Download Science 3rd prep. 1st term unit 3 lesson 2 The Solar System Millions

Science 3rd prep. 1st term unit 3 lesson 2
The Solar system
The Solar System
Millions of years ago, planets were originated in orbits around the sun to form
what is known as the solar system.
The solar system
The system consists of:
- the sun
-
Eight planets
Comets
Asteroids
Moons
** the planets and the other bodies were originated in solar system since 4600 million years
ago.
** solar system extends over 12000 million km. in the space.
** sun is the center of solar system and it is the dominant body (total mass 99% of solar
system)
Gravity in the solar system
Newton was the first one who discovered the earth's gravitational force.
The law of gravitation explain two points:
** the movement of planets around the sun.
** the movement of the moon around the earth.
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Ms.Marim
Science 3rd prep. 1st term unit 3 lesson 2
Newton’s law of universal gravitation.
The force of attraction between two bodies is directly proportional to the product of their
masses and is inversely proportional to the square of the distance between them.
Then he proved that the gravitational force makes:
1 – planets revolve around the sun in fixed orbits.
2 – the matter of each celestial body remains firm.
** if the gravitational force of celestial body was strong enough, it will attract gases towards
itself forming atmospheric envelope around it.
** law of universal gravitation is one of the basic laws of the universe.
Question
What happens if there is no attraction force between the sun and earth?
The earth will leave its orbit and float in random fashion in space and this will lead to
destruction of the earth.
Exercise
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2
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–
–
–
–
the
the
the
the
metal sphere represents the planet.
hand represents the sun
thread represents the gravitational force.
path of the metal sphere represent the orbit.
Enriching information
** Gravity keeps planets in their orbits around the sun and moons in their orbits around
the planets.
** the effect of gravity decreases by increasing the distance between the sun and the
planet.
Science , technology and society
Weightlessness
The continuous force of the Earth’s gravity on our bodies gives us
weight.
But, when you are inside a lift going downward fast, you feel that
you are lighter in weight.
weightlessness occurs in the spacecraft as astronauts fall down inside it with the same
speed so that they get weightless.
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Ms.Marim
Science 3rd prep. 1st term unit 3 lesson 2
Note
If the lift falls ( when the wire are cut) , you feel weightlessness.
Experiments are performed on both animals and plants in space to study the effects of
weightlessness on them. Also,
specific scientific experiments are done as they cannot be done on surface of the Earth.
Theories about the evolution of the solar system
There are many scientific and philosophical theories about the evolution of the solar system.
They are about twenty theories
These theories (as we shall see) are still unproved and subject to change.
Astronomers think that the most widely accepted model for explaining the formation and
evolution of our solar system is " the Solar Nebular Model" which states that :
** planets and other bodies were originated in the solar system from the matter that
remained from the evolution of the sun as follow:
1 – the sun was surrounded by solar nebula which is a sphere of gases and
dust.
2 – the solar nebula stated to rotate.
3 – during rotation , it turned into a flat rotating disk.
4 – most of the dust compressed forming four masses. (( mercury, Venus,
earth and mars ))
** some dust and ice combined with gases forming (( Jupiter, Saturn, Uranus and Neptune))
Solar nebula
It is a sphere f gases and dust from which the planets of the solar system were originated.
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Ms.Marim
Science 3rd prep. 1st term unit 3 lesson 2
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Most important theories
1 – Nebular theory
2 – Crossing star theory
The modern theory
1-Nebular theory (Laplace 1796)
The French scientist Pierre Simon Laplace published a research entitled ((world order)) and
that was in 1796.
This research included a vision of Laplace about the evolution of the solar
system.
This perception (which won great reputation for a century) has been affected
by two observations.
1 -There is something that looks like clouds or nebula in the space.
2 -The space contains many cloudy rings surrounding some planets such as rings of Saturn.
Assumptions of nebular theory:
The solar system was a glowing gaseous sphere revolving around itself. This sphere is called
nebula.
1 – the Nebula (glowing gaseous sphere)
-Over the time, the nebula gradually lost its heat so its size contracted and its revolving
speed around itself increased.
2- The gaseous rings
a. Under the effect of centrifugal force, the nebula lost its sphere
form and became in a form of a flat rotating disk.
b. Parts got separated from the flat rotating disk to form gaseous
rings that also rotate in the same direction in which the nebula rotates.
3-the formation of the solar system
- These gaseous circles were formed after the planets of the solar system got cooled and
frozen.
-
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The flaming mass that remained in the centre formed the sun.
Ms.Marim
Science 3rd prep. 1st term unit 3 lesson 2
Nebula:
It is a glowing gaseous sphere revolving around itself, from which the solar system was
originated.
2-The crossing star theory (Chamberlain and Molten 1905)
The crossing star theory is based on some assumptions:
The solar system was originally a big star which is the sun.
1- huge star approached the sun.
2-This star attracted the sun to it; an act
which led to a great expansion in the part of
the sun facing it.
3-This expanded part was exploded which led to:
** a gaseous line was formed of a great length from the sun
** The sun escaped from the gravity of that star due to the explosion.
4-The gaseous line started to condense due to the attraction forces and
then it cooled forming the planets.
The sun escaped from the gravity of the crossing star?
Due to the explosion of the expanded part of the sun.
3-The modern theory of the world (Alfred Hale,1944)
This theory is based on
- what is sometimes seen when a star glows for a short time to be one of the most shining
stars in the sky.
- After a day or two, its glow disappears gradually
to return as it was.
- The reason for that glow is not precisely known.
- It may be due to the explosion of the star as a
result of nuclear reactions that occur so suddenly
and violently that the star bombs huge amounts of
gaseous materials.
- Then, its size increases and accordingly its shining increases as well.
- When the bombed gases are cooled, its shining returns as it was.
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Ms.Marim
Science 3rd prep. 1st term unit 3 lesson 2
Assumptions of Alfred Hale (modern theory)
The solar system was originally a star rather than the sun:
1-The existence of a star rotating near the sun
2-The star was exposed to explosion due to huge nuclear reactions.
3-The force of the explosion led to
- the bombing of the star’s nucleus away from the gravity of the sun.
-A cloud of gas remained
4 –the gaseous cloud subjected to cooling and contraction processes forming
the mater of planets
5 – the attraction force of the sun controlled the orbits of planets around
it.
The difference in the length of the day and year from a planet to another
The earth revolves around its axis in a period of time estimated at one earth day, and it revolves
around the sun in a period of time estimated at one earth year.
Earth's day
It is the time taken by earth planet to complete one rotation around its axis.
Earth's year
It is the time taken by earth planet to complete one rotation around the sun.
Note
-
earth's years = 365.25 earth's day.
The earth's day = 24 earth's hour.
1 – Factored led to the difference in the length of the day:
1 -Radius of the planet earth.
2 - Speed of the planet rotation around its axis.
Day ; it is the period taken by the planet to make one complete rotation around its axis.
2 – Factors led to the difference in the length of the year;
1 -Distance between the planet and the sun.
2- Speed of the planet rotation around the sun
Year : it is the period taken by the planet to make one complete rotation around the sun.
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Ms.Marim
Science 3rd prep. 1st term unit 3 lesson 2
Activity:>>>Explaining the difference in the length of the year from a planet to
another.
Tools
Chalk to draw circles in the school playground.
Steps
1 -Go out the school playground with your classmates.
2-Choose five of your classmates different in weight and size.
3-One of your classmates stands in the middle of the playground (a).
4-Draw four circles with a united centre around that student.
5-Each student stands on one of the circles in a way that are on one straight line.
6- Give a signal to students to start moving in a circle around the centre.
7-Assign the time that each student takes to make a complete rotation
8-What is the reason for the difference in the time each student takes to make a complete
rotation
Observation
At equal speed, the time that each student takes to make a complete rotation increases as
the distance between the student and centre increase
Conclusion
The difference length of a year is due to:
1-Distance between the planet and the sun.
2- Speed of the planet rotation around the sun.
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Ms.Marim
Science 3rd prep. 1st term unit 3 lesson 2
Compared to the rest of planets of the solar system,
astronomers managed to determine the day and year for each planet in terms of the
earth day and year as shown in the following table
Planet
)Rotation around the axis Rotation around the sun
(earth day)
(earth year)
Mercury
59
0.24
Venus
243
0.62
The Earth
1
1
Mars
1.03
1.9
Jupiter
Saturn
Uranus
Neptune
0.41
12
0.43
29
0.72
84
0.67
165
We can conclude that:
The longest day is on Venus
The longest year is on Neptune
The shortest day is
The shortest year
on Jupiter
is on Mercury
Science , technology and society
Space suit:
- The first astronauts wore one space suit for the trip.
- Today, they wear clothes that differ due to missions they perform.
- There is a space suit to travel back and forth.
- There is also a normal type of special clothes to be
worn inside the spacecraft in its rotation.
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Ms.Marim
Science 3rd prep. 1st term unit 3 lesson 2
The important instruments to study the outer space
Special Equipments centered on earth and space in order to study the Sun.
1 – The solar telescope
Place : centered on the earth.
Use : forms a picture of the sun.
This type of telescope works on reflecting the sun rays downward to a mirror in a tunnel
under the Earth’s surface.
- the sunlight is gathered , then separated into a solar spectrum by the spectrometer
(( device that shows the different light waves of the sun.))
- Astronomers got most of their information about the sun from the study of its spectra.
- a picture of sun is formed in a monitoring room where astronomers can study its light.
Modern equipments
Astronomers use modern equipments on the surface of the Earth.
They also send them to space to get photos and information better
than what surrounds us.
2- Telescopes
Telescopes rotating in orbits around the Earth are better than that are been on surface of
the earth because :
-
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they can see celestial bodies more clearly.
They catch rays that can't be able to penetrate the earth's atmosphere.
Ms.Marim
Science 3rd prep. 1st term unit 3 lesson 2
Examples:
The Hubble telescope
- The Hubble telescope was launched in April in 1990 .
- It rotates around the earth at a height of 500 km. From its
location
,
- it collects photos since millions of years .These photos allow
astronomers an opportunity to study the evolution of the universe
after the Big Bang.
- Astronauts on a space shuttle regularly maintain this telescope in space.
3 – spacecrafts:
They revolve around other planets or land on them, sending discoveries
to the earth.
Most telescopes and spacecrafts are controlled by computers from he
surface of the earth.
Questions on lesson:
Complete the following statements;
1 – the sun is the center of ……………………………. And it represents …………….. % of the total mass
of the solar system.
2 – the solar system consists of ……………., eight planets, …………………… , comets and …………………..
3 – the force of attraction between two objects is …………………………. Proportional to the product
of their masses and is ……………………………. Proportional to the square of the distance between
them.
4 – as the distance between the planet and the sun increases, the sun's gravitational force
………………………………. And its motion becomes ……………………………….
5 – planets and other bodies were originated in the solar system from the matter tht
remained from the evolution of the ………………………….
6 – the solar nebula is considered a gaseous cloud of …………………. And ………………… gases and dust
of iron rocks and ……………………..
7 – scientist Laplace has been affected by two observations which are presence of
…………………. In the space and presence of rings of planet.
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Ms.Marim
Science 3rd prep. 1st term unit 3 lesson 2
8 – the scientist who found Nebular theory about the evolution of the solar system is
called…………………….
9 – according to nebular theory, the gaseous rings cooled down and frozen forming the
…………………………………. , while the flaming mass remained is the …………………………
10 – the scientist who established ………………………………… theory is Laplace. But the scientist who
established the modern theory of the world is ………………………………
11 – the earth revolves around ……………………. In a period of time estimated at one earth's day
and it revolves around ………………………. In a period of time estimated at one earth's year.
12 –the difference of the length of a day from a plane to another is due to ……………….. and
………………………………….
13 – the difference of the length of a year from a planet to another is due to …………………….
And …………………………..
14 – the shortest year is the year of ………………………. Planet.
15 – on Neptune , the year is ………………….. earth's year, while on ………………………. Is 84 earth's
year.
16 - ………………………….. telescope is used in studying the sun from the earth's surface.
Choose the correct answer
1 – solar system extends over …………………………………. Kilometer in the space
a. 15000 million
b. 1500 million
c. 12000 million
d. 4600 million.
2 – planets rotate around the sun by the effect of the gravity of ………………………
a. the sun
b.the Jupiter
c.the earth
d. the moon
3 - ……………………. Is the scientist who proved the presence of attraction force between any
two objects in the space.
a. Galileo
b.Isaac Newton
c. Max plank
d. Einstein
4 – the gravitational force between tow objects in the space is inversely proportional to ………
a. the product of their volumes
b. square of the distance between them.
c. square of the mass of each object.
d. no correct answer
5 – the weightlessness case takes place when the lift …………………………….
a. ascends with uniform speed.
b. descends with uniform speed.
c. descends with uniform acceleration.
d. falls when the carrying wires are cut.
6 - …………………… is from the gases of solar nebula
a. hydrogen
b. oxygen
c. Nitrogen
d. carbon dioxide.
7 - ……………….. is from the components of the dust of solar nebula.
a. iron
b.rocks
c. ice
d. all of the choices.
8 – in crossing star theory, planets formed due to……………………..
a. expansion of the crossing star .
b. explosion of a nebula.
c. expansion of a gaseous line from the sun towards the crossing star.
d. expansion of a gaseous line from the crossing star towards the sun.
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Ms.Marim
Science 3rd prep. 1st term unit 3 lesson 2
9 – the scientist who found the modern theory about the evolution of the solar system is ……..
a. chamberlain
b. Moulten
c. Alfred Hale
d. Laplace.
10 – in modern theory , bombing he star nucleus away was due to ………………..
a. the force of gravity
b. collision by asteroids.
c. drop in temperature
d. huge nuclear reactions.
11 – the time taken by Saturn planet to rotate around the sun is …………………..
a. 12 years.
b. 29 years
c. 84 years.
d. 165 years.
12 – the day on …………………… planet is longer than its year
a. Neptune
b. Venus
c. Mars
d. Uranus.
Give reasons for:
1 – sun is the dominant body in the solar system ?
…………………………………………………………………………………………………………………………………..
2 – the constancy of the planets in their orbits around the sun.
……………………………………………………………………………………………………………………………………
3 – the nebula lost its sphere form and became in a form of a flat rotating disk?
…………………………………………………………………………………………………………………………………..
4 – the difference in the length of the year from a planet to another?
…………………………………………………………………………………………………………………………………..
5 –the longest year is on Neptune?
…………………………………………………………………………………………………………………………………..
6 – the year in Venus is shorter than its day?
…………………………………………………………………………………………………………………………………….
7 – telescopes rotating around the earth are preferred than that on the earth's surface?
…………………………………………………………………………………………………………………………………..
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Ms.Marim