Download midterm review answers

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ASTRONOMY REVIEW
Directions: Answer the following open ended review questions. Utilize a diagram where appropriate and
do make sure that you label and describe the drawing.
EARTH’S MOTIONS:
1. Describe how Earth moves through space.
Earth moves through space by revolving around the Sun in an orbit and rotating on its axis. In
addition, Earth’s rotation keeps it upright and as a result wobbles on its axis. This wobble is
referred to as its precession.
2. How does Earth’s motion relate to time?
Earth’s rotation on its axis takes 1 day or 24 hours. Earth’s revolution accounts for our year, it
takes 365.25 days to revolve and orbit the Sun once.
3. What is the cause of day/night cycle on Earth?
Earth moves through space by revolving around the Sun in an orbit and rotating on its axis. In
addition, Earth’s rotation keeps it upright and as a result wobbles on its axis. This wobble is
referred to as its precession.
4. Describe a piece of evidence that supports the idea that Earth is rotating on its axis.
A pendulum suspended above Earth’s surface provides evidence that Earth is rotating on its
Axis. Once a pendulum is set in motion it will continue to move in the same direction. As the
pendulum swings, Earth rotates underneath the pendulum. An observer on the ground would
see that the Pendulum appears to change direction, but a pendulum cannot change directions.
The result is that Earth must rotate underneath the pendulum.
SEASON’S:
5. What is the cause of the seasons on Earth and the factors that help determine the season?
Earth’s seasons are caused by a combination of Earth revolution around the sun and it’s 23.5degree tilt. As a result different geographical regions receive changing angle of rays and length
of days. When the Sun’s rays strike at a lower angle over less time the geographical region will
become colder. On the other hand, when the Sun’s rays strike at a higher angle over more time,
the geographical region becomes warmer.
6. What is the angle at which Earth’s axis is tilted? Why is this important?
Earth is tilted on its axis at a 23.5-degree tilt. This is important because it causes different angles
are which the sunlight strikes Earth’s surface and different amounts of time the sun will be over
a geographical region.
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7. Draw a diagram of Earth for each season below. Label the following; all-important latitudes,
hours of daylight at each latitude, lightly shade in the night, and indicate the date.
Fall Equinox (Autumnal) – September 22,23
Winter Solstice – December 21, 22
12
0
12
12
12
24
Summer Solstice – June 20,21
Spring Equinox – March 20, 21
12
24
12
12
0
12
8. For each season above, draw the position of the sun in the sky at noon and the accompanying
shadow of the “building” (Relate this same to the tree on your paper).
Fall Equinox (Autumnal)
Winter Solstice
Summer Solstice
Spring Equinox
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GRAVITY AND ORBITAL MOTION:
9. What is the Universal law of gravity?
The Universal Law of Gravity is the force of attraction between all objects in the universe due to
an objects mass. Because objects have mass they bend the fabric of space-time, just like a
bowling ball would bend the fabric of a trampoline. The more massive the object, the more it
bends space and time.
10. Describe the 2 factors that determine the strength of the force of gravity?
The two factors that determine the strength of gravity between two objects are the combined
objects mass and the distance the objects are apart from one another.
11. What happens to the force of gravity when distance between 2 objects decrease?
When the distance between two objects decrease, the strength of gravity will increase. The
closer two objects are, the greater the gravitational force (an inverse relationship).
12. What happens to the force of gravity when the mass of an object increases?
When the mass of two objects combined increase, the strength of gravity will increase. The
more mass, the greater the gravitational force (a direct relationship).
13. Draw a diagram of an astronaut orbiting the Earth. Draw 2 arrows to indicate the factors that
create its orbit and then describe why the astronaut would feel weightless.
An astronaut would feel weightless because
he/she is in a constant state of free-fall. There is
no force pushing back on the astronaut and
therefore he/she does not feel his/her weight
even though gravity is still pulling on him/her. As
gravity pulls in, the forward inertia acts at a right
angle. The resulting path is a curve. Since the
Earth, Moon, etc. are spheroids; the astronaut
follows the curved path of the object he/she is
orbiting.
Orbital Path
Inertia
Gravity
THE MOON
14. Describe the relationship between the Earth and its Moon in terms of their relative motion.
The Earth and Moon together make up the Earth-Moon System. Although it appears that the
moon orbits the Earth, the moon actually orbits a common center of gravity between the Earth
and the Moon. It is located 900 miles from Earth surface and it is this point that revolves around
the Sun.
15. Do we see the entire Moon from Earth? Why or why not.
No we do not see the entire surface of the Moon. Only half of the Moon can be lit by the Sun at
one time. In addition, the Moon is in a synchronous orbit around the Earth-Moon barycenter
and revolves and rotates at the same rate. Therefore the near side of the Moon always faces
Earth and the far side always faces away.
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16. Where does the light of the Moon we see come from?
The light we see from the Moon is reflected off the Moon’s surface from the Sun.
17. Why does the Sun and the Moon appear similar in size?
The Sun and the Moon have the same angular diameter. The Sun is 400x the size of the moon,
but the Moon is 400x closer to Earth than the Sun. This cancels out the size difference between
the Sun and Moon and observers from Earth see them as roughly the same size.
18. Describe what moon phases are and what determines the moon phase an observer would see?
Moon phases are the portion of the lit Moon as seen from Earth. Moon phases are caused by
the relative positions of the Sun, Earth, and Moon. As we observe the Moon from Earth, we see
certain parts of the lit Moon.
19. Draw the phases of the moon in the appropriate box. Remember to shade in the shade, the
label each moon phase.
New
Waxing
Crescent
1st Quarter
Waxing
Gibbous
FULL
Waning
Gibbous
3rd Quarter
Waning
Crescent
New
20. Draw the position of the moon in respect to the Earth and Sun if the following moon
phase is seen from Earth. The dark area is the area not seen.
PHASE: Waning Crescent
PHASE: 1st Quarter
PHASE: Full Moon
PHASE: Waning Gibbous
PHASE: Waxing Gibbous
PHASE: New Moon
PHASE: Waxing Crescent
PHASE: 3rd Quarter
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21. What are the two types of eclipses? Draw a picture of each. The drawing should include
the Moon, Earth, Sun, Umbra and Penumbra. Identify the lunar phase each Moon is in as
well.
SOLAR ECLIPSE
LUNAR ECLIPSE
Umbra
New Moon
Penumbra
Umbra
Penumbra
Full Moon
Penumbra
22. Why don’t we experience a solar or lunar eclipse each time there is a full or new moon?
The plane of the Moon’s orbit is
tilted approximately 5-degrees in
reference to the Earth’s orbit
around the Sun. This means that the
Moon is either above or below the
Sun-Earth orbit. Only twice a year
is there a possibility of a lunar or
solar eclipse to occur.
23. What is the cause of tides on Earth.
The tides are caused by the gravitational pull from the Moon and partially the Sun.
24. Why do most geographical places on Earth go through 2 tidal cycles?
The Moon’s gravity creates two tidal bulges; one on either side of the moon. The low
tides are perpendicular to the high tides. The tides follow the Moon’s revolution, which is
much slower than Earth’s rotation. On a daily basis, Earth will rotate through a high tide,
low tide, high tide, and then a low tide in a 24-hour period.
25. What causes Earth to experience 2 tidal bulges; one on either side of the Moon?
Two tidal bulges or high tides are a result of two factors. The first is the fact that gravity
weakens with distance. The Moon will pull harder on the water closer to the Moon than
the water on the opposite side. In addition, Earth is moving around the common center of
gravity between the Earth-Moon System. This barycenter is located on the same side of
the Moon. This creates an outward force, like a Gravitron ride at the fair, in which the
water bulges on the opposite side as the Moon.
26. How long does a tide cycle last?
The time between high tide and low tide is roughly about 6 hours (a little more). The total
tidal cycle from high tide, to low tide, back to high tide is about 12 hours and 25 min. in
most places.
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27. Draw a picture of a Neap Tide and a Spring Tide. In the diagram, include the Sun, Moon
and Earth. Label the phase of the Moon and also draw the tidal bulges.
Spring Tide
Neap Tide
Planetary Laws of Motion
28. Identify the 3 laws of planetary motion in each box below, write a description of each law
and in the box below draw a diagram to represent the motion.
1st Law:
2nd Law:
3rd Law:
All orbits are elliptical with A planet will sweep out equal The closer the planet is to
the sun at one focus of the area in equal time. When the the Sun, the shorter the
ellipse and nothing at the planet is closer to the Sun it will period of revolution. The
other focus.
be moving the fastest because farther from the Sun, the
gravitational attraction is greater. longer the period of
When the planet is farthest from revolution.
the Sun, it will be moving the
slowest because gravity weakens
with distance.
Diagram
Diagram
Diagram
The Solar System
29. Identify the theory that most scientist accept as to the origin of the Solar System.
The Dust Cloud Theory describes the theory that most scientist accept as to the origin of
the Solar System. The Solar System started as a Nebula or cloud of gas and dust. The
Nebula began to condense under its own gravity. As it condensed the cloud started to
spin, compress and flatten out into a disc shape. The compression caused the cloud to
heat up and spark the process of nuclear fusion in the center creating a protostar.
Eventually globs of material started to collide and stick together and became
planetesimals. The inner planetesimals condensed more under hotter conditions and
became rocky planets while the outer planets where not as hot and where left as gas
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giants unable to condense. The planetesimals sweep out their orbits and the solar system
was created.
30. Describe the organization and relative size of the objects in the solar system.
SUN – Inner Planets – Asteroids – Outer Planets – Pluto – Kuiper Belt – Comets – Oort Cloud
31. Why are the inner planets rocky and the outer planets gas?
The Inner Planets are rocky and smaller due to the conditions under which they formed. The hot
conditions in which the planetesimals were created, allowed the inner planets to condense and
build bigger and heavier elements. The Outer Planets are gas giants. The cold conditions under
which they formed kept the gasses from condensing keeping the material light and spread out.
32. Describe the difference between the inner and outer planets.
INNER PLANETS
OUTER PLANETS
Size
Small
Huge
Surface
Solid Rocky Surface
Balls of Gas with No Surface
Density
Greater Density
Smaller Density
Atmosphere
Varied Atmosphere
Similar Atmospheres
Discovery
Known by the ancients
Not Known by the ancients
Rotation
Spin Slowly
Spin Quickly
Orbit
Orbit Fast
Orbit Slow
Moons
Few Moons
Lots of Moons
Rings
No Rings
Lots of Rings
Visits
Multiple Space Craft Visits
One space craft visit (same)
33. Describe the difference between a Meteoroid, Meteor, and Meteorite.
A meteoroid is a small chuck of rock in space. A meteor is a meteoroid that enters Earth’s
atmosphere and burns up. A meteorite is a meteor that strikes Earth’s surface.
34. Why is Pluto considered a dwarf planet? What region is Pluto located in and what objects
in the solar system can be found in this region?
In order to be considered a planet, the object must have these 3 characteristics.
1. YES: Orbit the Sun
2. YES: Sufficient mass to have rounded itself
3. NO: Cleared and ordered its orbit.
Pluto has the first 2 but lacks the 3rd characteristic and has not cleared its orbit. Pluto is
located in a region known as the Kuiper belt. The Kuiper Belt is a region that extends
past Neptunes orbit. Comets come from this region.
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THE SUN , RADIANT ENERGY, AND THE UNIVERSE
35. Describe what nuclear fusion is and where it takes place in the sun.
Nuclear fusion is the joining together of two smaller nuclei to make a larger atom. An
example is the fusing together of Hydrogen nuclei to make Helium inside the core of the
Sun. As a result of the fusion process, a little bit of mass is lost and is converted into
energy in the form of an electro-magnetic wave.
36. Describe what Electro-Magnetic Energy is and identify the different types of
electromagnetic energy.
Electro-Magnetic Energy is the energy released from the nuclear fusion reactions inside
the core of the Sun. This energy travels through the vacuum of space. The amount of
energy present relates to the type of radiation.
Low Energy
Large Wavelength
Low frequency
High Energy
Small Wavelength
High Frequency
37. Describe the accepted theory as to the origin of the Universe.
The Big Bang Theory is the most widely accepted theory by scientists as to the origin of
the universe. The Big Bang theory describes that the Universe started from a single point
and all matter that makes up our vast universe was located in this point. Something
caused this point to start expanding. Overtime the universe cooled, stardust clumped
together forming galaxies and stars. It is space itself that is expanding and pushing the
galaxies farther apart. The universe is continuing to expand.
38. Describe what the Red Shift is and why it provides evidence that supports the Big Bang
Theory.
The Doppler effect is the apparent change of the frequency of a wave as the wave moves
toward the observer then away. In order to prove that the universe is expanding, the
galaxies must be moving away from each other. The red shift (Doppler effect) provides
evidence that the universe is expanding because we see spectral absorption lines in
distance starlight continuing to shift to the Red or longer wavelength side of the
spectrum.
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THE H-R DIAGRAM
SUPER GIANTS
Rigel
Betelgeuse
LUMINOSITY (BRIGHTNESS)
Sirius A
Aldebaran
RED GIANTS
Sun
Alpha Centauri B
Axis (Y)
Sirius B
WHITE DWARFS
Axis (X)
O
SPECTRAL CLASS
B
SURFACE TEMPERATURE
A
F
G
K
M
Color in Box as Well
Answer questions 1 through 4 using the above H-R Diagram
39.
40.
41.
42.
43.
Write in the name of each group of stars on the H-R Diagram
Label each of the axis on the H-R Diagram
Draw in the spectral classes on the bottom of the H-R Diagram
Draw in the corresponding spectra in each of the spectral class boxes (Use color Pencils)
Place the order of the following stars from youngest (1), middle age (2), oldest (3).
1
Sun
3
Sirius B
2
Betelgeuse
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