Unit1 the universe and the earth

1) THE UNIVERSE
The Universe is made up of hundreds of
billions of galaxies separated by enormous
distances. Between them, there is empty
space
Galaxies usually are found in groups called
galaxy clusters
EMPTY SPACE GALAXIES
GALAXY CLUSTER

Our galaxy is an spiral shaped galaxy called the Milky Way. The Milky Way belongs to a
galaxy cluster called the Local Group. The Local group is made up of about 30 galaxies. The
closest galaxy to us is Andromeda

A galaxy is a large group of STARS, between 100 000 and 500
millions. Towards the centre of the Galaxy, the stars are close
together. An enormous cloud of gas and dust, called NEBULA,
surrounds the stars
Portion of the Carina Nebula
The Rosette Nebula
Within a galaxy we can find groups of stars
relatively close to each other. They are open
clusters.
are made up mainly of hydrogen and helium,
the two most abundant gases in the Universe. They
are so hot inside that they emit heat and light.
GALAXIES
STARS

Many stars have planets that revolve around them forming PLANETARY SYSTEMS, like our
Solar System
PLANETS are bodies which orbit some stars.
They do not emit light; they receive light from
the star and reflects it (that’s why we can see
them).
Some planets have SATELLITES or
moons, They are small bodies that
orbit a planet. The Earth’s natural
satellite is the Moon
PLANETAY
SYSTEMS:
They consist of a
central star which
have other bodies
orbiting around it

1.1) THE ORIGIN OF THE UNIVERSE
In 1965, scientists discovered that galaxies were moving
away from each other and that we live in an EXPANDING
UNIVERSE (like a swelling balloon). So, Millions of years
ago, the galaxies were closer.
The most accepted theory to explain the origin of the
universe is the BIG BANG THEORY. According to this
theory, the universe came into existence about 13.7 billion
years ago as a result of a big explosion which produced
the expansion of the universe
At first, the temperature of the
universe was very high. Gradually it
cooled, which made it possible for stars
and planets to form

WE LIVE IN AN EXPANDING UNIVERSE

1.2) DISTANCES AND UNITS OF MEASURAMENTS IN ASTRONOMY
The universe is so huge that we need special units of measurement to express the distances within it:
1) ASTRONOMICAL UNIT (AU): This is the
distance from the Earth to the Sun,
approximately 150 million km. This unit is
used to express distances within the solar
system.

2) LIGHT YEAR: This is the distance light travels in one year. Light travels at a speed of 300 000 km per
second, so in one year it ravels about 9.5 trillion km. Light years are used to measure distances of
objects outside the solar system.
• The closest star to the Sun,
Alpha Centauri, is about 4 light
years away.
• The Milky Way has a diameter of
about 100 000 light years.
• Andromeda is about 2.5 million
light year away from the Milky
Way.

2) THE SOLAR SYSTEM
Our understanding of the universe has changed throughout history:
1) GEOCENTRIC THEORY: Proposed by the
ancient Greeks (II BC). According to this
model, the Earth was the centre of the
Universe and the Sun, Moon and other
planets orbited the Earth.
2) HELIOCENTRIC THEORY: Proposed by
Nicolas Copernicus in 1542. In this model,
the Sun was the centre of the universe, and
planets and stars revolved around it.

3) In 1610, Galileo Galilei invented the
telescope and proved the heliocentric theory
4) The development of more and more
sophisticated astronomical equipment, like
telescopes and artificial satellites has change
our understanding of the universe. Today, we
have a different model:
• We know that the Sun is not the centre of
the Universe. It is a small star and that our
Solar System is a small part of a Galaxy
called the Milky Way.
• We also know that our Galaxy is one of
many, many galaxies in the universe.
• At the present, most experts agree that
there is no single place that can be
considered the centre of the universe.

2.1) THE STRUCTURE OF THE SOLAR SYSTEM
• The solar system was formed approximately 4.5 billion years ago from a nebula of gas and dust.
• Its shape is a flat disk with a STAR, the Sun, at its centre, and 8 PLANETS revolving around it.
• It also contains a huge number of smaller objects like moons, comets, asteroids and dwarf planets

THE SUN
Sun spots
Sun prominences
Nuclear reactions take place in its interior and
produce huge amounts of energy. As a result,
its Surface is about 6 000ºC and emits light
and heat.
• 25 % Helium
• 75% Hydrogen
• Radio: 696 000 km
• Rotation period: 26 days, 19 hours
• Orbit velocity: 270 Km/s
• Orbit period: 225.000.000 years
• Distance to the Earth: 150 000 000 km
• Sunlight: 8.3 minutes
• Temperature:
surface: 6 000 ºC
core: 15 000 000 ºC

Revolving around the Sun there are 8 planets: Mercury, Venus, Earth, Mars, Jupiter,
Saturn, Uranus and Neptune (in order of distance from the sun). They are divided into
two groups:
• The INNER PLANETS (rocky planets): Mercury, Venus, Earth and Mars
• The OUTER PLANETS (gas giant planets): Jupiter, Saturn, Uranus and Neptune
ASTEROIDS are small rocky fragments which also revolve around the Sun.
They are found into two belts:
• The asteroid belt between Mars and Jupiter
• The Kuiper belt beyond Neptune
Pluto was a
planet till year
2006. Now, it is
considered a
dwarf planet.
Eris and Ceres
are also dwarf
planets
PLANETS AND ASTEROIDS

Beyond the Kuiper belt, the OORT CLOUD is located, surrounding the solar system. It is made up of ice
and frozen gases. COMETS originate here and travel through the solar system orbiting the Sun (following
a very elongated path). When a comet approach the Sun the ice and gases evaporate and start shining,
forming the famous comet’s tail
THE OORT CLOUD AND COMETS

DWARF PLANETS
They are small bodies which revolve around the Sun, but they have not cleared their neighborhood
around its orbit. In other words, they share partially their orbit with other bodies. They are found in
the asteroid belt or in the kuiper belt

PLUTO
• Pluto was the coldest, smallest, and outermost
planet in our solar system until a few years
ago, when more objects were discovered.
• Pluto and its moon, Charon, were called double
planets because Charon is so large it seems less
of a moon than another planet.
• Pluto is among many other objects in the
Kuiper Belt. During each revolution around the
sun, Pluto passes inside Neptune's orbit for 20
years, making Neptune the outermost planet
for that time.
Size: Less than one-fifth the size of Earth
in diameter
Diameter: 2,290 km
Surface: A giant snowball of methane and
water mixed with rock
Atmosphere: Methane
Temperature: between -223° and -233°C
Rotation around the Sun: 248 Earth years

3) THE PLANETS: SMALL ROCKY PLANETS AND GAS GIANT PLANETS
INNER, TERRESTRIAL OR ROCKY PLANETS:
They are Mercury, Venus, Earth and Mars.
• They occupy the inner orbits of the solar
system (within the main asteroid belt)
• They are small compared to the rest
• Their surface is rocky (crust and mantle),
but they have a metallic core and they
have little or no atmosphere
• They have few or no satellite (Earth has
one, the Moon; Mars have 2, Deimos and
Phobos)
OUTER, JOVINS OR GAS GIANT PLANETS: They are
Jupiter, Saturn, Uranus and Neptune
• They occupy the outer orbits of the solar
system (outside the main asteroid belt)
• They are of enormous size (Jupiter is the largest
of the Solar System)
• They consist mainly of gases (thick
atmospheres), except a small rocky core
• They have great number of satellites (Jupiter
63, Saturn 60 and its famous ring, Uranus 27
and Neptune 14)

SOLAR SYSTEM PLANETS
MERCURY
• The smallest planet in the
Solar system (its diameter
is 1/3 of the Earth's
diameter).
• It lacks satellites and
atmosphere.
• Its outdoor temperature
undergoes extreme
variations, between 425ºC
at day to -170 °C at night.
• Its surface is covered with
numerous impact craters
from meteorites
• Revolution (1 Year) = 88
Earth days
VENUS
• It has similar size to the Earth and
also its internal structure is similar
(Iron core, rocky mantle and crust).
It is volcanically active, although it
has not been detected tectonic
plates like on the Earth.
• Its rotation is opposite to the other
planets. (An impact of a meteorite
turned it over)
• Its atmosphere is mainly carbon
dioxide, so that the greenhouse
effect is very powerful and its
average surface temperature is
480°C.
• Revolution (1 year) = 225 Earth days
EARTH
• It is the only planet that has 3/4
of its surface covered by water.
• It has a thin layer of gases that
form the atmosphere thanks to
which the average surface
temperature is maintained at
about 15°C. This allows existence
of liquid water and life on the
planet.
• It has a single satellite (the
Moon).
• It is the only planet that has plate
tectonics.
• Rotation around the Sun: 365.2
days. (Diameter = 12 756 km)

MARS
Olympus Mount is the largest volcano
in the solar system with 24 km altitude,
the base would occupy most of the
Iberian Peninsula• The Red Planet, about half-size of the Earth. It has 2 small satellites
(Deimos and Phobos).
• It has an atmosphere rich in carbon dioxid, but it is very thin, therefore
it barely possesses greenhouse effect. Its average surface temperature is
-55°C. In its atmosphere it has detected methane gas that could be
produced by organisms.
• The poles of Mars are covered with frozen water and frozen carbon
dioxide producing white polar ice caps
• At some point, long ago it had liquid water because on its surface there
are signs of erosion produced by a watercourse. Currently there is no
water on its surface, although it is believed that there could be water
under the icy poles.
• Rotation around the Sun: 687 Earth days (almost 2 Earth years)
• Its surface is the best known so far (it has been explored by robots: first
by the Pathfinder, then by the Spirit and the Opportunity) and it is the
target of the next manned mission.
• Its surface is abundant in impact craters and large reliefs indicating a
great external and internal activity. Mount Olympus, the largest volcano
in the Solar System is on it .
Elongated marks on its surface led to believe in
fantastic "channels" built by alien beings and
the existence of Martians and potential
invasions of the Earth. Ex.: The War of the
Worlds by Orson Wells

JUPITER • This is the largest planet in the Solar System (Its diameter is 11 times
the Earth's diameter). It has an intense magnetic field.
• Although it has some solid or liquid material inside, it is a purely
gaseous planet. Like the stars, it is made of hydrogen and helium, but
it does not meet the conditions to have nuclear fusion reactions.
• On its surface there are huge meteorological formations. The Great
Red Spot is a powerful windstorm twice the size of our planet.
• It has 63 satellites, four major (Io, Europa, Ganymede and Callisto)
were discovered by Galileo in 1610. It also has a system of 4 very faint
rings.
• Average temperature: -148°C
• Rotation around the Sun: 12 Earth years
SATURN
• The most characteristic feature of Saturn is that it has over 60 satellites
and a peculiar system of over 40 rings visible from the Earth, formed by
ice, dust and rock fragments orbiting at its equatorial plane.
• The bands on its surface are caused by high winds that can reach more
than 1 600km/h
• Its density is extremely low, even lower than that of water.
• Temperature: -178°C
• Rotation around the Sun: 29 Earth years!
Saturn is the
second largest
planet in the
Solar System (it
has a diameter
10 times greater
than the Earth)

URANUS
• Uranus has a diameter 4 times that of the Earth.
• Its main feature is that its axis of rotation is
almost horizontal to its orbit. (It's like it revolve
lying)
• It has 27 satellites, known so far and a ring
system (11 rings darker than those of Jupiter)
which is almost vertical because of the planet’s
rotational axis.
• Rotation around the Sun: 84 Earth years. So, each
pole alternates between 42 years of daylight and
42 years of darkness.
• It is blue-green due to methane in its atmosphere
NEPTUNE
• Neptune has a size slightly smaller than Uranus (its diameter is three
times that of the Earth).
• It’s the farthest planet to our Sun. It was discovered by mathematical
calculations and once given its position, it was observed with a
telescope.
• It has 14 satellites and a set of 4 very faint rings.
• Like Uranus its atmosphere has methane, which gives it its blue colour.
• Rotation around the Sun: 165 Earth years
• Its atmosphere is very dynamic and can produce giant hurricanes. Its
winds are the fastest in the Solar System, reaching 2.000 km/h.

THE RELATIVE SIZES OF THE SUN AND PLANETS

THE RELATIVE SIZES OF THE SUN AND OTHERS STARS

4) THE EARTH - A UNIQUE PLANET
The Earth has 5 characteristics that makes it unique among the planet of the solar system:
1) SURFACE TEMPERATURE: Due to its distance
from the Sun, its average temperature is about
15ºC. This makes possible for water to exist in
three states: ice, liquid and water vapor. It also
makes a water cycle possible
2) ATMOSPHERE: The Earth is the largest of the rocky
planets. It retains its atmosphere due to gravitational
force. It is a mixture of gases, made up mainly of
nitrogen and oxygen. Oxygen is used by many living
things for respiration. Carbon dioxide is essential for
photosynthesis
3) On the Earth there is a
considerable GEOLOGICAL
ACTIVITY, as erosion,
volcanoes, earthquakes and
mountain building

5) The Earth has MAGNETIC FIELD which surrounds it and protects living beings from
dangerous solar particle radiation.
4) SATELLITE: the Earth has a relatively large satellite, the Moon, which is responsible for
the ocean tides

4.1) THE FOUR MAJOR SYSTEMS OF THE EARTH
GEOSPHERE: Consist in the Earth’s
surface, its crust and mantle. It is
where the other systems are
located. It provides living things
with minerals salts
HYDROSPHERE: Consists in all the
water on the Earth. It can be liquid,
gaseous or solid, like ice and snow.
Water erodes the Earth’s surface.
All living things are made up mainly
of water
ATMOSPHERE: Consists in the layer
of gases surrounding the Earth. It is
a mixture of gases, mainly nitrogen
and oxygen. Oxygen is used by
many living things for respiration.
Carbon dioxide is essential for
photosynthesis. Weather
phenomena, like rain and wind,
erode rocks and distribute materials
BIOSPHERE: Consists in all living things on the Earth.
Living thins interact with each other and produce
changes in the landscape and the composition of
the air. They can also create rocky deposits, like coral
reefs

DAY NIGHT
Northern Hemisphere
Southern Hemisphere
equatorial plane
rotational axis
Rotation
The Earth takes
24 hours (one day)
to rotate once
on its axis.
5) THE MOVEMENTS OF THE EARTH: 5.1) ROTATION ON ITS AXIS
The rotation of the Earth is responsible for the cycle of day and night. Any point of the
Surface passes part of the 24 hour in sunlight (day) and the other part in darkness (night).
The length of day and night vary throughout the year due to the tilt of the axis.
The Earth rotates
from the west
towards the east

The Earth takes
365¼ days (one year)
to orbit the Sun once.
Revolutionecliptic plane
terrestrial orbit
5) THE MOVEMENTS OF THE EARTH: 5.2) REVOLUTION AROUND THE SUN
Revolution velocity:
107.000 km/h
Elliptic orbit, almost
circular
The Earth travels in
the opposite direction
clockwise
(counterclockwise)
Due to the tilt of the rotational axis of rotation , revolution has two important consequences:
- Revolution causes the annual cycle of seasons (winter, spring, summer and autumm)
- Part of the year one pole faces towards the Sun, so there is no night there. At the same
time, the other pole faces away from the Sun, so there is no day there.
The Earth
remains on the
imaginary
plane of the
ecliptic

6) THE SEASONS The seasons are caused by the tilt of the axis of rotation as
the Earth orbits the Sun. This tilt causes different parts of
the Earth to receive different amounts of sunlight during the
year.
WINTERSPRING
SUMMER AUTUMM
Artic circle
has 24 h of
darkness
WINTER
SOLSTICE:
Direct
sunlight at
Southern
Hemisphere
Artic circle
has 24 h of
light
SUMMER
SOLSTICE:
Direct
sunlight at
Northern
Hemisphere
SRPRING (VERNAL) EQUINOX: Direct sunlight at equator
AUTUMM (FALL) EQUINOX: Direct sunlight at equator
SOLSTICE are
the days when
the difference
in length
between day
and night is
the greatest
EQUINOX are the
days when day and
night are equal
length (12 h)
The shortest
day and
longest night
of the year
The shortest
night and
the longest
day of the
year

During the winter, the Sun’s rays
strike the Northern Hemisphere
at an angle. As a result they
deliver less heat, and the period
of light is shorter
During the summer, the Sun’s
rays strike the Northern
Hemisphere perpendicular to the
ground. As a result, they deliver
more heat, and the period of
light is longer
SUMMER
SOLSTICE
(21st June)
WINTER SOLSTICE
(21/22nd December)
EQUINOX: Direct sunlight at equator
EQUINOX: Direct sunlight at equator

WINTER
SOLSTICE:
Shortest day
Longest night
SUMMER
SOLSTICE:
Shortest night
Longest day
Day and night equal length (12h)
Day and night equal length (12h)

6.1) THE APPARENT MOVEMENT OF THE SUN
From the ground it seems that the Sun
orbits the Earth in an arc in the sky that
begins at dawn and ends at dusk. The daily
movement of the Sun is from east to west
In summer, the Sun moves high across the
sky and shadows are shorter
In winter, the Sun moves low across the sky
and shadows are longer
In spring, the Sun moves every day a little
higher in the sky. In autumn, the Sun moves
every day a little lower across the sky

Distance from the Earth:
385 000 Km.
Radio: 1238 Km.
Period of rotation: 27.3 days
Period of revolution: 27.3 days
7) THE MOON
MARIA (lunar “seas”)
are large dark plains of lava
CRATERS due to meteorites´ impacts
MOUNTAIN RANGES
Leibniz is the highest mountain
(6 000m.)
MOON SURFACE:

7.1) MOVEMENTS OF THE MOON
The Moon is the Earth’s only satellite. It is the largest
satellite in the Solar System (its radius is 1 738km).
The Moon rises in the east and sets in the west.
MOVEMENTS OF THE MOON:
• Rotation: The Moon takes about 28 days to rotate
once on its axis
• Revolution: The Moon takes about 28 days to orbit
the earth once. Its path is almost circular
Both periods are similar, as a result, THE SAME SIDE OF
THE MOON ALWAYS FACES THE EARTH. (The Moon
rotates while orbiting the Earth at the same velocity, so
there is a far side of the Moon we never see)

The dark side or far side is rough and filled
with craters and permanently rotated away
from our planet. By comparison, the near side
of the Moon is relatively smooth
To see the far
side of the
Moon, we have
to travel beyond
the lunar orbit

7.2) THE PHASES OF THE MOON
As the Moon orbits the Earth, its shape SEEMS to change. This is because we see it illuminated by the
Sun from different angles

NEW MOON: The Moon is between the
Sun and the Earth, The Moon is no visible
because the dark side of the Moon faces
the Earth
FIRST QUARTER: The Moon is
halfway between new Moon and full
Moon. The right half is illuminated
by the Sun. Its outline looks like a D
LAST QUARTER: The Moon is
halfway between full Moon and
new Moon. The left half is lit by the
Sun. Is outline looks like the letter C
FULL MOON: The Earth is
between the Sun and the
Moon. The illuminated side of
the Moon faces the Earth
Position 1
Position 3 Position 5
Position 7

ACTIVITY 1: Copy this diagram on your notebook and:
• draw on it arrows showing the sunlight rays
• draw also the lunar phases as they are seen from the Earth at positions 1, 3, 5 and 7
and name them.
ACTIVITY 2: Label the following lunar phases and match them with the positions showed in
the activity above

7.3) ECLIPSES
Eclipses take place when one celestial body totally or partially obscures another
celestial body. There are two types: solar eclipses and lunar eclipses
a) SOLAR ECLIPSE: It occurs when the Moon passes between The Earth and the Sun. The Moon’s
shadow hides the Sun, but only in some areas of the Earth:
• Where the Moon covers completely the solar disk (umbra area), there is a total solar eclipse
• Where the Moons covers the Sun only partially (penumbra area), there is a partial solar eclipse
The Moon is
between the Sun
and the Earth, so
only when the lunar
phase is NEW
MOON, a solar
eclipse can occur.
In Solar eclipses,
while partiality
phase spans more
than two hours, a
total solar eclipse
lasts only 2 or 3
minutes on average
(from a minimum of
just over 1m to a
maximum of 7m).

TOTAL SOLAR ECLIPSE
California, 1991
We can see:
- The Solar corona
(the outermost layer
of the Sun’s
atmosphere)
- Solar prominences
(in red)
Partial solar eclipse

b) LUNAR ECLIPSE: It occurs when the Moon passes through the shadow produced by the
Earth:
• If the Moon is totally hidden by the Earth’s shadow (umbra area), there is a total lunar
eclipse
• If the Moon is only partially hidden and partially visible (penumbra area), there is a partial
lunar eclipse
The Earth is
between the
Moon and the
Sun, so only when
it is FULL MOON a
lunar eclipse can
occur
A total lunar
eclipse last
approximately one
hour

LUNAR ECLIPSE
Partial lunar eclipse
Total lunar eclipse

Why don't we have eclipses every month?
5º
Because the orbit of the Moon isn’t in the ecliptic plane (it is tilt 5º). Eclipses only can occur
when the Moon crosses the ecliptic plane (nodes), what happens twice a “lunar month”;
and that must match with a (solar or lunar) eclipse position

7.4) THE TIDES The Earth and the Moon attract each other due to
the force of gravity. The effect of this force can be
seen in the oceans: their water move from one
place to another due to Moon’s gravitational
attraction and so, tides are caused
HIGH TIDES: The water level raises
on the side of the Earth closest to
the Moon, and also in the opposite
side
LOW TIDES: The water level
become lower in the other areas of
the Earth (water has gone to the
high tides areas)

- How many low and high tides
are there at a point on the Earth’s
surface throughout one day?
- How often does the tide change
at one point of the Earth’s
surface?
The Earth complete a rotation on
its axis in 24 hours. Think and
answer the questions:

SPRING TIDES: It occurs
when to the Moon’s
gravitational effect solar
gravitational effect is
added up. As a result, high
tide is higher than usual
and low tide is lower than
normal.
NEAP TIDES: It occurs when
Moon’s and Solar
gravitational effects work in
different directions. As a
result, high tide is lower
than usual and low tide is
higher than normal.

Unit1 the universe and the earth

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Unit1 the universe and the earth