The Earth’s Shadow

The Earth’s shadow is something everyone has seen countless times before and most likely not realized exactly what they were looking at. I have to confess that I was one of those people until I discovered what I was looking at. Now I look out for it whenever the skies are clear and I have a good view of the horizon.

During the day the Earth’s shadow will not be seen during the day as the shadow will be below the horizon. But come nightfall it is a different story and the shadow will be seen above the horizon.

(Click to Enlarge)

After the sun sets , or before the sun rises, we have that period known as twilight which lasts around 20 minutes and it is during this time that you will see the earth’s shadow.

In the picture above, I tried to recreate what the Earth’s shadow would look like from the point of an observer in Sydney looking west. In the picture the moon is getting ready to set below the horizon in the west and the sun is rising in the east out of frame of the picture.

Not really the best example but it should give you an example of what to look for.

The Earth’s shadow is thrown upon the atmosphere by the Earth and will normally be seen as a dark band just above the horizon in the opposite direction to the Sun. So if the sun is rising in the East, you would look for the shadow in the west….. and vice versa.

Above the blue band which is the Earth’s shadow you will see the Belt of Venus.

The Belt of Venus is the pinkish glow you can see in the sky either at sun rise or at sun set. and this can be seen roughly 10 to 20 degrees above the horizon. The Belt of Venus is always seperated from the horizon by the Earth’s shadow as seen above. The pink color is a result of the back scattering of red light from either the rising or setting sun.

~ by sydneystargazers on November 23, 2009.

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