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.
25. Venus is easiest to see in the evening when it is
( c) greatest eastern elongation.
29.Galileo's contribution to astronomy included
( c)making observations and conducting experiments that dispelled scientific objections to the Suncentered model
31. If you know a star's declination, you can determine your latitude if you also
(A) measure its altitude when it crosses the meridian
30. If stars existed but galaxies did not
(C) we would not exist because we are made of material that was recycled in galaxies.
27. A star that is located 30 degrees north of the celestial equator has
(a) Declination of 30 degrees
26.In the winter, your wristwatch tells
(a) apparent solar time
24. Jupiter is brightest when it is
(a) at Opposition
28. A star's path through your sky depends on your latitude and the star's
(a) declination
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.
32. When Einstein's theory of gravity (general relativity) gained acceptance, it demonstrated that Newton's theory had been
(b) Incomplete
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.
23 The time from one March equinox to the next is the (a) sidereal day. (b) tropical year. (c) synodic month. Course Hero
(b) tropical year.
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.
29. At latitude 50 degrees N the celestial equator crosses the meridian at altitude
(c) 40 degrees in the south
31.Which of the following is not true about a scientific theory ?
(c) A theory is essentially an educated guess.
30 At the North Pole on the summer solstice, the Sun
(c) circles the horizon at altitude 23 1/2 degrees
32. If you measure the Sun's position in your local sky, you can determine your longitude if you also
(c) know the universal time
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
9. State and explain the meaning of each of Kepler's laws of planetary motion
1. the orbit of each planet is an ellipse with the sun at one focus 2. as a planet moves around its orbit, it sweeps out equal areas in equal times 3. more distant planets orbit the sun at slower speeds, obeying the precise mathematical relationship p^2 = a^3
28.The N Celestial pole 35 * above your northern horizon This tells you that you are at
A Latitude 35*N.
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
11. What is the difference between a hypothesis and a theory in science?
A hypothesis attempts to answer questions by putting forth a plausible explanation that has yet to be rigorously tested. A theory, on the other hand, has already undergone extensive testing by various scientists and is generally accepted as being an accurate explanation of an observation.
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.
5. What do we mean by a model in science?
A model in science is a conceptual representation whose purpose is to explain and predict observed phenomena.
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.
2.Why did ancient people study astronomy? Describe an astronomical achievement of at least three ancient cultures.
Ancient people studied astronomy because of our curiosity and to keep track of time and season changes and navigation. which was essential for farming. Egyptians - huge obelisks that probably served as clocks Stonehenge - helped ancient cultures mark the seasons Aztecs - Temple Mayor used to mark the seasons Anasazi - sun dagger to mark the suns position on special dates such as summer and winter solstice Greek - Metonic cycle; 19 yr. cycle on which the dates of lunar phases repeat Babylonians - predicting eclipses with the help of 18 yr. Saros cycle
4. Distinguish among apparent solar time, mean solar time, standard time, daylight saving time, and universal time.
Apparent solar time is the time based on the actual location of the Sun in the sky, while mean solar time is based on making all days 24 hours long. The two differ because of the tilt of Earth's spin access and because Earth moves at different speeds in its orbit as it gets slightly closer to or farther from the Sun, so that the actual length of a day based on the Sun's position in the sky actually varies over the course of the year, with 24 hours as the average. Apparent solar time can be read directly from a sundial, while mean solar time is easier to obtain with mechanical or electronic clocks because all days are the same length. Standard time is the mean solar time over an east-west swath of Earth known as a time zone. Daylight saving time is simply standard time advanced by 1 hour. Universal Time (UT) is the mean solar time for Greenwich, England.
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.
12. what is the basic idea behind astrology? Explain why this idea seems reasonable in ancient times but in no longer accepted by scientists
Astrology: search for hidden influences on human lives based on the positions of planets and stars in the sky. Astrologers hoped to learn how the positions of the Sun, Moon, and planets influence our lives by charting the skies and seeking correlations with event on Earth. Astrology said that there is special meaning in the patterns of the stars in the constellations. This idea may have seemed quite reasonable in ancient times, when the stars were assumed to be fixed on an unchanging celestial sphere, but today we know that the patterns of the stars in the constellations are accidents of the moment. More over, the stars in a constellation don't necessarily have any physical association, because two stars that are close together in the sky might lie at vastly different distances. Astrology also places great importance on the positions of the planets among the constellation. Again, this idea might have seemed reasonable in ancient times, when it was thought that the planets truly wandered among the stars. Today we know that the planets only appear to wander among the star.
10. Describe the Sun's path through the local sky on the equinoxes and on the solstice for latitude 40°N. Do the same for the North Pole, and equator.
At 40°N latitude, the Sun will rise due east and set due west on the equinoxes. On these days it will cross the meridian at altitude 50° due south. On the summer solstice, the Sun will rise north of due east, cross the meridian at altitude 73.5° due south, and set north of due west. On the winter solstice, the Sun rises south of due east, crosses the meridian at altitude 26.5° due south, and sets south of due west. At the equator on the equinoxes, the Sun will rise due east, pass directly overhead, and set due west. On the summer solstice, the Sun will rise north of due east, cross the meridian at 66.5° to the north and set north of due west. On the winter solstice, the mirror image will occur: The Sun will rise south of due east, cross the meridian at 66.5° altitude to the south, and set south of due west. At the North Pole on the equinoxes, the Sun will skim the horizon, making a circle all around the horizon each day. On the summer solstice, the Sun will circle 23.5° above the horizon all day. On the winter solstice, we would not see the Sun at all. At the South Pole on the equinoxes, the Sun will skim the horizon, making a circle all around the horizon each day. On the summer solstice, the Sun would not appear at all. On the winter solstice, the Sun will circle 23.5° above the horizon all day.
9. Suppose you are at the North Pole. Where is the celestial equator? Where is the north celestial pole? Describe the daily motion of the sky. Do the same for the equator and for the latitude 40°N.
At the North Pole, the north celestial pole is directly overhead and the celestial equator circles the horizon. At the equator, the north celestial pole is on the northern horizon, and the celestial equator runs from due east to due west and through the zenith. At 40° north latitude, the north celestial pole is due north, 40° above the horizon. The celestial equator runs from due east to due west, passing through an altitude of 50° due south.
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
14. Several kilometers below its surface, Jupiter's moon Europa has an ocean of liquid water.
Can be evaluated scientifically, because the idea can in principle be tested by future spacecraft.
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
7. What was the Copernican revolution, and how did it change the human view of the universe?
Copernican revolution The dramatic change, initiated by Copernicus that occurred when we learned that Earth is a planet orbiting the Sun rather than the center of the universe (65). For the longest time, we thought the all the objects in the sky revolved around us, and that the earth was the center of the universe. Copernicus discovered a simple geometric relationships that allowed him to calculate each planet's orbital period around the Sun and its relative distance from the Sun regarding Earth-Sun distance (65). Resulting that the earth revolved around the sun and not us.
9Briefly explain the earth's daily rotation and annual orbit, defining the terms ecliptic plane, and axis tilt.
Daily the earth makes one full rotation, and orbits the sun once a year. Ecliptic Plane: The ecliptic plane is defined as the imaginary plane containing the Earth's orbit around the sun. In the course of a year, the sun's apparent path through the sky lies in this plane. Axis Tilt: In astronomy, axial tilt, also known as obliquity, is the angle between an object's rotational axis and its orbital axis, or, equivalently, the angle between its equatorial plane and orbital plane. It differs from orbital inclination
7. What are declination and right ascension? How are these celestial coordinates similar to latitude and longitude on Earth? How are they different?
Declination and right ascension are the coordinates we use to pinpoint positions on the celestial sphere. These are quite similar to latitude and longitude: Like latitude, declination is zero at the equator and is measured in degrees. But rather than say "north" or "south," we assign declinations positive or negative values. Right ascension is like longitude, except that it is usually measured in hours, minutes, and seconds rather than in degrees.
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).
8.Use the Cosmic Calendar to describe how the human race fits into the scale of time
If the age of the universe was placed into one calendar year, the modern human race would have evolved at 11:52 PM on December, 31.
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
6. Summarize the development of the greek geocentric model through Ptolemy. How did the Ptolemaic model account for apparent retrograde motion?
In this model each planet moved on a small circle whose center moved around the Earth on larger circles. These small circles accounted for the apparent retrograde motion but was very complex and had some smaller circles and some larger circles.
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).
15.My mean solar clock said it was 2:00 P.M., but my friend who lives east of here had a mean solar clock that said it was 2:11 P.M.
Mean solar time is different for every different longitude, so this statement makes sense if the friend lives the equivalent of 11 minutes of longitude east of you.
10 Describe the three hallmarks of science and how we can see them in the Copernican revolution. What is Occam's razor? Why doesn't science accept personal testimony as evidence?
Modern science seeks explanations for observed phenomena that rely solely on natural causes (72). Science progresses through the creation and testing of models of nature that explain the observations as simply as possible (72). A scientific model must make testable predictions about natural phenomena that would force us to revise or abandon the model if the predictions do not agree with observations (72). Each of these hallmarks is evident in the story of the Copernican revolution. The first shows up in the way Tycho's careful measurements of planetary motion motivated Kepler to come up with a better explanation for those motions. The second is evident in the way several competing models were compared and tested, most notably those of Ptolemy, Copernicus, and Kepler. We see the third in the fact that each model could make precise predictions about the future motions of the Sun, Moon, planets, and stars in our sky. When a model's predictions failed, the model was modified or ultimately discarded. Kepler's model gained acceptance in large part because its predictions were so much better than those of the Ptolemaic model in matching Tycho's observations (72). A principle often used in science, holding that scientists should prefer the simpler of two models that agree equally well with observations; named after the medieval scholar William of Occam (1285-1349). Science does not accept personal testimony, because there must be "No Agenda" what you may believer personal, does not have evidence to back up your allegations (G-9).
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.
13. The Yankees are the best baseball team of all time.
Nonscience, since it is based on personal opinion.
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
2. Define opposition, conjunction, and greatest elongation for planets. Explain both for planets closer than Earth to the Sun and for planets farther than Earth from the Sun.
Opposition:The point at which a planet appears opposite the Sun in our sky (90). Conjunction: (of a planet with the Sun) An event in which a planet and the Sun line up in our sky (90). Greatest Elongation for planets: For Mercury or Venus, the point at which it appears farthest from the Sun in our sky (90).
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 In what way is scientific thinking natural to all of us, and how does modern science build upon this everyday type of thinking?
Scientific thinking is natural to all for many reasons. It is natural to us because it deals with careful observations. Scientific thinking also goes along with trial and error. Trial and error is something that we use in everyday life. Modern science differs form everyday type of thinking because they are trained to organize everyday thinking. We are trained to do this in a way that makes it easier for them to share their discoveries.
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. Describe the origins of the Julian and Gregorian calendars. Which one do we use today?
The Julian calendar was developed at Julius Caesar's orders to correct problems with the older Roman calendar. It added an extra day every 4 years to keep the calendar more closely synchronized with the seasons. However, over many years this was still not quite accurate enough, and the Julian calendar drifted relative to the seasons. Pope Gregory XIII ordered the calendar to be fixed. His Gregorian calendar modified the leap-year pattern so that while it still normally occurs every 4 years, we do not have leap year in century years, except for years that are divisible by 400. Today we use the Gregorian calendar.
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.
3.Describe the astronomical origins of our day, week, month, and year.
The astronomical origins of the day are from the Earth's daily rotation on its axis. The week was named after the seven planets of ancient time. The ancient people saw the seven naked-eye objects that appear to more along the constellations, which is the 7 "planets" they saw. The length of the month comes from the moon and its cycle of different phases. Lastly, the year is based on the cycle of the seasons.
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.
8. What is an ellipse? Define its foci, semimajor axis, and eccentricity.
The shape of planetary orbits is in the shape of an ellipse which is essentially an oval. An ellipse can be drawn by moving a pencil along a string whose ends are tied to two tacks. The locations of the two tacks are the foci of the ellipse. The long axis of the ellipse is the major axis, and each half of the major axis is called a semimajor axis. The eccentricity of an ellipse describes to what extent an ellipse is stretched out in comparison to a circle.
21. The Summer solstice is east of the vernal equinox by 6 hours of right ascension.
The statement is true at all times.
17. Last night around 8:00 p.m., I saw Jupiter at an altitude of 45° in the south.
The statement makes sense, since it describes the position of Jupiter in their local sky.
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
11. What is special about the tropics of Cancer and Capricorn? Describe the Sun's path on the solstice at these latitudes. Do the same for the Arctic and Antarctic Circles
The tropics of Cancer and Capricorn are the most extreme latitudes (farthest north and south) where the Sun can ever be seen directly overhead. On the solstices (summer for Cancer, winter for Capricorn), the Sun will rise north of due east (south, for winter at Capricorn), pass directly overhead, and set north of due west (south, for winter at Capricorn). The Arctic and Antarctic Circles are the northernmost and southernmost points where the Sun will be seen at least briefly on every day of the year. Alternatively, these are the southernmost and northernmost latitudes where the Sun will appear above the horizon for an entire 24-hour day at least once a year. So on the summer solstice at the Arctic Circle, the Sun will be due north at midnight, just at the horizon. It will work its way east, growing higher in the sky, until it comes around to the meridian to the south, when it will be at 47° above the horizon. It will then continue off to the west, then north, sinking back toward the horizon. On the winter solstice, the Sun will just barely appear above the horizon due south at noon. For the Antarctic circle, this situation is exactly reversed.
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 apparent solar time was noon, but the Sun was just setting
This statement does not make sense, because apparent solar noon is defined as the time when the Sun is at its highest point on the meridian. If the Sun is at its highest point, it cannot be setting.
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 Even though my UT clock had stopped,I was able to find my longitude by measuring the altitudes of 14 different stars in my local sky.
This statement does not make sense because longitude determination requires comparing the positions of stars (or the Sun) in your location with their positions in a known location, and the latter requires knowing the time in that location. Thus, without a clock, you can't determine your longitude
18. When I looked into the dark lanes of the Milky Way with my binoculars, I saw what must have been a cluster of distant galaxies.
This statement does not make sense because we cannot see through the band of light we call the Milky Way to external galaxies; the dark fissure is gas and dust blocking our view.
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.)
20. Los Angeles is west of New York by about 3 hours of right ascension.
This statement does not make sense, because right ascension is a coordinate of the celestial sphere, not of Earth.
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
19. Today the Sun is at an altitude of 10° on the celestial sphere.
This statement does not make sense, because altitude is a coordinate of the local sky, not of the celestial sphere.
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
16. When the standard time is 3:00 P.M. in Baltimore, it is 3:15 P.M. in Washington,D.C.
This statement does not make sense, because standard time zones must be 1 hour apart, not 15 minutes apart. (Also, Baltimore and Washington, D.C., are in the same time zone.)
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.
18. The latitude of the stars in Orion's belt is about 5°N.
This statement does not make sense; Orion's belt is not on Earth, and hence does not have a latitude
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
13. Last night I saw Venus shining brightly on the meridian at midnight.
This statement seams false. I would require that Venus be at opposition to the Sun in the sky—and, because Venus is closer to the Sun than is Earth, it is never at opposition.
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
12 Briefly describe how you can use the sun or stars to determine your latitude and longitude.
When trying to determine the latitude if you find the north or south celestial pole. This is found by measuring the altitude of Polaris that lies within 1 degree of the north celestial pole. To determine the longitude by comparing the current position of a star in the sky. You have to know the time in order to figure out your latitude
What do we mean when we say the equinoxes and solstices are points on the celestial sphere? How are these points related to the times of the year called the equinoxes and solstice?
When we say the equinoxes and solstices are points on the celestial sphere this means where the sun is located. During these events the earth is at a particular position in its orbit. They show us where the sun is located in the ecliptic line
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.
1. explain the differences between (a) a sidereal day and a solar day, (b) a sidereal month and a synodic month, (c) a sidereal year and a tropical year, (d) a planet's sidereal period and its synodic period.
a. Sidereal day is a shorter day than a solar day. A solar day, is 4 minutes longer than a sidereal, and it is what we apparently see where the sun sets and rises. b. Sidereal month: sidereal month The time required for the Moon to orbit Earth once (as measured against the stars);about days. synodic month (or lunar month) The time required for a complete cycle of lunar phases, which averages about days. c. Sidereal Year:The time required for Earth to complete exactly one orbit as measured against the stars; about 20 minutes longer than the tropical year on which our calendar is based. Tropic year: The time from one spring equinox to the next, on which our calendar is based. d. A planet's sidereal period: of a planet) A planet's actual orbital period around the Sun (90). Synodic Period:(of a planet) The time between successive alignments of a planet and the Sun in our sky; measured from opposition to opposition for a planet beyond Earth's orbit, or from superior conjunction to superior conjunction for Mercury and Venus.
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).
4. What is a lunar calendar? How can it be kept roughly synchronized with a solar calendar?
lunar calendar have 29 days and others have 30 days, so that the average matches the 29 -day lunar cycle. A 12 month lunar calendar has only 354 or 355 days, or about 11 days fewer than a calendar based on the Sun (59, 60). It's synchronized with the solar calendar by roughly synchronized with solar calendars by taking advantage of an interesting coincidence: 19 years on a solar calendar is almost precisely 235 months on a lunar calendar. As a result, the lunar phases repeat on the same dates about every 19 years (a pattern known as the Metonic cycle) (60).
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
