- Historical models assumed Earth was the center of the solar system, with planets circling it. Copernicus developed the first sun-centered model. Galileo observed moons orbiting Jupiter, showing Earth was not uniquely orbited. - Earth rotates on a tilted axis once every 24 hours, causing day and night. Its yearly revolution around the sun and axial tilt cause the seasons. - The solar system includes the sun and objects that orbit it, such as planets, asteroids, comets, and other planetary bodies. It is located within the Milky Way galaxy.

1. Historical models of the
solar system

2. • The earliest models for the solar system assumed that the Earth
was at the center of the solar system.
• With the sun, moon and planets circling it.

3. Copernicus
• He developed the first detailed sun centered model of the solar system.
• In his time, they still observed with the naked eye.

4. Galileo
• He made improvements to the newly invented telescope.
• He observed moons orbiting Jupiter.
• Earth was not the only object that could be orbited.

5. At what degrees the Earth axis is tilted ?

6. The earth rotates around an imaginary
line called an axis

7. Earth spins around itself
Rotation – rotate

8. The earth rotates about its axis once every 24 hours or once a day.
Earth rotation causes day and night.

9. • As earth rotates, only half of Earth faces the sun.
As it rotates, the side that faces the sun has:
Day time
The other side of earth faces away from the sun has:
Night time

10. The sun rises towards the east
Continues to rise in the sky until midday
And then, it sets towards the west

12. How would night and day be different if Earth
did not rotate ?
Half of the Earth would always face the sun and have day
The other half of earth would always face away from the
sun and have night.

13. Where is Earth’s axis ?
Through its center

14. Why is one half of Earth lit?
It is facing the sun, so the sun is shining on it

15. Why is the other half of Earth dark ?
It is facing away from the sun, so there is no light on it.

16. • Earth is divided into two halves
• Northern hemisphere
• Southern hemisphere
• Equator

18. The northern hemisphere is tilting towards the sun.
The southern hemisphere is tilting away from the sun
Six months later the opposite happens.

19. • In June, northern hemisphere
is tilted toward the sun and
gets more rays.
• It has more hours of daylight
and warmer weather.
• It is summer there.
• In June, the southern hemisphere, is tilted
away from the sun and gets less rays.
• It has fewer hours of day and cooler
weather.
• It is winter there.

20. Th tilt of Earth’s axis and its orbit causes
the seasons

22. When it is summer in the united states, it is winter
in Chile. How can two places have a different season
at the same time?

24. What causes the seasons ?
Earth’s tilt on its axis as it revolves around the sun

25. In which direction does Earth’s northern hemisphere
point when it is winter there?
Away from the sun

26. In which direction does the northern hemisphere
point when it is summer there ?
Toward the sun

27. -In the summer, the sun rises early
and higher in the sun.
-It sets late in the evening.
-When the hemisphere is tilting
towards the sun (summer),
-The path is different when the
hemisphere is tilting away from
the sun (winter).

28. The sun is the only large luminous body in
the solar system.
We see the large objects like the moon
and planets, by the sunlight they reflect to
the Earth.

29. The vast distance
between two
objects in space
can be measured
by the time it
takes light to
travel between
them.

30. A light year is the distance travelled by light in a year.

31. A group of stars that seems to form a picture in the night sky.

32. • The early Greeks named constellations after animals or people
• Orion is constellation named after a hunter
• The positions of the constellations seem to change with the seasons.
• Because we see different parts of space as Earth revolves around the
sun.

34. What do you see when you look up at the night sky ?
Stars, the moon

35. Why do you think people in the southern hemisphere
see some different constellations than people in the
northern hemisphere ?
People who live in different hemispheres of Earth see
different parts of the sky

36. Moon

37. The moon is Earth’s
satellite.
A body that orbits a
larger body is called a
satellite

38. The mass of Earth is larger than the
moon.
Therefore,
Earth’s gravity exerts a stronger pull
on the moon.

39. • Only one side of the moon faces the Earth.
• It takes one month for the moon to complete one rotation
• It takes also (28) one month to make one revolution around Earth
As the moon moves around the
Earth, it also spins on its axis.
The speed at which it rotates makes
the moon always keep the same part
of it facing the Earth.
The other side of it is never seen
from the Earth.

40. Why do we see different shapes of the
moon through the month ?

41. What causes the moon’s appearance to change
in the night sky ?
As the moon revolves around Earth, different amounts
of its lit side can be seen from Earth.

42. Are there other planets that also revolve
around the sun?

43. Solar system

44. Solar system
Is made up of a star , planets and other bodies that
revolve around it.

45. What is at the center of the solar system ?

46. How many planets our solar system have?

48. MarsVenusMercury Earth
Uranus
Saturn
Neptune
Jupiter

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Naming

50. Pluto is no longer included in the list of planets in the solar system due to:
- Its small size
- Irregular orbit

51. Pluto is smaller than seven moons in our solar system
It cannot be seen without a telescope

57. There are other objects orbiting the sun
Asteroid
- Lumps of rock that revolves
around the sun.
It is made of rock and metal

58. Most asteroids are in the asteroid belt between Mars and Jupiter
The solar system does not end at the orbit of Neptune
There is a Kuiper belt .

60. There are other objects orbiting the sun
Comet
It is a ball of rock and frozen gases

63. • The sun is not the center of the universe as people once believed.
•It is on an arm of a spiral galaxy called the milky way

65. The milky way as seen from Earth

66. Eclipse
Is when one object in space casts a shadow onto another

67. Solar eclipse

68. When the moon is directly between the sun and Earth,
the shadow of the moon falls on a part of Earth
During a solar eclipse, the sunlight is completely blocked by the
moon.
Solar eclipse

69. Lunar eclipse
Occurs when the moon moves through Earth’s shadow

70. Lunar eclipse

71. How do we know what the surfaces of the inner
planets look like ?
Space probes have taken pictures of these planets and
sent them back to Earth

72. Which force pulls on Earth and holds it in
orbit around the sun ?
The sun’s gravity

73. Which force holds the moon in orbit around
Earth?
Earth’s gravity

74. Why does the sun have a much greater force of
gravity than Earth?
The sun’s gravity is greater because it is a much
larger body

75. What are the two types of movements of Earth
and the moon?
They rotate and revolve

76. What do Earth and the moon revolve around ?
Earth revolves around the sun
The moon revolves around Earth

77. Mass
The mass of an object is the amount of matter or
‘stuff’ it contains
An elephant contains more matter than a
mouse, so it has a greater mass.

78. Mass is measured in kilograms, kg
A 100 kg object has a greater mass than a 5 kg object
An object's mass stays the same wherever it is. So a 5 kg mass on
Earth has a 5 kg mass on the Moon.

79. Weight
The weight of an object is the gravitational force between the
object and the Earth.
weight = mass × gravitational field strength
This means that a 2 kg object on the Earth’s surface has a weight of
20 N (2 kg × 10 N/kg = 20 N)

80. Mass and weight
The mass of an object stays the same wherever it is, but its weight can
change.
The Moon is smaller and has less mass than the Earth, so
its gravitational field strength is only about one-sixth of the
Earth’s. So, for example, a 120 kg astronaut weighs 1200
N on Earth but only 200 N on the Moon. Remember that
their mass would still be 120 kg.

81. Watch video