because its the earths shadow. it cant be seen fom earth ..
When the moon passes through the earth's penumbra there is a partial eclipse of the moon for those on the side of the earth facing the moon. If it passes through the umbra, the eclipse is total.
You're on exactly the right track, and you're thinking exactly right.But it's not exactly the "moon's" penumbra ... it's the penumbra ofthe moon's shadow.
Apulse
People in the penumbra during a solar eclipse will see a partial eclipse, where the sun is only partially covered by the moon. This results in a crescent shape of sunlight rather than a total blockage. The amount of sunlight that is blocked will depend on how close they are to the umbra, the central region of the shadow.
Umbra and penumbra when referred to the moon describes the shadow which is formed when light is blocked from the sun, by the moon. This shadow which falls on the Earth and has two distinct regions; a partially shadowed area which is the penumbra and the centre point a totally dark umbra. We on Earth looking skyward and watching the shadow pass as the Earth revolves would describe the penumbra as a partial eclipse and the umbra as a total eclipse.
When the moon passes through the earth's penumbra there is a partial eclipse of the moon for those on the side of the earth facing the moon. If it passes through the umbra, the eclipse is total.
The largest part of the Moon's shadow is the penumbra.
Penumbra
You're on exactly the right track, and you're thinking exactly right.But it's not exactly the "moon's" penumbra ... it's the penumbra ofthe moon's shadow.
-- It's not possible for the moon to be in the penumbra of the moon's shadow,any more than it's possible for you to stand anywhere in your own shadow.-- When all or part of the moon is in the penumbra of the EARTH's shadow, a penumbraleclipse ... practically imperceptible to casual observers ... is occurring.-- When any part but not all of the moon is in the UMBRA of the Earth's shadow, thena partial lunar eclipse is occurring. Then, at least part of the remainder of the moon mustalso be in the PENUMBRA of the Earth's shadow at the same time.
Please note that in a penumbra lunar eclipse there is nothing to see; nothing spectacular. If you look at the Moon, you might not even notice that there is an eclipse going on; it will just get a bit darker (more on one side than on the other). There was a penumbra eclipse on 25 May 2013; there is going to be another one on 18 October 2013.
penumbra or umbra.
Apulse
People in the penumbra during a solar eclipse will see a partial eclipse, where the sun is only partially covered by the moon. This results in a crescent shape of sunlight rather than a total blockage. The amount of sunlight that is blocked will depend on how close they are to the umbra, the central region of the shadow.
I think you are asking what is the lighter part of the Earth's shadow on the Moon that surrounds the darkest part. The penumbra is this lighter part of the shadow. The darkest part is the umbra.
You will see a partial eclipse if you are in the penumbra.
Umbra and penumbra when referred to the moon describes the shadow which is formed when light is blocked from the sun, by the moon. This shadow which falls on the Earth and has two distinct regions; a partially shadowed area which is the penumbra and the centre point a totally dark umbra. We on Earth looking skyward and watching the shadow pass as the Earth revolves would describe the penumbra as a partial eclipse and the umbra as a total eclipse.