the current theory of the formation of the moon from an impact! I was thinking the same, but I wonder if the smaller moon would've still been bigger than Pluto? Yousuf Khan |
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BBC News - Earth may once have had two moons
"Yousuf Khan" wrote in message ... BBC News - Earth may once have had two moons http://www.bbc.co.uk/news/science-environment-14391929 "For decades, scientists have been trying to understand why the near side of the Moon - the one visible from Earth - is flat and cratered while the rarely-seen far side is heavily cratered and has mountain ranges higher than 3,000m" Really? The fact that one side of the moon is partially shadowed from asteroid impacts by earth wouldn't have anything to do with it? |
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BBC News - Earth may once have had two moons
On 03/08/2011 9:17 PM, Vince Morgan wrote:
"Yousuf wrote in message ... BBC News - Earth may once have had two moons http://www.bbc.co.uk/news/science-environment-14391929 "For decades, scientists have been trying to understand why the near side of the Moon - the one visible from Earth - is flat and cratered while the rarely-seen far side is heavily cratered and has mountain ranges higher than 3,000m" Really? The fact that one side of the moon is partially shadowed from asteroid impacts by earth wouldn't have anything to do with it? How do you figure the Earth shadows the Moon from impacts? Asteroids can whiz in between the Earth and Moon quite regularly. If it comes in closer to the Moon, then it may likely hit the Moon. Also the Moon's didn't always rotate in sync with its Earth orbit. That tidal locking occurred only after several billion years. Certainly at around the time that the craters were forming on the Moon, during the Late Heavy Bombardment, the Earth and Moon were only 100 million years old, and the Moon hadn't yet tidally locked at that point. Yousuf Khan |
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BBC News - Earth may once have had two moons
On 8/3/11 9:07 PM, Yousuf Khan wrote:
Also the Moon's didn't always rotate in sync with its Earth orbit. That tidal locking occurred only after several billion years. Certainly at around the time that the craters were forming on the Moon, during the Late Heavy Bombardment, the Earth and Moon were only 100 million years old, and the Moon hadn't yet tidally locked at that point. Yousuf Khan Do you know when the moon did become tidally locked? If so When? If not, why couldn't it have become tidally locked right away? What's your evidence? |
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BBC News - Earth may once have had two moons
Yousuf Khan wrote:
On 03/08/2011 9:17 PM, Vince Morgan wrote: "Yousuf wrote in message ... BBC News - Earth may once have had two moons http://www.bbc.co.uk/news/science-environment-14391929 "For decades, scientists have been trying to understand why the near side of the Moon - the one visible from Earth - is flat and cratered while the rarely-seen far side is heavily cratered and has mountain ranges higher than 3,000m" Really? The fact that one side of the moon is partially shadowed from asteroid impacts by earth wouldn't have anything to do with it? How do you figure the Earth shadows the Moon from impacts? Asteroids can whiz in between the Earth and Moon quite regularly. If it comes in closer to the Moon, then it may likely hit the Moon. Also the Moon's didn't always rotate in sync with its Earth orbit. That tidal locking occurred only after several billion years. Certainly at around the time that the craters were forming on the Moon, during the Late Heavy Bombardment, the Earth and Moon were only 100 million years old, and the Moon hadn't yet tidally locked at that point. Yousuf Khan Given the much greater strength of tidal forces when the Moon was closer to Earth after its formation, I would have expected synchronism to have taken place pretty quickly. Though it is true that large impacts on the Moon might be able to break the synch, it would be re-established after a few million years. I thought the difference between the two hemispheres was attributed mainly to the relative thickness of the crust. On the near side, the thinner crust meant that magma could flow to the surface without too much difficulty, but on the farside with its thicker crust, this would not happen easily, hence the absence of maria. -- Mike Dworetsky (Remove pants sp*mbl*ck to reply) |
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BBC News - Earth may once have had two moons
Dear Yousuf Khan:
"Yousuf Khan" wrote in message ... On 03/08/2011 9:17 PM, Vince Morgan wrote: "Yousuf wrote in message ... BBC News - Earth may once have had two moons http://www.bbc.co.uk/news/science-environment-14391929 "For decades, scientists have been trying to understand why the near side of the Moon - the one visible from Earth - is flat and cratered while the rarely-seen far side is heavily cratered and has mountain ranges higher than 3,000m" Really? The fact that one side of the moon is partially shadowed from asteroid impacts by earth wouldn't have anything to do with it? How do you figure the Earth shadows the Moon from impacts? Asteroids can whiz in between the Earth and Moon quite regularly. If it comes in closer to the Moon, then it may likely hit the Moon. True. The Earth shadows some "normal" impacts (path includes Earth at some point), but otherwise will have little effect. Also the Moon's didn't always rotate in sync with its Earth orbit. That tidal locking occurred only after several billion years. If it lobed off the Earth, it may have been nearly locked, day one. Certainly at around the time that the craters were forming on the Moon, during the Late Heavy Bombardment, the Earth and Moon were only 100 million years old, and the Moon hadn't yet tidally locked at that point. Maybe, not "certainly". Do note however that the lunar crust is "much" thinner on the side facing Earth, so it would not have supported much in the way of mountains during the Late Heavy Bombardment, whereas the far side (with its lack of radiative heat sink at ~293K) could have gotten much stiffer, sooner. David A. Smith |
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BBC News - Earth may once have had two moons
"Yousuf Khan" wrote in message
... BBC News - Earth may once have had two moons http://www.bbc.co.uk/news/science-environment-14391929 A better news reference is http://www.nature.com/news/2011/1108....2011.456.html The actual paper is at http://www.nature.com/nature/journal...ture10289.html As is Nature's style, its first paragraph acts as an abstract and contains the key results, but you will need a subscription or payment to view more than this. In article , "Vince Morgan" writes: The fact that one side of the moon is partially shadowed from asteroid impacts by earth wouldn't have anything to do with it? Probably not. The Earth subtends very little solid angle in the Moon's sky. Also, you have to explain not only the surface terrain differences but also differences in (at least) crust thickness and chemical composition. -- Help keep our newsgroup healthy; please don't feed the trolls. Steve Willner Phone 617-495-7123 Cambridge, MA 02138 USA |
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BBC News - Earth may once have had two moons
On 04/08/2011 2:34 AM, Mike Dworetsky wrote:
Given the much greater strength of tidal forces when the Moon was closer to Earth after its formation, I would have expected synchronism to have taken place pretty quickly. Though it is true that large impacts on the Moon might be able to break the synch, it would be re-established after a few million years. I thought the difference between the two hemispheres was attributed mainly to the relative thickness of the crust. On the near side, the thinner crust meant that magma could flow to the surface without too much difficulty, but on the farside with its thicker crust, this would not happen easily, hence the absence of maria. Well, I found the following site which estimates that it took around 7 million years for the Moon to lock on Earth. shatters.net • View topic - Moon Systems, Tidal Locking and Age http://www.shatters.net/forum/viewtopic.php?f=7&t=13956 Which is remarkably quick in my mind, I had thought it would take several hundred million years at the quickest. Yousuf Khan |
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