CHAPTER 1 ASTRONOMY REVIEW
EARTH, MOON, AND SUN
SECTION ONE: EARTH IN SPACE
Astronomy-The study of the moon, stars, and other objects in space.
Axis-The imaginary line that passes through Earth’s center and the north and south poles.
Earth’s rotation on its axis causes night and day.
Revolution-The movement of one object around another object.
Orbit-Earth’s path as it revolves around the sun.
The ancient Egyptians created one of the first calendars by counting the number of days between each first appearance of the star Sirius in the morning sky. They found that this was about 365 days.
Earth has seasons because its axis is tilted as it moves around the sun. When the north end of Earth’s axis is tilted toward the sun, the northern hemisphere has summer, and the southern hemisphere has winter.
Latitude-A measurement of distance from the equator measured/expressed in degrees from north and south.
When the sun is overhead at either 23.5 degrees south or 23.5 degrees north, at noon, this is known as a solstice. It happens two days each year.
Halfway between solstices, neither hemisphere is pointed toward or away from the sun (so its straight up and down). On these days at noon the sun is directly overhead at the equator. This happens twice a year and is called an equinox. During equinoxes the amount of night and the amount of day are almost equal. The vernal or spring equinox occurs around March 21. The autumnal or fall equinox occurs around September 23.
SECTION TWO AND BEYOND : PHASES,ECLIPSES, AND TIDES
The positions of the moon, earth, and the sun cause the phases of the moon, eclipses, and tides.
The moon rotates once every 27.3 days.
The phase of the moon you see depends on how much of the sunlit side of the moon faces Earth.
New Moon-The sun lights the side of the moon facing away from Earth. The side of the moon that faces Earth is dark.
Waxing Crescent-You see more and more of the lighted side of the moon.
First Quarter-You see half of the lighted side of the moon.
Waxing Gibbous-The moon continues to wax.
Full Moon-You see the whole lighted side of the moon.
Waning Gibbous-The fraction of the lighted side of the moon that you see gets smaller each day.
Third Quarter-You can see half of the moon’s lighted side.
Waning Crescent-You see a crescent again.
One cycle takes about 29.5 days.
When the moon’s shadow hits Earth or Earth’s shadow hits the moon, an eclipse occurs.
Eclipse-Occurs when an object in space comes between the sun and the third object and casts a shadow on that object.
There are two types of eclipses: solar and lunar.
Solar Eclipse-Occurs when the moon passes between Earth and the sun, blocking the sunlight from reaching Earth.
Umbra-The darkest part of the moon’s shadow, is cone-shaped.
Penumbra-The largest part of the moon’s shadow.
Lunar Eclipse-Occurs at a full moon when Earth is directly between the moon and the sun.
When the moon is in Earth’s umbra, you see a total lunar eclipse.
When the moon is partly in Earth’s umbra a partial eclipse occurs. This happens when the Earth, moon, and sun are not perfectly aligned.
Tide-The rise and fall of water.
Gravity is the force that pulls the moon and Earth toward each other.
Tides occur mainly because of differences in how much the moon pulls on different parts of the Earth.
High tides occur when the force of the moons gravity on the moon itself is stronger than the force of the moon’s gravity on Earth.
The Tide Cycle is when water flows away from specific points, causing low tides to occur. As Earth rotates, one high tide stays on the side of Earth, facing the moon. The second high tide stays on the opposite side of Earth. Every location on Earth sweeps through two high tides and two low tides in a twenty-five hour cycle.
A Spring tide is when the combined forces produce a tide with the greatest difference between low and high tides.
A Neap tide is when an arrangement produces a tide with the least difference between low and high tide.
Local tide effects: many different land forms can change due to changes in tides.
The Intertidal Zone: the strip of land that is under water at high tide and becomes dry land at low tide
Rockets and Satellites:
A rocket moves forward when gas expelled from the rear of the rocket push it in the opposite direction.
Satellite: Any natural or artificial object that revolves around an object in space, just like the moon revolves the earth.
Satellites and space stations are used for communications, navigation, collecting weather data, and research.
Geosynchronous orbits: when satellites revolve around the earth at the same rate that the earth rotates.
A space station is a large satellite in which people can live for long periods.
Telescope-A device built to study distant objects by making them appear closer.
Features on the moon’s surface includes craters, highlands, and maria.
Crater- A round pit on the moon’s surface.
Maria- Dark flat areas on the moon’s surface.
Much of what scientists have learned about the moon came from detailed study of the moon rocks gathered by astronauts.