Astronomy Practice Questions & Homework - Chapter 02

Based on what you have learned from your rankings in Parts A and B, why is it generally hotter in summer than in winter? A. The Sun is higher in the sky in summer. B. Earth rotates more rapidly in summer. C. We are closer to the Sun in the summer. D. We have more hours of daylight in summer.

A. The Sun is higher in the sky in summer. D. We have more hours of daylight in summer. Correct Two factors make it warmer in the summer: (1) the Sun is higher in the sky, which means more direct sunlight; (2) we have more total hours in sunlight each day. Notice that both factors are a result of Earth's axis tilt relative to the Sun, which is why we say that axis tilt is the cause of the seasons.

If there is going to be a total lunar eclipse tonight, then you know that: A. the Moon's phase is full. B. the Moon's phase is new. C. the Moon is unusually close to Earth.

A. the Moon's phase is full.

In winter, Earth's axis points toward the star Polaris. In spring: A. the axis also points toward Polaris. B. the axis points toward Vega. C. the axis points toward the Sun.

A. the axis also points toward Polaris.

Beijing and Philadelphia have about the same latitude but very different longitudes. Therefore, tonight's night sky in these two places: A. will look about the same. B. will have completely different sets of constellations. C. will have partially different sets of constellations.

A. will look about the same.

When it is summer in Australia, the season in the United States is A. winter. B. summer. C. spring

A. winter.

In reality, the Moon's orbit about Earth is tilted (by about 5°) with respect to Earth's orbit about the Sun. As a result, the actual number of solar eclipses that occur each year is approximately _____. A. 0 B. 2 C. 12 D. 24

B. 2 There are generally two periods of time each year when eclipses are possible — the "eclipse seasons" — and there is a solar eclipse of some type (partial, total, or annular) during each of these eclipse seasons. (Because the time between eclipse seasons is less than six months, in some years there is a third eclipse season and hence a third solar eclipse.)

What conditions must exist for a solar eclipse to occur? A. The only condition is that the phase of the Moon must be new. B. The phase of the Moon must be new and the Moon must be passing through Earth's orbital plane. C. The only condition is that the phase of the Moon must be full. D. The phase of the Moon must be full and the Moon must be passing through Earth's orbital plane.

B. The phase of the Moon must be new and the Moon must be passing through Earth's orbital plane. The two points at which the Moon's orbit crosses the Earth's orbital plane are called the nodes of the Moon's orbit. So another way to state the conditions for a solar eclipse is that (1) it must be new moon, and (2) the Moon must be at or quite near one of the nodes of its orbit.

If the Sun rises precisely due east: A. you must be located at Earth's equator. B. it must be the day of either the spring or fall equinox. C. it must be the day of the summer solstice.

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

A week after full moon, the Moon's phase is: A. first quarter. B. third quarter. C. new.

B. third quarter.

Suppose Earth's axis had no tilt. Would we still have seasons? Why or why not?

Because each point on Earth would receive the same amount of sunlight at different times of the year. Each point would receive the same amount of light in the daytime, and the same amount of darkness at night. The only way to experience different climates would be to change positions of Earth on Earth's surface. Without the axial tilt, climate is non-dependent on seasonal change, and only the position on Earth's surface because of direct versus indirect rays of sunlight.

Two stars that are in the same constellation: A. must both be part of the same cluster of stars in space. B. must both have been discovered at about the same time. C. may actually be very far away from each other.

C. may actually be very far away from each other.

What are circumpolar stars? Are more stars circumpolar at the North Pole or in the United States? Explain.

Circumpolar stars remain perpetually above the horizon, circling counterclockwise around the north celestial pole each day. More stars are circumpolar in the United States because stars near the south celestial pole never rise above the horizon at all.

Suppose that instead of being inclined to Earth's orbit around the Sun, the Moon's orbit was in the same plane as Earth's orbit around the Sun. (Click "Show Moon with flat orbit" to see this situation.) In this hypothetical situation, approximately how many solar eclipses would occur each year? A. 0 B. 1 C. 2 D. 12 E. 24

D. 12 If the Moon orbited Earth in the same plane that Earth orbits the Sun (the ecliptic plane), we would have a solar eclipse at every new moon. Because there are about twelve new moons in a year, we would have twelve solar eclipses. Of course, this isn't what really happens. Continue to Part B to study the real situation.

If you could change the layout of the solar system, which of the following would cause a lunar eclipse to occur at least once every month in this hypothetical situation? A. Make the Moon orbit Earth twice as fast. B. Change the Moon's orbital plane so it tilts the opposite way. C. Relocate the Moon to twice its current distance from Earth. D. Change the Moon's orbital plane so it is in the same plane as Earth's orbit around the Sun.

D. Change the Moon's orbital plane so it is in the same plane as Earth's orbit around the Sun. Good work! You correctly visualize that the Moon's orbit has to be in line with Earth's orbit in order for a lunar eclipse to happen just about every month.

What conditions must exist for a lunar eclipse to occur? A. The only condition is that the phase of the Moon must be new. B. The phase of the Moon must be new and the Moon must be passing through Earth's orbital plane. C. The only condition is that the phase of the Moon must be full. D. The phase of the Moon must be full and the Moon must be passing through Earth's orbital plane.

D. The phase of the Moon must be full and the Moon must be passing through Earth's orbital plane. The two points at which the Moon's orbit crosses the Earth's orbital plane are called the nodes of the Moon's orbit. So another way to state the conditions for a lunar eclipse is that (1) it must be full moon, and (2) the Moon must be at or quite near one of the nodes of its orbit.

Briefly describe the Moon's cycle of phases. Can you ever see a full moon at noon? Explain.

Half of the moon is always lit by sunlight, but from Earth, we can only see more, less, or the entire half of the moon lit up because we see a different angle of the moon than the angle of the sun. If the moon appears completely lit, then we are experiencing the same angle of the moon as from the sun.

What are latitude and longitude? Does the sky vary with latitude? Does it vary with longitude? Explain.

Lines of latitude are lines that stretch from east to west. Lines of latitude are always parallel. Lines of longitude stretch from north to south. Line of longitude widen at the equator, and narrow at the poles. The sky does not vary with latitude because those are parallel lines. The sky does vary with longitude because the distance between each line changes closer to the poles than the equator.

Why does the local sky look like a dome? Define horizon, zenith, and meridian. How do we describe the location of an object in the local sky?

The local sky looks like a dome because the person in the center is standing on a plane. This plane is the Earth, and the sky is everything above the Earth. Horizon is the boundary between Earth and sky. Zenith is the point directly overhead. Meridian is an imaginary half-circle stretching from the horizon due south, through the zenith, to the horizon due north. We describe the location of an object in the sky by using one of eight cardinal directions, as well as, using height: high, low, below horizon.

What is the zodiac, and why do we see different parts of it at different times of year?

The sun appears between Earth and different constellations, and which ever constellation appears the most distant from Earth's orbit is the current zodiac. The zodiac depends on where the Earth is, while orbiting the Sun, and one orbit around the sun takes a full year. The zodiacs divide the orbit into 13 unequal parts. Zodiac is an egocentric view of the stars and constellations from Earth.

What are constellations? How did they get their names?

They are groups of stars that are visible in defined patterns from Earth. They got their names from Ancient Greece.

Why don't we see an eclipse at every new and full moon? Describe the conditions needed for a solar or lunar eclipse.

We don't see an eclipse because the moon must be centered between the sun and Earth or centered on opposite sides of the Earth. Non-ecliptic new and full moons appear above or below this center. Solar eclipse happens when moon is between sun and Earth. Lunar eclipse happens when Earth is between moon and sun.

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.

North Celestial Pole, Vernal Equinox, North Pole, Equator, Celestial Equator, Ecliptic, and South Pole are all things that need to be marked on your celestial sphere.

What is precession, and how does it affect the sky that we see from Earth?

Precession is caused by gravity's effect on a tilted, rotating object. Since the Earth is tilted and rotating, the sun's and moon's gravitational forces act on the Earth by straightening out the planet's bulging equator. This precession causes the tilt to change directions every 26,000 years.

Briefly describe key facts about the solstices and equinoxes.

Summer solstice experiences more sunlight in the northern hemisphere. Winter solstice experiences less sunlight in the southern hemisphere. Spring equinox is a time when Earth's tilt moves from being away from the sun to toward the sun. Fall equinox is a time when Earth's tilt moves from being toward the sun to away from the sun.