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Exam Review:
Earth in the Universe Summary Notes:
1. The beginning of the universe is currently explained by the Big Bang theory. It states the universe
began when a super dense, small ball of matter began to move outward about 13.8 billion years
ago. According to scientists that use the Doppler effect, the matter is still moving outward. They
call this a red shift since the wavelengths are increasing in wavelength when an object moves
away.
2. The origin of our solar system is explained in the Nebular Hypothesis. This theory states the solar
system originated from a cloud of rotating gas and dust that begins to condense and spin faster.
The material began to increase in heat; nuclear fusion began to occur. The star we call the sun
formed. As the material cooled it formed solid particles to form which collided together until they
eventually grew large enough to be the 4 inner planets which include Earth. Just after Earth’s
formation the impact of meteorites and the breaking down (decay) of radioactive isotopes caused
Earth to heat up. Earth then began to lose heat. Gravity keeps the planets in orbit around the sun.
3. The spinning motion (rotation)of Earth caused it to form a sphere that bulges in the center.
4. The universe is made up of a group of galaxies. These galaxies are grouped together into clusters.
Our galaxy is part of the Local Group. The name of our galaxy is the Milky Way. Within our galaxy
there are many stars. Our planet belongs to the planetary system called the solar system. The solar
system is made up of planets which orbit the Sun (which is a star). Therefore, Earth is considered
to be a satellite planet of one particular star.
5. Kepler’s Laws of Motion are used to explain planetary orbits.
a. Kepler’s First Law of Motion explains that the Earth orbits the sun in an elliptical (oval)
pathway.
b. Kepler’s Second Law of Motion explains that if a planet is going to sweep equal areas in the
same amount of time, it must travel more rapidly when it is nearer to the sun and more
slowly when it is farther from the sun.
c. Kepler’s Third Law of Motion explains the length of time it takes a planet to orbit the sun
and its distance to the sun are proportional.
6. Earth is not stationary; it is in constant motion.
a. Earth revolves around the sun in an elliptical pathway that takes 365.25 days to complete.
We call the amount of time it takes for the Earth to orbit the Sun a year. Every 4th year, this
produces what we call Leap Year. A year with an additional calendar day in February. The
point where it is closest is called the perihelion and the point it is furthers away is the
aphelion.
b. Earth rotates on an imaginary axis. Earth’s rotation around its imaginary axis produces
night and day. It takes 23 hours and 56 minutes for the Earth to make one rotation on its
axis. Due to the counterclockwise motion (if observed from the North Pole) the sun
appears to rise in the east and set in the west.
i. This axis is tilted 23.5 degrees. This tilt causes the seasons (fall, spring, winter, and
summer) as Earth revolves around the Sun.
1. Precession explains when there is a change in the direction of Earth’s
imaginary axis. This does not change how much the axis is tilted. The
change in the direction of the axis does not affect the seasons.
2. Due to the moon, the axis wobbles as it moves. It moves back and forth
about ½ a degree. This wobbling is called nutation. The movement takes 18
years to occur. This movement can produce a very slight increase or
decrease in the seasonal effects.
7. Barycenter is the point between 2 objects where they balance each other. You can think of this as
the base (center) of the teeter totter. It is the center of mass between where 2 stars orbit each
other. Scientists use this to calculate the mass of binary stars. The sun is not stationary in our solar
system. As it moves the planets tug or pull on it. This causes it to orbit the barycenter of the solar
system.
8. Tides are the periodic rise and fall of the ocean surface due to the gravitational pulls of the moon
and the sun on Earth’s surface.
9. There are 2 types of nuclear reactions: fusion and fission. Fusion occurs when the nuclei of lighter
elements combine to make a larger element. Fusion makes a bigger element. Fusion results in the
formation of a star. Fission is when a nucleus is broken down into smaller elements. Fusion is like
division. The element gets smaller. Fission breaks down uranium-235 to produce nuclear energy.
10. The electromagnetic waves are shown on the electromagnetic spectrum.
11. Solar energy travels from the sun to Earth through a process called radiation. Radiation travels
outward in all directions from its source. Radiation can travel through the empty vacuum of space.
Summarize how energy flows from the sun to the Earth through space. Solar energy can be
absorbed the clouds and land/water surfaces, reflected or scattered back to space or
12. Earth’s 23.5 degree tilt produces the 4 seasons: winter solstice, summer solstice, autumnal
equinox and vernal equinox.
a. Summer solstice: June 21,22; 1st official day of summer in Northern Hemisphere; North
Pole tilts towards the sun; sun’s rays strike Earth at a 90 degree angle along the Tropic of
Cancer; sun follows its highest place in the sky; Northern Hemisphere has the most hours
of daylight; Arctic Circle has 24 hours of weak daylight; Southern Hemisphere has more
hours of darkness; Antarctic Circle has 24 hours of darkness
b. Winter solstice: December 21 or 22; North Pole tilts away from the sun; sun’s rays strike
Earth at a 90 degree angle along the Tropic of Capricorn; first day of winter in the Northern
Hemisphere; Earth is halfway through its orbit around the sun; Northern Hemisphere has
more hours of darkness than daylight
c. Autumnal equinox: September 22 or 23; sun’s rays strike Earth at 90 degree angle along
the equator; hours of daylight and darkness are equal around the world; North Pole does
not point towards or away from the sun
d. Vernal equinox: March 21 or 22; sun’s rays strike Earth at 90 degree angle along the
equator; first day of spring in Northern Hemisphere; hours of daylight and darkness are
equal around the world; North Pole does not tilt towards or away from sun
13. Earth experiences differential heating. Land surfaces heat and cool much more quickly than water.
Recall being at the beach and how the sand heats much more quickly during the day than the
water. As the sun goes down, the sand cools down fairly quickly. The water maintains its
temperature. Another example would be when you go to the beach on the first hot day and the
sand gets very warm, but the water temperature does not experience the rapid temperature
increase.
14. Solar energy is transformed into chemical energy through photosynthesis.
At no
15. Earth’s magnetic field protects the Earth from dangerous particles by causing them to move around
the Earth. The bubble of the magnetic field around the Earth is called the magnetosphere. It protects
Earth from solar winds, streams of energetic charged particles emitted from the sun. If these particles
reached Earththey would strip away the upper atmosphere including the ozone layer which protects
us from receiving too much ultraviolet radiation.
Sample Questions:
1. Name the point in Earth’s orbit where it is closest to the sun.
a. Apogee
b. perigee
c. aphelion
d. perihelion
2. Which statement below best describes where the sun’s vertical rays strike the Earth at noon on the vernal
equinox?
a. Tropic of Cancer
b. Tropic of Capricorn C. equator
D. North Pole
3. Identify the season when the sun’s rays reach their highest angle in the Northern Hemisphere.
a. Spring
b. winter
c. fall
d. summer
4. Which term below is used to identify the wobbling motion made by Earth’s axis s it turns in space?
a. Precession
b. gravity
c. plasticity
d. nutation
5. Which term describes the moon’s position when its gravitational pull most strongly affects Earth’s tides?
a. Apogee(furthest away) b. perigee(closest)
c. countercurrent
6. Which statement below would best describe spring tides?
a. Spring tides are especially high and low tides that occur which occur twice a month.
b. Spring tides are especially high and low tides that occur when the moon is in the first quarter and
the third quarter phase.
c. The spring tides are not especially high or low.
7. Which process in the nebular hypothesis results in the formation of a star?
a. Nuclear fusion
c. Both of the above
b. Neither of the above
d. Neither of the above
8. Identify the phase of the moon that a neap tide would occur during.
a. Full moon
b. new moon c. first-quarter moon d. third-quarter moon e. a and c f. c and d
9. The tidal ranges of lakes and other minor bodies of water are so small that they are almost invisible. Why
might this be so?
a. The amount of water is so much more that the moon’s gravity does not impact it.
b. There is significantly less water for the moon to pull on.
c. Lakes are more greatly impacted by the gravitational pull of the sun than the moon.
10. Name the galaxy that you live in.
a. Local Cluster B. Milky Way C. Tri-Sun Galaxy
D. none of the above
11. Which statement below best explains differential heating of land and water?
a. Water heats and cools much more quickly than land.
b. Water heats more quickly than land and cools more quickly than land.
c. Land heats and cools more quickly than water.
d. Land heats more quickly than water and cools slower than water.
12. Which motion of Earth is responsible for creating its bulge in the center?
a. Nutation
b. precession c. revolution d. rotation
13. Which statement below best describes Earth’s pathway around the sun according to Kepler’s First Law of
Motion?
a. It travels in a perfectly circle pattern.
C. It changes every 10 years by 15 degrees.
b. It travels in an elliptical pathway.
D. both A and C
14. According to Kepler’s Second Law of Motion, where would a planet travel faster in its orbit around the sun?
a. When it is closest to the sun.
b. c. When it is farthest away from the sun.
c. When it is halfway between the point where it closest to the sun and farthest from the sun.
d. It will always travel the exact same speed.
15. Name the motion of Earth that is responsible for creating the calendar year.
a. Nutation
b. precession c. revolution d. rotation
16. Which electromagnetic wave has the longest wavelength?
a. Infrared light b. visible light c. ultraviolet light
d. X-ray
17. Which motion of Earth is responsible for the apparent sunrise in the eastern sky and the sun appearing to
set in the western sky?
a. Nutation
b. rotation
c. revolution d. precession
18. Identify the cause of the seasons.
a. Earth’s 23.5 degree tilt
b. nutation
c. precession
d. proximity to the sun
19. Name the movement of Earth that produces hours of dark and hours of light.
a. Nutation
b. precession c. revolution d. rotation
20. State where the sun’s rays will hit at noon on the vernal equinox.
a. Equator
b. Tropic of Cancer
c. North Pole d. Tropic of Capricorn
21. During what season do the sun’s rays reach their highest angle in the Northern Hemisphere?
a. Fall
b. spring
c. summer
d. winter
22. Earth’s axis slowly but continuously points in different directions. Identify the motion.
a. Precession
b. revolution c. rotation
d. Both a and c
23. Which object is largest?
a. Galaxy
b. Sun
c. a planet
d. cluster of galaxies