Astronomy exam 1

If the United States obtained all its energy from oil, how much oil would be needed each year?

1 x 10^13 liters

Consider the indicated events in the history of the universe that have helped make human life possible. Rank the events based on when they occurred, from longest ago to most recent. To rank items as equivalent, overlap them. Note: If two events occurred within seconds of each other, rank them as equivalent.

1. The Big Bang, The Universer Begins to Expand 2. Elements like Carbon and Oxygen begin to exist 3. Nuclear fusion begins in the Sun 4.Earliest life on Earth 5. Dinosaurs go extinct 6. Earliest humans

Both models

1. moon rises in east, sets in west each day 2. a distant galaxy rises in east, sets in west each day 3. stars circle daily around north or south celestial pole

Sun-centered only

1. positions of nearby stars shift slightly back and forth each year 2. mercury goes through a full cycle of phases

1 light-hour in kilometers

1.08 x 10^9 km

1 light-minute in miles

1.12 x 10^7 mi

How far would it be from the Milky Way Galaxy to the most distant galaxies in the observable universe on this scale?

1.4 km

1 light-day in miles

1.61 x 10^10 mi

1 light-minute in kilometers

1.80 x 10^7 km

1 light-second in miles

1.86 x 10 ^5 mi

1 light-day in kilometers

2.59 x 10^10 km

Suppose we wanted to make a scale model of the Local Group of Galaxies, in which the Milky Way Galaxy was the size of a marble (about 1 cmcm in diameter). How far from the Milky Way Galaxy would the Andromeda Galaxy be on this scale?

25 cm

1 light-second in kilometers

3.00 x 10^5 km

The acceleration of gravity on Earth is approximately 10 m/s2 (more precisely, 9.8 m/s2). If you drop a rock from a tall building, about how fast will it be falling after 3 seconds?

30 m/s

How far would the Sun be from Alpha Centauri on this scale?

4.4×10−5cm

Compare the energy of a 1-megaton hydrogen bomb to the energy released by a major earthquake.

5

1 light-hour in miles

6.72 x 10^8 mi

Which person is weightless?

A child in the air as she plays on a trampoline.

Precession

A slow motion of Earth's axis that traces out a cone over a period of 26,000 years

The following diagrams are the same as those from Part A. This time, rank the pairs from left to right based on the size of the acceleration the asteroid on the left would have due to the gravitational force exerted on it by the object on the right, from largest to smallest.

According to Newton's second law, the asteroid with the largest acceleration will be the one that has the strongest gravitational force exerted on it by the object on the right. That is why the ranking here is the same as the ranking for Part A.

If you wanted to document the apparent retrograde motion of Mars, you would need to measure and record Mars's position among the constellations over a period of several months.

Apparent retrograde motion can be observed by noticing changes in Mars's position among the constellations. Note that a complete period of apparent retrograde motion unfolds while Earth moves a significant fraction of its orbit, which takes several months.

If you actually performed and compared the two trials chosen in Part C, you would find that, while the basketball and marble would hit the ground at almost the same time, it would not quite be exact: The basketball would take slightly longer to fall to the ground than the marble. Why?

Because air resistance has a greater effect on the larger ball. The larger size and lower density of the basketball means it will encounter more air resistance than the marble, so it will take slightly longer to reach the ground.

Earth is slightly closer to the Sun in January than in July. How does the area swept out by Earth's orbit around the Sun during the 31 days of January compare to the area swept out during the 31 days of July?

Both areas are the same. Kepler's second law tells us that a planet always sweeps out equal areas in equal times. Therefore, Earth sweeps out the same area in any 31-day period, no matter what month it is.

Assume you have completed the two trials chosen in Part A. Which of the following possible outcomes from the trials would support Newton's theory of gravity? Neglect effects of air resistance.

Both balls fall to the ground in the same amount of time. Newton's theory of gravity predicts that, in the absence of air resistance, all objects on Earth should fall with the same acceleration of gravity, regardless of mass. This means that balls dropped from the same height should take the same amount of time to reach the ground.

Consider the statement "There's no gravity in space." This statement is:

Completely false.

Sun Centered Model

Copernicus's model, with the planets moving around the sun

Earth Centered Model

Early Greeks thought planets the sun moon and stars rotated around the earth

What is really happening in space during the periods when we see Mars going through apparent retrograde motion?

Earth is passing by Mars in its orbit around the Sun- As the video shows, Mars's periods of apparent retrograde motion begin as Earth approaches the orbital position where it will pass Mars and end after Earth has passed Mars. In other words, apparent retrograde motion occurs as Earth "laps" Mars in their respective orbits around the Sun.

Kepler's first law states that the orbit of each planet is an ellipse with the Sun at one focus. Which of the following statements describe a characteristic of the solar system that is explained by Kepler's first law? Earth is slightly closer to the Sun on one side of its orbit than on the other side. All the planets orbit the Sun in nearly the same plane. Inner planets orbit the Sun at higher speed than outer planets. Pluto moves faster when it is closer to the Sun than when it is farther from the Sun. Venus orbits the Sun faster than Earth orbits the Sun. The Sun is located slightly off-center from the middle of each planet's orbit.

Earth is slightly closer to the Sun on one side of its orbit than on the other side. The Sun is located slightly off-center from the middle of each planet's orbit. None of the planets has a perfectly circular orbit, which means that all planets (including Earth) are closer to the Sun on one side of their orbit than on the other. The Sun's off-center position arises because it is located at a focus of each planet's elliptical orbit, rather than at the center of the ellipse.

According to the law of universal gravitation, what would happen to Earth if the Sun were somehow replaced by a black hole of the same mass?

Earth's orbit would not change.

Observations: a. Stars can shine brightly for billions of years. b. The Andromeda Galaxy is similar in structure to our own Milky Way. c. All planets orbit the Sun in the same direction and nearly the same plane. d. More distant galaxies are moving away from us faster than nearby galaxies.

Explanations: a. The universe is expanding because it began with a Big Bang. b. The Andromeda and Milky Way galaxies formed in the same way. c. Stars shine with energy generated by nuclear fusion in their cores. d. The orderly orbits of planets arose from their formation in a rotating gas cloud. The distinction between an observation and an explanation is very important in science, but keep in mind that it can sometimes be a bit fuzzy. For example, we have classified the statement "Stars can shine brightly for billions of years" as an observation because we have observational techniques (covered later in your textbook) that allow us to measure the ages of stars; in contrast, although the statement "Stars shine with energy generated by nuclear fusion in their cores" is consistent with many observations, our conclusion that the energy source is fusion depends on our understanding of the physics that should occur inside stars. Note also that our ideas of observation and explanation can change with time. For example, the statement "Earth orbits the Sun" is something we now consider an observed fact, but in the past it would have been considered only one potential explanation for what we see in the sky (and an alternate explanation of "everything orbits Earth" was favored for thousands of years).

True Moon rises in east, sets in west Mercury goes through a full cycle of phases stars circle daily around north or south celestial pole positions of nearby stars shift slightly back and forth each year a distant galaxy rises in east, sets in west each day

False we sometimes see a crescent Jupiter a planet beyond Saturn rises in west, sets in east

If you want to make a rocket turn left, you need to:

Fire an engine that shoots out gas to the right.

When a spinning ice skater pulls in his arms, he spins faster because _________.

His angular momentum must be conserved, so reducing his radius must increase his speed of rotation.

Kepler's third law states that a planet's orbital period, p, is related to its average (semimajor axis) orbital distance, a, according to the mathematical relationship p2=a3p2=a3. Which of the following statements describe a characteristic of the solar system that is explained by Kepler's third law? Pluto moves faster when it is closer to the Sun than when it is farther from the Sun. Inner planets orbit the Sun at higher speed than outer planets. Venus orbits the Sun faster than Earth orbits the Sun. The Sun is located slightly off-center from the middle of each planet's orbit. Earth is slightly closer to the Sun on one side of its orbit than on the other side. All the planets orbit the Sun in nearly the same plane.

Inner planets orbit the Sun at higher speed than outer planets. Venus orbits the Sun faster than Earth orbits the Sun. From the relationship p2=a3p2=a3, it follows that planets closer to the Sun must orbit at higher average speeds than planets farther from the Sun. For example, Venus must orbit the Sun faster than Earth because Venus is closer to the Sun.

Why is Newton's version of Kepler's third law so useful to astronomers?

It can be used to determine the masses of many distant objects.

Chapter 3 What practical value did astronomy offer to ancient civilizations?

It helped them keep track of time and seasons, and it was used by some cultures for navigation.

Which of the following planets has essentially no seasons at all? Uranus (axis tilt = 97.9°) Neptune (axis tilt = 29.6°) Jupiter (axis tilt = 3.1°) Mars (axis tilt = 25.2°)

Jupiter (axis tilt = 3.1°)

Choose the correct definition and two examples of kinetic energy.

Kinetic energy is the energy an object has due to its motion. Two examples are a car driving down the highway or the movements of the molecules of liquid in a cup of hot coffee.

All of the following statements are true. Which one can be explained by Kepler's second law?

Mars moves faster in its orbit when it is closer to the Sun than when it is farther from the Sun. Kepler's second law tells us that a planet moves faster in its orbit when it is closer to the Sun (near perihelion) than when it is farther (near aphelion). This law applies to all planets and therefore explains the statement about Mars.

At most times, Mars appears to move eastward relative to the stars. The exceptions are during its periods of apparent retrograde motion, when Mars appears to move westward relative to the stars.

Most of the time stars move westward in the video, which means Mars is moving eastward relative to them. But if you play the entire video, you'll see three periods of apparent retrograde motion, during which the stars turn around and move eastward, meaning that Mars moves westward relative to the stars.

Which of the following planets should have the most extreme seasons? Mars (axis tilt = 25.2°)Uranus (axis tilt = 97.9°)Jupiter (axis tilt = 3.1°)Neptune (axis tilt = 29.6°)

Neptune (axis tilt = 29.6°)

The following diagrams are the same as those from Part A. Again considering only the two objects shown in each pair, this time rank the strength, from strongest to weakest, of the gravitational force acting on the object on the right.

Newton's third law tells us that the gravitational force exerted on the asteroid on the left by the object on the right will be equal in magnitude, but opposite in direction to the gravitational force exerted on the object on the right by the asteroid on the left. That is why the ranking here is the same as the ranking for Part A.

The Sun-centered system offers a simple explanation for observations of apparent retrograde motion. Should these facts alone have been enough to convince the ancient Greeks that Earth really does go around the Sun?

No, because the Greeks had an Earth-centered model that also accounted for apparent retrograde motion-In their Earth-centered model, the Greeks explained retrograde motion by imagining that planets moved around small circles that in turn moved around larger circles around Earth. Because this model made reasonably accurate predictions of planetary positions and fit with other philosophical ideas that they held, the Greeks had no compelling reason to reject it, even though the Sun-centered model offered a simpler explanation for apparent retrograde motion.

Kepler's second law states that as a planet orbits the Sun, it sweeps out equal areas in equal times. Which of the following statements describe a characteristic of the solar system that is explained by Kepler's second law? Pluto moves faster when it is closer to the Sun than when it is farther from the Sun. Earth is slightly closer to the Sun on one side of its orbit than on the other side. Inner planets orbit the Sun at higher speed than outer planets. All the planets orbit the Sun in nearly the same plane. The Sun is located slightly off-center from the middle of each planet's orbit. Venus orbits the Sun faster than Earth orbits the Sun.

Pluto moves faster when it is closer to the Sun than when it is farther from the Sun. The same ideas holds for any object orbiting the Sun: An object must move faster when it is closer to the Sun and slower when it is farther from the Sun.

Choose the correct definition and two examples of potential energy.

Potential energy is energy that is stored. Two examples of potential energy are breakfast cereal, which has chemical potential energy, and a heavy book on the top shelf at the library, which has gravitational potential energy.

Choose the correct definition and two examples of radiative energy

Radiative energy is energy in light. Sunlight carries this form of energy, as do other forms of light including X-rays and radio waves.

apparent retrograde motion

Retrograde motion is an APPARENT change in the movement of the planet through the sky. It is not REAL in that the planet does not physically start moving backwards in its orbit. It just appears to do so because of the relative positions of the planet and Earth and how they are moving around the Sun.

Einstein's theory, like Newton's, predicts that, in the absence of air resistance, all objects should fall at the same rate regardless of their masses. Consider the following hypothetical experimental results. Which one would indicate a failure of Einstein's theory?

Scientists dropping balls on the Moon find that balls of different mass fall at slightly different rates. Dropping the balls on the Moon removes any potential effects due to air resistance, so a result in which mass affects the rate of fall would directly contradict the prediction of Einstein's (as well as Newton's) theory.

Which of the following is a general difference between a planet and a star?

Stars glow in infrared and visible light, while planets glow only in the infrared.

What does the fact that we always see the same face of the Moon tell us?

The Moon rotates with the same period that it orbits Earth.

Rank the following items according to their size (diameter) from left to right, from largest to smallest.

The Universe The local supercluster The local group The milky way galaxy Our solar system The Sun Jupiter Earth

Which of the following statements does NOT use the term angular size or angular distance correctly? The angular distance between those two houses in the distance is 30 degrees. You can use your outstretched hand against the sky to estimate angular sizes and angular distances. The angular size of the Sun is about the same as that of the Moon. The angular distance between those two bright stars in the sky is about 2 meters.

The angular distance between those two bright stars in the sky is about 2 meters.

You discover an asteroid that orbits the Sun with the same 1-year orbital period as Earth. Which of the following statements must be true? The asteroid shares the same orbit around the Sun as Earth. The asteroid will eventually collide with Earth. The asteroid has a more eccentric orbit than Earth. The asteroid has the same perihelion distance as Earth. The asteroid's average (semimajor axis) distance from the Sun is 1AU.

The asteroid's average (semimajor axis) distance from the Sun is 1AU. - Kepler's third law tells us that an object's average orbital distance can be calculated from its orbital period using the formula p^2=a^3 (where p is the planet's orbital period in years and a is its average orbital distance in AU ). Therefore, all objects that share Earth's orbital period of 1 year must also share Earth's average orbital distance of 1AU .

Which of the following examples describes a situation where a car is experiencing a net force?

The car is making a gradual turn.

Precession, and the correct explanation of how does it affect what we see in our sky?

The direction in which Earth's rotation axis points in space changes slowly over the centuries, and we call this change "precession." Because of this movement, the celestial poles and therefore the pole star change slowly in time.

your weight will be greater than normal when the elevator is moving upward with increasing speed. For which of the following other motions would your weight also be greater than your normal weight?

The elevator moves downward while slowing in speed. In a downward-moving elevator, the elevator can be slowing only if it has an upward acceleration. As you know from Part A, an upward acceleration will give you an increased weight. Therefore, in an elevator that moves downward while slowing in speed, the acceleration is upward and your weight is greater than normal.

Consider a time when Mars is in the middle of one of its periods of apparent retrograde motion. During this time, Mars appears brightest in our night sky and crosses the meridian around midnight.

The middle of a period of apparent retrograde motion occurs when Mars is closest to Earth in its orbit and in a full phase as viewed from Earth, which is why it is brightest in our sky at that time. It is also directly opposite the Sun in the sky at that time, which is why it crosses the meridian at midnight.

Each diagram shows a single experimental trial in which you will drop a ball from some height. In each case, the ball's size, mass, and height are labeled. Note that two diagrams show a basketball, one diagram shows a bowling ball of the same size but larger mass, and one diagram shows a much smaller marble with the same mass as the basketball. You have a timer that allows you to measure how long it takes the ball to fall to the ground. Which pair of trials will allow you to test the prediction that an object's mass does not affect its rate of fall?

The simplest way to test the effects of mass is to compare the results of two trials that are identical except for the mass of the balls. In the language of experimental design, we say that the mass is the "variable of interest" for this experiment, and we therefore hold the other variables (size and height) constant so that they cannot affect the results.

Which of the following best describes why we have seasons on Earth?

The tilt of Earth's axis causes different portions of Earth to receive more or less direct sunlight at different times of year.

Consider again the experimental trials from Part A. This time, you wish to test how the size of an object affects the rate of its fall. Which pair of trials should you compare?

The variable of interest is now size, so appropriate trials to compare are those in which size differs but other variables are constant.

Which of the following best describes the fundamental difference between two different chemical elements (such as oxygen and carbon)?

They have different numbers of protons in their nucleus

Which of the following can you observe about Venus with the naked eye? Select all that apply. Venus is visible at midnight when it is in its full phase When Venus is brightest, it is visible all night long Venus sometimes shines brightly in the western sky shortly after sunset Venus sometimes shines brightly in the eastern sky shortly before dawn

Venus sometimes shines brightly in the western sky shortly after sunset Venus sometimes shines brightly in the eastern sky shortly before dawn Venus always remains close to the Sun in our sky. Therefore, when it is visible, it is either in the evening sky for up to a few hours after sunset or in the morning sky for up to a few hours before dawn.

As the Moon orbits, What do we see from Earth that occurs for the same reason?

We always see the same face of the Moon - the Moon rotates exactly once for each orbit around Earth, which is an example of what we call synchronous rotation.

If stars existed but galaxies did not:

We would not exist because we are made of material that required recycling in galaxies.

Suppose you are in an elevator car when the elevator cable breaks. Which of the following correctly describes what happens and why.

You float weightlessly within the elevator car because you and the elevator both begin to accelerate downward at the same rate Once the cable breaks, you and the elevator car both fall with the acceleration of gravity. This means you are no longer pressing against the scale or the elevator floor, so you float weightlessly within the car -- though only until you and the car hit the ground!

Chapter 4 Suppose you lived on the Moon. Which of the following would be true? Your mass would be less than your mass on Earth, but your weight would be the same as it is on Earth. Your weight would be less than your weight on Earth, but your mass would be the same as it is on Earth. Both your weight and your mass would be less than they are on Earth. Both your weight and your mass would be the same as they are on Earth.

Your weight would be less than your weight on Earth, but your mass would be the same as it is on Earth.

Falsifiability

a feature of a scientific theory, in which it is possible to collect data that will prove the theory wrong a scientific claim is falsifiable if it could in principle be shown to be false by observations or experiments, even if those observations or experiments have not yet been performed.

Meridian

a line of longitude

In science, a broad idea that has been repeatedly verified so as to give scientists great confidence that it represents reality is called _________.

a theory

According to current scientific estimates, when did the Big Bang occur?

about 14 billion years ago-Scientists estimate the age of the universe by measuring the expansion rate, from which they can determine how long it has taken the universe to reach its current size. Current estimates put this age at about 14 billion years.

The Andromeda Galaxy is faintly visible to the naked eye. When you look at the Andromeda Galaxy, the retina of your eye is absorbing light that has traveled through space for ______ to reach you.

about 2 ½ million years - The distance to the Andromeda galaxy is about 2 ½ million light-years, which means light takes about 2 ½ million years to travel from the Andromeda galaxy to us. Therefore, the light that you see from Andromeda travelled through space for 2 ½ million years before being absorbed by your retina.

On a scale where the Sun is about the size of a grapefruit and the Earth is about 15 meters away, how far away are the nearest stars besides the Sun?

about the distance across the United States

Suppose that someone in the Andromeda galaxy had a super-telescope through which they were looking at Earth right now. They would see Earth ______.

as it was about 2 ½ million years ago- The approximately 2 ½-million-light-year distance between Earth and the Andromeda galaxy means that light takes about 2 ½ million years to travel this distance. Therefore, just as we see the Andromeda galaxy as it was about 2 ½ million years ago, someone looking right now from Andromeda would see us as we were about 2 ½ million years ago.

The following five diagrams show pairs of astronomical objects that are all separated by the same distance ddd. Assume the asteroids are all identical and relatively small, just a few kilometers across. Considering only the two objects shown in each pair, rank the strength, from strongest to weakest, of the gravitational force acting on the asteroid on the left

asteroid - sun asteroid- earth asteroid-moon asteroid-asteroid asteroid-atom Because the distance is the same for all five cases, the gravitational force depends only on the product of the masses. And because the same asteroid is on the left in all five cases, the relative strength of gravitational force depends on the mass of the object on the right. Continue to Part B to explore what happens if we instead ask about the gravitational force acting on the object on the right.

Scientific thinking is _________.

based on everyday ideas of observation and trial-and-error experiments

Which of the following lies in the ecliptic plane? a. A line connecting Earth and Polaris b. Earth's equator c. Earth's orbital path around the Sun d. A line connecting Earth's north and south poles

c. Earth's orbital path around the Sun- The ecliptic plane is defined by Earth's orbital path around the Sun.

What is the circumference of Tirth?

circumference of Tirth = 2.6×10^4 km

In January, Earth's rotation axis points in the direction of the star Polaris. Where does it point in July? a. Toward the star Sirius b. Toward a star 47° away from Polaris c. Toward a star 23 ½° away from Polaris d. Toward the star Polaris

d. Toward the star Polaris- Earth's axis does not noticeably change its orientation in space over the course of each year, so it remains pointed toward Polaris at all times. Note: The axis is not quite perfectly pointed at Polaris, but points within 1° of it. Moreover, as you'll learn in Chapter 2, the orientation of Earth's axis in space gradually changes due to a motion known as precession. However, the rate of precession is so slow that it would take several centuries before the change was noticeable to the naked eye.

According to the universal law of gravitation, if you triple the distance between two objects, then the gravitational force between them _________.

decreases by a factor of 9

We divide the electromagnetic spectrum into six major categories of light, listed below. Rank these forms of light from left to right in order of increasing wavelength. To rank items as equivalent, overlap them.

gamma rays X rays ultraviolet visible light infrared radio waves Notice that these wavelengths span an enormous range. The wavelengths of gamma rays can be smaller than the size of an atomic nucleus, while the wavelengths of radio waves can be many meters (or even kilometers) long. Visible light spans only a very narrow range of wavelengths, from about 400 nanometers at the blue (violet) end to about 700 nanometers at the red end.

Which Venus phase would be impossible to see (from Earth) if Venus orbited Earth as described in Ptolemy's Earth-centered model?

gibbous (nearly full) Phases that show more than a crescent are not possible in Ptolemy's Earth-centered model, so a gibbous or full Venus could never occur if Venus orbited Earth.

Suppose you are in an elevator. As the elevator starts upward, its speed will increase. During this time when the elevator is moving upward with increasing speed, your weight will be __________.

greater than your normal weight at rest- Increasing speed means acceleration, and when the elevator is accelerating upward you will feel a force pressing you to the floor, making your weight greater than your normal (at rest) weight.

On the cosmic calendar, which compresses the history of the universe into a single year, about when did life arise on Earth?

in September-Earth formed in early September on the cosmic calendar. Life apparently arose on Earth within less than a billion years after that, which means it was still in September (because each month on the cosmic calendar represents about 1.2 billion years).

On the cosmic calendar, which compresses the history of the universe into a single year, about when did Earth form?

in early September-The cosmic calendar compresses the 14-billion-year history of the universe into 1 year, which means that each month represents about 1.2 billion years. The solar system's age of 4 ½ billion years therefore puts its birth in early September.

When Einstein's theory of gravity (general relativity) gained acceptance, it demonstrated that Newton's theory had been:

incomplete

Chapter 5 Which forms of light are lower in energy and frequency than the light that our eyes can see?

infrared and radio

We never see a crescent Jupiter from Earth because Jupiter __________.

is farther than Earth from the Sun An object must come between Earth and the Sun for us to see it in a crescent phase, which is why we see crescents only for Mercury, Venus, and the Moon.

Angular distance

is the angle of length between the two directions originating from the observer and pointing toward these two objects.

If the Sun rises precisely due east,

it must be the day of either the spring or fall equinox.

On the cosmic calendar, which compresses the history of the universe into a single year, about when did early humans first walk on Earth?

just a few hours before midnight on December 31- The cosmic calendar compresses the 14-billion-year history of the universe into 1 year, which means that each day represents about 1/365 of 14 billion years, or about 40 million years. Early humans arose just a few million years ago, which therefore means just a few hours before the present moment (the stroke of midnight on December 31) on the cosmic calendar.

Suppose you are in an elevator that is moving upward. As the elevator nears the floor at which you will get off, its speed slows down. During this time when the elevator is moving upward with decreasing speed, your weight will be __________.

less than your normal weight at rest- Even though the elevator is still moving upward, the fact that its speed is slowing means that the acceleration is downward. The situation is rather like that of a ball that is still on its way up after you throw it: the ball slows as it goes upward because of the downward acceleration of gravity. Because the acceleration of the elevator is downward, your weight is lower than normal.

Two stars that are in the same constellation:

may actually be very far away from each other. Submit

In Ptolemy's Earth-centered model, when would Venus appear directly behind the Sun as viewed from Earth?

never In the Earth-centered model, Venus always remains somewhere between Earth and the Sun, and never appears behind the Sun in our sky.

Chapter 2 Which of the following celestial objects do NOT rise in the east and set in the west, as viewed from the Earth? (Assume that all of these objects are visible from your location on Earth, and that none of them are circumpolar.) galaxies stars the Sun the MoonAll of these objects rise in the east and set in the west.

of these objects rise in the east and set in the west.

The term observable universe refers to _________.

that portion of the universe that we can see in principle, given the current age of the universe

Consider Earth and the Moon. As you should now realize, the gravitational force that Earth exerts on the Moon is equal and opposite to that which the Moon exerts on Earth. Therefore, according to Newton's second law of motion __________.

the Moon has a larger acceleration than Earth, because it has a smaller mass Newton's second law of motion, F=ma, means that for a particular force F, the product mass x acceleration must always be the same. Therefore if mass is larger, acceleration must be smaller, and vice versa.

Angular size

the angle an object appears to span in your field of view

When you are standing on a scale in an elevator, what exactly does the scale measure?

the force you exert on the scale Your presence in an elevator cannot change either your mass or the gravitational force exerted on you by Earth. The scale measures the force that is exerted on it, which in an elevator is a combination of the force due to gravity and a force due to the elevator's acceleration.

Perihelion

the point in the orbit of a planet, asteroid, or comet at which it is closest to the sun.

Consider the hypothetical observation "a planet beyond Saturn rises in west, sets in east." This observation is not consistent with a Sun-centered model, because in this model __________.

the rise and set of all objects depends only on Earth's rotation Earth rotates from west to east, so objects in the sky must appear to go across our sky from east to west.

law of universal gravitation

the scientific law that states that every object in the universe attracts every other object

Which of the following best describes what we mean by the universe?

the sum total of all matter and energy

Suppose that two objects collide. Which of the following things is NOT the same both before and after the collision?

the total temperature of the objects

The ancient Greeks get a lot of attention for their contributions to science because _________.

they were the first people known to try to explain nature with models based on reason and mathematics, without resort to the supernatural

Neither model

we sometimes see a crescent jupiter

The star Betelgeuse is about 600 light-years away. If it explodes tonight,

we won't know about it until about 600 years from now.

Compare the Sun's annual energy output to the energy released by a supernova.

~10^11