Moon crossing the face of the earth
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:thumbsup: One question: In this picture, the Moon is between Earth and Sun. The camera is between Moon and Sun. Now, the Sun is illuminating both Moon and Earth. Should not the Moon be seen brighter than Earth; the Moon is closer to the Sun, and hence more brightly illuminated. However, the Moon is seen as dull, and the Earth as bright. Can this apparent brightness of Earth be attributed to the blue water all around? Whereas Moon is without water, and may be absorbing more light than it reflects? Is something not correct in the above argument?
Avijnata wrote:
Can this apparent brightness of Earth be attributed to the blue water all around? Whereas Moon is without water, and may be absorbing more light than it reflects?
The reflectiveness of a planet or moon is called its Albedo. If it reflected nothing, it would have an albedo of 0; if it reflected everything, it would have an albedo of 1. The Earth has an albedo of 0.37 whereas the full moon has an albedo of 0.12. So, the Earth reflects about 3 times as much of the light as the moon does. That is why it is brighter in the picture. Your guess that it is the water (but includes clouds as well as oceans) that are the main reflecting agents is correct; on the moon you only have the surface dust etc (called the regolith).
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Avijnata wrote:
Can this apparent brightness of Earth be attributed to the blue water all around? Whereas Moon is without water, and may be absorbing more light than it reflects?
The reflectiveness of a planet or moon is called its Albedo. If it reflected nothing, it would have an albedo of 0; if it reflected everything, it would have an albedo of 1. The Earth has an albedo of 0.37 whereas the full moon has an albedo of 0.12. So, the Earth reflects about 3 times as much of the light as the moon does. That is why it is brighter in the picture. Your guess that it is the water (but includes clouds as well as oceans) that are the main reflecting agents is correct; on the moon you only have the surface dust etc (called the regolith).
:thumbsup: Very nicely explained. Thanks.
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Avijnata wrote:
Can this apparent brightness of Earth be attributed to the blue water all around? Whereas Moon is without water, and may be absorbing more light than it reflects?
The reflectiveness of a planet or moon is called its Albedo. If it reflected nothing, it would have an albedo of 0; if it reflected everything, it would have an albedo of 1. The Earth has an albedo of 0.37 whereas the full moon has an albedo of 0.12. So, the Earth reflects about 3 times as much of the light as the moon does. That is why it is brighter in the picture. Your guess that it is the water (but includes clouds as well as oceans) that are the main reflecting agents is correct; on the moon you only have the surface dust etc (called the regolith).
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The reflectiveness of a planet or moon is called its Albedo
"planets or moon" only? No, sorry, Albedo is much more General :-D
Well, yeah. But it's really difficult to measure the albedo of a star or black hole... :laugh:
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:thumbsup: One question: In this picture, the Moon is between Earth and Sun. The camera is between Moon and Sun. Now, the Sun is illuminating both Moon and Earth. Should not the Moon be seen brighter than Earth; the Moon is closer to the Sun, and hence more brightly illuminated. However, the Moon is seen as dull, and the Earth as bright. Can this apparent brightness of Earth be attributed to the blue water all around? Whereas Moon is without water, and may be absorbing more light than it reflects? Is something not correct in the above argument?
I think if remember the moons actual colour is a sort of dirty grey rather than the yellow commonly associated with it. I seem to remember there was a Mythbusters episode devoted to it. the reoglith does reflect at an angle to seem bright or something!:confused:
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Well, yeah. But it's really difficult to measure the albedo of a star or black hole... :laugh:
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Of a star not really, of a black hole yes...very difficult where limes likes to go :laugh:
It's probably the other way round: Albedo of a black hole[^] But a star? The light emitted is so huge that it's going to be really difficult to spot the reflection, even if the star emitting it is pretty close! :laugh: That's my guess, anyway.
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It's probably the other way round: Albedo of a black hole[^] But a star? The light emitted is so huge that it's going to be really difficult to spot the reflection, even if the star emitting it is pretty close! :laugh: That's my guess, anyway.
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Yes I agree. But fact is Albedo of stars are Facts, Albedo of black hole are theory, at this time. Also looking Forward to _really_ prove the later ones :) Not really the final explanation, but also not the worst one, for an overview good enough: https://en.wikipedia.org/wiki/Albedo[^]
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I think if remember the moons actual colour is a sort of dirty grey rather than the yellow commonly associated with it. I seem to remember there was a Mythbusters episode devoted to it. the reoglith does reflect at an angle to seem bright or something!:confused:
glennPattonBackInThePUB wrote:
the moons actual colour is a sort of dirty grey
Yes, we saw that in the moon landing video. Everythnig's grey up there. :badger:
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glennPattonBackInThePUB wrote:
the moons actual colour is a sort of dirty grey
Yes, we saw that in the moon landing video. Everythnig's grey up there. :badger:
Yup, but as I recall the 'video' cameras were black & white
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Yup, but as I recall the 'video' cameras were black & white
That's all they had to be.
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That's all they had to be.
Point, mind you a neighbour of my parents bought a colour TV to see it!
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Point, mind you a neighbour of my parents bought a colour TV to see it!
Maybe to see Louis Armstrong? :~
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Avijnata wrote:
Can this apparent brightness of Earth be attributed to the blue water all around? Whereas Moon is without water, and may be absorbing more light than it reflects?
The reflectiveness of a planet or moon is called its Albedo. If it reflected nothing, it would have an albedo of 0; if it reflected everything, it would have an albedo of 1. The Earth has an albedo of 0.37 whereas the full moon has an albedo of 0.12. So, the Earth reflects about 3 times as much of the light as the moon does. That is why it is brighter in the picture. Your guess that it is the water (but includes clouds as well as oceans) that are the main reflecting agents is correct; on the moon you only have the surface dust etc (called the regolith).
Very good answer, the only thing is that clouds typically have a far greater albedo than the oceans.
Cheers, विक्रम "We have already been through this, I am not going to repeat myself." - fat_boy, in a global warming thread :doh:
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:thumbsup: One question: In this picture, the Moon is between Earth and Sun. The camera is between Moon and Sun. Now, the Sun is illuminating both Moon and Earth. Should not the Moon be seen brighter than Earth; the Moon is closer to the Sun, and hence more brightly illuminated. However, the Moon is seen as dull, and the Earth as bright. Can this apparent brightness of Earth be attributed to the blue water all around? Whereas Moon is without water, and may be absorbing more light than it reflects? Is something not correct in the above argument?
I also think you are imagining the Sun as being much closer to us than it is. The Moon is a bit more than a light second away from us. The distance to the Sun is eight light MINUTES, or 500 times as great. So the Moon was one fifth of a percent, a factor of 0.002, closer to the Sun when the image was taken than Earth was. I think you'd be hard pressed to notice the effect of this difference even if the two bodies had exactly the same albedo.
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I also think you are imagining the Sun as being much closer to us than it is. The Moon is a bit more than a light second away from us. The distance to the Sun is eight light MINUTES, or 500 times as great. So the Moon was one fifth of a percent, a factor of 0.002, closer to the Sun when the image was taken than Earth was. I think you'd be hard pressed to notice the effect of this difference even if the two bodies had exactly the same albedo.
Yes, you're right. Agree. But, does the position of the camera also count, in whatever small way? The camera is closer to the Moon than to the Earth. My answer would be: Keeping a much brighter object farther away from the camera would register more on camera film than a dull object kept closer.
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Avijnata wrote:
Can this apparent brightness of Earth be attributed to the blue water all around? Whereas Moon is without water, and may be absorbing more light than it reflects?
The reflectiveness of a planet or moon is called its Albedo. If it reflected nothing, it would have an albedo of 0; if it reflected everything, it would have an albedo of 1. The Earth has an albedo of 0.37 whereas the full moon has an albedo of 0.12. So, the Earth reflects about 3 times as much of the light as the moon does. That is why it is brighter in the picture. Your guess that it is the water (but includes clouds as well as oceans) that are the main reflecting agents is correct; on the moon you only have the surface dust etc (called the regolith).
So does the Moon absorb more energy than the Earth. We know it doesn't so what happens?
