What is a solar eclipse?
What is a solar eclipse?
KEY TERMS corona: outer layer of the sun's atmosphere solar eclipse: passing of the moon between the Earth and the sun
103
LESSON 18
What is a solar eclipse?
Everyone has seen shadows. You have seen shadows of trees, buildings, and fences. How often have you noticed your own shadow following you? You can see a shadow right now! Just hold your hand close to this page. What do you see on the page? What is a shadow? A shadow is an area of darkness. It forms when an object gets in the way or blocks light. Every object that blocks light forms a shadow. The Earth and moon are no exceptions. The Earth and moon block the sun's light. They cast huge cone-shaped shadows deep into space. The Earth and moon are always moving. Sometimes the Earth moves behind the moon. Part of the Earth is in the moon's shadow. For the people at this place on Earth, the moon blocks out, or eclipses, the sun. The eclipsed area becomes dark. For a short period of time, it looks like it is night time. A solar eclipse [SOH-ler uh-CLIPS] takes place when the sun, moon and Earth are in a straight or almost straight line with the moon between the sun and the Earth. A solar eclipse does not last long — no longer than a few minutes in any one place. Since scientists know a lot about the orbits of the Earth and the moon, they can accurately predict: • when an eclipse will take place • where it will take place • how long it will last
104
UNDERSTANDING A SOLAR ECLIPSE Figure A shows a solar eclipse. Study it and answer the questions. Identify the following by letter.
1. sun 2. Earth 3. moon 4. moon's orbit A shadow has a dark middle part, and a lighter outer part. 5. What do we call the darker middle part'? 6. What do we call the lighter outer party
Figure A
7. Which part of the shadow covers a wider area?
Figure B shows a multiple exposure of a solar eclipse. The top left shows the sun before the moon moves in front of it. In the following images, the moon appears to cover up more and more of the sun. The sun then reappears at the bottom right.
Figure B 105
TOTAL SOLAR ECLIPSES There are two main kinds of solar eclipses — total solar eclipses, and partial solar eclipses. Figure C shows the sun during a total solar eclipse. The sun is completely blocked. Only light from its rim or corona [kuh-ROH-nuh] can be seen. Look back at Figure A. 1. Where on Earth would you be to see what is shown in Figure C? x, y, z
2. This area is called the umbra, penumbra
3. It is an area of full light, reduced light, complete darkness
Figure C Total solar eclipse PARTIAL SOLAR ECLIPSE Figure D shows the sun during a partial eclipse. Part of the sun seems "chopped off." Look back at Figure A again. 4. Where would you be to experience a partial solar eclipse?
x, y, z
5. This area is called the umbra, penumbra
6. It is an area of full light, reduced light, complete darkness
7. Imagine that you are in area "z." Would
Figure D
Partial solar eclipse
you see an eclipse? 8. Why?
106
THE PATH OF A SOLAR ECLIPSE
Europe
North America
Africa Atlantic Ocean area of partial solar eclipse (penumbra)
Pacific Ocean
South America
Figure E During an eclipse, the moon moves in its orbit around the Earth and the Earth rotates. Therefore, the place on the surface of the Earth that is in the moon's shadow changes. As the eclipse moves slowly across the Earth, different people in different places see it at different times. Figure E shows the path of the total solar eclipse of February 26, 1979. The next such eclipse that can be seen from North America will be in the year 2017.
107
TRUE OR FALSE
In the space provided, write "true" if the sentence is true. Write "false" if the sentence is false. 1. A solid object can cast a shadow. 2. The Earth and moon cast shadows. 3. Light is needed for a shadow to form. 4. During a solar eclipse, we cannot see the moon. 5. During a solar eclipse, the Earth is between the sun and the moon. 6. A solar eclipse can be seen from any part of the Earth that is having daylight at the time of the eclipse. 7. The place to see a solar eclipse changes. 8. A solar eclipse lasts a long time. 9. Partial solar eclipses can be seen in more places than total solar eclipses.
10. You can always see the sun's corona.
MATCHING
Match each term in Column A with its description in Column B. Write the correct letter in the space provided. Column A
108
Column B
1. umbra
a) sun's halo
2. penumbra
b) darker part of a shadow
3. solar eclipse
c) usually are not in a line
4. corona
d) sun blocked out
5. sun, Earth, and moon
e) lighter part of a shadow
FILL IN THE BLANK
Complete each statement using a term or terms from the list below. Write your answers in the spaces provided. Some words may be used more than once. solar eclipse Earth partial shadows
sun eclipse moves blocks
total darkness moon corona
1. A shadow is an area of 2. A shadow forms when an object 3. The
and
light block the sun's light. They
cast long, cone-shaped 4. Sometimes the shadow of a heavenly body blocks out another heavenly body. This is called an 5. The blocking out of the sun by the moon's shadow is called a 6. A solar eclipse occurs when the
is between the
and the 7. When the moon blocks out all of the sun, we have a
solar
eclipse. 8. When the moon blocks out a part of the sun, we have a solar eclipse. 9. During a total eclipse, we can see only the sun's rim. This is called the
10. The place where you can see a solar eclipse
across part of the
Earth's surface.
_ -ING OUT A solar eclipse can take place only during one moon phase. Which phase is it? Why?
109
SCIENCE EXTRA Lunar Prospector Not long after the start of the mission, large amounts of hydrogen were found. This discovery led scientists to believe that there is ice on the moon.
You can use the Internet to share in the excitement of NASA's first trip to the moon in over 25 years. Just log on to NASA's Web site at www.nasa.gov. You can learn about the spacecraft Lunar Prospector and what it discovered on its journey to the moon. Lunar Prospector was sent to explore the surface of the moon on January 6, 1998. After traveling through space, on-board engines were fired. This put Lunar Prospector into an orbit around the poles. Following this path, Prospector mapped the entire surface of the moon. Lunar Prospector carried instruments to find out about the chemistry of the moon. A Gamma Ray Spectrometer helped study the chemistry of the moon's surface. Another instrument aboard was a Neutron Spectrometer. This instrument is used to find hydrogen. It is one of the elements in water.
110
Other data showed that the moon has a small core. This information backs up the theory that the moon was torn away from the Earth. This may have happened when something about the size of Mars smashed into the Earth. Scientists ended the Lunar Prospector mission on July 31, 1999. They successfully completed a controlled crash of the spacecraft into a crater on the moon. Spacecraft have been studying the moon for over 40 years. In 1959, Russia sent the first space ship to the moon. NASA then sent its own space ships to the moon. The goal was to learn about the surface of the moon. Americans wanted to land astronauts on the moon. On July 20, 1969, Neil Armstrong landed the Apollo II spacecraft on the moon. He was the first man to walk on the moon. Other missions were sent to the moon. Rock samples were collected and returned to the Earth. Over 800 pounds of rock have been collected for scientists to study. There is still much we do not know about the moon. Many scientists believe that we should return to the moon and conduct more studies. There might be clues which could help us understand how the Solar System began.
KEY TERMS corona: outer layer of the sun's atmosphere solar eclipse: passing of the moon between the Earth and the sun
103
LESSON 18
What is a solar eclipse?
Everyone has seen shadows. You have seen shadows of trees, buildings, and fences. How often have you noticed your own shadow following you? You can see a shadow right now! Just hold your hand close to this page. What do you see on the page? What is a shadow? A shadow is an area of darkness. It forms when an object gets in the way or blocks light. Every object that blocks light forms a shadow. The Earth and moon are no exceptions. The Earth and moon block the sun's light. They cast huge cone-shaped shadows deep into space. The Earth and moon are always moving. Sometimes the Earth moves behind the moon. Part of the Earth is in the moon's shadow. For the people at this place on Earth, the moon blocks out, or eclipses, the sun. The eclipsed area becomes dark. For a short period of time, it looks like it is night time. A solar eclipse [SOH-ler uh-CLIPS] takes place when the sun, moon and Earth are in a straight or almost straight line with the moon between the sun and the Earth. A solar eclipse does not last long — no longer than a few minutes in any one place. Since scientists know a lot about the orbits of the Earth and the moon, they can accurately predict: • when an eclipse will take place • where it will take place • how long it will last
104
UNDERSTANDING A SOLAR ECLIPSE Figure A shows a solar eclipse. Study it and answer the questions. Identify the following by letter.
1. sun 2. Earth 3. moon 4. moon's orbit A shadow has a dark middle part, and a lighter outer part. 5. What do we call the darker middle part'? 6. What do we call the lighter outer party
Figure A
7. Which part of the shadow covers a wider area?
Figure B shows a multiple exposure of a solar eclipse. The top left shows the sun before the moon moves in front of it. In the following images, the moon appears to cover up more and more of the sun. The sun then reappears at the bottom right.
Figure B 105
TOTAL SOLAR ECLIPSES There are two main kinds of solar eclipses — total solar eclipses, and partial solar eclipses. Figure C shows the sun during a total solar eclipse. The sun is completely blocked. Only light from its rim or corona [kuh-ROH-nuh] can be seen. Look back at Figure A. 1. Where on Earth would you be to see what is shown in Figure C? x, y, z
2. This area is called the umbra, penumbra
3. It is an area of full light, reduced light, complete darkness
Figure C Total solar eclipse PARTIAL SOLAR ECLIPSE Figure D shows the sun during a partial eclipse. Part of the sun seems "chopped off." Look back at Figure A again. 4. Where would you be to experience a partial solar eclipse?
x, y, z
5. This area is called the umbra, penumbra
6. It is an area of full light, reduced light, complete darkness
7. Imagine that you are in area "z." Would
Figure D
Partial solar eclipse
you see an eclipse? 8. Why?
106
THE PATH OF A SOLAR ECLIPSE
Europe
North America
Africa Atlantic Ocean area of partial solar eclipse (penumbra)
Pacific Ocean
South America
Figure E During an eclipse, the moon moves in its orbit around the Earth and the Earth rotates. Therefore, the place on the surface of the Earth that is in the moon's shadow changes. As the eclipse moves slowly across the Earth, different people in different places see it at different times. Figure E shows the path of the total solar eclipse of February 26, 1979. The next such eclipse that can be seen from North America will be in the year 2017.
107
TRUE OR FALSE
In the space provided, write "true" if the sentence is true. Write "false" if the sentence is false. 1. A solid object can cast a shadow. 2. The Earth and moon cast shadows. 3. Light is needed for a shadow to form. 4. During a solar eclipse, we cannot see the moon. 5. During a solar eclipse, the Earth is between the sun and the moon. 6. A solar eclipse can be seen from any part of the Earth that is having daylight at the time of the eclipse. 7. The place to see a solar eclipse changes. 8. A solar eclipse lasts a long time. 9. Partial solar eclipses can be seen in more places than total solar eclipses.
10. You can always see the sun's corona.
MATCHING
Match each term in Column A with its description in Column B. Write the correct letter in the space provided. Column A
108
Column B
1. umbra
a) sun's halo
2. penumbra
b) darker part of a shadow
3. solar eclipse
c) usually are not in a line
4. corona
d) sun blocked out
5. sun, Earth, and moon
e) lighter part of a shadow
FILL IN THE BLANK
Complete each statement using a term or terms from the list below. Write your answers in the spaces provided. Some words may be used more than once. solar eclipse Earth partial shadows
sun eclipse moves blocks
total darkness moon corona
1. A shadow is an area of 2. A shadow forms when an object 3. The
and
light block the sun's light. They
cast long, cone-shaped 4. Sometimes the shadow of a heavenly body blocks out another heavenly body. This is called an 5. The blocking out of the sun by the moon's shadow is called a 6. A solar eclipse occurs when the
is between the
and the 7. When the moon blocks out all of the sun, we have a
solar
eclipse. 8. When the moon blocks out a part of the sun, we have a solar eclipse. 9. During a total eclipse, we can see only the sun's rim. This is called the
10. The place where you can see a solar eclipse
across part of the
Earth's surface.
_ -ING OUT A solar eclipse can take place only during one moon phase. Which phase is it? Why?
109
SCIENCE EXTRA Lunar Prospector Not long after the start of the mission, large amounts of hydrogen were found. This discovery led scientists to believe that there is ice on the moon.
You can use the Internet to share in the excitement of NASA's first trip to the moon in over 25 years. Just log on to NASA's Web site at www.nasa.gov. You can learn about the spacecraft Lunar Prospector and what it discovered on its journey to the moon. Lunar Prospector was sent to explore the surface of the moon on January 6, 1998. After traveling through space, on-board engines were fired. This put Lunar Prospector into an orbit around the poles. Following this path, Prospector mapped the entire surface of the moon. Lunar Prospector carried instruments to find out about the chemistry of the moon. A Gamma Ray Spectrometer helped study the chemistry of the moon's surface. Another instrument aboard was a Neutron Spectrometer. This instrument is used to find hydrogen. It is one of the elements in water.
110
Other data showed that the moon has a small core. This information backs up the theory that the moon was torn away from the Earth. This may have happened when something about the size of Mars smashed into the Earth. Scientists ended the Lunar Prospector mission on July 31, 1999. They successfully completed a controlled crash of the spacecraft into a crater on the moon. Spacecraft have been studying the moon for over 40 years. In 1959, Russia sent the first space ship to the moon. NASA then sent its own space ships to the moon. The goal was to learn about the surface of the moon. Americans wanted to land astronauts on the moon. On July 20, 1969, Neil Armstrong landed the Apollo II spacecraft on the moon. He was the first man to walk on the moon. Other missions were sent to the moon. Rock samples were collected and returned to the Earth. Over 800 pounds of rock have been collected for scientists to study. There is still much we do not know about the moon. Many scientists believe that we should return to the moon and conduct more studies. There might be clues which could help us understand how the Solar System began.
