Unit 4 Review: Earth's Place in the Universe

​Rotation and Revolution

• Earth rotates on its axis like a spinning top.

• This rotation takes 24 hours and gives us day and night.

• The Sun appears to rise and set because of Earth’s rotation.

💡 Think About It: If Earth stopped spinning, what would happen to day and night?

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Rotation – Earth's Daily Spin

• Earth revolves around the Sun in an oval-shaped orbit.

• One full revolution takes 365 days, which makes one year.

• The path Earth follows is called its orbit.

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Revolution – Earth’s Yearly Journey

 Rotation vs. Revolution

​🌞 Quick Check: What causes day and night? Rotation or revolution?

• Earth is tilted at 23.5 degrees as it orbits the Sun.

• This tilt changes how sunlight hits different parts of Earth.

• More direct sunlight = warmer temperatures (summer)

• Less direct sunlight = cooler temperatures (winter)

Why Do We Have Seasons?

​☀️ Think About It: What would happen if Earth had no tilt?

• When the Northern Hemisphere tilts toward the Sun, it is summer there and winter in the Southern Hemisphere.

• When the Northern Hemisphere tilts away, it is winter there and summer in the Southern Hemisphere.

• Areas near the equator get sunlight year-round, so they don’t have big season changes.

🌍 Did You Know? The North and South Poles can have 6 months of daylight or 6 months of darkness!

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​How do seasons work?

• Summer Solstice (June 21): Longest day in the Northern Hemisphere.

• Winter Solstice (December 21): Shortest day in the Northern Hemisphere.

• Spring (March 21) and Fall (September 21) Equinoxes: Equal daylight and night everywhere!

🌞 Quick Check: Why do days get shorter in the fall?

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Solstices and Equinoxes

• The Moon does not make its own light; it reflects the Sun’s light.

• As the Moon orbits Earth, different parts of it are lit up, creating phases.

• One full cycle of phases takes about 29.5 days.

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​Why does the moon change shape?

​🌙 Think About It: If the Moon didn’t move, would we still see phases?

• Waxing = The Moon is growing brighter (from New Moon to Full Moon).

• Waning = The Moon is getting darker (from Full Moon to New Moon).

• The First and Last Quarter Moons look like half-moons!

🌍 Did You Know? The same side of the Moon always faces Earth because its rotation and revolution have the same pace.

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​Waxing vs. Waning

Tides

• Tides are the rise and fall of ocean water levels on Earth.

• They are caused by the gravitational pull of the Moon and, to a lesser extent, the Sun.

• Earth experiences two high tides and two low tides in a 24-hour period.

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​What Are Tides?

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💡 Fun Fact: The Bay of Fundy in Canada has the highest tides in the world—water levels can change by more than 50 feet (15 meters)!

• The Moon’s gravity pulls on Earth’s water, creating a bulge (high tide) on the side facing the Moon.

• A second bulge occurs on the opposite side of Earth due to inertia.

• Areas not in the bulges experience low tide.

​How the Moon Affects Tides?

• Spring tides happen when the Earth, Moon, and Sun are aligned (during full moon and new moon), creating the highest high tides and the lowest low tides.

• Neap tides happen when the Moon and Sun form a 90-degree angle (during first and third quarter moons), causing weaker tides.

​Spring and Neap Tides

An eclipse happens when one object in space blocks sunlight.

There are two main types:
🌞🌑 Solar Eclipse: The Moon blocks sunlight and casts a shadow on Earth.

🌍🌕 Lunar Eclipse: The Earth blocks sunlight, making the Moon dark.
Eclipses don’t happen every month because the Moon’s orbit is tilted.

🧐 Quick Question: Why don’t we have eclipses every month?

What is an Eclipse?

• Happens during a New Moon 🌑.

• The Moon moves between Earth and the Sun, blocking sunlight.

• There are three types:

  
  🔴🌑 Total: The Moon completely covers the Sun.
  🌓 Partial: Only part of the Sun is covered.
  ☀️⭕ Annular: The Moon is farther away and leaves a ring of sunlight.

  
  ⚠️ Never look at a solar eclipse without protection! Use special eclipse glasses. 😎

​Solar Eclipse

• Happens during a Full Moon 🌕.

• The Earth moves between the Sun and the Moon, casting a shadow on the Moon.

• There are two types:
  🔴 Total: The Moon is fully in Earth’s shadow and looks red.
  🌘 Partial: Only part of the Moon is dark.

• The Moon looks red in a total eclipse because Earth’s atmosphere filters sunlight.

🌕 Fun Fact: A lunar eclipse can be seen from anywhere on Earth where it is nighttime!

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Lunar Eclipse

• Closest planet to the Sun. 🌞

• Extreme temperatures: very hot during the day, freezing at night. ❄️🔥

• No atmosphere, so it can’t trap heat.

• No moons.

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​Mercury

• Similar in size to Earth. 🌎

• Thick, dense atmosphere traps heat, making it the hottest planet. 🔥

• Covered with thick clouds of sulfuric acid.

• No moons.

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​Venus

• The only planet with liquid water, solid ice, and water vapor. 💧❄️☁️

• Has one moon. 🌕

• Supports life because its appropriate distance from the sun, right temperature and oxygen-rich atmosphere.

​Earth

• The “Red Planet” due to iron oxide (rust) on its surface. 🔴

• Has a thin atmosphere, ice caps, rift valleys, and volcanoes. 🌋

• Could have supported life in the past.

• Two small moons.

​Mars

• Largest planet in the solar system.

• Has at least 66 moons!

• The Great Red Spot is a giant storm. 🌪️

​Jupiter

• The second-largest planet.

• Made mostly of hydrogen and helium.

• Has at least 60 moons and the most visible rings.

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​Saturn

• Bluish-green color due to methane in the atmosphere.

• Two sets of rings.

• Made of ice and rock. ❄️

• Rotates on its side!

​Uranus

• Farthest planet from the Sun.

• Deep blue with large storms. 🌪️

• Has 13 moons and several rings.

​Neptune

• Gravity keeps planets in orbit around the Sun. ☀️🪐

• The force of gravity works over long distances, shaping galaxies.

• Earth's gravity is the strongest force acting on the Moon. 🌍🌕

Gravity in the Universe

• Scientists used telescopes to discover new planets, stars, and asteroids. 🔭

• The biggest challenge of space travel is escaping Earth’s gravity. 🚀

• Early space exploration relied on ground-based telescopes.

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​Space Exploration

• Telescopes like Hubble and James Webb provide detailed images of space.

• Space telescopes help us study distant planets and galaxies.

Space Telexcopes