Group 4
Avis Armstrong, Axell Becerra, Abygail Martinez, America Garza
Ch1- 1, 2, 3, 4, 7, 13, 15, 18, 20
1. Briefly describe the major levels of structure (such as planet, star, galaxy) in the
universe.
A planet (Earth) is in a solar system which consists of the Sun, planets and their moons, and
other small objects. The Solar System belongs to the Milky Way Galaxy. A galaxy is a great
island of stars (containing- thousands, millions, billions, and trillions). The MWG is in the Local
Group with other galaxies, and the local group belongs to the Local Supercluster, which
comprises the universe.
2. Define astronomical unit and light-year.
An Astronomical Unit is the average distance from the Earth and the Sun (150million km).
Usually used to describe distance within our solar system.
A light-year is the distance that light can travel in 1 year (~10 trillion km). Usually used to
describe distances of stars and galaxies.
3. Explain the statement, “The farther away we look in distance, the further back we look in
time.”
Light takes time to reach the Earth. If a star is 8 light-years away and it means it takes 8 years for
the light to reach the Earth and we are looking at the star as it was 8 years ago.
4. What do we mean by the observable universe? Is it the same thing as the entire universe?
The portion of the entire universe that can be seen from Earth. Only a small portion of the entire
universe. (can only see 14 billion years worth)
7. In what sense are we “star stuff”?
Stellar material is recycled and nuclear reactions that ended stellar lives such as carbon, nitrogen,
oxygen, and iron; which is what people and Earth are made of.
Does It Make Sense?
Decide whether or not each of the following statements makes sense (or is clearly true or false).
Explain clearly; not all of these have definitive answers, so your explanation is more important
than your chosen answer.
13. Our solar system is bigger than some galaxies..
This does not make sense. A galaxy is made of hundreds of billions of stars. Each solar system
revolves around 1 star. Our solar system is only a small part of one galaxy.
15. It will take me light-years to complete this homework assignment!
A light year is a measure of distance, not of time. This does not make sense
18. NASA will soon launch a spaceship that will photograph our Milky Way Galaxy from
beyond its halo.
While this sounds pretty cool, this does not make sense. The galaxy extends thousands of light
years in each direction. It would take thousands of years to travel beyond the halo of the milky
way galaxy.
20. Photographs of distant galaxies show them as they were when they were much younger
than they are today.
This doesn’t seem like it makes sense, but indeed it does. The light from these galaxies takes so
long to reach the distance our cameras can see that we are essentially looking at them in the past.
Ch2-1, 4, 6, 9, 10, 13, 15, 16, 17, 20, 24
1. What are constellations? How did they get their names?
- Constellations are patterns recognized in the stars across the sky, with well-defined
borders. These patterns helped locate constellations, which are essentially regions of
the sky. The names and borders of the 88 official constellations were chosen in 1928
by the International Astronomical Union (IAU), mostly influenced by Western
traditions, tracing back to civilizations of the ancient Middle East for Northern
Hemisphere constellations and names originating with 17th-century European
explorers for those in the Southern Hemisphere
4. Why does the local sky look like a dome? Define horizon, zenith, and
meridian. How do we describe the location of an object in the local sky?
The local sky appears as a dome or hemisphere due to our perspective from Earth,
seeing only half of the celestial sphere at any moment. The horizon is the boundary
between Earth and sky, the zenith is the point directly overhead, and the meridian is
an imaginary half-circle stretching from the horizon due south through the zenith to
the horizon due north. Object locations in the sky are described by their altitude
above the horizon and direction along it.
6. What are circumpolar stars? Are more stars circumpolar at the North
Pole or in the United States? Explain.
Circumpolar stars remain perpetually above the horizon, circling around the
celestial pole. In the Northern Hemisphere, these stars circle counterclockwise
around the north celestial pole. More stars are circumpolar at the North Pole
compared to the United States due to the North Pole's proximity to the celestial pole,
causing stars to never set below the horizon.
9. Suppose Earth’s axis had no tilt. Would we still have seasons? Why or
why not?
- If Earth had no axis tilt, we would not have seasons. Seasons are caused by the tilt
of Earth's axis, not by variations in Earth's distance from the Sun. Without this tilt,
the distribution of sunlight on Earth would not vary through the year as it currently
does.
10. Briefly describe key facts about the solstices and equinoxes.
- The solstices and equinoxes mark the four special moments in the year that
correspond to specific positions in Earth’s orbit. The June solstice and the
December solstice mark the times when the Northern Hemisphere is most directly
tipped toward or away from the Sun, respectively. The March and September
equinoxes occur when the Northern Hemisphere transitions between being tipped
slightly away from and toward the Sun, leading to equal day and night lengths.
13. Why do we always see the same face of the Moon?
- We always see the same face of the Moon due to its synchronous rotation; it rotates
on its axis in the same amount of time it takes to orbit Earth. This synchronous
rotation ensures that the same side of the Moon is always facing Earth.
15. What do we mean by the apparent retrograde motion of the planets?
Why was this motion difficult for ancient astronomers to explain? How
do we explain it today?
- The apparent retrograde motion of the planets is their occasional westward motion
against the background of stars, contrasting with their usual eastward path. This
motion puzzled ancient astronomers who adhered to an Earth-centered universe
model. Today, we understand this motion as a perspective effect observed when
Earth, moving faster in its orbit, overtakes and passes another planet.
16. What is stellar parallax? How did an inability to detect it support the
ancient belief in an Earth-centered universe?
- Stellar parallax is the apparent shift in a star's position against the background of
more distant stars, observed as Earth moves around the Sun. It's the most direct
method to measure a star’s distance, utilizing observations made 6 months apart
from opposite points of Earth’s orbit. The small annual shifts, or parallax angles,
are used to calculate the distance to stars, with the formula distance in parsecs being
1 over the parallax angle in arcseconds.
Does It Make Sense?
Decide whether or not each of the following statements makes sense (or is clearly true or false).
Explain clearly; not all of these have definitive answers, so your explanation is more important
than your chosen answer.
17. The constellation Orion didn’t exist when my grandfather was a
child.
- This statement does not make sense. Constellations, including Orion, are patterns
recognized and named by cultures throughout human history. Orion, as a
constellation with well-defined borders, has been a part of the night sky visible from
Earth for thousands of years, much longer than the lifetime of anyone's grandfather
.
20. I live in the United States, and during a trip to Argentina, I saw many
constellations that I’d never seen before.
This statement makes sense. The night sky's appearance changes depending on the
observer's latitude, or how far north or south they are on the Earth's surface. The
Southern Hemisphere, including Argentina, offers views of constellations not visible
or less prominently visible from the Northern Hemisphere, such as the United
States. This difference is due to the Earth's curvature and orientation in space.
24. If Earth’s orbit were a perfect circle, we would not have seasons.
This statement is misleading and essentially false. The Earth's axis tilted, rather
than the shape of its orbit around the Sun, serves as Earth's primary season-causing
factor. Varying angles and sunlight quantities strike different parts of our planet at
various times due to this axial tilt relative to its orbital plane. Consequently, we
experience seasonal changes because of this phenomenon involving Earth's axial tilt.
This axial tilt, regardless of Earth's orbit being a perfect circle, actively induces the
seasons on our planet. The elliptical nature of Earth's orbit introduces a slight
variation in its distance from the Sun - an element that minimally influences this
seasonal shift.
Ch4-1, 2, 4, 5, 6, 9, 10, 13, 15, 16, 19, 23, 24
1. Define speed, velocity, and acceleration. What are the units of acceleration? What is the
acceleration of gravity?
-Speed – the rate at which an object is moving
-Velocity – speed in a certain direction
- Acceleration – change in velocity, either speed or direction
-Units of acceleration – meters per second or m/s2
Acceleration of gravity – the acceleration of a falling object on earth, 9.8/m2
2. Define momentum and force. What do we mean when we say that momentum can be
changed only by a net force?
-Momentum – the product of an object's mass and velocity (momentum=mass x velocity)
-Force - anything that can cause a change in momentum
Since force is always present in some way, momentum is only changed by the loss or gain in
force, or “net force” or “overall force.”
4. State Newton’s three laws of motion. For each law, give an example of its application.
- An object moves at constant velocity if there is no net force acting upon it. An example of this
would be placing an round object on the floor of a moving bus, as long as the bus continues to
move at the same speed with no bumps or elevation, that round object would stay I place. As
soon as the bus increases speed or hits a bump, the round object will move.
- How net force affects and object’s motion – force= rate of change in momentum, or force =
mass x acceleration. Example: pushing a car will take more force or effort than pushing a bicycle
even though both have wheels, the car has more mass
-For every force, there is always an equal and opposite reaction force. Example: When you swim
your body moves forward and the water moves backward, or vice versa
5. Describe the laws of conservation of momentum, of angular momentum, and of energy.
Give an example of how each is important in astronomy.
-Conservation of momentum: The law of conservation of momentum states that the total
momentum of a closed system remains constant if no external forces act upon it. Mathematically,
it can be expressed as: Total Initial Momentum=Total Final Momentum. The conservation of
momentum is important in astronomy for understanding the dynamics, evolution, and
interactions of celestial objects, particularly in systems like binary stars where gravitational
forces dominate the behavior of the objects involved.
- Conservation of Angular Momentum: The law of conservation of angular momentum states
that the total angular momentum of a system remains constant if no external torques act upon it.
Mathematically, it can be expressed as: Total Initial Angular Momentum = Total Final Angular
Momentum Total Initial Angular Momentum = Total Final Angular Momentum. Our solar
system itself is an example of conservation of angular momentum, it is what causes moons to
orbit around planets and the planets to orbit around the sun. The closer the planet, the greater the
velocity.
- Conservation of Energy: The law of conservation of energy states that energy cannot be created
or destroyed, only transformed from one form to another. In a closed system, the total energy
remains constant. Mathematically, it can be expressed as total initial energy = total final energy,
and total initial energy = total final energy. The principle of conservation of energy explains that
as an object descends towards the Earth's surface, it gradually loses gravitational potential
energy. To uphold this conservation, the object must accelerate as it falls. Eventually, it reaches
the ground and comes to a halt. At this juncture, its kinetic energy transforms into heat and sound
energy. This is vital to the study of astronomy in predicting the rate at which objects move in
space.
6. Define kinetic energy, radiative energy, and potential energy, with at least two examples of
each.
Kinetic energy is the energy of motion. We are constantly surrounded by Kinetic energy, which
can be as simple as a person walking or as complex as flying an airplane.
Radiative energy is the energy from light. Examples would be radiation from the sun itself, as
well as X-ray machines or radio waves.
Potential Energy is stored energy; examples are a roller coaster at the highest point before it falls
or a tightened rubber band or slingshot before it is released.
9. Summarize the universal law of gravitation both in words and with an equation.
Every mass attracts every other mass through a force called gravity.
The strength is directly proportional to their masses.
The strength of gravity between 2 objects decreases with the square of the distance between their
centers.
Doubling the distance between two objects weakens the force of gravity by a factor of 2^2 or 4
Fg=G((M1M2)/d^2)
10. What is the difference between a bound and an unbound orbit? What orbital shapes are
possible?
BOUND: An object goes around another object over and over again
UNBOUND: Paths that bring an object close to another object just once
*The types of orbits create different shapes known as the conic sections (circle, ellipse, parabola,
hyperbola)
13. Explain how the Moon creates tides on Earth. Why do we have two high and low tides
each day? How do the tides vary with the phase of the Moon?
Tides are caused by the gravitational attraction between the Moon and different parts of the
Earth. This gravitational pull creates a stretching force, known as tidal force, which results in two
tidal bulges on opposite sides of the Earth. As the Earth rotates, any location experiences two
high tides each day as it passes through these bulges, with low tides occurring halfway between
them. Despite occurring twice a day, the two daily high tides actually come slightly more than 12
hours apart due to the Earth's rotation and the Moon's orbital motion. Tides vary based on the
relative positions of the Moon and Sun. During new and full moons when their tidal forces align,
we experience pronounced spring tides with higher high tides and lower low tides. Conversely,
during first and third quarter moons when the tidal forces oppose each other, we observe smaller
neap tides with less extreme tidal ranges.
Does It Make Sense?
Decide whether or not each of the following statements makes sense (or is clearly true or false).
Explain clearly; not all of these have definitive answers, so your explanation is more important
than your chosen answer.
15. I’ve never been to space, so I’ve never experienced weightlessness.
Does not make sense. Any time we are in a “free fall” we experience weightlessness. If I jump in
the air, while I’m on my way back down to earth, I am experiencing weightlessness.
16. Suppose you could enter a vacuum chamber (a chamber with no air in it) on Earth.
Inside this chamber, a feather would fall at the same rate as a rock.
Yes, this does make sense. Air resistance, not mass or weight, is the only thing keeping the
feather and rock from falling at the same rate; with no air resistance in play, they would fall at
the same rate.
19. If the Sun were magically replaced with a giant rock that had precisely the same mass,
Earth’s orbit would not change.
Yes, this makes sense; the Earth orbits the Sun based on its gravitational pull based on the Sun’s
mass and distance from the Earth.
23. When I drive my car at 30 miles per hour, it has more kinetic energy than it does at 10
miles per hour.
This does make sense because as kinetic energy will increase with any increase in velocity.
24. Someday soon, scientists are likely to build an engine that produces more energy than it
consumes.
This does not make sense with the conservation energy law, which tells us that energy cannot
appear out of nowhere.
Ch5-1, 2, 3, 4, 10, 13, 18, 20
1. What is the difference between energy and power? What units do we use to measure power?
* Power is defined as the quantity of work completed in a specific length of time, whereas
energy is the capacity to perform labor. Power is measured in watts, whereas power is
measured in kilowatt-hours in the SI. These terms refer to physical ideas.
2. What are the four major ways light and matter can interact? Give an example of each from
everyday life.
* The four major ways light and matter can interact are through emission, absorption,
transmission, and reflection/scattering. A light reflection off a mirror is an example.
3. Why do we say that light is an electromagnetic wave? Describe the relationship among
wavelength, frequency, and speed for light.
* We say it because it is an oscillation of electric and magnetic fields
This may be explained by the interaction of magnetic and electric forces. We refer to light as an
electromagnetic wave as it is a moving vibration of both an electric and magnetic field. There is
a crucial link between the three when discussing light waves since the speed of every wave is
equal to its wavelength times its frequency. The frequency decreases with increasing wavelength
and vice versa.
4. What is a photon? In what way is a photon like a particle? In what way is it like a wave?
*This may be explained by the interaction of magnetic and electric forces. We refer to light as an
electromagnetic wave as it is a moving vibration of both an electric and magnetic field. There is
a crucial link between the three when discussing light waves since the speed of every wave is
equal to its wavelength times its frequency. The frequency decreases with increasing wavelength
and vice versa.
10. Describe the energy levels that we find for electrons in atoms. Under what circumstances can
energy level transitions occur?
*Not only hydrogen, but all atoms have quantized energy levels for electrons. Quantized refers to
abrupt shifts without a transitional state. Only when an electron receives or loses the precise
amount of energy separating two energy levels can there be an energy level transfer.
13. How can we use emission or absorption lines to determine the chemical composition of a
distant object?
*Because hydrogen emits and absorbs light at certain wavelengths, you may tell if a far-off cloud
is composed of hydrogen if it generates a particular spectrum with distinct absorption lines. Ions
from each chemical leave distinct "fingerprints."
Does It Make Sense?
Decide whether or not each of the following statements makes sense (or is clearly true or false).
Explain clearly; not all of these have definitive answers, so your explanation is more important
than your chosen answer.
18. Because of their higher frequencies, x-rays must travel through space faster than radio waves.
Yes it is true, Because X-rays are more energetic and have a higher frequency than radio waves,
they will traverse space more quickly.
20. If you had x-ray vision, you could read this entire book without turning any pages.
* This is false, because you would not be able to resolve the letters on individual pages if you
were utilizing x-ray vision.