However, as we mentioned, the Moon’s orbit is tilted relative to the plane of Earth’s orbit about the Sun by about 5° (imagine two hula hoops with a common center, but tilted a bit). If the path of the Moon in the sky were identical to the path of the Sun (the ecliptic), we might expect to see an eclipse of the Sun and the Moon each month-whenever the Moon got in front of the Sun or into the shadow of Earth. At position 4, the Moon is farther away and thus cannot cover the Sun completely a ring of light thus shows around the Sun, creating what is called an “annular” eclipse. At positions 2 and 3, the eclipse is partial. In (b) you see what the Sun and Moon would look like in the sky at the four labeled points. Four points in the shadow are labeled with numbers. Notice the dark umbra and the lighter penumbra. (a) The shadow cast by a spherical body (the Moon, for example) is shown. Figure 4.21 illustrates the appearance of the Moon’s shadow and what the Sun and Moon would look like from different points within the shadow.įigure 4.21 Solar Eclipse. As you can imagine, the most spectacular eclipses occur when an object enters the umbra. The shadows of Earth and the Moon consist of two parts: a cone where the shadow is darkest, called the umbra, and a lighter, more diffuse region of darkness called the penumbra. Let’s look at how these happen in more detail.

When the Moon passes into the shadow of Earth, people on the night side of Earth see the Moon darken in what is called a lunar eclipse. When the Moon’s shadow strikes Earth, people within that shadow see the Sun at least partially covered by the Moon that is, they witness a solar eclipse. In general, an eclipse occurs whenever any part of either Earth or the Moon enters the shadow of the other. This shadow in space becomes apparent whenever another object moves into it. As a result, the Moon, as seen from Earth, can appear to cover the Sun, producing one of the most impressive events in nature.Īny solid object in the solar system casts a shadow by blocking the light of the Sun from a region behind it. Although the Sun is about 400 times larger in diameter than the Moon, it is also about 400 times farther away, so both the Sun and the Moon have the same angular size-about 1/2°. One of the coincidences of living on Earth at the present time is that the two most prominent astronomical objects, the Sun and the Moon, have nearly the same apparent size in the sky. Explain why lunar eclipses are much more common than solar eclipses.Differentiate between a total and partial solar eclipse.Describe what causes lunar and solar eclipses.By the end of this section, you will be able to:

Lunar eclipse diagram 2017