ch. 3 homework - cycles of the sun and moon

How far away (in km) is the Moon (3,480 km linear diameter) from the Earth if it has this angular diameter on the sky? Solving for D in the small angle formula gives us: Dkm = dkm · 2.06 ✕ 105 arc seconds/radian𝜃as Dkm = ?

(3480km)*(2,06*10^5) / 1760 = 407318.18 or 4.06e+5(4.07*10^5)

one year is the amount of time it takes Earth to __________ around the Sun.

revolve

the moon _________ around the Earth in approximately 29.5 days.

revolves

the Earth ___________ once every 24 hours.

rotates

the moon _____________ once on its axis for every revolution around Earth.

rotates

Where are all southern stars circumpolar?

south pole

Where is the south celestial pole seen at the zenith?

south pole

Where is the Sun directly overhead at local noon on June 21st?

the Tropic of Cancer

Where are celestial poles seen on the horizon?

the equator

Where do all stars rise and set?

the equator

Where is the sun is at the zenith twice during the year

the equator

Considering the location of the Sun in the sky through a year, where on Earth would you expect to find the greatest range of temperatures?

the poles

Where is the Sun over the zenith only once a year?

tropic of Cancer and tropic of Capricorn

You are located in St. Louis, MO, United States. Your friend is located in Rio de Janeiro, Brazil. You see a waning gibbous in your clear night sky. What phase, if any, will your friend see if the night sky in Rio de Janeiro is also clear? A. waning crescent B. waning gibbous C. third quarter moon D. waxing gibbous E. waxing crescent F. first quarter moon G. new moon H. full moon I. The moon cannot be visible from both St. Louis and Rio de Janeiro on the same night.

waning gibbous

Do all locations on Earth see approximately a new moon (that is if we could actually "see" a new moon?

yes

The moon does not always pass through the center of the shadows. Imagine that the orbit of the moon carries the moon through Earth's shadow so that only the lower half of the moon's disk passes through the umbral shadow. What is this eclipse called?

partial lunar eclipse

Imagine that the orbit of the moon carries the moon through Earth's shadow so that the moon's disk just misses the umbral shadow. What would this be called?

penumbral lunar eclipse

Where are all northern stars circumpolar?

north pole

Where is the north celestial pole seen at the zenith?

north pole

If the Moon is 0.49° across on the sky, we need to first figure out how big that is in arc seconds. (Give the number of arc seconds in one degree, and then give the angular diameter in arc seconds.) 1 degree = Nas arc seconds = 3600 arc sec 𝜃as = 𝜃deg · Nas arc seconds/degree 𝜃as = ?

0.49*(3600/1) = 1764

How many times larger than the Moon is the diameter of Earth's umbral shadow at the Moon's distance?

3 moon diameters

The Moon takes 27.3 days to return to its original position with respect to the stars. How many degrees does the Moon move across the sky in 1 hour? How does this compare to the width of a full moon (0.49-0.55 degrees)?

360 degrees / (27.3days*24hours) = about 0.5 This is about the same as the moon's width.

At perigee, the Moon is 365,000 km from Earth. At apogee, it is 406,000 km away. How many times larger does the Moon appear to us during perigee than at apogee? The linear diameter of the Moon is 3,480 km. 𝜃p/𝜃a = ?

406,000/365,000 = 1.1123

Why are there seasons?

Because the axis of the Earth is always pointing towards Polaris, either the northern hemisphere or southern hemisphere gets direct sunlight depending on the time of year. Over the year we have seasons because of this. At the equator, it stays about the same throughout the year and that's why they don't have intense seasons. In addition to the axis tilt, the sun's path(the ecliptic) compared to Eath's celestial equator defines the seasons. In the northern hemisphere, the sun is north of the celestial equator, so days are long and warm. However, in the winter, the sun is south of the celestial equator, so days are short and cold.

Where is the Sun directly overhead at local noon on December 21st?

Tropic of Capricorn

When does a lunar eclipse occur? a. at the full moon b. at the new moon c. at the first-quarter moon d. at the third-quarter moon

a. at the full moon

Identify the phases of the Moon if at sunset in the Northern Hemisphere the Moon is in each of the following positions. a.) near the eastern horizon b.) high in the southern sky c.) in the southeastern sky d.) in the southwestern sky

a. b. c. d.

During a total eclipse of the moon, where is the moon located? a. in the umbra of Earth's shadow b. in the penumbra of Earth's shadow c. in the umbra of the moon's shadow d. in the penumbra of the moon's shadow

a. in the umbra of Earth's shadow

The Moon is in its first quarter phase. What fraction of the near side is dark? What fraction of the far side is dark?

both one half

Which of the following describes the moon as it enters the penumbra? a. It is fully darkened. b. It is turned rusty red. c. It is dimmed slightly. d. none of these

c. It is dimmed slightly.

Why do solar eclipses happen only at the new moon? a. A solar eclipse can occur only when the Sun is between the Earth and the Moon. b. Solar eclipses can and do occur during other phases of the lunar cycle. c. 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. d. Since the shadow of the Earth extends directly away from the Sun, a solar eclipse can occur only when the Earth is between the Moon and the Sun.

c. 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.

Which direction does the moon move around the earth?

counter clockwise

Why do solar eclipses not happen every new moon? a. Solar eclipses do occur every new moon at some location on Earth. b. Solar eclipses don't occur every new moon because of variations in the intensity of light from the Sun. c. Solar eclipses don't occur every new moon because of variations in the Moon's orbital distance from Earth. d. Solar eclipses don't occur on every new moon because of the Moon's orbital tilt.

d. Solar eclipses don't occur every new moon because of the Moon's orbital tilt.

Why does the moon glow rusty red when it is totally eclipsed? a. Blue light is scattered out of sunlight in Earth's atmosphere. b. The moon receives sunlight bent through Earth's atmosphere. c. Sunsets and sunrises generally glow red. d. all of these

d. all of these

Through which of the following must the moon pass in order for a total lunar eclipse to occur? a. the penumbra of the moon's shadow b. the umbra of the moon's shadow c. the penumbra of Earth's shadow d. the umbra of Earth's shadow

d. the umbra of Earth's shadow

We can see total solar eclipses because of which of the following? a. The linear diameters of the sun and the moon are almost equal. b. The moon always shows the same face to the Earth. c. The distances to the sun and the moon are about the same. d. Total solar eclipses would be visible on any planet with a moon. e. The angular diameters of the sun and the moon are almost equal.

e. The angular diameters of the sun and the moon are almost equal.

Where are the north circumpolar stars seen?

everywhere north of the equator

Imagine that the orbit of the moon carries the moon so far north that it does not enter Earth's penumbral shadow. What would this be called?

no eclipse would occur