Earth’s shadow extends about 1,400,000 kilometers (870,000 miles) into space, in the direction opposite the sun. There are several good times to think about and be aware of Earth’s shadow. Follow the links below to learn more:
See Earth’s shadow any evening, ascending in the east. You can see Earth’s shadow any clear evening ascending in the eastern sky. The shadow is a deep blue-grey, and it’s darker than the blue of the twilight sky. The pink band above the shadow is called the Belt of Venus.
Notice: Earth’s shadow ascends in the east at the same rate that the sun is setting below the western horizon
The shadow of the Earth is big. You might have to turn your head to see the whole thing. And, just so you’ll recognize it more easily, remember that the shadow is curved, in just the same way that the whole Earth is curved.
You can also see the Earth’s shadow in the west before sunrise.
When the sun, the Earth and the moon are aligned in space (nearly or perfectly), with the Earth in between the sun and moon, then Earth’s shadow falls on the moon’s face. Then people on Earth see the shadow gradually turn a bright full moon dark in an eclipse of the moon.
As seen from Earth’s surface, there are typically two or more lunar eclipses every year. Some are total, some are partial, some are a subtle kind of eclipse known as penumbral.
During a lunar eclipse, a very small amount of light from the sun filters through Earth’s atmosphere onto Earth’s shadow on the moon. It’s why – at the middle part of a total lunar eclipse – the shadow on the moon looks reddish.
Bottom line: Check out Earth’s shadow. You might see it as an ascending line of darkness in the east just after sunset. Or you might see it brushing the moon’s face during a lunar eclipse. Or think about night as a shadow, when you’re standing outside in darkness after sunset … maybe tonight.
Deborah Byrd created the EarthSky radio series in 1991 and EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. "Being an EarthSky editor is like hosting a big global party for cool nature-lovers," she says.