C

1. SCIENCE TO THE
CONTEMPORARY
WORLD
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2. I THE UNIVERSE
1. The composition of the universe
The universe is made up of:
* Ordinary visible matter (stars, planets & hot
intergalactic gas): 0.4%.
* Normal non-luminous matter (black holes and
intergalactic gas): 3.6%
* Dark Matter: 21%
* Dark Energy: 75%
1.1 Normal matter forms 4% of the universe and is
made up of atoms of chemical elements.
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3. In normal matter known, between 70% and 75% is
hydrogen.
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4. 1.2 Dark matter
• It constitutes 21% of the universe.
We do not know its composition because:
* it’s can not be seen.
* it does not emit or reflect light or radiation.
• It can not be detected with current technical
means.
Its behavior is the same as gravitational normal
matter.
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5. Scientists postulated its existence when
calculating the mass of stars, dust and gas of a
galaxy found that its value was not enough to
explain the intensity of gravitational forces in the
galaxy, between galaxies, or their movement.
Spiral galaxy
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6. 1.3 Dark energy
• It constitutes 75% of the universe, it is distributed
homogeneously in space and its composition is
unknown.
How was it discovered?
Scientists, studying the explosion of the stars, saw
that the universe is expanding faster now than
before and felt that this energy is the cause of this
acceleration.
• Dark energy opposes the attraction between
galaxies and causes accelerated separation
between them. 6

7. • Its existence was confirmed by studying the
cosmic background radiation.
• The cosmologists believe that dark energy:
* Determines the expansion of the universe.
* Determines the evolution of the universe.
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8. l
The galaxy cluster
Abell 1689 is famous
for the way it bends
light in a
phenomenon called
gravitational lensing.
Study of the cluster
has revealed secrets
about how dark
energy shapes the
universe.

9. 2. The origin of the Big Bang. The Big Bang theory.
In 1948, George Gamow proposed that the
universe was created after a large explosion, the
Big Bang.
This theory explains that 13.7 billion years ago, all
matter in the universe was concentrated in a very
small area. When the explosion occurred, the
matter was propelled in all directions.
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10. Consequently the matter was concentrated in
certain areas of space, leading to the first stars and
galaxies. Since then, the universe is constantly
evolving.
According to this theory, as a result of the explosion
all matter in the universe was created and, as this
was expanding, time and space were created.
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11. 3.Confirmation of the Big Bang theory
3.1 Cosmic background radiation.
Studying a very sensitive microwave receiver,
scientists realized there was a strange radiation
that came equally from all points of space.
It is electromagnetic radiation that fills the
Universe. This radiation can only be detected with
a radio telescope which makes it show as a faint
glow.
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12. The cosmic background radiation is radiation
left over from early development of the
universe, and it is a proof of the Big Bang
theory.
This cosmic microwave radiation is the glow of
the big bang, and microwave comes as a result of
the expansion of the universe, which shows that
it had a beginning.

13. 4. The evolution of the universe
a) After the explosion, the universe was hot and
dense.
b) One second later, at a temperature of about 1013
K, the elementary particles that were formed
(electrons, neutrons,protons) interacted with the
photons resulting in a hot gaseous phase of matter
and radiation.
The universe was opaque and there were no
atomic nuclei.
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14. c) A few minutes after the Big Bang, the
temperature dropped quickly allowing the fusion of
protons and neutrons resulting nuclei of hydrogen
and helium atoms. Then the temperature dropped
further and nuclear fusion stopped.
d) 300000 years after the Big Bang, the temperature
dropped and the first atoms of hydrogen were
formed. Consequently, the photons were separated
from matter and the universe became transparent
to light. This initial radiation is currently being
registered as background radiation of cosmic
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microwaves.

15. Studies show that the universe was not uniform
because there were areas that had a higher density.
These denser regions of space where gravity was
higher, attracted matter to them. While matter was
accumulating, dense objects began to form leading
to the first stars and galaxies.
Lagoon nebula
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16. When the universe was between 5000 and 6000
million years and half the current size, there was
already dark energy.
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17. 5.The evolution of the universe according to the
Big Bang theory
a) Big Crunch
This theory postulates that the average density of
the universe is enough to stop its expansion. Then
the universe begins to contract at a single point
(implodes).
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18. b) Big Freeze
The expansion of the universe will continue
forever. If so, the universe will cool as it expands,
eventually becoming too cold to sustain life.
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19. c) Big Rip.
The universe does not contract, but expands as it
reaches a point where all that exists is broken, like
a handkerchief in the hands of two children
pulling hard on each to the opposite side.
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20. II. GALAXIES AND STARS
First galaxies began to form one billion years after
the Big Bang.
The stars contained in these galaxies were
formed at different times and, after evolving,
died.
6. Galaxies
Galaxies are formed by visible matter (stars, gas
clouds and dust), dark matter and dark energy,
gravitationally bound.
There are over 1011 galaxies. Each contains a
variable number of stars. 20

21. Galaxies move in space and, although sometimes
collide violently, usually move away from each other.
- Galaxy Group: it’s a set of galaxies and contains less than
50 galaxies.For example: Local Group (contains the Milky
Way), Hickson 44.
- Galaxy Cluster: Is larger than a group and usually contains
between 50 to 1000 galaxies. For example: Virgo, Coma.
- Supercluster: Is the largest collection of galaxies and
contain many groups and clusters. For example: Local
Supercluster
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22. - Quasar is the brightest object in the universe.
It’s a massive and extremely remote celestial
object, emitting exceptionally large amounts of
energy, and typically having a starlike image.
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23. Black hole: is a region of space where there is a
concentration of high density material, such that
the gravitational force is so high that neither light
nor matter can escape. So anything that is within its
event horizon can’t escape it.
The term "black hole" should not be understood
as a "hole" in the usual sense of the term, but as a
region of space from which nothing can escape, not
even light. This is why they are called "black".
In the center of a black hole, there is always a
singularity, a point of infinite density and gravity.
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24. Supermassive black hole
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25. 6.1 Structures of galaxies
Inside of a galaxy the following structures can be
observed:
a) Star cluster. It’s a group of stars held together
by gravity effect.
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26. b) Nebula. It’s an interstellar cloud of dust,
hydrogen, helium and other gases.
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27. c) Multiple star system. Many stars we see in the
sky, in fact, are systems composed of groups of two,
three, four or more stars held together by gravity
that orbit a common center.
Alpha Centauri
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28. 6.2 Types of galaxies
There are three main types of galaxies: Elliptical,
Spiral, and Irregular.
Elliptical (M49) Irregular (The Large
Magellanic Cloud)
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29. Barred spiral
Spiral
(Coma Berenices) 29

30. a) Elliptical galaxies
They have very little gas and dust. Because gas
and dust are found in the clouds that are the
birthplaces of stars, we should expect to see very
few young stars in elliptical galaxies. In fact,
elliptical galaxies contain primarily old, red stars.
They come from the collision and joining of other
galaxies. They typically have a black hole in the
center.
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31. b) Spiral galaxies
The arms of a normal spiral galaxy are filled with
stars and gas clouds. Spiral galaxies have a central
bulge, or nucleus, from which a number of arms
curve out.
NGC 3310
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32. c) Irregular galaxies
They are made up of young stars and a high
quantity of dust and interestelar gas. Besides,
they don't have nucleus.
They have a wide variety of shapes and
characteristics.
They are frequently the result of collisions
between galaxies or gravitational interactions
between galaxies.
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33. 7. Stars
Concept: Stars are spherical bodies that produce
heat, light, ultraviolet rays, x-rays, and other
forms of radiation. They are composed largely of
gas (hydrogen, helium) and plasma, a
superheated state of matter composed of
subatomic particles.
Our universe likely contains more than 100 billion
galaxies, and each of those galaxies may have
more than 100 billion stars.
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34. 7.1 Appearance
a) Brightness.
Their brightness is a factor of how much energy
they put out and also how far away from Earth
they are.
b) Color/temperature.
Stars in the heavens may also appear to be
different colors because their temperatures are
not all the same. Hot stars are white or blue,
whereas cooler stars appear to have orange or
red hues.
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35. c) Size.
Stars may occur in many sizes, which are classified
in a range from dwarfs to supergiants. Supergiants
may have radii a thousand times larger than that of
our own sun.
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36. 7.2 Formation of a star
Stars form from massive clouds of dust and gas in
space.
Gravity pulls the dust and gas together.
As the mass falls together it gets hot. A star is
formed when it’s hot enough for the hydrogen
nuclei to fuse together to make helium. The
fusion process releases energy which keeps the
core of the star core.
During this stable phase in the life of a star, the
force of gravity holding the star together is
balanced by the high pressure due to the high
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37. temperatures.
When all the hydrogen has been used up in the
fusion process larger nuclei begin to form and the
star may expand to become a red giant.
When all the nuclear reactions are over a small
star, like our Sun, may begin to contract under the
pull of gravity. It becomes a white dwarf which
fades and changes colour as it cools.
A larger star with more mass will go on making
nuclear reactions, getting hotter and expanding
until it explodes as a supernova.
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38. An exploding supernova throws hot gas and dust
into space leaving a neutron star which eventually
shrinks to a black hole.
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39. 7.3 Lyfe cycles of stars
A star goes through a life cycle. This is determined
by the size of the star.
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40. - Stars about the same size as our Sun follow the
left hand path:
Main sequence star red giant white dwarf
black dwarf
- Stars much bigger than out Sun:
Main sequence star red super giant
supernova neutron star or black hole
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41. III SOLAR SYSTEM EXPLORATION
To study the solar system, scientists use the
information provided by spacecraft, probes, space
telescopes ... located in astronomical
observatories.
8.1 The solar system
It consists of the Sun and a large amount of
planetary bodies, attached to the Sun by the force
of gravity, planets, asteroids, comets and
meteorites.
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42. It formed about 4500 million years ago from gas
and cosmic dust of a nebula located in one of the
spiral arms of the Milky Way. When this nebula
became a rotating disk, the Sun was formed in the
center and the other materials formed all planetary
bodies in the system.
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43. 8.2 The information that comes to the Earth
Often meteorites fall to Earth, remnants of
planetary bodies that give us valuable information
about the composition and evolution of the solar
system.
a) Comets
Comets are celestial bodies rarely seen in our sky
because they have a very eccentric orbits and are
only visible when they approach the sun. 43

44. When they are away from the Sun, are spherical
with small size and formed mainly by ice, dust ,
methane, ammonia in solid state , because they are
at a very low temperature.
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45. As they approach the Sun, the temperature rises
and core components start to melt and evaporate,
and also carry dust particles that form the coma and
the tail of a comet. Each time they pass near the
Sun, lose a fraction of its mass. Sometimes, the
remains of the tail can reach us.
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46. b) Asteroids
Most asteroids that fall to Earth are pieces of
asteroids, rocky bodies smaller than the satellites.
They are especially abundant in the asteroid belt
between Mars and Jupiter, made u p of thousands of
asteroids among them (Pallas Athene, Vesta and
Hygiea).
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47. 47

48. c) Meteorites
Meteorites, asteroids fragments or remnants of
comets, travel through space at high speed. They
are gravitationally attracted by the sun and collide
with the bodies that are in its path, producing
large impact craters.
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49. When they reach the Earth, if they are small, they
burn when enter the atmosphere and look like a
light across the sky at high speed.
Meteorites are often divided into three overall
categories based on whether they are dominantly
composed of:
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50. - rocky material (stony meteorites). They are
found in the upper layers of asteroids.
- metallic material (iron meteorites). They are
found in the core of asteroids.
- mixtures (stony–iron meteorites)