Astronomy Ch 2
35. If there is going to be a total lunar eclipse tonight, then you know that:
( a ) the Moon's phase is full.
29.Galileo's contribution to astronomy included
( c)making observations and conducting experiments that dispelled scientific objections to the Suncentered model
30. If stars existed but galaxies did not
(C) we would not exist because we are made of material that was recycled in galaxies.
31. The age of our solar system is about
(a) one-third of the age of the universe.
27. The total number of stars in the observable universe is roughly equivalent to
(a) the number of grains of sand on all the beaches on Earth.
32. The fact that nearly all galaxies are moving away from us, with more distant ones moving faster, helped us conclude that
(a) the universe is expanding.
36. When we see Saturn going through a period of apparent retrograde motion, it means
(b) Earth is passing Saturn in its Orbit.
29. Could we see a galaxy that is 50 billion light-years away?
(b) No, because it would be beyond the bounds of our observable universe.
34. The fact that we always see the same face of the Moon tells us that the Moon
(b) The Moon's rotation period is the same as its orbital period
28. When we say the universe is expanding, we mean that
(b) the average distance between galaxies is growing with time.
26. If we represent the solar system on a scale that allows us to walk from the Sun to Pluto in a few minutes, then
(b) the planets are marble size or smaller and the nearest stars are thousands of miles away.
30.Which of the following is not true about scientific progress?
(b)Science advances only through the scientific method.
25. The star Betelgeuse is 600 light-years away. If it explodes tonight,
(c ) We will not know about it until about 600 years.
31.Which of the following is not true about a scientific theory ?
(c) A theory is essentially an educated guess.
8. What is the zodiac, and why do we see different parts of it at different times of the year?
1) zodiac- constellations along the ecliptic 2) we see different parts of the zodiac at different times of year because the suns apparent location along the ecliptic, appearing to move eastward, determines which constellations we see in the background at different times of the year
30. In winter, Earths axis points toward the star Polaris , In spring, tha axis points toward
A Polaris
31. When it is Summer in Australia , the season int he United states is
A Winter
29. Beging and Philadelphia have about the same latitude but different longitudes. Therefore tonights night sky in the two places
A look about the same.
1. Briefly describe the major level of structure (such as planet, star, galaxy) in the universe.
A star is a large, glowing ball of gas that produces heat and light through nuclear fusion. A planet is a moderately large object that orbits a star and shines primarily by reflecting light from its star. A moon is an object that orbits a planet. A solar system is comprised of the sun and the material that orbits it. A galaxy is a great island of stars in space containing millions and trillions of stars held together by gravity and orbiting a common center. A cluster or group is a collection of galaxies bound together by gravity. A super cluster is a giant region in which clusters and groups of galaxies are tightly packed together. A universe is the total sum of all matter and energy.
12. What key observations lead us to conclude that the universe is expanding, use the raisin cake model to explain?
As the universe expands galaxies which are further away from us appear to move more rapidly away from us, the raisin cake model helps to explain this. When the cake enters the oven, the raisins are all equally dispersed. As the cake is baked it expands equally, so the raisin that was located beyond the closest raisin appears to move faster due to the equal expansion of the cake. So the raisin that was 2 cm away when it entered the oven is now 6 cm away after the baking process.
32. If the Sun rises precisely due east
B It must be the day of either the March or September Equinox
33.A week after full moon, the Moon's phase is
B third quarter
23. In the Greek geocentric model, the retrograde motion of a planet occurs when
B)The planet actually goes backward in its orbit around Earth
27. Two stars that are in the same constellation
C May actually be far away from each other.
25. When we say a planet has a highly eccentric orbit, we mean that
C)in some parts of its orbit it is much closer to the Sun than in other parts.
20.Newton's law of gravity works as well for explaining orbits of planets around other stars as it does for explaining the planets in our own solar system.
Can be evaluated scientifically by observing extrasolar planets.
22. A huge fleet of alien spacecraft will land on Earth and introduce an era of peace and prosperity on January 1, 2020
Can be evaluated scientifically by seeing whether or not the aliens show up on the appointed date.
18. Children born when Jupiter is in the constellation Taurus are more likely to be musicians than other children.
Can be evaluated scientifically by testing and finding the astrological signs of musicians. In fact, it has been tested and turns out not to be true— making continued belief in it nonscience
16. There is no liquid water on the surface of Mars today .
Can be evaluated scientifically. This idea has been tested by the study of Mars.
6.What are circumpolar stars? Are more stars circumpolar at the North Pole or in the United States? Explain.
Circumpolar stars are stars that never actually set from a given latitude on earth because of their proximity from either celestial pole. Since the United States is lower on the latitude lines than the North Pole, some stars would become invisible along the horizon. Therefore, more circumpolar stars are visible from the North Pole, not the United States. The closer the person is to the north celestial pole, the more circumpolar stars they will be able to see orbiting that particular celestial pole
26.Earth is closer to the Sun in January than in July. Therefore, in accord with Kepler's second law. ..
Earth travels faster in its orbit around the Sun in Janurary than in july
23. Which of the following correctly lists our "cosmic address" from small to large?
Earth, solar system, Milky Way Galaxy, Local Group, Local Supercluster, universe
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) Fg= force of gravitational attrition G= 6.67 E -11 (gravitational constant)
3.What us free-fall, and why does it make you weightless? Briefly describe why astronauts are weightless in the Space Station.
Free-fall The condition in which an object is falling without resistance; objects are weightless when in free-fall (114). Astronauts are weightless because they are in free-fall. Astronauts are weightless the entire time they orbit Earth because they are in a constant state of free-fall (114).
12.Briefly describe the moon's cycle of phases. Can you ever see a full moon at noon?
In each cycle of lunar phases, the appearance of the moon and the times it arises and sets changes depending on its relative location to the sun as it orbits Earth. Each cycle takes about 29.5 days. Half of the moon always faces the Sun and is illuminated. But the amount of this illuminated half we see depends on where the Moon is in its orbit. As a result we see a combo of the bright and dark faces of the moon. We can't see a full Moon at noon, because the full Moon occurs when it is opposite the Sun in the sky. The full moon reaches its highest point in the sky at midnight . Thus it arises around the sunset and sets around the sunrise.
.6. What do we mean when we say that the universe is expanding, and how does expansion lead to the idea of the Big Bang and our current estimate of the age of the universe?
In saying that the universe is expanding it is implying that the average distance between the galaxies are increasing as time goes on. Because an expansion has to start somewhere there birth the Big Bang theory and the current age of earth estimate at 14 billion years old
10. Briefly describe our solar systems location and motion within the Milky Way Galaxy.
In the milky way galaxy, the earth's solar system is located at about 27,000 light years from the milky way's galactic center and orbits approx. per 230 million years
7.What are latitude and longitude? Does the sky you observe vary as you change latitude? Does it vary with longitude? Explain.
Latitude measures north and south; Longitude measures east and west. The local sky does vary in latitude but not longitudinally. This is due primarily because of the fact that the earth rotates on its axis which makes the local sky appear to move as the earth orbits, because it varies only in latitude in a 24-hour period everyone on earth would have had the same view of the sky.
8. What do we mean by mass-energy? Explain the formula E=m^2.
Mass-energy: mass itself is a form of potential energy (122). Einstein's formula simply states that "E is the amount of potential energy, m is the mass of the object, and c is the speed of light. This equation tells us that a small amount of mass contains a huge amount of energy" (122). It tells us that mass can be converted into other forms of energy, it also tells us that energy can and explored several subcategories that are especially important in astronomy: thermal energy, gravitational potential energy, and mass-energy (122).
2. Define Momentum and force. What do we mean when we say that momentum can be changed only by net force?
Momentum: is the product of its mass and velocity that is momentum =mass*velocity (112). Force: The only way to change an object's momentum (112). A change in momentum occurs only when the net force is not zero. Changing an object's momentum means changing its velocity, as long as its mass remains constant. A net force that is not zero therefore causes an object to accelerate. Conversely, whenever an object accelerates, a net force must be causing the acceleration (112).
4.State Newton's three laws of motion. For each law, give an example of its application.
Newton's First law: An object moves at constant velocity if there is no net force upon it (115). Ex: A car driving on a straight road theoretically, should continue traveling on that straight road, but if you come to a stop or lay off the gas pedal that would be consider as a force to slow it down. If the car were in space, by newton's first law it should continue at its constant velocity, but gravity would eventually alter its speed and direction. Newton's second law: force = mass X acceleration. (force = rate of change in momentum) (116). Ex: helps us understand the force on a car moving around a curve or a planet orbiting the Sun. In the case of the car, the inward force comes from friction between the tires and the road. The tighter the curve or the faster the car is going, the greater the force needed to keep the car moving around it. If the inward force due to friction is not great enough, the car skids outward (117). Newton's Third Law: For any force, there is always an equal and opposite reaction force (117). Ex: Your body always exerts a gravitational force on Earth identical to the force that Earth exerts on you, except that it acts in the opposite direction. Of course, the same force means a much greater acceleration for you than for Earth (because your mass is so much smaller than Earth's), which is why you fall toward Earth when you jump off a chair, rather than Earth falling toward you (117).
11. What is dark matter? Where does it reside in our galaxy? What makes dark matter and dark energy so mysterious and so important?
Nonluminous material that is postulated to exist in space and that could take any of several forms including weakly interacting particles (cold dark matter) or high-energy randomly moving particles created soon after the Big Bang (hot dark matter). Studies of other galaxies indicate that they are also made of mostly dark matter, which means that this matter significantly outweighs the ordinary matter that makes up planets and stars. This also means that dark matter must be the dominant source of gravity that led to the formation of galaxies, clusters, and super clusters.
19Aliens can manipulate time so that they can abduct people and perform experiments on them without the people ever realizing they were taken .
Nonscience, because it offers no way to test whether the abductions really occur
21. God created the laws of motion that were discovered by Newton .
Nonscience, since it is an idea that cannot be tested scientifically.
15. My house is haunted by ghosts who make the creaking noises I hear each night.
Nonscience. The noises may be real, but no evidence is offered for concluding that they are caused by ghosts.
2. Define astronomical unit and light-year.
One astronomical unit (AU) is the average distance between the earth and the sun, approximately 93 million miles. A light year (ly) is the distance that light can travel in one year, which is about 6 trillion miles
12. Explain why orbits cannot change spontaneously, how a gravitational encounter can cause a change. How can an object achieve escape velocity?
Orbits cannot change spontaneously, because As long as no other object causes the planet to gain or lose orbital energy, its orbital energy cannot change and its orbit must remain the same (126). One way that two objects can exchange orbital energy is through a gravitational encounter, in which they pass near enough so that each can feel the effects of the other's gravity (127). If an object gains enough orbital energy, it may achieve escape velocity and leave the gravitational influence of the object it was orbiting (133).
1. 1.Define Speed, velocity, and acceleration. What are the units of acceleration? What is the acceleration of gravity?
Speed: how far an object will go in a certain amount of time (111). Velocity: provides the speed and its direction of an object (111). Acceleration: When the objects velocity is changing in any way (111). Units of Acceleration: Meters per second, Mph Acceleration of gravity: The acceleration of a falling object. (111)
7. Define temperature and thermal energy. How are they related? How are they different?
Temperature: Measures the average kinetic energy of the particles (120). Thermal Energy: subcategory of kinetic energy, which represents the collective kinetic energy of the many individual particles (atoms and molecules) moving randomly within a substance like a rock or the air or the gas within a distant star (120). Thermal energy gets its name because it is related to temperature, but temperature and thermal energy are not quite the same thing (120). They are different in which Thermal energy depends on temperature, because a higher average kinetic energy for the particles in a substance means a higher total energy (121).
5.Explain why we can measure only angular sizes and angular distances for objects in the sky. What are arcminutes and arcseconds?
The angular size of an object is the angle it appears to span in a humans Field of vision and is the distance between a pair of objects that appears to separate them. Angular size and angular distance is used to describe an object's place in the sky because our lack of depth percepTion. Arcminutes and arcseconds are more precise forms of astronomical measurement and each degree is separated into arcminutes and further subdivided into arcseconds
15. What do we mean by the apparent retrograde motion of the planets? Why was it difficult for ancient astronomers to explain but easy for us to explain?
The apparent retrograde motion of the planets is the observed movement of the planets in the sky as they pass a certain point they would appear to move backwards in their orbit. This data did not fit into the ancient astronomer's model of an Earth centered system. Later other astronomers came up with the concept of epicycles to attempt to explain the retrograde movement. The epicycles were a clear method for recreating the movement. The issue was that the data did not exactly match up and still they could not accurately predict the motion of the planets. It is easier for modern astronomy to explain the motion after the onset of the sun centered system paired with the elliptical orbit all data fell into place and accurate predictions could be made. It is also technology that aids in this data. Being able to see through great zooms the phases of the planets as they passed the sun allows us to further confirm this concept.
5. Using techniques described in the chapter, put the following into perspective: the size of our solar system, the distance to nearby stars, the size and number of stars in the Milky Way galaxy, and the number of stars in the Observable Universe.
The best way to put our solar system into perspective is by referring to the voyager model, this model allows us to view our entire solar system as a city block. Within this model the distance from the sun to Pluto is about 600 meters, or 1/3 of a mile. Based on the scaling of the voyager model, the distance from the sun to the next closest star (Alpha Centauri) is the distance from Washington, DC to California. In order to scale the Milky Way galaxy one must make the scale 1 billion times smaller to that of the voyager model, this now make the size of one light-year roughly 1 millimeter. Scaled down to this size, the Milky Way galaxy now becomes the size of a football field. Within the Milky Way galaxy there are more than 100 billion stars. If an individual attempted to count all the stars in the Milky Way galaxy (even at a rate of 1 star per second) it would take more than 3000 years. Within the observable universe there are roughly 100 billion galaxies, so if there are roughly 100 billion stars in each of the 100 billion galaxies, the number of stars within the observable universe is comparable to the number of dry grains of sand on all of the earths beaches.
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 dome shape arises from the fact that we see only half of the celestial sphere at any particular moment from any particular location, while the ground blocks the other half from view (27). Horizon: The boundary between Earth and sky (27). Zenith: The point directly overhead (27). Meridian: an imaginary half-circle stretching from the horizon due south, through the zenith, to the horizon due north (27). We can pinpoint the position of any object in the local sky by stating its direction along the horizon (sometimes stated as azimuth, which is degrees clockwise from due north) and its altitude above the horizon (27).
11. What is precession, and how does it effect what we see in our sky?
The precession is a gradual wobble that changes the orientation of the Earth's axis in space. Earth rotates around every 24 hours and its axis precesses every 26,000 years. It affects our view of the sky because it changes the constellations associated with solstices and equinoxes. Since those two correspond to points on the Earth's orbit, which depend on the direction the axis points to in the space, the positions in the orbits gradually shift along Earth's orbit.
10. Briefly describe key facts about the solstices and the equinoxes.
The summer solstice in June is when the northern hemisphere is most directly tipped towards the sun and receives most direct sunlight. The winter solstice in December is when the northern hemisphere receives the least direct sunlight. The spring equinox in March is when the northern hemisphere goes from being tipped slightly away from the sun to slightly towards it. The fall equinox in September is when the northern hemisphere is starting to tip away from the sun
10 .What is the difference between a bound and an unbound orbit? What orbital shapes are possible?
They are different in which an unbound orbit comes close to an object around once, while bond orbits go around another object over and over. Bound orbits are ellipses, and unbound orbits can be either parabolas or hyperbolas (124).
17.The constellation Orion didn't exist when my grandfather was a child.
This does not make sense because the names were chosen in 1928. If your grandpa was really old it is possible.
17. Dogs are smarter than cats .
This question might be argued both ways, but probably is nonscience, since "smarter" is not well-defined.
19. The observable universe is the same size today as it was a few billion years ago.
This state-ment does not make sense, because the universe is growing larger as it expands. F
14. The universe is billions of light-years in age.
This statement does not make sense because it uses the term "light-years" as a time, rather than a distance
22. Because nearly all galaxies are moving away from us, we must be located at the center of the universe.
This statement does not make sense, as we can tell when we think about the raisin cake model. Every raisin sees every other raisin moving away from it, so in this sense no raisin is any more central than any other. (Equivalently, we could say that every raisin— or galaxy—is the center of its own observable universe, which is true but very different from the idea of an absolute center to the universe.)
21. Last night I saw Jupiter right in the middle of the Big Dipper. (Hint: Is the Big Dipper part of the zodiac?)
This statement does not make sense, because Jupiter, like all the planets, is always found very close to the ecliptic in the sky. The ecliptic passes through the constellations of the zodiac, so Jupiter can appear to be only in one of the 12 zodiac constellations—and the Big Dipper (part of the constellation Ursa Major) is not among these constellations.
19.Last night the Moon was so big that it stretched for a mile across the sky .
This statement does not make sense, because a mile is a physical distance, and we can measure only angular sizes or distances when we observe objects in the sky.
17. Astronomers recently discovered a moon that does not orbit a planet.
This statement does not make sense, because a moon is defined to be an object that orbits a planet. F
15. It will take me light-years to complete this homework assignment.
This statement does not make sense, because it uses the term "light- years" as a time, rather than as a distance.
18. NASA soon plans to launch a spaceship that will photograph our Milky Way Galaxy from beyond its halo.
This statement does not make sense, because of the size scales involved: Even if we could build a spaceship that traveled close to the speed of light, it would take tens of thousands of years to get high enough into the halo to photograph the disk, and then tens of thousands of years more for the picture to be transmitted back to Earth. F
22. Last night I saw Mars move westward through the sky in its apparent retrograde motion
This statement does not make sense, because the apparent retrograde motion is noticeable only over many nights, not during a single night. (Of course, like all celestial objects, Mars moves from east to west over the course of EVERY night.
24.If Earth's orbit were a perfect circle, we would not have seasons
This statement does not make sense. As long as Earth still has its axis tilt, we'll still have seasons.
21. At a nearby park, I built a scale model of our solar system in which I used a basketball to represent Earth.
This statement does not make sense. On a scale where Earth is the size of a basketball, we could not fit the rest of the solar system in a local park. (A basketball is roughly 200 times the diameter of Earth in the Voyage model described in the book. Since the Earth- Sun distance is 15 meters in the Voyage model, a basketball-size Earth would require an Earth- Sun distance of about 3 kilometers, and a Sun- Pluto distance of about 120 kilometers. F
25. Because of precession, someday it will be summer everywhere on Earth at the same time .
This statement does not make sense. Precession does not change the tilt of the axis, only its orientation in space. As long as the tilt remains, we will continue to have opposite seasons in the two hemispheres.
23. Although all the known stars appear to rise in the east and set in the west, we might someday discover a star that will appear to rise in the west and set in the east
This statement does not make sense. The stars aren't really rising and setting; they only appear to rise in the east and set in the west because EARTH rotates.
16. Someday, we may build spaceships capable of traveling a light-year in only a decade.
This statement is fine. A light-year is the distance that light can travel in 1 year, so traveling this distance in a decade would require a speed of 10% of the speed of light.
13. Our solar system is bigger than some galaxies.
This statement makes no sense. A galaxy is composed of hundreds of billions of stars, while our solar system is 'just' the stuff orbiting one star, our sun. Our solar system is a tiny part of the Milky Way Galaxy, being much smaller than it.
26. This morning I saw the full moon setting at about the same time the Sun was rising
This statement makes sense, because a full moon is opposite the Sun in the sky
20.I live in the United States, and during my first trip to Argentina I saw many constellations that I'd never seen before .
This statement makes sense, because the constellations visible in the sky depend on latitude. Since Argentina is in the Southern Hemisphere, the constellations visible there include many that are not visible from the United States.
20. Photographs of distant galaxies show them as they were when they were much younger than they are today.
This statement makes sense, because when we look far into space we also see far back in time. Thus, we see distant galaxies as they were in the distant past, when they were younger than they are today T
7.In what sense are we Star Stuff?
This statement sums up the fact that the carbon, nitrogen and oxygen atoms in our bodies, as well as atoms of all other heavy elements, were created in previous generations of stars over 4.5 billion years ago.
14.What is tidal friction? What effect does it have on Earth? How does it explain the Moon's synchronous rotation?
Tidal Friction: Friction within an object that is caused by a tidal force (g-14). Tidal forces stretch the actual Earth, which creates tidal friction. Basically, the Moon's gravity tries to keep the tidal bulges on the Earth-Moon line, but Earth's rotation tries to move the bulges around with it. This causes two things to happen to Earth. First, Earth's rotation slows very slightly. Second, the Moon becomes farther from Earth. Earth's tidal forces on the Moon cause the Moon's synchronous rotation. In the past, the Moon probably did rotate faster, but its rotation gradually slowed until it reached a point where the Moon and its tidal bulges rotate at the same rate.
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 created by the difference in the force of attraction between the Moon and different parts of Earth (129). This difference in attraction creates a "stretching force;' or tidal force, that stretches the entire Earth to create two tidal bulge (128). Earth's rotation carries any location through each of the two bulges each day, creating two high tides. Low tides occur when the location is at the points halfway between the two tidal bulges. The two "daily" high tides actually come slightly more than 12 hours apart. Because of its orbital motion around Earth, the Moon reaches its highest point in the sky at any location about every 24 hours 50 minutes, rather than every 24 hours (129). Tides vary with the phasing of the moon for example, "When the tidal forces of the Sun and the Moon work together, as is the case at both new moon and full moon, we get the especially pronounced spring tides"(129). And "when they work against each other at first and third-quarter moons, we get smaller neap tides" (129).
11.What do we need to know if we want to measure an object's mass with Newton's version of Kepler's third law? Explain.
Used to measure orbital period and distance in any units and also shows the relationship between orbital periods and average distance depends on the masses of orbiting objects This also explains the orbital period only is effected by distance, not mass
14. Why don't we see an eclipse at every new and full moon?
We don't see an eclipse b/c the Earth, Moon, and the Sun aren't in line with each other on every new and full moon. Solar eclipse only occurs when the Moon is new and is close enough to the ecliptic that its shadow partially or completely reaches the Earth. Since the moon's orbit is slightly inclined to the ecliptic, it only aligns perfectly twice in its orbit of the Earth. So to have an eclipse, the phase of the Moon must be full (for a lunar) or new (for a solar) and each must occur during one of the periods when the two points in each orbit where the Moon crosses the surface are aligned with the Sun and the Earth.
5. Describe the law of conservation of angular momentum and conservation of energy. Give an example of how each is important to astronomy.
What are the laws of conservation of momentum, conservation of angular momentum, and conservation of energy? For each, give an example of how it is important in astronomy. Law of conservation of... Momentum= the total momentum of interacting objects cannot change as long as no external force is acting on them.. aka. Total momentum is conserved. Ex. Reps Newton's 1st law of constant motion b/c there's no net forces in space to affect things. Therefore, objects must continue to move exactly as they have been moving. Ex. 2. When you jump off the ground, you actually push the Earth backwards, but its huge mass renders no acceleration. Angular momentum= As long as there is no external torque, "twisting force," the total angular momentum of a set of interacting objects cannot change.. Both orbital and rotational Ex. Earth's angular momentum= (m X v X r) mass, velocity/radius of orbit. Ex. Basically, as long as Earth isn't transferring any of its angular momentum of orbit or rotation to another object, it keeps orbiting and rotating at the same rate. Energy= Energy cannot appear out of nowhere or disappear into nothing. They can only gain/lose energy by exchanging it with something else. Ex. Everything that's happened in the universe has been caused by an exchange of energy and matter. Ex. 2. Planetary interiors cool with time b/c they radiate energy into space Ex. 3. Sun became hot b/c of energy released by the gas that formed it.
3.Explain the statement the farther away we look in distance, the further back we look in time.
What the statement, "the further away we look in the distance, the further back we look in time", refers to when we are looking at a star about 8 years away, we are seeing that star as it was 8 years ago.
2. Suppose you were making a model of the celestial sphere with a ball. Briefly describe all the things you would need to mark on your celestial sphere.
When making a celestial sphere, one would need to mark the celestial north pole, which is directly over Earth's north pole. You'd also need to mark the celestial south pole, directly over Earth's south pole; and the celestial equator which is a projection of Earth's equator into space. Finally the ecliptic, which is the path the sun follows as it appears to circle around the celestial sphere once each year
24. Which of the following was not a major advantage of Copernicus's Sun-centered model over the Ptolemaic model?
a. It made significantly better predictions of planetary positions in our sky, this answer is correct as stated in the text book page 39, the primary problem was that while Copernicus had been willing to overturn Earth's central place in the cosmos, he held fast to the belief that heavenly motion must be in perfect circles.
24. An astronomical unit is
a. The earths average distance from the sun
27.According to Kepler's third law
b. Jupiter orbits the Sun at a faster speed than Saturn, this is true as stated in the text book Kepler's third law of planetary motion states that more distant planets orbit the Sun at a slower average speeds, obeying the precise mathematical relationship.
13. Why do we always see the same face of the Moon?
because the rotational period is exactly the same as the orbital period, the same portion of the Moon's sphere is always facing the Earth
28.Tycho Brahe's contribution to astronomy included
collecting data that enabled Kepler to discover the laws of planetary motion.
6.. Define kinetic energy, radioactive energy, and potential energy, with at least two examples for each.
inetic Energy: Energy of motion. Ex: Falling rocks, orbiting planets, and the molecules moving in the air (119). Radioactive energy:Energy carried by light. Ex: light can alter molecules in our eyes thereby allowing us to see-or warm the surface of a planet (119). Potential Energy: Stored energy. Ex: a rock perched on a ledge has gravitational potential energy because it will fall if it slips off the edge, and gasoline contains chemical potential energy that can be converted into the kinetic energy of a moving car (120).
9. Suppose Earth's axis had no tilt. Would we still have seasons? Why or why not?
no because the tilt of the axis is what causes the two different hemispheres to experience opposite seasons in relation to the way sunlight falls differently on earth at different times of year
16.What is stellar parallax? How did an inability to detect it support the ancient belief in an earth-centered universe?
stellar parallax- the apparent shift in the position of a nearby star (relative to distant objects) that occurs as we view the star from different positions in the earth's orbit of the sun each year, this supported an earth centered universe because they thought if earth rotated around the sun then the stars would get closer at certain times of the year
4. What do we mean by the observable universe? Is it the same thing as the entire universe?
the part of the universe that could be observed in principle, including things that may require future technologies No, the entire universe is larger than our observable universe.
1.What are constellations? How did they get their names?
• A constellation is a well-defined region of the sky whose familiar borders and patterns help us locate the constellation. Members of the International Astronomical Union officially chose the names in 1928. • Greeks, Persians, and romans came up with a lot of the names, the IAU just made them official for us. • The groupings are arbitrary. China or places outside the IAU have their own constellations
3.On a clear, dark night, the sky may appear to be "full" of stars. Does this appearance accurately reflect the way the stars are distributed in space? Explain.
• No, they lie at very different distances from earth even though they may appear to lie on a celestial field. We lack depth perception from earth because the visible stars are so far away. • The gaps between stars are visible, but the distribution of the stars as you see them it in the sky is not uniform. There appear to be way more stars in the milky way. • Can see about 5,000 stars on a clear night with the naked eye
