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CHAPTER

6W H AT I S S PAC E ?

Space: astronomical phenomena

Space! It’s where Earth, the Moon, the Sun, and all the planets and stars were born. Throughout history, humans have studied the sky in order to better understand the events that have unfolded there. It wasn’t until the 1960s that astronauts were able to travel into space to observe Earth and the Moon from a new perspective.

Today, we use special devices like space telescopes to study the solar system and the galaxies around us. Thanks to this research, some celestial bodies are now more familiar than ever. Take stars, for instance. We know that they emit light, like our nearest star, the Sun. We also know that planets revolve around stars and that natural satellites revolve around planets. But where does space start, exactly?

To scientists, space is the region beyond the thermosphere (the outermost layer of Earth’s atmosphere), 500 km above sea level.

In this chapter, you will learn about light and its properties.Then, you will discover different astronomical phenomena that have to do with light, like the cycle of day and night, the seasons, the phases of the Moon and eclipses.

The Earth 198 and space

13846_ess_trad_ch6_198-223_ep3.indd 198 2016-11-23 11:57 AM

Light is a type of radiation that is visible to the human eye. This radiation carries energy from a natural source (like the Sun) or an artificial source (like a light bulb).

D E F I N I T I O N

LightThe Sun, like other stars, emits light. We feel its effects because it is relatively close to Earth. Other stars are very far away, in other solar systems or even in other galaxies. Their light is much dimmer and we don’t feel their heat. But what is light? What are its properties?

What is light? Without the Sun, the world would be dark and very cold. Actually, without the Sun’s light, life wouldn’t exist at all; if it did, it would look very different. Plants need the Sun’s energy to make their food and release oxygen. And many living organisms depend on that oxygen to survive.

6.1

6.1.1

Properties of lightIn the following section, you will learn about seven properties of light.

Property 1Light is a type of radiation that is visible to the human eye.

X-rays, microwaves and ultraviolet (UV) rays are all types of radiations, like light. However, the human eye can’t see these without specialised tools.

You can’t see anything if your eyes are shut or if you’re in a dark room. Humans and most animals can see because the eye is able to detect light rays.

Chapter 6 199 Space: astronomical phenomena


Sheet of white paper

Mirror

Property 5Light travels in a straight line.

Property 6When light hits an object, part of it is reflected (bounced back) and part of it is absorbed.

Properties of light (continued)

Property 2Light can come from a natural source (like the Sun) or an artificial source (like a light bulb).

Property 3The Sun’s light carries energy. That’s why it’s also known as “luminous energy.”

Property 4Light travels extremely fast—up to 300 000 km/s!

In fact, light travels so fast it appears to be instantaneous. When you turn on a lamp, the light from the light bulb looks like it appears instantly.

Some objects, like mirrors, only reflect light in one direction. Other objects, like a sheet of paper, reflect light diffusely (in many different directions).

A rocket can travel up to 17 km/s, or 61 200 km/h. At that speed, it would take more than three months to travel from Earth to the Sun. Sun’s light takes only 8 minutes to reach Earth. The speed of light is actually the fastest speed there is.

Objects absorb different amounts of light depending on their colour. (See property 7.)

The Sun doesn’t only provide us with light; it provides us with heat as well. When the Sun’s light hits an object, part of the luminous energy is absorbed and converted into thermal energy. That increases the object’s temperature.

If you shine a flashlight on something, you’ll see that light doesn’t travel around the object. It travels only in a straight line. That’s what causes shadows.

Natural source

Artificial source



Properties of light (continued)

Light is a form of radiant energy. Its properties affect us: they provide us with heat and allow us to see. Many astronomical phenomena depend on the properties of light: the cycle of day and night, the seasons, the phases of the Moon and eclipses. We’ll look a little closer at each of these in the following sections.

Decomposition of lightEnglish scientist Isaac Newton is well known for his experiments with light. Other scientists had already managed to decompose light using a prism, but Newton was the first to understand that white light was a mixture of different coloured rays of light. Not only was he able to decompose light, he was able to do the opposite as well. He took light rays that had been separated by one prism and sent them through a second prism, which turned them back into white light.

Isaac Newton (1642–1727)

1 6 7 2 E N G L A N D

Property 7White light (or natural daylight) is a mixture of all the colours of the rainbow.

Objects that absorb light rays completely appear black. Those that don’t absorb any light appear white, because they’re reflecting all of the colours at the same time. Other objects can appear to be other colours depending on the rays they absorb and reflect. (See Property 6.)

Rainbows occur when drops of rain are illuminated by the Sun. The water splits the white light into all of its separate colours. A glass prism works to split light in much the same way.



MAIN CELESTIAL BODIES IN THIS CHAPTER

THE SUN

• The Sun was formed from a cloud of gas (made mostly of hydrogen and helium) around 4.5 billion years ago.

• It is 150 million kilometres from Earth. That’s 600 000 times the distance between Québec and Montréal!

• It has a diameter of 1.4 million kilometres. Its radius is 109 times that of Earth.

• At its centre, its temperature is around 14 million degrees Celsius.

• It has a mass 330 000 times greater than that of Earth.

• The Sun exerts its gravitational pull on eight planets. Like Earth, Mercury, Venus, Mars, Jupiter, Saturn, Uranus and Neptune orbit the Sun.

THE EARTH

• Earth was formed around 4.5 billion years ago.

• It is the third planet from the Sun. It has only one natural satellite: the Moon.

• Earth is round, but slightly flattened at the poles. Its diameter is 12 760 km. It has a radius of 6380 km.

• Its average surface temperature is 14°C.

• It has a mass of 6 × 1024 kg.

• Earth orbits the Sun in 365.25 days. It also completes a rotation on its axis once every 24 hours.

THE MOON

• The Moon was formed around 4.5 billion years ago.

• It is Earth’s only natural satellite.

• The Moon is the closest celestial body to Earth. It is 384 400 km away. That’s 1500 times the distance between Québec and Montréal!

• It has a diameter of 3476 km, which is a quarter of Earth’s diameter. It has a radius of 1738 km.

• Its temperature goes from 127°C during the day to -173°C at night.

• Its mass is 81 times less than Earth’s.

• The Moon orbits Earth in approximately 28 days. It takes the same amount of time to rotate on its axis. That’s why it always shows the same surface.

• To see the hidden side of the Moon, you’d need to travel into space using a rocket or an artificial satellite.



A C T I V I T I E S 1. Link each image (on the left) to the property of light it represents (on the right).

• White light is a mixture of all the colours of the rainbow.

• Light can be absorbed or reflected by the objects it hits.

• Light can travel nearly 300 000 km/s.

• Light travels in a straight line.

• The Sun’s light carries an energy called “luminous energy.”

• Light can come from a natural or a an artificial source.

a) A kitten sees itself in a mirror.

•

b) Stars are very far away from us.

•

c) Solar panels turn light into electricity.

•

d) You need a lamp to light a room at night.

•

e) Rainbows occur when it rains and it is sunny at the same time.

•

f) Sometimes, Sun’s rays are visible when they travel through clouds.

•



2. Name the property of light that each statement is demonstrating.

a) The classroom’s wall is green.Light can be absorbed or reflected by the objects it hits (property 6).

b) When ice cream is left in the sun, it melts quickly.The Sun’s light carries energy (property 3).

c) You can point a laser to a very specific spot.Light travels in a straight line (property 5).

3. Indicate whether the following objects are sources of natural (N), artificial (A) or reflected (R) light.

a) Jellyfish light up the surface of the ocean at night. N

b) Shipwreck survivors launch a flare to make finding them easier. A

c) A monarch butterfly’s wings are very colourful. R

d) During a full moon, the Moon appears round. R

e) In Hawaii, you can see lava flowing from a volcano at night. N

4. Indicate whether the following objects reflect light in one direction or in many directions.

a) An apple. Many directions.

b) A kite. Many directions.

c) A mirror. One direction.

d) A golden ring. One direction.

5. Why does this horse look black?When white light hits the surface of this horse, all of the colours

are absorbed. None of them are reflected. That’s why it looks

black.



Earth’s rotation is the planet’s spinning on an axis (invisible line) that passes through its poles. In other words, Earth turns on itself. This movement takes 24 hours and takes place from west towards east. It’s what causes day and night and vice versa.

D E F I N I T I O N

Every day, the Sun rises, travels through the sky, then sets again. Night follows day. It has been this way for billions of years. A long time ago, people believed that day and night were caused by the Sun revolving around Earth. We now know that’s not true.

What is Earth’s rotation? Day and night are caused by the Earth rotating on its axis.

6.2

6.2.1

Cycle of day and night

The apparent motion of the SunYou have been told over the years that the Sun rises in the east, appears to be in the south at noon and sets in the west. That makes it seem like the Sun is moving through the sky.

Day turns into night and back into day again because Earth is rotating on itself.

The Sun illuminates only half of Earth at one time. The other half remains dark. To people on the border between the light side and the dark side, the Sun will appear to be rising or setting.

South

EastWest

The Sun’s “motion” is actually due to Earth’s rotation. As Earth turns, the Sun gradually appears in the sky.At noon, the Sun reaches its highest point in the sky—the south.



What is Earth’s tilt? As you have no doubt noticed, day and night vary in length depending on the location and time of year. That’s because Earth rotates on its own axis, but it’s slightly tilted relative to the Sun.

6.2.2

The length of day and night The following diagram will show you the way Earth’s tilt affects the length of day and night.

The length of day and night varies throughout the year because Earth is tilted relative to the Sun. This tilt also causes seasons (see page 209).

Sun’s light

Northern Hemisphere

Southern Hemisphere

Axis of rotation

Angle of tilt (23º)

South Pole

Day Night

North Pole

Equator

Axis perpendicular to orbit

The equator is an imaginary line that circles Earth halfway between its poles. It serves as a border between the Northern and Southern Hemispheres.

In this illustration, the Southern Hemisphere is tilted towards the Sun. In that part of the world, it is summer.• The South Pole is constantly in the light because it is tilted towards

the Sun. There is continuous day.• Elsewhere in the Southern Hemisphere, there is more light than

darkness: the days are longer than the nights.• If you look at the yellow dot on the illuminated half of the Southern

Hemisphere, you’ll see that it spends more time in the daylight than in darkness.

In this illustration, it is winter in the Northern Hemisphere.• The North Pole is in the

darkness because it is tilted away from the Sun. At the North Pole, it is night for six months of the year.

• Elsewhere in the Northern Hemisphere, there is more darkness than light: the nights are longer than the days.

• If you look at the green dot on the illuminated half of the Northern Hemisphere, you’ll see that it spends less time in the daylight than in darkness.

What is Earth’s revolution?, p. 209

D E F I N I T I O N

Earth’s tilt is the angle formed by its axis of rotation and an imaginary axis that runs perpendicular to its orbit. That angle is approximately 23º.



A C T I V I T I E S 1. Which of Earth’s movements is associated with the cycle of day and night? Earth’s rotation on its axis.

2. Where would the Sun be in the sky for someone in each place on the globe? In the east (the Sun is rising).

In the south (it is noon).

In the west (the Sun is setting).

3. Look at the diagram on page 206, then answer the following question. In that diagram, is day longer than night in Québec? Explain your answer.No, in that diagram days are shorter than nights because the Northern

Hemisphere is tilted away from the Sun.

4. In Canada, we set the clocks forward an hour in the spring and turn them back in the fall in order to get as much daylight as possible. Why are days not the same length everywhere in the world and in all seasons?Because Earth is tilted relative to the Sun. When the Northern Hemisphere is

tilted towards the Sun, day is longer than night in Canada. When the Southern

Hemisphere is tilted toward the Sun, night is longer than day in Canada.

5. True or false? If a statement is false, correct it.

a) If it’s day in the Northern Hemisphere, it’s night in the Southern Hemisphere.False. Day starts at the same time in all areas that are located on the border

between the darkness and the daylight.

b) In the summer, days at the North Pole are longer than days at the equator.True.

c) If it’s night at the North Pole, it’s day at the South Pole.True.

CB

AA

B

C



6. Using the properties of light, explain why it is generally warmer during the day than it is at night. During the day, part of the Sun’s energy is absorbed by the atmosphere and

the surface of the ground. That energy is converted into heat. The more light

there is, the hotter it is.

7. These images show the Arctic region at different times of year. The red dot indicates the North Pole. Look at the images, then answer the questions.

a) Earth’s axis of rotation passes through two specific points. Name them.Earth’s axis of rotation passes through the North and the South Pole.

b) How long do day and night last at the North Pole in image A?The sun is up 24 hours a day (no night).

c) How long do day and night last at the North Pole in image B?Day and night each last 12 hours.

d) How long do day and night last at the North Pole in image C?It is dark 24 hours a day (no day).

e) What is the angle of Earth’s tilt?23º

A B C

Summer Spring or fall Winter



Earth’s revolution is the movement of the planet around the Sun. The planet travels in an oval pathway called an “orbit.” Earth’s orbit takes 365.25 days. This orbit, combined with the Earth’s tilt, causes seasons.

D E F I N I T I O N

SeasonsWhy do the seasons change? How can it be winter in Québec and summer in South America?

What is Earth’s revolution? As Earth orbits the Sun, it passes through four astronomical seasons.

6.3

6.3.1What is Earth’s tilt?, p. 206

Seasons, solstices and equinoxesThe diagram below shows how seasons occur in the Northern Hemisphere. The seasons are opposite in the Southern Hemisphere.

Solstices and equinoxes mark the beginnings of the seasons.

A solstice is a time of year when Earth’s position indicates the start of summer or the start of winter.• During the summer solstice, the Northern Hemisphere is

tilted as far towards the Sun as it can be. Days are longer than nights. It is also warmer because the Sun’s rays are more direct.

• During the winter solstice, the Northern Hemisphere is tilted as far away from the Sun as it can be. Nights are longer than days. It is also colder because the Sun’s rays are slanted and indirect (see image).

An equinox is a time of year when Earth’s position indicates the start of spring or fall. During an equinox, day and night are the same length.

SPRINGWINTER

SUMMER FALL

In astronomy, a “season” is the time it takes Earth to go from an equinox to a solstice or from a solstice to an equinox.

Direct rays

Indirect rays

Winter solstice: around December 21

Fall equinox: around September 21

Spring equinox: around March 21

Summer solstice: around June 21

N

N

N

N



Effects of Earth’s revolution What are the consequences of Earth’s revolution?

Earth experiences different seasons because it revolves around the Sun and is tilted at a certain angle.

Our calendar says that a year is 365 days long, but Earth’s revolution actually takes 365.25 days. This means, there is an “extra” quarter day (0.25 of a day) each year. To make up for that, every four years we have a “leap year” that lasts 366 days.

At the North Pole, it is never day at the beginning of winter because the Sun does not illuminate areas that are inside the Arctic Circle. At the beginning of summer, it is never night (the Sun is always visible). This photo shows the Sun’s various positions in the Alaskan sky during a summer day. Notice that the Sun goes down, but does not set.

At the equator, day and night are almost always the same length (approximately 12 hours). People in Brazil, South America, don’t generally notice much difference in the length of day and night throughout the year.

Currently, we say that December 21 is the winter solstice. And in Canada, that day does in fact mark the beginning of winter. But in the Southern Hemisphere, it actually marks the beginning of summer. That’s because the expression “winter solstice” was created by astronomers in the Northern Hemisphere.

The Earth’s revolutionGalileo (Galileo Galilei, in Italian) built his own telescope; it was an early ancestor of the telescopes we know today. In 1610, through his observations, he discovered that Jupiter had four natural satellites, that Venus had phases like the Moon, that Saturn had a ring and that the Sun turned on its axis. Galileo became convinced that Earth was just another planet, not the centre of the Universe. He confirmed that Earth revolved around the Sun, even though people at the time believed that the Sun revolved around the Earth. Galileo Galilei

(1564–1642)

1 6 1 0 I T A LY



A C T I V I T I E S 1. What am I?

a) I am the season that starts with day and night being the same length, but ends with night being longer than day.Fall.

b) I am the shortest day of the year in the Northern Hemisphere.Winter solstice.

c) I am a time of year when day and night are the same length everywhere on Earth.Equinox.

d) I am the season when temperatures are hottest and the days start to decrease in length.Summer.

e) I am Earth’s movement around the Sun.Earth’s revolution.

2. Complete the text using words from the following list.

The seasons are caused by Earth’s revolution around the Sun and the

23° tilt of its axis of rotation .

3. In winter, Québec can experience some beautiful sunny days. However, it can still be quite cold on those days. Explain why the days are colder in the winter than in the summer, even if the Sun is out.In winter, the Northern Hemisphere is tilted away from the Sun. The Sun’s rays

hit this region indirectly and at an angle. Furthermore, days are shorter

than nights, so there is less sun overall.

Angle of rotation

Axis of rotation

Climates

Earth’s

Revolution

Rotation

Seasons

Sun

Tilt



4. Look at the following images, then answer the questions.

A B

E

C D

a) On images A, B, C and D, draw an arrow indicating the direction of the Sun’s rays.

b) In the boxes on image E, write the corresponding letter from images A through D.

c) On each of the positions in image E, draw a red arrow indicating the direction that Earth is rotating.

d) On image E, draw blue arrows to show the direction of Earth’s revolution.

e) Which image shows the summer solstice? Image A.

f) Which image shows the midnight sun in the Arctic Circle? Image A.

C

A

B

D



The phases of the Moon describe the parts of the Moon that are illuminated by the Sun as seen from Earth. The Moon does not emit its own light. If it’s bright, it’s only because it’s reflecting the Sun’s light. As with Earth, part of the Moon is always illuminated by the Sun while the rest is in darkness.

D E F I N I T I O N

Phases of the Moon The Moon has been revolving around Earth for several billion years. All you need to do is look at the night sky to see where the Moon is in its journey around Earth.

What are the phases of the Moon? The Moon appears to be ever-changing, growing rounder or thinner with each passing night. Why is that?

6.4

6.4.1

Names of the phases of the Moon Before we look at how each phase is formed, we need to learn their names. “Gibbous” means “hunchbacked.”

1. New moon

5. Full moon

3. First quarter

7. Last quarter

2. Waxing crescent

6. Waning gibbous

4. Waxing gibbous

8. Waning crescent



Sequence of the Moon’s phases The following illustration explains how the Moon’s phases are formed.

As the Moon revolves around Earth, we see it from different angles. The different aspects of the Moon correspond to its phases.

1. The first lunar phase is the “new moon.” The Moon is between Earth and the Sun. We can’t see a new moon from Earth because the part that’s illuminated is facing towards the Sun.

2. As the Moon revolves around Earth, its illuminated side becomes visible. It starts to look like a thin crescent, which we call the “waxing crescent.”

3. Day by day, the crescent becomes thicker. During the “first quarter,” the Moon looks like a half circle.

4. A few days later, the Moon is almost full. At that point, we say it’s “waxing gibbous.”

5. When the Moon is on one side of Earth and the Sun is on the other, we can see the whole side of the Moon. It’s known as the “full moon.”

6. After the full moon, we see less and less of its illuminated side. We call that process “waning”: the phase after the full moon is called “waning gibbous.”

7. The next phase is the “last quarter.”

8. Finally, the Moon is reduced to a thin sliver (“waning crescent”) before disappearing into a new moon once again.

Sun’s light

Phases as we see them

1. New moon

2. Waxing crescent

8. Waning crescent

7. Last quarter

6. Waning gibbous

5. Full moon

4. Waxing gibbous

3. First quarter

Moon’s revolution



A C T I V I T I E S 1. Name the phases of the Moon that correspond to each statement.

a) The Moon is emerging from the dark; we see only a thin sliver in the sky. Waxing crescent.

b) Even on a beautiful starry night, we can’t see the Moon. New moon.

c) The Moon is almost full. It’s missing only a thin sliver. Waxing gibbous.

d) The Moon has almost disappeared again after the last quarter. Waning crescent.

2. a) Where is Earth situated during a full moon?Earth is situated between the Sun and the Moon.

b) Where is the Moon during a new moon?The Moon is situated between Earth and the Sun.

3. The following diagrams show the Sun (S), the Moon (M) and Earth (E) in different positions. Name the phases of the Moon that correspond to each diagram.

4. Here are two phases of the Moon. Draw a diagram showing the position of the Moon, the Earth and the Sun for each phase.

S E

M

S E

M

a) New moon. b) Last quarter.

c) Waxing crescent. d) Full moon.

a) b)

S EM S E

M

S EM

S E M



A. First quarter

B. Full moon

C. Last quarter

D. New moon

E. Waning crescent

F. Waning gibbous

G. Waxing crescent

H. Waxing gibbous

5. This image shows the Moon’s orbit around Earth. Look at the image, then answer the questions.

a) In the circles, draw the phases of the Moon as it is seen in the sky.

b) Write the letter corresponding to each phase in the boxes.

6. The Moon is not a star. It does not produce light. In your own words, explain why we can see different phases of the Moon.The Moon reflects light from the Sun. At any given time, only half of the Moon

is illuminated by the Sun. Because the Moon revolves around Earth, different

parts are illuminated depending on its position between Earth and the Sun.

D

E

G

C

A

F

H

B



Solar eclipsesDuring a solar eclipse, the Moon passes between Earth and the Sun. The Sun, the Moon and Earth are aligned so that the Moon blocks the Sun’s light during the day.

A solar eclipse can be total or partial, depending on where you are on Earth.

An eclipse happens when the Sun or the Moon disappear (either completely or partially) during a time when they’re supposed to be visible in the sky.

During a solar eclipse, the Moon passes between Earth and the Sun.

During a lunar eclipse, Earth passes between the Sun and the Moon.

D E F I N I T I O N

Eclipses You’ve probably already heard about eclipses. You might have even tried to watch one. If it was a solar eclipse, someone likely told you not to look directly at it because Sun’s rays can hurt your eyes. But why does the Sun disappear in the middle of the day?

What is an eclipse? There are two kinds of eclipses: solar eclipses and lunar eclipses.

6.5

6.5.1

During a solar eclipse, the Moon casts an umbra on a small area of Earth. People living in that area will see a total eclipse. Solar eclipses can last around 2 hours, during which time the light gradually disappears. Total darkness lasts only 8 minutes at most.

When the Moon blocks only part of the Sun, it’s called a “partial eclipse.”

In an umbra zone, an obstacle (in this case, the Moon) blocks all light coming from the source (in this case, the Sun). In a penumbra zone, the obstacle blocks only part of the light.

Phases of the Moon, p. 213

Sun’s light

Umbra (total darkness)

Total eclipse zone

Partial eclipse zone

Penumbra (partial darkness)



OBSERVING SOLAR ECLIPSES

Total solar eclipses happen only every 18 months on average. To see a total solar eclipse, you have to be in the umbra zone (the part of Earth where there is no more light). This area isn’t very big. At most, it’s 270 km in diameter. That’s why it’s so rare to see a total eclipse.

Partial eclipses are more common. You just need to be in a penumbra (an area where there is still some light). These areas can be up to 6000 km in diameter.

Here is the list of partial and total solar eclipses from 2014 to 2024. The next total solar eclipse that will be visible in Southern Québec will occur on April 8, 2024.

DATE TYPE OF ECLIPSE PLACES WHERE THE ECLIPSE WILL BE VISIBLE

October 23, 2014 Partial Northern Pacific Ocean, North America

March 20, 2015 Total Iceland, Europe, Northern Africa, Northern Asia

September 13, 2015 Partial Southern Africa, Southern Indian Ocean, Antarctic

March 9, 2016 Total Eastern Asia, Australia, Antarctic

August 21, 2017 Total North America, Northern South America

February 15, 2018 Partial Antarctic, Southern South America

July 13, 2018 Partial Southern Australia

August 11, 2018 Partial Northern Europe, Northeast Asia

January 6, 2019 Partial Northeast Asia, Northern Pacific Ocean

July 2, 2019 Total Southern Pacific Ocean, South America

December 14, 2020 Total Pacific Ocean, Southern South America, Antarctic

December 4, 2021 Total Antarctic, Southern Africa, Southern Atlantic Ocean

April 30, 2022 Partial Southeast Pacific Ocean, Southern South America

October 25, 2022 Partial Europe, Northeast Africa, Middle East, Western Asia

April 8, 2024 Total North America, Central America

A total solar eclipse

Source: NASA, 2012

Solar eclipses from 2014 to 2024



Penumbra

Umbra

Path of a lunar eclipse

Sun’s light

Lunar eclipses During a lunar eclipse, Earth passes between the Sun and the Moon. The Sun, the Moon and Earth are aligned so that Earth blocks the Sun’s light from reaching the Moon. The Moon is in Earth’s umbra.

Like a solar eclipse, a lunar eclipse is a phenomenon caused by the properties of light.

A total lunar eclipse happens when the entire Moon is blocked out by Earth’s umbra. This type of eclipse lasts much longer than a total solar eclipse (around 2 or 3 hours).

Unlike solar eclipses, lunar eclipses generally happen at night and are visible on the half of Earth that’s facing away from the Sun. Lunar eclipses can also be observed directly without risking damage to your eyes. They happen only during a full Moon.

During a lunar eclipse, Earth’s umbra covers the Moon. That’s why the Moon appears to go dark. It can then appear to turn a reddish colour, because only a few red and orange light rays can get through.

Why aren’t there eclipses every full moon or new moon?

The Moon doesn’t revolve around Earth in the same direction that Earth revolves around the Sun. If that was the case, we’d see around 25 solar or lunar eclipses each year. The Moon’s orbit is tilted 5° 9’ relative to Earth’s orbit. The orbits meet only in two places. Furthermore, the Moon needs to align with both the Sun and Earth to cause an eclipse. For those reasons, we don’t have eclipses during each full moon or new moon.



A C T I V I T I E S 1. In each of these images, the Sun (S), the Moon (M) and Earth (E) are aligned.

a) Which of these images is showing a solar eclipse? Image A.

b) Which one is showing a lunar eclipse? Image B.

c) Which one would look like a solar eclipse to someone standing on the Moon? Image B.

2. What is a partial eclipse?A partial eclipse is what we see when the Moon is in Earth’s penumbra or vice

versa. As a result, only part of the Sun’s or the Moon’s surface is hidden.

3. True or false? If a statement is false, explain why.

a) A lunar eclipse always happens during a full moon.True.

b) A solar eclipse can be seen only in the part of Earth that is in the Moon’s umbra.False. A partial eclipse can also be seen in the part of Earth that is in the

Moon’s penumbra.

c) Solar eclipses are visible only at night.False. The Sun isn’t visible at night, so it can’t disappear. Solar eclipses are

only visible during the day.

d) It is possible to have a partial solar or lunar eclipse.True.

e) Lunar eclipses are visible everywhere on Earth where it’s night.True.

S EM S E M

A B



M

4. Look at the following image, then answer the questions.

a) In black, colour the Moon’s umbra on Earth.

b) In brown, colour the Moon’s penumbra on Earth.

c) Draw an arrow pointing to the total eclipse zone.

5. Look at the following image, then answer the questions.

a) In black, colour Earth’s umbra on the Moon.

b) Can everyone on Earth see a lunar eclipse at the same time? Explain your answer. No. Only people who live on opposite side of the Sun, thus night.

OR Yes, because the entire Moon is in Earth’s umbra zone.

6. a) How long can total darkness from a solar eclipse last? 8 minutes.

b) How long does a total lunar eclipse last? 2 or 3 hours.

c) During which phase of the Moon does a solar eclipse happen? New moon.

d) During which phase of the Moon does a lunar eclipse happen? Full moon.

S

ES M

E



Chapter 6 Review1. Using the properties of light, explain why leaves look green. White light contains all of the colours of the rainbow. When the white light hits

an object, some of the luminous rays are absorbed while the rest are reflected.

The leaf absorbs all of the colours in white light except for green. We see the

green light reflected by the leaf and say that the leaf looks green.

2. In this chapter, you have learned about several different phenomena. Check ( ) the boxes corresponding to the properties of light responsible for each phenomenon.

3. Name the movement of Earth or the Moon that causes each phenomenon.

a) Day and night. Earth’s rotation.

b) Seasons. Earth’s revolution.

c) Phases of the Moon. Moon’s revolution.

d) Eclipses. Earth’s and Moon’s revolutions.

PROPERTYCYCLE OF DAY

AND NIGHTSEASONS

PHASES OF THE MOON

SOLAR AND LUNAR ECLIPSES

1. Light is a type radiation that is visible to the human eye.

2. Light can come from a natural or an artificial source.

3. The Sun’s light carries energy.

4. Light travels extremely fast.

5. Light travels in a straight line.

6. When light hits an object, part of it is reflected and part of it is absorbed.

7. White light is a mixture of all the colours of the rainbow.



4. The following images show Earth at three different times in the same year. Look at the images, then answer the questions.

a) Under each image, write the event being shown.

b) In image A, which season is starting in the Southern Hemisphere? Winter.

c) In image C, which season is starting in the Southern Hemisphere? Summer.

d) In image B, which season is starting in the Northern Hemisphere? Spring. OR Fall.

5. a) Explain why solar eclipses happen only during a new moon.In order for a solar eclipse to happen, the Moon has to be between Earth

and the Sun. In this position, the visible side of the Moon is not illuminated:

this is the new moon.

b) Explain why lunar eclipses happen only during a full moon.During a lunar eclipse, Earth passes between the Sun and the Moon. At that

time, the Moon is in position for a full moon.

Summer solstice.

Spring or fall equinox.

Winter solstice.

A B C



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