Lesson 3 Reading Guide - KC

Eclipses and Tides • What is a solar eclipse? • What is a lunar eclipse? • How do the Moon and the Sun affect Earth’s oceans? Lesson 3 Reading Guide - KC

Eclipses and Tides • umbra • penumbra • solar eclipse • lunar eclipse • tide Lesson 3 Reading Guide - Vocab

Shadows—the Umbra and the Penumbra Light from the Sun and other wide sources cast shadows with two distinct parts. Lesson 3-1

Shadows—the Umbra and the Penumbra (cont.) • The umbrais the central, darker part of a shadow where light is totally blocked. • The penumbrais the lighter part of a shadow where light is partially blocked. Lesson 3-1

Shadows—the Umbra and the Penumbra (cont.) • If you stood within an objects penumbra, you would be able to see only part of the light source. • If you stood within an objects umbra, you would not see the light source at all. Lesson 3-1

Solar Eclipses • During the new moon phase, Earth, the Moon, and the Sun are lined up and the Moon casts a shadow on Earth's surface. • When the Moon’s shadow appears on Earth’s surface, a solar eclipseis occurring. Lesson 3-2

During a total solar eclipse, the Moon appears to cover the Sun completely. You can only see a total solar eclipse from within the Moon’s umbra. Lesson 3-2

The sky becomes dark enough that you can see stars • A total solar eclipse will last no longer than about 7 minutes. Lesson 3-2

Solar Eclipses(cont.) • You can see a partial solar eclipse from within the Moon’s much larger penumbra. • The Sun’s appearance changes during an eclipse as the moon moves in the sky. • The stages of a partial solar eclipse are similar to the stages of a total solar eclipse, except that the Moon never completely covers the Sun. Lesson 3-2

Solar Eclipses(cont.) • Solar eclipses do not occur during every new-moon phase. • The next solar eclipse will occur in the US on August 21, 2017 Lesson 3-2

The Moon’s orbit is tilted slightly compared to Earth’s orbit. As a result, during most new moons, Earth is either above or below the Moon’s shadow. Lesson 3-2

Lunar Eclipses A lunar eclipseoccurs when the Moon moves into Earth’s shadow. Lesson 3-3

Lunar Eclipses(cont.) When the entire Moon moves through Earth’s umbra, a total lunar eclipse occurs. Lesson 3-3

Lunar Eclipses(cont.) • When only part of the Moon passes through Earth’s umbra, a partial lunar eclipse occurs. • Lunar eclipses can only occur during a full moon phase, when the Moon and the Sun are on opposite sides of Earth. • Unlike a total solar eclipse, you can see a total lunar eclipse from anywhere on Earth. Lesson 3-3

Lunar Eclipses(cont.) Lesson 3-3

Lunar Eclipses(cont.) Why is the Mood red during an eclipse? • The Earth’s atmosphere filters some sunlight and allows it to reach the Moon’s surface • The blue light is removed—scattered down to make a blue sky over those in daytime • Remaining light is red or orange • Some of this remaining light is bent or refracted so that a small fraction of it reaches the Moon • Exact appearance depends on dust and clouds in the Earth’s atmosphere Lesson 3-3

Tides • A tideis the daily rise and fall of sea level. • It is primarily the Moon’s gravity that causes Earth’s oceans to rise and fall twice each day. • The Moon’s gravity is slightly stronger on the side of Earth closer to the Moon and slightly weaker on the side of Earth opposite the Moon. Lesson 3-4

Tides(cont.) The gravitational differences cause tidal bulges in the oceans on opposite sides of Earth. Lesson 3-4

Tides(cont.) • High tides occur at the tidal bulges, and low tides occur between them. • Because the Sun is so far away from Earth, its effect on tides is about half that of the Moon. Lesson 3-4

Tides(cont.) Spring tides occur during the full moon and new moon phases, when the Sun’s and the Moon’s gravitational effects combine and produce higher high tides and lower low tides. Lesson 3-4

Tides(cont.) A neap tide occurs a week after a spring tide, when the Sun, Earth, and the Moon form a right angle and the Sun’s effect on tides reduces the Moon’s effect. Lesson 3-4

Shadows from a wide light source have two distinct parts. Lesson 3 - VS

The Moon’s shadow produces solar eclipses. Earth’s shadow produces lunar eclipses. Lesson 3 - VS

The positions of the Moon and the Sun in relation to Earth cause gravitational differences that produce tides. Lesson 3 - VS

If the Moon’s shadow appears on Earth’s surface, which of these is occurring? A.lunar eclipse B. tide C. solar eclipse D. neap tide Lesson 3 – LR1

What causes Earth’s tides? A. the Moon’s gravity B. the Moon’s tilted orbit C. Earth’s gravity D.the Moon’s umbra Lesson 3 – LR2

Which of these refers to the central, darker part of a shadow where light is totally blocked? A.umbra B.penumbra C.lunar eclipse D.tide Lesson 3 – LR3

Do you agree or disagree? 5. A solar eclipse happens when Earth moves between the Moon and the Sun. 6. The gravitational pull of the Moon and the Sun on Earth’s oceans causes tides. Lesson 3 - Now

Lesson 3 Reading Guide - KC