Unit 3 — Astronomy and the Solar System

The third unit of the programme: the solar system, telescopes and satellites, comets and the risk of collision, and the difference between astronomy and astrology.

يتكوّن الدرس من 11 أجزاء: The Solar System، Telescopes, Satellites and Space Exploration، Comets, Asteroids and Collisions، Astronomy and Astrology، How the Universe Is Organised، Size, Dimensions and Weight: Using the Metric System، Satellites in Present-Day Societies، A Short History of Space Travel، Presenting a Heavenly Body and the Astronomy Booklet، Deductive and Concessive Reasoning: Defending an Opinion، Key Vocabulary and Useful Expressions.

The Solar System

1. What the solar system contains

The solar system is the Sun together with everything that orbits it: eight planets and their moons, dwarf planets, asteroids, comets and dust.

The eight planets, in order of distance from the Sun:

2. Two families of planets

The **inner planets** are small, rocky, dense and have few moons or none.
The **outer planets** are huge, made mainly of gas or ice, less dense, and have many moons and rings.

Between the two families lies the asteroid belt.

3. Useful words about movement

Remember the pair: the Earth rotates in 24 hours and revolves in 365 days.

4. The Moon

The Moon is the Earth's only natural satellite. It has no atmosphere, so it has no weather, no sound and enormous differences of temperature between day and night. Its surface is covered with craters left by impacts.

The Moon does not produce light; it reflects the light of the Sun. What we call the phases of the Moon is the changing proportion of its lit half that we can see from the Earth.

5. Check yourself

Name the eight planets in order of distance from the Sun.
Give two differences between the inner and the outer planets.
Explain the difference between *to rotate* and *to revolve*.

Telescopes, Satellites and Space Exploration

1. The telescope

A telescope is an instrument used for observing distant objects. It gathers far more light than the human eye, which is why it shows objects too faint to be seen directly.

Describing the purpose of something is a grammar point of this unit:

A telescope is **used for observing** the stars. *(used for + gerund)*
A telescope is **used to observe** the stars. *(used to + stem)*
A telescope is an instrument **whose purpose is to observe** distant objects.

2. The Hubble Space Telescope

The Hubble Space Telescope was placed in orbit around the Earth so that its view would not be disturbed by the atmosphere. From the ground, air movement blurs the image of a star; above the atmosphere, that problem disappears.

Hubble has allowed astronomers to measure the age of the universe more precisely, to photograph the birth of stars, and to observe galaxies billions of light years away.

3. Telecommunication satellites

A satellite is any body that orbits a planet. A telecommunication satellite is an artificial one that receives a signal from one point on the Earth and sends it back to another.

Artificial satellites of different kinds are used for:

telephone and internet links between continents;
television broadcasting;
weather forecasting;
navigation and the location of vehicles;
observation of crops, forests and pollution.

4. Asking about measurement

The exam often asks you to form these questions.

5. Units used in astronomy

The **light year**: the distance light travels in one year, about 9.5 thousand billion kilometres. It measures distance, not time.
The **astronomical unit**: the average distance between the Earth and the Sun.

6. Check yourself

Give two ways of saying what a telescope is used for.
Why was Hubble placed above the atmosphere?
Write the question that asks for the distance between the Earth and the Moon.

Comets, Asteroids and Collisions

1. The small bodies

Learn the last three together: the same object changes name according to where it is.

2. What a collision would do

This is the classic exam question: *What would happen if a comet collided with the Earth?*

The answer is built in the second conditional, because the situation is imagined.

If a large comet **hit** the Earth, it **would create** an enormous crater.
The impact **would raise** a cloud of dust that **would block** sunlight for months.
Temperatures **would fall**, and plants **would die** for lack of light.
If the object **fell** into the ocean, it **would cause** giant waves.
Many species **would disappear**, as the dinosaurs probably did.

3. Should we spend money on space?

The unit ends with an argumentative topic: *Is the budget devoted to space exploration wasted money?*

Arguments that it is wasted

Millions of people lack water, food and medical care on the Earth.
The sums involved could finance schools and hospitals.
Some missions bring no immediate benefit.

Arguments that it is not

Space research has produced everyday technology: satellite forecasting, GPS, new materials, medical imaging.
Watching the Earth from orbit is how we measure deforestation and pollution.
Detecting a dangerous asteroid early may one day save millions of lives.
Scientific knowledge has a value that is not only economic.

4. Writing the newspaper article

A **headline**, short and striking.
A first paragraph answering *what, who, where, when*.
Two or three paragraphs of detail, one idea each.
A closing sentence: a consequence, or an open question.

5. Check yourself

What is the difference between a meteor and a meteorite?
Write two sentences in the second conditional about a collision with a comet.
Give one argument for and one against spending money on space exploration.

Astronomy and Astrology

1. Two words that look alike

The confusion is common in English as it is in Arabic, and the exam plays on it.

2. What makes astronomy a science

It **observes** with instruments that anyone can use again.
It **measures**, and states the uncertainty of each measurement.
It builds a **hypothesis** and then looks for the observation that could contradict it.
It **publishes**, so that other astronomers can check the result.

A prediction such as *an eclipse will begin at 14:32 on that day* can be shown to be wrong. A prediction such as *you will meet an important person* cannot.

3. Making hypotheses and suppositions

This is the grammar point attached to the unit.

**If** the universe **is** expanding, galaxies **must be** moving away from us. *(deduction)*
The planet **may** have water under its surface. *(possibility)*
The mission **might** be delayed. *(remote possibility)*
**Suppose** a signal came from another star, how would we answer it?
**What if** the comet changed its path?

Note the verbs that are not normally used in the continuous form: *believe, know, seem, appear, contain, belong, consist of, mean, understand*.

> We say *This galaxy contains billions of stars*, not *is containing*.

4. Comparing in the exam

Two comparisons are constantly required in this unit.

Superiority

Jupiter is **larger than** the Earth. *(short adjective + -er)*
Mars is **more accessible than** Venus. *(long adjective)*

Equality

Venus is **almost as large as** the Earth.
Mercury is **not as cold as** Neptune.

5. Check yourself

Give three differences between astronomy and astrology.
Why can an astronomical prediction be proved wrong, and a horoscope not?
Complete: *Saturn is ______ (big) than Mars but ______ (large) as Jupiter.*

How the Universe Is Organised

From the Earth to the universe

Astronomers describe the universe as a series of systems, each one placed inside a bigger one. Learn the order from the smallest to the largest:

Keep the key difference in mind: a star shines by itself, whereas a planet only reflects the light of its star.

Our address in space

A good way to remember this organisation is to write the "cosmic address" of a pupil living in Algeria:

Algeria → the Earth → the solar system → the Milky Way → the Local Group → the universe

Figures worth remembering

Light travels at about **300,000 km per second**. Light from the Sun takes about **8 minutes** to reach the Earth.
The nearest star after the Sun, **Proxima Centauri**, is about **4.2 light years** away.
The **Milky Way** is a spiral galaxy which contains hundreds of billions of stars. The solar system lies far from its centre.
The nearest large galaxy, **Andromeda**, is about **2.5 million light years** away.
The universe contains billions of galaxies. It is about **13.8 billion years** old; the solar system is about **4.6 billion years** old.

Reading: Looking up at night (a text written for this lesson)

On a clear night far from the lights of the city, you can see a few thousand stars with the naked eye. They all belong to our own galaxy. Most of them are much farther away than they seem: their light has travelled for years, sometimes for centuries, before reaching us. This means that we never see a star as it is now, but as it was when its light left it. The pale band of light which crosses the sky on dark summer nights is the Milky Way itself, seen from the inside. It is made of so many distant stars that our eyes cannot separate them.

Cohesion: finding what a reference word refers to

The method: look backwards for the nearest noun that agrees in number and in meaning, then put it in the place of the reference word and reread the sentence. If the sentence still makes sense, your answer is right. Remember that *this* and *that* can refer to a whole idea, not only to one noun.

Check yourself

Put in order: galaxy, moon, universe, planet, solar system.
Why do we see a distant star as it was in the past?
What does *which* refer to in the last two sentences of the text?

Size, Dimensions and Weight: Using the Metric System

The metric system

The metric system is used in science all over the world and in daily life in Algeria. It is a decimal system: each unit is ten, a hundred or a thousand times bigger or smaller than another. Prefixes tell you the relation:

The basic units: length → the metre (m); mass → the kilogram (kg); capacity → the litre (l); time → the second (s); temperature → the degree Celsius (°C). A tonne is 1,000 kg.

Writing and reading numbers in English

A **comma** separates thousands and a **point** separates decimals: *12,742 km*, *4.2 light years* (read "four point two").
*Hundred, thousand, million, billion* take no **-s** after a number: *three million kilometres*, but *millions of stars*.
Use **about, nearly, almost, more than, less than** to round a figure: *about 150 million kilometres*.

Nouns and adjectives of dimension

Five ways to give a dimension

**be + number + unit + adjective**: *The probe is 3 metres long.*
**be + number + unit + in + noun**: *Mars is about 6,800 km in diameter.*
**have + a + noun + of**: *Mars has a diameter of about 6,800 km.*
**a compound adjective** before a noun, with no -s on the unit: *a 3-metre-long probe*.
**weigh**: *The probe weighs 500 kg.*

Mass and weight

Your mass (in kilograms) is the quantity of matter in your body: it is the same everywhere. Your weight is the force with which gravity pulls you, so it changes from one world to another. Gravity on the Moon is about one sixth of the Earth's, so an astronaut with a mass of 80 kg still has a mass of 80 kg there, but he weighs about six times less.

Information transfer: from a table to a paragraph

Model paragraph: Mars is about half the size of the Earth: its diameter is about 6,800 km, whereas the Earth's is about 12,750 km. Unlike Jupiter, a gas giant about eleven times wider than the Earth, Mars is a small rocky planet. Like the Earth, it has a day of about 24 hours, but its year is almost twice as long. While the Earth has only one moon, Mars has two small ones and Jupiter has dozens.

Rules: never copy the table line by line; turn the figures into sentences, round them, and compare with *whereas, while, like, unlike, twice as… as*.

Check yourself

Give the nouns of *long, wide, deep* and *heavy*.
Write the size of Mars in two different ways.
Compare the length of a day on the Earth and on Jupiter in one sentence.

Satellites in Present-Day Societies

Natural and artificial satellites

A satellite is a body that orbits a larger one. The Moon is the Earth's natural satellite; an artificial satellite is a machine that people have placed in orbit. Thousands of artificial satellites now go round the Earth, and modern life depends on them far more than most people realise.

Five families of satellites

Two kinds of orbit

**Low orbit**: a few hundred kilometres above the ground. The **International Space Station** flies at about 400 km and goes round the Earth in about an hour and a half.
**Geostationary orbit**: about 36,000 km above the equator. A satellite there goes round the Earth in one day, exactly the time the Earth takes to rotate, so it seems motionless in the sky. That is why a satellite dish can stay pointed at the same place.

Algeria in space

Algeria launched its first satellite, Alsat-1, in 2002, to observe its territory. In 2017 it added Alcomsat-1, a communication satellite. Images from space help to follow the advance of the desert, forest fires and the growth of cities.

A modern problem: space debris

Old satellites, empty rocket stages and fragments stay in orbit for years. They travel so fast that even a small piece can damage a working satellite. Space agencies now try to plan the end of each mission so that satellites do not add to this rubbish.

Discussing the importance of satellites

In a whole-class discussion, an imaginary situation helps: *What would happen if all satellites stopped working tomorrow?*

If all satellites stopped working, weather forecasts **would become** less reliable.
Ships and planes **would have to** navigate with older methods.
People in remote villages **would lose** their television and part of their internet.
Farmers and rescue services **would no longer receive** images of fires and floods.

Useful expressions: *In my view…*, *I strongly believe that…*, *Without satellites, we would…*, *I agree with you, but…*, *That is true; however…*

Check yourself

Name three families of satellites and say what each one does.
Why does a geostationary satellite seem not to move?
Give two consequences of a world without satellites, in the second conditional.

A Short History of Space Travel

The title of the unit

On 20 July 1969, the lunar module of Apollo 11 landed on the Moon. A few hours later, the American astronaut Neil Armstrong became the first human to walk on its surface. As he stepped onto the ground, he said: "That's one small step for man, one giant leap for mankind." The title of the unit echoes these words. Mankind means all human beings: one step for a single man was a huge achievement for the whole human race.

A timeline of space travel

The language of history

**Past simple** for dated events: *Gagarin flew into space in 1961.*
**Passive** when the object matters more than the people who acted: *Sputnik 1 was launched in 1957.*
**Present perfect** with *since* for a situation that continues: *Astronauts have lived on the station since 2000.*
**Time markers**: *first, then, after that, four years later, eventually, since then*.

Sentence ordering with cohesive devices

The exam gives you jumbled sentences to put in order. Use three clues:

**The opening sentence** contains no reference word and no connector that needs something before it.
**Reference words** (*it, they, these, this*) point back to something already mentioned.
**Dates and time markers** (*four years later, since then*) give the chronology.

Put these sentences in order:

(a) Four years later, it sent the first human into space.
(b) In 1957, the Soviet Union launched the first artificial satellite.
(c) The Americans answered by landing astronauts on the Moon in 1969.
(d) These successes started a long competition with the United States, often called the space race.
(e) Since then, the two countries have often worked together, for example on the International Space Station.

Answer: b – a – d – c – e. Sentence (b) is the only one that needs nothing before it; *it* in (a) refers to the Soviet Union; *these successes* in (d) sums up (b) and (a); (c) answers the competition; *since then* in (e) closes the story.

Check yourself

Who was the first human in space, and when?
Put in the passive: *The Soviet Union launched Sputnik 1 in 1957.*
What does *mankind* mean in the title of the unit?

Presenting a Heavenly Body and the Astronomy Booklet

Planning an oral presentation

A presentation of about three minutes follows a clear plan:

**Introduction**: greet the audience, name the heavenly body and say why you chose it.
**Identity**: what kind of body it is and where it is in the solar system.
**Physical features**: size, composition, temperature, atmosphere, surface.
**Movement**: the length of its day and of its year.
**Remarkable facts**: what makes it special.
**Conclusion**: sum up, thank the audience and invite questions.

Signposting expressions

Tips: speak from short notes, not from a full text; look at your listeners; round your figures; show one picture or one diagram.

Two ID cards (for the project)

Jupiter

Type: gas giant, the fifth planet from the Sun.
Diameter: about 143,000 km, about eleven times the Earth's.
Mass: more than 300 times the mass of the Earth.
Composition: mainly hydrogen and helium.
Day: less than 10 hours. Year: almost 12 Earth years.
Moons: dozens, including Io, Europa, Ganymede and Callisto, discovered by Galileo in 1610. Ganymede is the largest moon in the solar system.
Remarkable feature: the Great Red Spot, a giant storm larger than the Earth.

Mars

Type: rocky, the fourth planet from the Sun.
Diameter: about 6,800 km, about half the Earth's.
Distance from the Sun: about 228 million km.
Day: about 24 hours 40 minutes. Year: 687 Earth days.
Moons: two small ones, Phobos and Deimos.
Atmosphere: very thin, mainly carbon dioxide. Average temperature: about −60 °C.
Remarkable features: its red colour, due to iron oxide (rust) in its soil, and Olympus Mons, the largest volcano in the solar system.

From the ID card to the presentation (model opening, written for this lesson)

"Good morning, everyone. Today I'm going to talk about Mars, the fourth planet from the Sun. People call it the Red Planet, and as you can see on this picture, its colour is really striking: it comes from rust in its soil. Let me start with its size. Mars is about half as wide as the Earth, and its day lasts about 24 hours and 40 minutes, almost like ours."

The astronomy booklet

The project has three sections:

**A short history of space travel**: use the timeline of the previous part, with dates and the passive.
**ID cards about two major planets**, like the two above, with a picture each.
**A short imaginary dialogue with a famous astronomer**. Choose the astronomer, collect real facts about his or her life and work, write the interviewer's questions, and build each answer only on those facts. Present the dialogue clearly as imaginary, and never add discoveries the person did not make.

Facts you may use for Galileo Galilei (1564–1642): he turned a telescope to the sky in 1609–1610; in January 1610 he discovered four moons of Jupiter; he observed mountains and craters on the Moon and the phases of Venus; he defended the idea of Copernicus that the Earth revolves around the Sun.

Remember also that many bright stars still carry names of Arabic origin, such as Aldebaran, Altair, Deneb and Vega, a trace of the work of medieval Muslim astronomers.

Check yourself

Give the six stages of an oral presentation.
Write two lines of an ID card about Jupiter.
Write two questions for an imaginary dialogue with Galileo.

Deductive and Concessive Reasoning: Defending an Opinion

Three types of reasoning

An argumentative text tries to convince. The way it moves from ideas to a conclusion is its reasoning.

Deductive: *All planets orbit a star. Mars is a planet. Therefore, Mars orbits a star.* The conclusion is only as solid as the general rule it starts from.

Inductive: *Satellites have improved forecasts, navigation and communication. This shows that space research benefits daily life.*

Concessive: *Admittedly, space missions are expensive. However, they bring technologies that everybody uses.*

Concession in three steps

**Concede**: recognise what is true in the opposite opinion.
**Counter**: show why it does not change your position.
**Conclude**: restate your opinion.

Grammar reminders: *although / even though* + a clause; *despite / in spite of* + a noun or an -ing form; *however / nevertheless* begin a new sentence or clause.

Model short article (written for this lesson)

Is Space Worth the Money?

Every year, governments spend enormous sums on rockets, probes and telescopes, and many citizens wonder whether this money would be better used on the ground. It is true that millions of people still lack clean water, schools and hospitals, and nobody can ignore their needs. However, the choice is not as simple as it seems.

Since modern life depends on satellites for forecasts, communications and navigation, any country that wants to develop must invest in space. This is why many countries, Algeria among them, have launched their own satellites. Moreover, watching the sky protects us: a dangerous asteroid detected early leaves time to act.

Admittedly, some missions bring no immediate profit. Yet the knowledge they produce often leads to practical inventions years later. In short, the space budget is not wasted money but an investment in our future, provided that it is spent wisely.

*Paragraph 1 concedes; paragraph 2 deduces (since… must); paragraph 3 concedes again and concludes.*

A speech in defence of an opinion

A speech is written to be heard, so it speaks to the listeners directly:

greet them: *Ladies and gentlemen, dear friends…*
state the opinion early: *I firmly believe that…*
ask **rhetorical questions**: *Can we really live without satellites today?*
use **we** and **you**, short sentences and repetition;
answer the opposite view with a concession;
end with a **call to action**: *Let us support…*

From ideas to the final draft

**Brainstorm**, then **select the relevant ideas**: keep only those that answer the topic. In a text about the space budget, a paragraph on horoscopes is irrelevant.
**Draft** quickly, following your plan.
**Edit**: check content, organisation and connectors, tenses, agreement, spelling and punctuation. Teachers often use symbols: **Sp** (spelling), **T** (tense), **WW** (wrong word), **WO** (word order), **Agr** (agreement), **P** (punctuation), **^** (missing word).

Example of editing: *If we would invest more, we will discover more.* (T) → *If we invested more, we would discover more.*

Check yourself

Write a deductive sentence with *since… therefore*.
Write a concessive sentence with *admittedly… however*.
Give three features of a speech that an article does not need.

Key Vocabulary and Useful Expressions

1. Core vocabulary

2. Nouns formed from verbs

The unit asks you to form nouns and to shift the stress.

3. Stress shift from noun to verb

Some two-syllable words change their stressed syllable according to their function: the noun is stressed on the first syllable, the verb on the second.

a **REC**ord → to re**CORD**
an **IN**crease → to in**CREASE**
a **PRE**sent → to pre**SENT**
an **OB**ject → to ob**JECT**
a **CON**flict → to con**FLICT**

4. Forming the plural

Regular: *planet → planets*, *star → stars*.
Nouns in *-s, -x, -ch, -sh* take **-es**: *gas → gases*, *flash → flashes*. Nouns ending in a consonant + *-y* change *-y* into **-ies**: *galaxy → galaxies*.
Scientific nouns of Greek or Latin origin keep an irregular plural:

5. Expressions for the written part

The solar system **consists of** eight planets.
Jupiter is **by far** the largest planet.
**Unlike** the Earth, Venus has no liquid water.
**Both** Venus **and** the Earth are rocky planets.
Venus is **similar to** the Earth **in** size, **whereas** Jupiter is entirely different.
Space research **has led to** everyday technology.

6. Check yourself

Give the noun formed from *to explore*, *to collide* and *to discover*.
Give the plural of *hypothesis*, *phenomenon* and *nucleus*.
Which syllable is stressed in *record* when it is a verb?

الجزء الأول من الدرس مفتوح للجميع، وبقيته مع الاشتراك.