Earth,Moon and Sun
Section 1 Earth in space
How does earth move in space?
Earth moves through space in two major ways rotation and revolution.
The imaginary line that passes through earths center and the North and South poles is earths axis.Earths rotation causes day and night.
It takes earth about 24 hours to rotate once. Each 24 hour cycle of day and night is called a day.
Revolution is the movement of one object around another. One complete revolution of earth around the sun is called a year.
What causes the cycles of seasons on earth?
The yearly cycle of the seasons is caused by the tilt of earths axis as it revolves around the sun. Sunlight hits earths surface closest to the equator. Near the poles sunlight arrives at a steep angle. Summer and winter are caused by earths tilt as it revolves around the sun. When the sun is farthest north or south of the equator is known as a solstice. The solstice happens around June 21 each year.Halfway between the solstices,neither hemisphere is tilted toward or away from the sun. This happens twice a year when the noon sun is directly over the equator. Each of these days is called an equinox (equal night).
Section 2 Gravity and Motion
What determines the strength of the force of gravity between two objects ?
The strength of the force of gravity between two objects depends on two factors: The masses of the objects and the distance between them.According to the law of universal gravitation, all objects around you including earth are pulling on you, Just as you are pulling them.Mass is the amount of matter in an object. and the force of gravity on an object is known as weight. The force of gravity decreases rapidly as distance increase.
What two factors combine to keep the moon and earth in orbit?
Newton concluded that two factors- inertia and gravity combine to keep earth in orbit around the sun and the moon in orbit around earth. Earths gravity keeps pulling the moon towards it, to stop the moon from moving in a straight line.
Section 3 Phases ,Eclipses and tides
What causes the phases of the moon?
The changing relative positions of the moon, earth and sun cause the phases of the moon,eclipses, and tides. The phase of the moon that you see depends on how much of the sunlit side of the moon faces earth.
What are the solar and lunar eclipses?
When the moons shadow hits earth or earths shadow hits the moon, an eclipse occurs. A solar eclipse occurs when the moon passes directly between earth and the sun, blocking sunlight from earth. During a lunar eclipse earth blocks sunlight from reaching the moon.
What causes the tides?
Tides are caused mainly by differences in how much the moons gravity pulls on different parts of earth.
Section 4 Earth's Moon
What features are found on the moons surface?
Features on the moons surface include maria,craters and highlands.The maria's are flat dark areas on the moon. Craters are large round pits that are on the moon. The highlands cover most of the moons surface.
What are some characteristics of the moon?
The moon is dry and airless. Compared to earth the moon is small and has large variations in its surface temperature.
How did the moon form?
Scientists theorize that a planet sized collided with earth to form the moon.