Astronomy final exam week 1-3

Based on what you know about Newton and gravity, select all of the correct statements from the following list: - An object in a uniform circular orbit is not accelerating. - Forces always occur in pairs. - Changes in motion require force. - A change in motion is called acceleration. - Since Earth is much more massive, it exerts more gravitational force on the Moon than the Moon does on Earth. This is why the Moon orbits Earth and not vice-versa. - The force of gravity is directly proportional to the distance between the objects exerting the gravity.

- Forces always occur in pairs. - Changes in motion require force. - A change in motion is called acceleration.

Select the following statements that are true relating to the moons cycle of phases: - The moon orbits eastward around Earth once every 29.53 days. - Lunar eclipses happen infrequently—usually once every few years or so. - Quarter phases occur between the new and full phases. - The moon's phase changes because the moon rotates on its axis, causing differing parts of the side illuminated by the sun to face Earth. - The lunar phase changes as the moon passes in and out of Earth's shadow. - During the new phase, no direct sunlight reaches the side of the moon facing Earth. - Since a full moon occurs when the moon is on the opposite side of Earth as the sun, it is only visible at night.

- Quarter phases occur between the new and full phases. - During the new phase, no direct sunlight reaches the side of the moon facing Earth. - Since a full moon occurs when the moon is on the opposite side of Earth as the sun, it is only visible at night.

Select the following statements that are true the sky and the celestial sphere: - The apparent rotation of the sphere is caused by Earth's rotation. - The celestial equator is an imaginary line in the sky directly above Earth's equator. - The celestial sphere is still useful even though it is no longer accepted as physical reality. - From knowing the angular distance between two stars on the celestial sphere one can find the actual distance between them. - Precession is literally a wobbling of Earth's rotational axis. At one time or another all of the celestial sphere will be visible from a given location. - The angular distance of the celestial north pole from the horizon is equal to half your latitude.

- The apparent rotation of the sphere is caused by Earth's rotation. - The celestial equator is an imaginary line in the sky directly above Earth's equator. - The celestial sphere is still useful even though it is no longer accepted as physical reality. - Precession is literally a wobbling of Earth's rotational axis.

Select the following statements that are true about the cycles of the sun: - The constellations that lie along the ecliptic are those of the zodiac. - The ecliptic is a real path that the sun actually follows. - Due to the tilt of the ecliptic, the sun is only visible in the northern hemisphere for half the year and the southern hemisphere half the year - Only the sun being higher in the sky causes warmer weather; the amount of time it is above the horizon has nothing to do with it. - In the summer the sun is higher in the sky than in the winter. -The ecliptic's tilt is caused by the tilt of Earth's rotational axis. - In the summer the sun is above the horizon longer than in the winter.

- The constellations that lie along the ecliptic are those of the zodiac. - In the summer the sun is higher in the sky than in the winter. - The ecliptic's tilt is caused by the tilt of Earth's rotational axis. - In the summer the sun is above the horizon longer than in the winter.

Select the following statements that are true about the relative sizes of objects and the distances between them: - The sun is about 100 times the diameter of Earth. - The solar system is part of our galaxy. - Earth is about 4 times the diameter of the moon. - The sun is actually very large for a star.Galaxies are the largest objects in the universe. - Our galaxy is thousands of light-years across. - Clouds, filaments, and walls are structures within galaxies.

- The sun is about 100 times in the diameter of earth - the solar system is part of our galaxy - earth is about 4 times the diameter of the moon - our galaxy is thousands of light-years across

Select the following statements that are true about how astronomers talk about huge astronomical distances: - Scientific notation is used for very large numbers, but not very small numbers. - A light-year is larger than an astronomical unit.Astronomers use the metric system for calculations. - The distances to stars are measured in light years. - A light-year is the time light takes to travel one astronomical unit. - The metric system is more complex than the English system. - The astronomical unit is the distance across the solar system.

- a light-year is larger than a astronomical unit -astronomers use the metric systems for calculations - the distances to stars are measured in light years

Select the following statements that are true about where Earth is in relation to the sun, other planets and galaxies: - The sun is not part of the Milky Way. - Earth and most of the other planets orbit the sun in nearly circular elliptical orbits. - Galaxies are composed of billions of stars. - Clouds, filaments, and walls are structures within galaxies. - Earth rotates around the sun, which is the reason we see the sun rise and set. - The Milky Way is a spiral galaxy. - The sun is a star.

- earth and most of the other planets orbit the sun in nearly circular elliptical orbits - galaxies are composed of billions of stars - the Milky Way is a spiral galaxy - the sun is a star

1) Why do solar eclipses happen only at new moon? 2) Why not every new moon?

1) Since the shadow of the Moon extends directly away from the Sun, a solar eclipse can occur only when the Moon is between the Earth and the Sun. 2) Solar eclipses don't occur every new moon because of the Moon's orbital tilt.

Kepler's Second Law

As a planet moves around its orbit, it sweeps out equal areas in equal times

Why is the amount of solar heating less on a clear day in January at northern latitudes than on a clear day in July?

Both the sun is above the horizon for less than 12 hours in January in the north and at low sun angles, the received sunlight is spread over a larger surface area.

What is responsible for the observed motion of a star along the celestial equator?

Earth's rotation on its axis.

Which of the following statements about eclipses of the Sun is true? - The ancient Greeks and Romans could not see eclipses of the Sun, they are a modern sight that's only become visible to us recently - For a total eclipse of the Sun to happen, the Moon must get directly in front of the Sun, as seen from Earth - An eclipse of the Sun is visible somewhere on Earth each month. - When a total eclipse of the Sun is visible, it can be seen over half the Earth each time - During a total eclipse of the Sun, the Sun moves into the Earth's shadow

For a total eclipse of the Sun to happen, the Moon must get directly in front of the Sun, as seen from Earth

You are sitting next to a person who has twice as much weight. You get up and move one seat over, doubling your distance from them. Did the gravitational force between you increase, decrease, or stay the same?

Gravitational force decreased.

Why does the sun move relative to the stars as observed from Earth?

It is due to Earth revolving around the sun.

The Earth is closest to the Sun in which month of the year?

January

The scientist who formulated the three laws of planetary motion by analyzing the data on the precise location of planets in the sky was _____.

Johannes Kepler

Why did Newton conclude that gravity has to be mutual and universal?

Newton's third law stated that for every action there is an equal and opposite reaction = gravity must be mutual. ...the Sun, the planets, and all their moons attract each other- must be mutual gravitation = so it is universal

When it is autumn in Asia, what season is it in Antarctica? (Hint: Consider a world map.)

Spring

In Ptolemy's model, how do the epicycles of Mercury and Venus differ from those of Mars, Jupiter, and Saturn?

The epicycles of Mercury and Venus were attached to a line joining Earth and the Sun. The epicycles of Mars, Jupiter, and Saturn revolved around Earth independently of the Sun.

Kepler's First Law

The orbit of each planet around the Sun is an ellipse with the Sun at one focus.

Kepler's Third Law

The square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit.

What is the difference between speed and velocity?

The velocity of an object indicates both the object's speed (rate of motion) and its direction of motion.

The 17th century astronomer who kept a roughly 20 year continuous record of the positions of the Sun, Moon, and planets was _____.

Tycho Brahe

Week 1

Week 1

Week 2

Week 2

Why can't the Moon be eclipsed when it is halfway between the nodes of its orbit?

When the Moon is halfway between the nodes, it would be approximately 5° above or below the ecliptic, and hence, could not be directly opposite the Sun.

Does Tycho's model of the Universe explain the phases of Venus that Galileo observed? Why or why not?

Yes. In Tycho's model all planets except Earth orbit the Sun, and the Sun orbits Earth once each day. In this model Venus shows a full set of phases.

Which statement below best describes the difference between your mass and your weight?

Your mass is a measure of the amount of matter that you contain and your weight is a measure of the amount of gravitational pull that you experience.

Newton showed that to change the direction in which an object is moving, one needs to apply _____.

a force

From a particular location on Earth, why can we see many more total eclipses of the Moon than total eclipses of the Sun?

a total lunar eclipse is visible over a much larger part of the Earth's surface than a total solar eclipse

a) Why did Copernicus have to keep small epicycles in his models? b) Which planet has the longest duration of retrograde motion as viewed from Earth? c) Which planet has the shortest duration of retrograde motion as viewed from Earth?

a) His model did not predict planetary positions as well as the Ptolemaic system. b) Neptune c) Mars

a) What did Plato propose about all heavenly motion? b) Why did Plato propose what he did about heavenly motion and the shape of heavenly objects? c) What effect did Plato's proposal have on future astronomers?

a) It is in circular paths. b) because he believed the sphere to be the most perfect geometrical form c) His idea of a sphere being the most perfect geometric form influenced astronomical theories for literally hundreds of years.

a)How does Kepler's first law of planetary motion overthrow one of the basic beliefs of classical astronomy? b)How about Kepler's second law?

a) Kepler's first law says that the orbits of the planets are ellipses, rather than perfect circles or series of epicycles. b) Kepler's second law says that the planets speed up and slow down during their orbits, rather than remain in uniform motion.

a) A car is on a circular off ramp of an interstate and is traveling at exactly 25 mph around the curve. Does the car have velocity? b) Does the car have acceleration? c) Is the car decelerating?

a) Yes b) Yes c) No

Explain how each of Galileo's telescopic discoveries contradicted the Ptolemaic theory: a) Surface features on the Moon: b) Stars that are too faint to be seen with the naked eye: c) The moons of Jupiter: d) Sunspots: e) The phases of Venus:

a) showed that a heavenly body could be imperfect b) does not support or contradict the Ptolemaic theory c) showed that a heavenly body could have satellites d) showed that a heavenly body could be imperfect e) showed that a planet orbited the Sun

At what location on Earth is an observer that has the South Celestial Pole directly overhead?

at Earth's South Pole (90 degrees South latitude)

At what location on Earth is an observer that has the Celestial Equator pass through the point directly overhead?

at Earth's equator (0° latitude)

According to Kepler's third law, there is a relationship between the time a planet takes to revolve around the Sun and its _____.

distance from the Sun

The way scientists know that a hypothesis in astronomy is a reasonable description of nature is to _____.

do experiments and observations about the predictions of the hypothesis

The five naked-eye planets and three telescopic planets that wander among the stars in the sky are always near which of the following?

ecliptic

By the term universe, astronomers mean _____.

everything that we can observe

When a planet, in its orbit, is closer to the Sun, it _____.

moves faster than average

If you could see the sun and stars during the daytime for several weeks, you would notice that the sun does which of the following?

moves slowly eastward relative to the stars

What phase of the Moon must it be to have a solar eclipse?

new moon

When the Sun and Moon are lined up and pull together, the tides they raise are called _____.

spring tides

If the tilt of Earth's axis were to change from 23.5 degrees to 0 degrees, what celestial circles would coincide for all observers?

the Celestial Equator and the Ecliptic

Why does the Moon show phases in the course of a month?

the angle the Moon makes with the Sun changes and we see differing amounts of reflected sunlight

Which of the following descriptions is a definition of an astronomical unit (AU)? - one ten-millionth of the distance between the equator and the North Pole - the average distance between Earth and the sun - the distance between the sun and Proxima Centauri - the distance that light travels in one year - the distance between the king's nose and the tip of his middle finger

the average distance between Earth and the sun

The period of the moon's rotation on its axis is _____.

the same as its revolution around the Earth

The seven days of the week are named after _____.

the seven "wandering" objects in the Sky that were visible to the ancients

Which of the following is the Earth NOT located in? -The Virgo supercluster - the Local Group of galaxies -the solar system - the Milky Way Galaxy - we are located in all of the above

we are located in all of the above

week 3

week 3

A single star in the process of forming starts by spinning slowly (while it is quite large and relatively cool.) As the star collapses under the pull of its own gravity, its size decreases. As a result, its rate of spinning _____.

will increase