Allen Independent School District / Overview



Rotation vs. Revolution

Throughout a 24 hour period, Earth will make one rotation on its axis.

• One rotation= 24 hours= 1 day/night

As the Earth is rotating, it appears as if the Sun is moving across the sky (apparent movement).

• East to west- the Sun is stationary, but the Earth is turning – so the sun appears to rise in the east & set in the west.

• Earth’s rotation causes Day and Night on our planet.

Everyday examples of rotation:

1. A basketball spinning on your finger

2. Turning on your toes 3. Spinning in a chair

The rotation of the Earth also causes shadows to change.

Shadows are longest in the early morning and at dusk (just before sunset).

Shadows are shortest at noon 12:00pm because the Sun is directly overhead.

The Earth takes 1 year (approximately 365 days) to make a revolution around the Sun.

• 1 revolution= 1 orbit around the Sun

• Revolution plus the tilt of the Earth causes the seasons

• The moon is considered a natural satellite of the Earth since it revolves around the Earth.

Everyday examples of revolution:

1. Walking around a table. 2. Running around a track

The fact that moon rotates on its axis in the same amount of time that it makes one rotation around the sun is why we only see one side of the moon!

Seasons: The Earth has seasons because its axis is tilted.

The Earth rotates on its axis as it revolves around the sun, but its axis always points the same direction.

The tilt of the axis causes certain parts of the Earth to be further away from the sun than others. Ex: When the Northern Hemisphere is tilted toward the sun the Southern Hemisphere is tilted away from the sun.

The areas tilted toward the sun experience their summer season.

The areas tilted away from the sun experience their winter season.

During Earth’s orbit around the sun, there are also times when the sun shines equally on both the North and South Hemispheres. This occurs in spring and fall times.

If the Earth weren’t tilted on its axis, each part of the Earth would always receive the same amount of sunlight and therefore their weather would remain the same throughout the year!

An Equinox is when both the north and south hemispheres have the same amount of sunlight – happens in March & September.

A Solstice occurs when sunlight is the most uneven between the north and south hemispheres. This is either the longest or shortest day of the year - happens in June & December.

Earth vs. Moon

|Earth |Moon |

|75% water |Water in the form of ice only – located in craters. |

| | |

| |Rotates once every 28 days |

|Rotates once every 24 hours | |

| |Revolves around the Earth= 28 days |

|Revolves around the Sun= 365 ¼ days | |

| |Has mountains, craters, canyons, plains, maria, and |

|Has mountains, craters, canyons, rocks, plains, |rock |

|rivers, oceans, etc. | |

| |Made up of rock |

|Made up of 4 layers- inner core, outer core, mantle,| |

|and crust | |

| | |

|Supports life |No signs of life |

| | |

|Has an atmosphere (78% nitrogen, 21% oxygen, 0.9% |No atmosphere |

|argon, and 0.03% carbon dioxide) | |

| | |

|Has seasons and weather |No seasons or weather |

| | |

|Gravitational pull – 9.8 m/s2 |About 1/6 the Gravitational pull of the Earth |

| | |

|Diameter 12756 km |Diameter is about ¼ the size of the Earth |

Sun Facts

➢ The sun is an average sized star in our galaxy – The Milky Way Galaxy

➢ The sun is one of trillions of stars in space.

➢ 93,000,000 miles away from Earth

➢ The sun is the only star in our solar system.

➢ The sun is a ball of hot burning gases, mainly Hydrogen and Helium.

➢ The sun does rotate on its axis.

➢ The sun diameter is about 110 times the diameter of the Earth.

➢ The sun does have an atmosphere (photosphere, chromosphere, and corona are the outer layers)

➢ Sunspots that appear on the chromosphere are darker, cooler areas on the sun.

➢ In the Corona (cloud of plasma on the outer surface of the sun) you can find:

▪ Sunspots- dark, cooler areas on the surface

▪ Prominence- arching storms

▪ Solar flares – explosions on the sun

▪ Solar wind – particles that slip through the magnetic field of the sun and go into space.

Really, Really, Really Important stuff about the Sun!

❖ The sun is the center of our solar system

❖ Source of energy for all cycles

1. Light Energy

▪ Needed for photosynthesis, nitrogen cycle, and carbon dioxide cycle

▪ Without it= no plants, no oxygen, no life

2. Heat Energy

▪ Needed for the water cycle

▪ Without it= no precipitation, everything would be too cold and freeze

3. Solar Energy

▪ Needed for all cycles, for heat, for electricity, etc.

Gravity

Force that holds planets in orbit

• The Sun’s gravitational pull keeps the planets on their paths. The Sun’s gravity is about 28 times that of the Earth.

• Inertia keeps the planets moving.

The Earth’s gravity keeps objects on the Earth from floating away and pulls them toward the ground, but it also keeps the Moon in orbit around the Earth.

The pull between the Moon and Earth causes tides.

**Gravity on the Moon is 1/6 the gravity on Earth.

• Steve weighs 60 pounds on Earth. He only weighs 10 pounds on the Moon.

• Steve’s mass stays the same.

Can you name the planets in order?

Remember this!

• Sun

• My Mercury

• Very Venus

• Energetic Earth

• Mother Mars

• Just Jupiter

• Served Saturn

• Us Uranus

• Nachos Neptune

• Pluto is considered a dwarf planet now due to its small size.

• It is smaller than our moon!

Moon Phases

Why does the Moon keep changing its shape every night? Unlike the Sun, the Moon does not produce its own light. The light we see from the Moon is reflected from the Sun’s light.

The Sun only shines on one side of the Moon at a time. As the Moon orbits the Earth, we can see different parts of the light side, depending on the locations of the Sun, Earth, and Moon. The changes we see in the Moon are called moon phases.

When the Sun and Moon are on opposite sides of Earth, we can see the full moon, because we see the whole sunlit side. When the Moon is directly in between Earth and the Sun, we cannot see the Moon at all; it is a new moon. It takes two weeks for the Moon to travel halfway around the Earth in its orbit, from full moon to new moon. After the full moon the moon is waning as it grows smaller; this is a gibbous moon. After the new moon, it is waxing as it grows bigger; this is a crescent moon.

Complete the picture on the right by coloring in the shadowed portions of the moon at each phase and labeling the phases. Start the new moon at the circle directly between the Earth and the Sun and go counter clockwise.

Tides

Tides are the rising and falling of the ocean as a result of the gravitational pull of the moon.

There are two high tides at a specific location every 24.5 hours. There is a high tide on the side of the Earth facing the moon due to the moon’s gravity and on the side of the Earth directly opposite from the moon due to the inertia of the ocean waters.

Approximately twice a month the Earth has a spring tide and a neap tide.

[pic]

Spring tide = an “extra high” high tide that occurs when the sun, earth, and moon are aligned and the gravitational pull of the moon and sun work together.

Neap tide = a “lower than normal” high tide that occurs when the moon is at a right angle to the sun and the gravitational pulls of the moon and the sun oppose each other.

Theories of the Universe

Geocentric model of the universe was established by ancient Greek philosophers and astronomers such as Ptolemy and Aristotle. In this model the Earth is the center of the universe and all the planets (and the moon) revolve around it.

Heliocentric model of the universe was developed by Copernicus and proven by Galileo. It placed the sun in the center of the universe with the planets orbiting the sun. It replaced the Geocentric model.

Space Race

The space race between the U.S.A. and the U.S.S.R. (Russia) began in the late 1950’s. Present John F. Kennedy challenged the nation to put a man on the moon by 1970!

1st American in space : Alan Shepard

1st American to orbit the Earth: John Glen

1st American to walk on the moon: Neil Armstrong

2nd American to walk on the moon: Buzz Aldrin

Commander of the Apollo 11 mission – moon mission – Michael Collins

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