SOLAR ECLIPSES
Video Summary
Every now and then, the Sun, Earth,
and Moon align so that, when viewed
from the Earth, the Moon eclipses the
Sun’s light. Solar eclipses are fairly
common—the Moon will block out
some portion of the Sun at least twice
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a year. However, it is still a special
event to be able to witness a total solar eclipse. In this video segment adapted from
NASA, learn how solar eclipses happen and why they are so difficult to witness.
Topics Covered:
– Earth and Space Science: Earth in the Universe
Recommended for Grades 3-8
Media Type: QuickTime Video
Video Length: 1m 53s
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Discussion Questions
 What is happening to the Sun as seen from Earth during a solar eclipse?
Either describe or draw it.
 Why can a solar eclipse happen only during a new Moon phase?
 What would a solar eclipse look like if the Moon were smaller than it is now?
 Using two balls of quite different sizes, see if you can demonstrate why the
Moon and Sun appear to be the same size when viewed from Earth.
 Based on what you now know about a solar eclipse, try to explain what happens
during a lunar eclipse. (Hint: They only can happen when there is a full Moon!)
Background Essay
The Moon cycles through its phases during its 29.5-day orbit around Earth. While the Sun
always illuminates half of the Moon, the apparent shape of the Moon as seen from Earth
depends on Earth’s relative position. For example, at full moon, the Moon appears as a
full disk because Earth is between the Moon and the Sun and the illuminated side faces
Earth. But at new moon, when the Moon is between the Sun and Earth, the Moon seems
to be gone because the lit side faces away from Earth. A solar eclipse is only possible
during the new moon phase, when the Moon’s shadow can be cast on Earth. During the
full moon, Earth’s shadow can be cast on the Moon, resulting in a lunar eclipse.
Solar Eclipses
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© 2007 WGBH Educational Foundation. All rights reserved.
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There are several different types of eclipses, corresponding to how the Sun, Earth, and
Moon align. The shadows of the Moon and Earth each have two parts. The umbra is the
central part of the shadow where sunlight is completely blocked; the penumbra is the
outer area where sunlight is only partially blocked. Depending on which part of the
Moon’s shadow is cast on Earth, a solar eclipse can be partial, annular, or total.
Similarly, there are three types of lunar eclipses—penumbral, partial, and
total—depending on which section of Earth’s shadow the Moon passes through.
Eclipses do not happen at the new and full moon every month because, for most of its
orbit, the Moon is above or below the ecliptic plane—the plane of Earth’s orbit around
the Sun. Only when the Moon’s orbit crosses through the ecliptic plane, can the Sun,
Moon, and Earth align to produce an eclipse. This occurs at least twice a year, at varying
times, for a period of a few weeks. During such seasons, there will always be a solar
eclipse and a lunar eclipse. Occasionally, the three bodies also align at other times of the
year, producing up to seven eclipses in one year.
Though eclipses are common, total eclipses are quite rare. It is a special treat to witness a
total solar eclipse, which happens only about once every 1.5 years, lasts only a few
minutes, and is only visible along a narrow path. Lunar eclipses, on the other hand, can
last as long as a couple of hours, are often easily observed with the naked eye, and are
visible from the entire nighttime side of Earth.
To learn more about total solar eclipses, check out Total Solar Eclipse Animation.
To learn more about the total solar eclipse in 1991, check out Eclipse of the Century.
To learn more about the Sun, check out Characteristics of the Sun.
To learn more about the Moon’s role in eclipses, check out Phases of the Moon.
Professional Development Courses Using This Resource:
– Teaching Earth and Space Science
– Earth in Time and Space
Curricular Standards Correlations:
NSES, Project 2061, MCREL, and state standards correlations available at
www.teachersdomain.org. (Free registration required for your specific state standards correlated to this resource.)
Source: NASA/JPL-Caltech
Materials used courtesy of: NASA/JPL-Caltech
Collection developed and produced for Teachers’ Domain by:
Collection funded by:
”Teachers‘ Domain is proud to be a Pathways portal to the National Science Digital Library.”
Solar Eclipses
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