SPACE TEK3.8 CD

Student Expectation

The student is expected to construct models that demonstrate the relationship of the Sun, Earth, and the Moon, including orbits and positions; AND identify the planets in Earth’s Solar System and their position in relation to the Sun.

Key Concepts

• Models can be used to represent the Moon orbiting Earth and Earth orbiting the Sun.
• Each of the planets in our Solar System orbit the Sun.
• The closest planet to the Sun is Mercury, followed by Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.

Fundamental Questions

• How can we use models to represent the orbits of the Moon and Earth?
• What are the eight planets of our Solar System and what is their position in relation to the Sun?
• How can we remember the order of the planets from the Sun?

For thousands of years, Earth was thought to be the center of the Universe with everything in the heavens orbiting Earth. The Sun as the center of our Solar System was not widely accepted until several centuries ago. Today, we know that the Sun is an average yellow star in our Milky Way Galaxy. Earth with its solitary moon is one of eight major planets orbiting the Sun. Note: Pluto was reclassified as a dwarf planet and is not considered a major planet when listing the planets of the Solar System.

Key Concept 1: Models can be used to represent the Moon orbiting Earth and Earth orbiting the Sun.

Making models involving the Sun, Earth, and the Moon requires an understanding of their physical characteristics, size, and position in the Solar System. Although these celestial bodies are spheres, they lack many other similarities. Earth is four times larger than the Moon, and 100 Earths would fit across the Sun. The Sun is a star; a ball of flaming, glowing gases. Earth is a planet, and the Moon is a satellite (natural bodies that orbit planets); both are spheres of rock, but after that, their similarities fade.

Earth and its satellite, the Moon, are actually very different. The Earth is covered three quarters in water and has an atmosphere that sustains life, whereas, the Moon has no atmosphere, no liquid water, and is devoid of life. The Moon’s surface is scarred and cratered from billions of years of meteorite impacts. There is no water or atmosphere to cause erosion on the Moon, so the lunar surface has remained unchanged for millions of years. Unlike the Moon, the atmosphere of Earth causes most of the meteoroids aimed at Earth to burn up before they reach the ground. Very different from the Moon, Earth’s surface has oceans of water, along with landforms covered with forests, plants, and living creatures. Earth’s oceans are affected by the Moon’s gravity, making the water bulge on opposite sides of Earth to create high and low tides.
The Moon orbits or revolves around Earth once about every 28 days. From Earth, the angle between the Sun and the Moon changes as the Moon revolves around Earth causing different parts of the face of the Moon to be illuminated by sunlight (moon phases).

Although the Moon appears to be close to Earth, it actually is 30 Earth diameters away.

The special relationship between Earth and Sun allows life to flourish on Earth. No other planet in our Solar System can support life as we know it. The distance between Earth and the Sun, about 93 million miles, allows for the warmth and energy needed for survival. The Sun heats Earth and provides light during the day, and darkness and a cooling down period during the night as the planet rotates in its 24-hour cycle. Rotation of Earth on its axis, as well as its yearly orbit around the Sun, also causes seasonal changes due to the angle of the Sun. Less direct rays of the Sun result in winter. More direct and intense rays cause summer. If the Northern Hemisphere tilts toward the Sun, it has summer and conversely, if the Southern Hemisphere tilts toward the Sun, it experiences summer. Humans have adapted around the globe to these daily and seasonal changes.

Students are expected to represent the natural world using models, such as the Sun, Earth, and Moon system or volcanoes, and identify their limitations, including size, properties, and materials. Students need to understand that models can never be exact representations of reality, and must identify the specific limitations involved in those models. Making models also helps replicate the movements between Earth, the Moon, and the Sun that would otherwise be difficult to see given the great distances in space. Be sure students discuss the limitations involved in their exploration models, which are intended to demonstrate relative movement of the three celestial bodies, not a true representation of size or distance.
For example, the balloon Sun is too small (One million Earths should fit inside the Sun model.); the Moon is not soft like the marshmallow (The Moon model should be hard.); and the Moon is too close to Earth on the model. (It should be 30 Earth diameters away.) With Earth the size of a Ping Pong ball (about 1.5 inches), the distance between Earth and the balloon Sun is too close. (The balloon Sun would have to be about four meter sticks away from the Earth to represent the 93,000,000 miles distance between Earth and the Sun.) Regardless of the model used, when students understand the limitations involved, they can avoid misunderstandings in science.

Key Concept 2: Each of the planets of our Solar System orbit the Sun.

Orbiting (revolving or going around) the Sun are planets, their assorted rings and moons, asteroids, meteoroids, comets, and a host of frozen worlds. Within our Solar System are eight major planets (listed from nearest the Sun to the farthest): Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.

The four planets closest to the Sun (Mercury, Venus, Earth, and Mars) are called the small, rockyInner Planets. Mercury, the smallest planet, has a cratered surface that looks like the Moon. Named for the swift messenger of the gods, Mercury is the fastest planet to orbit the Sun with a year only 88 days long. Venus, the second planet from the Sun and similar in size to Earth, is covered in a thick atmosphere of carbon dioxide with temperatures that make Venus the hottest planet. Known for the longest day in the Solar System, Venus spins so slowly that by the time it has orbited the Sun, it has spun just once on its axis. Earth, the third planet from the Sun, is noted for its life, water covering three quarters of its surface, and its one moon. Mars, the fourth planet from the Sun, is called the “Red Planet” due to iron oxide (rust) in the soil. Mars is a cold, lifeless, rocky desert where water once flowed on its ancient surface. Mars is known for polar ice caps, the largest volcano and the longest valley in the Solar System, and two moons.

Separating the Inner Planets from the Outer Planets is the Asteroid Belt. Most asteroids (space rocks) revolve in their own orbits located between the orbits of Mars and Jupiter. They can range in size from very large, irregularly shaped chunks of rock to simple dust particles. Jupiter, Saturn, Uranus, and Neptune are the four gas giants that make up the Outer Planets. They are characterized by freezing temperatures, many moons, and ring systems. Jupiter, largest of all planets, has the most moons (63+ and counting) and a giant Red Spot, a famous storm that has lasted over 400 years. Saturn is known for the largest ring system and has close to 60 moons. Uranus, a green, glowing gas giant, has 27 moons and orbits the Sun tipped on its side, the result of an ancient impact. The last major planet is a blue gas giant named aptly for Neptune, the Roman God of the Sea, and has 13 moons.

Note:

The International Astronomical Union, the recognized authority in naming heavenly objects, formally classified Pluto as a dwarf planet in 2006. The dwarf planet Pluto and thousands of similar icy worlds orbit beyond Neptune in the outer Solar System.

Key Concept 3: The closest planet to the Sun is Mercury, followed by Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.

“My very educated mother just served us nachos” is a phrase that uses the first letter of each planet to represent the planets in order from the Sun. (Students can create their own planet sentence.) When exploring the spacing of the planets in the Solar System, students should observe that the inner planets are spaced quite close together, while the gas giants are spaced much farther apart at surprisingly even intervals.