HW Ch 2

Each of the following figures shows Earth with a different axis tilt. (Assume that Earth's rotation period is unchanged.) Each also shows a person located in Florida (not to scale). Rank the figures based on how much time the person spends in daylight during a 24-hour period, from most to least.

(tilt of north pole) 23.5 deg towards sun, 0 deg, 23.5 deg away from sun, 45 deg away from sun, 90 deg away from sun Notice that the figure with the most daylight shows that it is summer in Florida (because the Northern Hemisphere is tilted toward the Sun). The figure with the second-most daylight is the case with no tilt (tilt = 0°), for which there would always be the same 12 hours of daylight and 12 hours of darkness each day. The remaining three cases all show Florida in winter (the Northern Hemisphere is tilted away from the Sun), and the amount of winter daylight becomes shorter for the more extreme tilts.

Estimate the diameter of the supergiant star Betelgeuse, using its angular diameter of about 0.05 arcsecond and distance of about 600 light-years.

1.38x10^9 km

The Sun has an angular diameter of about 0.5 deg and an average distance of about 150 million km. What is the Sun's approximate physical diameter?

1.3x10^6 km

A large boulder has a volume of 1000 cubic meters and a mass of 3,200,000 kilograms. What is the density of the boulder, in grams per cubic centimeter?

3.2 g/cm^3

The surface area of a small moon is 50,000 square kilometers, which is equivalent to _____ square meters. (Recall that 1 kilometer = 1000 meters.)

50,000 x 1000^2

Part complete The following figures are the same as those from Part A. This time, consider the seasonal differences that occur as Earth orbits the Sun with the different axis tilts. Rank the figures on the basis of the seasonal temperature differences you would expect between summer and winter, from the one with the most extreme seasonal differences to the one with the least extreme. To rank items as equivalent, overlap them.

90 deg, 45 deg, 23.5 deg, 0 deg The greater the axis tilt, the more extreme the seasonal temperature differences. This is true because on any parcticular summer day, greater axis tilt means longer daylight and a higher summer Sun, making summers warmer. Similarly, on any winter day, a greater axis tilt means shorter daylight and a lower winter sun, making winters colder. That is why this ranking shows the figures in order of declining axis tilt, with the two having the same axis tilt ranked equal.

You've now seen that Earth's varying distance cannot be the cause of our seasons. So what is the cause of the seasons? D

A. Earth's speed varies in its orbit around the Sun, giving us summer when Earth is moving fastest and winter when Earth is moving slowest. B. The seasons are caused by variation in the amount of rainfall (or snowfall) in different places at different times of year. C. The tilt of Earth's axis causes the Northern Hemisphere to be closer to the Sun than the Southern Hemisphere in summer, and vice versa in winter. D. The tilt of Earth's axis causes different portions of the Earth to receive more or less direct sunlight at different times of year.

Which of the following planets has essentially no seasons at all? C

A. Mars (axis tilt = 25.2°) B. Neptune (axis tilt = 29.6°) C. Jupiter (axis tilt = 3.1°) D. Uranus (axis tilt = 97.9°)

Which of the following planets should have the most extreme seasons? D

A. Mars (axis tilt = 25.2°) B. Neptune (axis tilt = 29.6°) C. Jupiter (axis tilt = 3.1°) D. Uranus (axis tilt = 97.9°)

Beijing and Philadelphia have about the same latitude but different longitudes. What can be said about the tonight's night sky in these two places? B

A. The sky will have completely different sets of constellations. B. The sky will look about the same. C. The sky will have partially different sets of constellations.

Based on what you have learned from your rankings in Parts A and B, which statement best describes how variation in the Earth-Sun distance affects the seasons? A

A. The variation in Earth-Sun distance over the course of each year has virtually no effect on the seasons. B. No matter where you live or what the seasons, it is generally hotter when Earth is closer to the Sun and colder when Earth is farther from the Sun. C. Summer occurs when Earth is closer to the Sun and winter occurs when Earth is farther from the Sun.

Based on what you have learned from your rankings in Parts A and B, which of the following planets would you expect to have seasons most like Earth's? B

A. Uranus (axis tilt = 97.9°) B. Mars (axis tilt = 25.2°) C. Jupiter (axis tilt = 3.1°)

The north celestial pole is 35 deg above your northern horizon. What does it tell you? A

A. You are at latitude 35N. B. You are at latitude 35S. C. You are at longitude 35E. D. You are at longitude 35E.

A week after full moon, the Moon's phase is: B

A. first quarter. B. third quarter. C. new.

If there is going to be a total lunar eclipse tonight, then you know that: A

A. the Moon's phase is full. B. the Moon's phase is new. C. the Moon is unusually close to Earth.

If the Sun rises precisely due east, B

A. you must be located at Earth's equator. B. it must be the day of either the March or the September equinox. C. it must be the day of the June solstice. D. you must be located on the Southern Pole

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

Circumpolar stars are stars that never appear to rise or set from a given location, but are always visible on any clear night. From the North Pole, every visible star is circumpolar, as all circle the horizon at constant altitudes. In contrast, a much smaller portion of the sky is circumpolar from the United States, as most stars follow paths that make them rise and set.

Compare your answer to the size of our Sun. The diameter of the Sun is 1.39 million km.

D_betelgeuse / D_sun = 990

Compare your answer to the average Earth-Sun distance.

D_betelgeuse / d_sun-earth = 9.2

Compare your answer to the actual value of 1390000 km.

For the values given, we estimate the size to be about 1,300,000 kilometers. We are told that the actual value is about 1,390,000 kilometers. The two values are pretty close and the difference can probably be explained by the Sun's actual diameter not being exactly 0.5° and the distance to the Sun not being exactly 150,000,000 kilometers.

Suppose the distance to the Moon were twice its actual value. Would it still be possible to have a total solar eclipse? Why or why not?

If the Moon were twice as far from the Earth, its angular size would be too small to create a total solar eclipse. It would still be possible to have annular eclipses, though the Moon would cover only a small portion of the solar disk.

Refer to the data in the introduction. Rank the seasons for the Southern Hemisphere based on Earth's distance from the Sun when each season begins, from closest to farthest.

summer, fall, spring, winter

Time of Year || Earth-Sun Distance March (northern spring) equinox = 149.0 mil km June (northern summer) solstice = 152.0 mil km September (northern fall) equinox = 150.2 mil km December (northern winter) solstice = 147.2 mil km Refer to the data in the introduction. Rank the seasons for the Northern Hemisphere based on Earth's distance from the Sun when each season begins, from closest to farthest.

winter, spring, fall, summer