© Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 1 of 41 KS4 Physics Earth and Beyond

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 20051 of 41

KS4 Physics

Earth and Beyond


Earth and Beyond

The solar system

The life cycles of stars

The Universe

Summary activities

In orbit

Contents


I don’t think so!

Copernicus

The centre of the Universe?

Hundreds of years ago, people thought that the Earth was the centre of the Universe and that the Sun and planets rotated around the Earth!

Nicholas Copernicus, was a Polish astronomer who lived in the 17th century, He studied the stars and discovered that the Earth and the other planets actuallyrotate around the Sun.


What types of objects make up the Solar System?

1. _____________

2. _____________

3. _____________

4. _____________

5. _____________

the Sun

the planets

moons

asteroids

comets

Which of these objects are light sources?

Components of the solar system

The Sun is a star and a light source. It is a massive ball of hot glowing gas and gives out huge amounts of heat and light energy.


not to scale

The four inner planets are

small, dense and mostly

made of rock.

The outer planets, apart from Pluto, are made of liquefied gases such as

hydrogen, carbon dioxide and ammonia.

The asteroids, between Mars and Jupiter, are pieces of rock with

diameters from a few km up to 1000 km.

Pluto, the outermost planet,

is believed to be made of rock

and ice.

The planets


Most of the planets travel around the Sun in near-circular orbits.

Comets also travel around the Sun but in very elliptical orbits.

For most of its orbit, a comet is a long way from the Sun.

The head of the comet is a lump of ice and dust a few kilometres across.

The tail only appears when the comet is near the Sun. It consist of gas and dust which are released by the heat of the Sun.

Comets


As the Earth moves through space, it collides with lumps of material which burn up in the atmosphere.

These are called meteors and can be seen as streaks of light in the night sky.

A large meteor may not burn up completely and hits the Earth with a lot of energy. This is called a meteorite.

A meteorite impact is one theory to explain why the dinosaurs became extinct.

Meteors and meteorites


The Sun is the star at the centre of the Solar System. It is the largest object and contains about 98% of the total mass in the Solar System.

The Sun is a massive ball of hot, glowing gas and is mostly made of hydrogen and helium. It is more than 4.5 billion years old!

The Sun

Scientists once thought that the Sun was powered by chemical reactions but this couldn’t explain how it has managed to stay ‘burning’ for billions of years.

There must be another process producing the Sun’s energy.

Scientists now know that this process is nuclear fusion.


In nuclear fusion reactions, lighter atomic nuclei are joined together (fused) to form heavier atomic nuclei.

This process releases massive amounts of energy.

In our Sun, a typical star, hydrogen is being fused to form helium. This provides the energy for life on Earth.

When all the hydrogen is used up, other elements will be fused together to make even heavier elements.

Not all elements are made in this way. The heaviest elements, some of which are found in your body, can only be made when stars explode.

Nuclear fusion


The Sun is the source of energy for life on Earth. Where does this energy come from?

What would happen on Earth if the Sun suddenly disappeared?

The Sun is powered by nuclear fusion reactions. Atomic nuclei are joined together (fused) due to the very high pressures inside the Sun.

There would be no light, all plants would die (no photosynthesis), all animals would die (no food source) and temperatures would drop. It would lead to the end of all life on Earth!

The Sun as our energy source


Earth and Beyond

The solar system


The Universe

Summary activities

In orbit

Contents




Lighter stars, like our Sun, follow this life cycle:

Nebula collapses due

to its own gravity.

Forms a star likeour Sun. Expands

to form a red giant.

Outer layers of star drift away to leave a dense white dwarf.

Very small nebulae form failed stars.

Small stars


Stars that are much heavier than our Sun follow this life cycle:

Larger nebula collapses due to its

own gravity.

Forms a star more massive than our Sun.

Expands to form a

massive red giant.

Red giant collapses violently

in a supernova explosion.

Very dense neutron star

formed.

Massive stars


The end of the life cycle of really massive stars is different to that of massive stars.

After a really massive red giant collapses in a supernova explosion, it leaves a star so dense that not even light can escape its gravitational pull. This is called a black hole!

Some scientists believe that there are black holes at the centre of galaxies.

If light cannot escape a black hole, then how can a black hole be observed?

Really massive stars


How can a black hole be observed?

A black hole cannot be seen directly and even if it could it wouldn’t be black!

A black hole is ‘seen’ by observing the effect it has on nearby matter.

X rays

Black holes

If there is a star nearby, matter from the star will spiral into the black hole and as it does so the matter emits X ray radiation which can be detected.


This causes the ‘nebula’ to collapse.

Gravity causes a dust and gas cloud to condense into a smaller volume.

As the nebula collapses, temperatures and pressures inside the nebula increase.

When the temperature and pressure are great enough

nuclear fusion starts.

Eventually gravity and the outward pressure of escaping energy is

balanced. At this stage, it is called a star.

What is the correct order for these sentences about how a star is formed?

Birth of a star


Use these words below to complete the life cycles of different stars:

Comparing the life cycles of stars

nebulasmall nebula

large nebula

white dwarf

star like our Sun

red giant

neutron star

massive red giant

star larger than our Sun

supernova


Comparing the life cycles of stars

nebulasmall nebula

large nebula

white dwarf

star like our Sun

red giant

neutron star

massive red giant

star larger than our Sun

supernova


1. What two elements make up most of our Sun?

2. What is a nebula?

3. What process has allowed the Sun to emit light and heat radiation over billions of years?

4. Which is the most dense, a white dwarf or a neutron star?

5. Describe the possible fate of a star similar to our Sun.

hydrogen and helium

A huge cloud of gas and dust from which a star is born.

nuclear fusion

neutron star

red giant white dwarf

Questions about stars


Earth and Beyond

The solar system


The Universe

Summary activities

In orbit

Contents


1. What force keeps the planets in orbit around the Sun?

2. Which planet shown will feel this force…

a) …the strongest? b) …the weakest?

the Sun’s gravity

Orbiting the Sun

not to scale


1. What are the two types of satellite?

2. Give an example of each type?

natural and artificial

natural – the Moon

artificial – navigation, spy, military, weather, communications

To view the Universe above the Earth’s atmosphere which can obstruct view from Earth.

Questions about satellites

3. Why are certain satellites, such as the Hubble Space Telescope, put into space?


geostationary orbitSatellite stays above the same location on the Earth’s surface. This means that the speed of its orbit matches the Earth’s rotation.

polar orbit

Artificial satellites – different orbits

The satellite’s orbit passes over the poles, whilst the Earth spins underneath. This allows large areas of Earth to be seen and is used for mapping andweather monitoring.


Polar Geostationary

Height of orbit

Orbital speed

Orbits per day

Orbit position

Example

Complete this the table comparing the different types of orbits that artificial satellites can follow?

low high

fast slow

3 - 4 1

over poles above equator

weather communications

Comparing orbits


communications

spy

weather

navigation

Do these uses of satellites involve a polar orbit or a geostationary orbit?

Which type of orbit?

geostationary

geostationary

polar

polar and geostationary

monitoring ocean temperatures

polar


Earth and Beyond

The solar system


The Universe

Summary activities

In orbit

Contents


Size in the Universe


a star

a planet

a galaxy

the Universe

the Solar System

There are nine of these in our Solar System. The Earth is one.

Our Sun is one.

Billions of stars together - ours is called the Milky Way.

The Sun, planets, moons, asteroids and comets make up this.

All the galaxies and everything else.

Matching words and definitions


a galaxy a star the Universe

Identify the different bodies


Think about the noise a plane makes as it passes you.

As the plane approaches, it sounds higher pitched...

…as it moves away from you, it sounds lower pitched.

This apparent shift in frequency is called the Doppler effect.

The Doppler effect

The same thing happens with light:

The wavelength of light emitted by approaching objects appears to be shortened (blue-shifted);

The wavelength of light emitted by receding objects appears to be increased (red-shifted).


Edwin Hubble (1889-1953) was a famous scientist who examined the light from nearby galaxies. He made two important observations:

From his observations, Hubble made these conclusions:

1. That most galaxies were moving away from our own;

2. The further away a galaxy was, the faster it was moving away from us;

3. That the Universe must be expanding.

1. That most of the galaxies’ light was shifted towards the red end of the spectrum;

2. The further away a galaxy was, the more its light was red-shifted.

Hubble and the expanding Universe

Edwin Hubble (1889-1953) was a famous scientist who examined the light from nearby galaxies. He made two important observations:

From his observations, Hubble made these conclusions:

1. That most galaxies were moving away from our own;

2. The further away a galaxy was, the faster it was moving away from us;

3. That the Universe must be expanding.

1. That most of the galaxies’ light was shifted towards the red end of the spectrum;

2. The further away a galaxy was, the more its light was red-shifted.


The big-bang theory states that the Universe is expanding due to a large ‘explosion’ (big bang) billions of years ago.

Evidence to support this theory includes:

1. The Cosmic Microwave Background Radiation (CMB), which is thought to be an ‘echo’ of the initial explosion.

2. Hubble’s observations about red-shifted light.

This theory gives rise to different fates for the Universe:

1.If the mass of the Universe is large enough, it will eventually start to contract due to gravity – closed Universe.

2.If the mass of the Universe is smaller, it will expand forever as there is not enough gravity to halt its expansion – open Universe.

The big-bang theory


The steady state theory states that the Universe is expanding and, as it expands, matter is created to maintain a uniform universal density of matter.

Evidence to support this theory is Hubble’s observations about red-shifted light.

However, the steady state theory has become less popular since the discovery of Cosmic Microwave Background Radiation (CMB).

Steady state theory


If there are aliens, they would have

contacted us by now.

The Universe is so big, even if there are aliens, they are too far away for

us to ever meet them.

Life exists on Earth and only on Earth.

If there are aliens they will probably not look

like you or me.

For life to exist there must be liquid water, on a planet or moon

and oxygen.

We are all aliens, life began on comets and

asteroids and transferred to the Earth when they

collided with it.

There are many different opinions about life in the Universe:

Are we alone?

There are 1021 stars in the universe. There must be

life on planets aroundsome of them.


Many people believe that we are not the only intelligent life in the Universe.

The challenge for scientists is to find evidence of other life.

Is there life out there?


Earth and Beyond

The solar system


The Universe

Summary activities

In orbit

Contents


Glossary (1)

black hole – An object in space that forms after a really massive star collapses in a supernova. Its gravity is so strong that nothing can escape its pull.

comet – A lump of rock and ice which has a very elliptical orbit around the Sun.

galaxy – A vast collection of billions of stars.geostationary orbit – The path of a satellite that stays

above the same position on the Earth’s surface and orbits at the same speed as the Earth rotates.

meteor – A lump of material from space that burns up in the Earth’s atmosphere.

meteorite – A large meteor that does not completely burn up in the Earth’s atmosphere and crashes to Earth.

nebula – A massive cloud of gas and dust in which a staris formed.


Glossary (2)

neutron star – The very dense core that remains after a massive red giant collapses in a supernova.

nuclear fusion – The process in which lighter atomic nuclei are joined together to form heavier atomic nuclei and a massive amount of energy is released.

polar orbit – The path of a satellite which passes over the North and South poles.

satellite – Any object that is in orbit around a larger object. red giant – A star that has expanded and has a red glow. supernova – The huge explosion that occurs when a

massive red giant is at the end of its life.white dwarf – The core that remains after the outer layers

of a small red giant drift away.


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Multiple-choice quiz

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© Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 1 of 41 KS4 Physics Earth and Beyond