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RE: Science Porn
February 10, 2016 at 7:59 am
(This post was last modified: February 10, 2016 at 8:02 am by Alex K.)
Steel, this must be wrong 
Is the surface of the moon really in thermal equilibrium with the light it reflects? I think this is a crucial difference between the sun and the moon.
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RE: Science Porn
February 10, 2016 at 8:30 am
Which portion are you saying is incorrect?
"There remain four irreducible objections to religious faith: that it wholly misrepresents the origins of man and the cosmos, that because of this original error it manages to combine the maximum servility with the maximum of solipsism, that it is both the result and the cause of dangerous sexual repression, and that it is ultimately grounded on wish-thinking." ~Christopher Hitchens, god is not Great
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RE: Science Porn
February 10, 2016 at 8:32 am
(February 10, 2016 at 7:59 am)Alex K Wrote: Is the surface of the moon really in thermal equilibrium with the light it reflects? I think this is a crucial difference between the sun and the moon.
Wouldn't it have to be? Otherwise the surface of the moon would either store thermal energy or run out, yeah?
"There remain four irreducible objections to religious faith: that it wholly misrepresents the origins of man and the cosmos, that because of this original error it manages to combine the maximum servility with the maximum of solipsism, that it is both the result and the cause of dangerous sexual repression, and that it is ultimately grounded on wish-thinking." ~Christopher Hitchens, god is not Great
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RE: Science Porn
February 10, 2016 at 8:52 am
(This post was last modified: February 10, 2016 at 9:08 am by Alex K.)
(February 10, 2016 at 8:32 am)SteelCurtain Wrote: (February 10, 2016 at 7:59 am)Alex K Wrote: Is the surface of the moon really in thermal equilibrium with the light it reflects? I think this is a crucial difference between the sun and the moon.
Wouldn't it have to be? Otherwise the surface of the moon would either store thermal energy or run out, yeah?
The energy captured by the moon rock by absorbing sunlight is reemitted by the rock as infrared thermal radiation which is added to the reflected light, and this way the moon is keeping the balance (*). This thermal radiation of the moon has the same low temperature as the rock and very different properties compared to the sunlight that is reflected directly, doesn't it. At first glance, it seems to me that it is with this IR thermal radiation (which is in th. equilibrium with the moon) that RMs argument would work, not with the reflected sunlight (which is not in th. equilibrium with the moon).
To elaborate, assume that the moon, for the sake of simplicity, absorbs half the sunlight and reflects half, then its thermal radiation and the reflected sunlight will have roughly the same power. HOWEVER, the emitted thermal radiation will be low-frequency (low-temperature) IR, whereas the reflected sunlight will simply be *dim* but higher-frequency light which, if you look at its spectrum, actually belongs to a temperature of thousands of degrees, but is greatly attenuated in intensity because the sun is far away.
(*) The power emitted by a body goes with the temperature to the fourth power, so the moon will heat up until the ~ T^4 thermal radiation carries away the same radiation power that the absorbed sunlight deposits in the rock.
The fool hath said in his heart, There is a God. They are corrupt, they have done abominable works, there is none that doeth good.
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RE: Science Porn
February 10, 2016 at 9:14 am
I'm not saying I'm definitely 100% right, but I feel relatively confident with my argument.
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RE: Science Porn
February 10, 2016 at 9:21 am
(This post was last modified: February 10, 2016 at 9:22 am by Edwardo Piet.)
Starcraft/the Outstanding Bimbo Man Wrote:[...]
![[Image: wait.png]](https://images.weserv.nl/?url=what-if.xkcd.com%2Fimgs%2Fa%2F145%2Fwait.png)
[...]
LMFAO!!!
Good old Issac Asimov.
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RE: Science Porn
February 10, 2016 at 9:42 am
(February 10, 2016 at 8:52 am)Alex K Wrote: (February 10, 2016 at 8:32 am)SteelCurtain Wrote: Wouldn't it have to be? Otherwise the surface of the moon would either store thermal energy or run out, yeah?
The energy captured by the moon rock by absorbing sunlight is reemitted by the rock as infrared thermal radiation which is added to the reflected light, and this way the moon is keeping the balance (*). This thermal radiation of the moon has the same low temperature as the rock and very different properties compared to the sunlight that is reflected directly, doesn't it. At first glance, it seems to me that it is with this IR thermal radiation (which is in th. equilibrium with the moon) that RMs argument would work, not with the reflected sunlight (which is not in th. equilibrium with the moon).
To elaborate, assume that the moon, for the sake of simplicity, absorbs half the sunlight and reflects half, then its thermal radiation and the reflected sunlight will have roughly the same power. HOWEVER, the emitted thermal radiation will be low-frequency (low-temperature) IR, whereas the reflected sunlight will simply be *dim* but higher-frequency light which, if you look at its spectrum, actually belongs to a temperature of thousands of degrees, but is greatly attenuated in intensity because the sun is far away.
(*) The power emitted by a body goes with the temperature to the fourth power, so the moon will heat up until the ~ T^4 thermal radiation carries away the same radiation power that the absorbed sunlight deposits in the rock.
As someone on the experimental park... I say we gather on a full moon night and test it! Anyone has a big lens?
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RE: Science Porn
February 10, 2016 at 9:48 am
Great, I've got my box of chalk right here, I thought you bring the 100 ton lens!!!
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RE: Science Porn
February 10, 2016 at 9:51 am
(This post was last modified: February 10, 2016 at 9:52 am by Alex K.)
I googled, and these people here agree with me exactly
http://physics.stackexchange.com/questio...-moonlight
in particular this:
MSalters Wrote:Your argument about black-body radiation from the moon holds for a new moon. I'll bet that agrees with your gut feeling. With a full moon, you're discussing reflected sunlight which isn't in thermal equilibrium with the moon surface
The fool hath said in his heart, There is a God. They are corrupt, they have done abominable works, there is none that doeth good.
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RE: Science Porn
February 10, 2016 at 10:02 am
(This post was last modified: February 10, 2016 at 10:14 am by Alex K.)
I am beginning to suspect that it is true that one indeed cannot heat something to very high temperatures using scattered light from the moon because the intensity can never become larger than that on the moon surface directly (the etendue argument), but that RMs last reason he gives using the thermal equilibrium is wrong.
The fool hath said in his heart, There is a God. They are corrupt, they have done abominable works, there is none that doeth good.
Psalm 14, KJV revised edition
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