Download IS Chapter 14 Notes

14-1 The Sky from Earth
The moon and planets shine by reflected sunlight.
orbit- path of an object as it revolves around object in space
satellite – a body that orbits a planet
ex
moon – brightest object in the night sky (most of the time)
-takes approximately 29 days to go from full moon to another full moon.
planet – an object that orbits a sun
- is large enough to be made round by its own gravity
- has cleared the area of its orbit
- 8 in our solar system
- Venus is the brightest planet in our night sky at dawn and dusk, second brightest
object in the night sky after the moon
-planets closest to the sun are seen at sunrise and sunset, planets farther from the sun
are seen during the night
meteor – streak of light (“shooting star”) produced when a small object burns up after
entering Earth’s atmosphere
comet – cold mixture of dust and ice that gives off a long tail of light as it orbits the sun
star – a giant ball of hot gas mainly composed of hydrogen and helium
constellation – a pattern or group of stars that people imagine represents a figure, animal, or
object
-western culture has 88 common constellations
-names come from ancient Greek which came from Egypt and Mesopotamia
and some names come from Latin
-Polaris (North Star at the moment) is located in the constellation Ursa Minor
(which contains the group of stars known as the Little Dipper) above the
North Pole
14-2 Earth in Space
Earth moves in space in 2 major ways:
1. rotation – spin of Earth around an imaginary central line called the axis from west to east
-causes day and night with side not facing the sun is night
-the sun appears to move west across the sky
-Earth’s one rotation on its axis is a day and takes 24 hours to complete
2. revolution – Earth’s travel around the sun called a year, which takes 365.25 day
-Earth’s path or orbit around the sun is an elongated circle call an ellipse
-calendar – system of organizing time that defines the beginning, the length and divisions of a
year for 365 days
-leap year – a year every 4 years that has an extra day, February 29 to make up for the .25 days
that a normal calendar year does not allow
reasons for the seasons: 1. Earth’s axis is tilted 23.50
2. Earth’s revolution around the sun
Near the equator the sunlight hits Earth’s surface from directly overhead therefore it is generally warmer.
Near the poles, sunlight arrives at a steep angle spreading out over a greater distance making it cooler than at
the equator.
solstice – 2 days of the year on which the sun reaches its greatest distance north or south of the equator
-farthest north is the summer solstice (longest daylight of the year of approximately 15 hours around
June 21) in the Northern Hemisphere
-farthest south is the winter solstice (shortest daylight of the year of approximately 9 hours around
December 21) in the Northern Hemisphere
equinoxes- (means equal night) approximately 12 hour daylight, 12 hour night, twice per year
-halfway between solstices neither hemisphere is tilted toward the sun
-vernal (spring) equinox around March 21 marks the beginning of spring in the Northern
Hemisphere
-autumnal equinox around September 22 marks the beginning of fall in the Northern Hemisphere
14-3 Gravity and Motion
gravity – force that attracts all objects toward each other
Newton’s law of universal gravitational state that every object in the universe attracts every
other object
force of gravity’s strength between 2 objects depends on:
1. mass of the objects
2. distance between the objects
inertia – tendency of an object to resist change in motion
Newton’s 1st law of motion – objects at rest will stay at rest and objects in motion will stay in
motion in a straight line with a constant speed and direction unless acted upon by a force
The law of inertia and the force of gravity combine to keep planets such as Earth in orbit
around the sun and satellites such as the moon in orbit around planets.
14-4 Phases and Eclipse
Phases of the moon are the different shapes of the moon that change daily caused by the motions and
positions of the moon around the Earth and the Earth around the sun.
new moon - when the moon is in between the sun and Earth with no reflected sun light reaching Earth
(all reflected sunlight returns toward the sun)
crescent moon – thin curved slice, less than half of the sunlight is reflected to Earth
first quarter moon – approximately 1 week after the new moon when the moon appears half lighted
gibbous moon – more than half of the sunlight is reflected to Earth
full moon – when the Earth is in between the sun and the moon with all sunlight reflected to Earth
making the appearance of a circle
third quarter moon – approximately 1 week after the full moon when the moon appears half lighted
waxing – reflected sunlight area appears to grow larger each night (between new moon and full moon)
waning – reflected sunlight area appears to get smaller each night (between full moon and new moon)
moon’s rotation on its axis is the same time as moon’s revolution around Earth (a day on the moon = month
on the moon) so the same side of the moon always faces Earth (never see the far side of the moon)
moon’s orbit round the Earth is slightly tilted compared to Earth’s orbit around the sun so the moon travels
above, below, and on rare occasions in line between the Earth and the sun
eclipse – partial or total blocking of on object in space from another
1. solar eclipse – new moon phase during the daylight, when moon passes DIRECTLY between the sun
and the Earth, blocking sunlight from Earth by the moon’s shadow
-dangerous to view with the unaided eye
2. lunar eclipse – full moon phase during the night when Earth is DIRECTLY between the moon and the
sun, Earth’s shadow blocks sunlight from reaching the moon
umbra – dark vivid part of a shadow causing a total (solar or lunar) eclipse
penumbra – hazy larger part of the shadow surrounding the umbra causing a partial (solar or lunar) eclipse
A lunar eclipse is visible to more people on Earth than a solar eclipse.
14-5 Tides
tides – rise and fall of ocean water that goes through a cycle every 12.5 hours rising for
approximately 6 hours and falling for approximately 6 hours
- caused by the difference in pull of gravity from the moon and sun with Earth
-at any one time on Earth, 2 places have high tides and 2 places have low tides
-spring tides – (meaning to jump) during the new moon and full moon phases
-the sun and the moon pull in the same direction (00 or 1800 angles)
producing greater high tides and therefore lower low tides
-the Earth, sun, and moon are nearly in a straight line
-happens twice per month
-neap tides – during the first quarter and third quarter phases
- the sun and the moon pull Earth at right angles (900) producing tides with
the least difference between high and low tides
-happens twice per month
14-6 Earth’s Moon
characteristics of the moon:
-1/4 the size of Earth
-diameter of 3,476 km
- 1/8 the mass of the Earth
- 1/6 the gravity of the Earth (divide a mass on Earth by 6 to get the mass on the moon)
-similar density to Earth’s outer layer
-approximately 384,403 km from Earth (approximate because its orbit is elliptical)
-dry although has a thin layer of water in the soil
-airless because it has no atmosphere due to weak surface gravity
-since it has no atmosphere the temperature differs largely from 1300 to -1700
irregular surface due to moonquakes, volcanic activity, and meteoroid impacts
Surface features of the moon:
-craters – large round pits caused by meteoroids (chunks of rock or dust from space)
-maria – dark flat lowland area formed by lava flows sometime after craters’ impacts
-highlands – light-colored mountains making up most of the moon’s surface
Origin of the moon – best theory is the Collision-ring Theory stating a planet sized object
collided with the Earth. Material from the object and Earth’s outer layer was
ejected into orbit around Earth where a ring was formed. Gravity caused this
material to clump together forming the moon