THE SUN AND THE EARTH_MOON SYSTEM The Earth and the Solar System Lesson 2

Lesson objectives: Vocabulary: The student will be able to: Explain solar and lunar eclipses Identify and describe the phases of the Moon and explain why they occur Explain how movements of the Earth and Moon affect Earth’s tides. Vocabulary: Crescent Gibbous Lunar eclipse Penumbra Solar eclipse umbra

INTRODUCTION: The Earth, moon, and Sun are linked together in space due to the gravitational pull that exists among them. Monthly or daily cycles continually remind us of these links. Every month, you can see the Moon change. This is due to where it is relative to the Sun and the Earth. In one phase, the moon is brightly illuminated, thus a full moon. But in the opposite face it is completely dark, thus a new moon. When the moon is in the right position, it causes an eclipse. The daily tides are another reminder of the Moon and the Sun. They are caused by the pull of the Moon and the Sun on the Earth.

SOLAR ECLIPSES When the moon passes directly between the Earth and the Sun, it causes a solar eclipse. The Moon casts a shadow on the Earth and blocks our view of the Sun. This happens only when all three are lined up in the same plane. This plane is called the ecliptic. The ecliptic is the plane of Earth’s orbit around the sun. The Moon’s shadow has two distinct parts. The umbra is the inner, cone-shaped of the shadow. It is the part in which all of the light has been blocked. The penumbra is the outer part of Moon’s shadow. It is where the light is only partially blocked. During a solar eclipse, the Moon casts a shadow on the Earth. The dark shadow is the umbra and the lighter shadow is the penumbra.

SOLAR ECLIPSE: (continued) A total eclipse occurs when the Moon’s shadow completely blocks the sun. If only part of the Sun is out of the view, it is a partial solar eclipse. Solar eclipses are rare events and they usually only last a few minutes. This is because the Moon’s shadow only covers a very small area on Earth and Earth is turning very rapidly. During a solar eclipse, it’s easy to see the Sun’s corona and solar prominences. http://eclipse.gsfc.nasa.gov/solar.html

Solar Eclipse

A LUNAR ECLIPSE Sometimes a full moon moves through Earth’s shadow. This is a lunar eclipse. During a lunar eclipse, the Moon travels completely in the Earth’s umbra. During a partial eclipse, only a portion of the Moon enters Earth’s umbra. When the Moon passes through Earth’s penumbra, it is a penumbral eclipse. Since Earth’s shadow is large, a lunar eclipse lasts for hours. Anyone with a view of the Moon can see a lunar eclipse. Partial lunar eclipses occur at least twice a year, but total lunar eclipses are less common. The moon glows with a dull red coloring during a total lunar eclipse. This phenomena is called the blood moon.

A LUNAR Eclipse

The Phases of the moon The Moon does not produce any light of its own. It only reflects light from the Sun. As the Moon moves around the Earth, we see different parts of the Moon lit up by the Sun. This causes the phases of the Moon. As the Moon revolves around Earth, it changes from fully lit to completely dark and back again. A full moon occurs when the whole side facing Earth is lit. This happens when Earth is between the Moon and the Sun. About one week later, the Moon enters the quarter-moon phase. Only half of the Moon’s lit surface is visible from Earth, so it appears as a half circle. When the Moon moves between Earth and the Sun, the side facing Earth is completely dark. This is called the new moon phase.

The Phases of the moon

The phases of the moon: (continued) Sometimes you can just barely make out the outline of the new moon in the sky. This is because some sunlight reflects off the Earth and hits the moon. Before and after the quarter-moon phases are the gibbous and the crescent phases. During the crescent moon phase, the moon is less than half lit. It is seen as only a sliver or crescent shape. During the gibbous moon phase, the moon is more than half lit, but it is not full. The Moon undergoes a complete cycle of phases about every 29.5 days.

Lunar and Solar Eclipses