UNIT 2: MOTION
UNIT 3: PLANETARY MOTION, PHASES, SEASONS, AND ECLIPSES
II. UNIT 3: PLANETARY MOTION, PHASES, SEASONS, AND ECLIPSES
a. Unit Introduction:
CT State Grade Level Expectations (Draft)
GRADE-LEVEL CONCEPT 1: u Gravity is the force that governs the motions of objects in the solar system.
1. Earth is part of a system of celestial bodies that are grouped together around a central star, the Sun. This system includes objects of different masses and composition such as planets, moons, asteroids, minor planets, and comets. These objects move in predictable paths determined by gravity.
2. Gravity is a force of attraction between two objects. The strength of gravitational force depends on the total mass of the two objects and the distance between them. The greater the total mass, the greater the force of gravity. The greater the distance between two objects, the less the force of gravity.
3. The difference between an objectís mass and its weight is explained by gravity. Mass is the measure of the amount of matter in an object; weight is the force of gravity between an object and the celestial body it is on. Bodies in the solar system have different masses; therefore the same object has a different weight on each celestial body.
4. Objects in the solar system are held in their predictable paths by the inward-pulling gravitational attraction of the very massive sun. The interaction of the center-pulling force of gravity with a moving objectís inertia (tendency to keep moving) keeps one object in circle-like motion (revolution) around another. This causes planets to orbit around the center of the solar system and moons to orbit around planets.
5. The Earth and other planets move through space in two ways: rotation on an axis and revolution around the sun. Earth revolves around the sun in a near-circular path, explaining cyclical phenomena such as seasons and changes in visible star patterns (constellations).
6. The time it takes for an object to complete one revolution around the sun depends on the speed at which it is moving and the size of its orbit. Objects more distant from the sunís gravitational pull move slower than those that are closer. Earthís period of revolution is about 365 days (year); planets that are more distant from the sun take longer to orbit (revolve) around the sun, resulting in longer years.
GRADE-LEVEL CONCEPT 2: u The motion of the Earth and moon relative to the sun causes daily, monthly and yearly cycles on the Earth.
1. Earth rotates around an axis or rotation, a line going through the center of the earth from the north pole to the south pole. The tilt of Earthís axis relative to its orbital path, combined with the spherical shape of the earth, cause differences in the amount and intensity of the sunís light striking different latitudes of the earth.
2. Earth experiences seasons as northern or southern hemispheres are tilted toward the sun over the course of its 365-day revolution period. Earthís tilt causes seasonal differences in the height of the perceived path of the sun and the number of hours of sunlight. Seasons are not related to a change in distance between the Earth and the Sun, since that distance changes very little.
3. The moon changes its position relative to the earth and sun as it revolves around the earth in a period of about 29 days. The same half of the moon is always reflecting light from the Sun; some of the reflected light reaches Earth. Phases of the moon are explained by changes in the angle at which the sunís light strikes the moon and is reflected to Earth. The relative position of the Sun, Earth and moon can be predicted given a diagram of a moon phase.
4. Eclipses occur when the moon, Earth and sun occasionally align in specific ways. A solar eclipse occurs when the when the moon is directly between the Earth and the sun (during new moon phase) and the moon blocks the sunís light, creating a moving shadow on parts of the earth. A lunar eclipse occurs when the Earth is directly between the moon and the sun (full moon phase), the Earth blocks the sunís light, casting a shadow over the moon.
Ocean tides on Earth are caused by the moonís gravitational force pulling on large bodies of water as the Earth and moon move around each other daily. The regular daily and monthly movement of the water (tides) can be predicted.
c. Essential Questions:
d. Essential Concepts:
e. Essential Skills: