The Interior

The Earth can be considered to have four distinct layers. The central portion, called the inner core, is believed to be solid. It is extremely hot and consists mainly of iron and nickel. These metals are ferromagnetic, meaning that they can be magnetized. Surrounding the inner core is a liquid iron and nickel layer called the outer core. This liquid flows in huge eddies that are thought to be responsible for the magnetization of the core and hence for the existence of the geomagnetic field....

Test Part

Do not refer to the text when taking this test. A good score is at least 30 correct. Answers are in the back of the book. It is best to have a friend check your score the first time so that you won't memorize the answers if you want to take the test again. 1. The polar ice caps of Mars consist of (c) frozen water and carbon dioxide. (d) white sand exposed by the action of dust storms. (e) clouds in the upper atmosphere. (a) tends to grow in size by accumulating stray meteors and comets. (b)...

Web Sites

Encyclopedia Britannica Online, www.britannica.com Eric's Treasure Troves of Science, www.treasure-troves.com Sky and Telescope, www.skypub.com Weather Underground, www.wunderground.com absolute field of view, 433-435, 509 antimatter, 101, 343, 345-347,485-486 binoculars (Cont.) optics in, 506-507 size specifications of, 505-506 black hole, 335, 354-360, 375, 376-379, 471 black dwarf, 348, 471 blackbody, 464-465 blackbody radiation, 464-465 blue shift, 363 blue supergiant, 327 Bode, Johann E.,...

Ariel

Ariel is, in terms of size, practically a twin of Umbriel. It measures 1,160 km (720 mi) in diameter. It is much closer to Uranus, orbiting at a mean altitude of 190,000 km (120,000 mi). It takes only 21 2 Earth days to orbit once around the planet. Like all the other moons of Uranus, Ariel orbits in a nearly perfect circle and keeps the same face toward Uranus all the time. Ariel reflects about twice as much light as Umbriel, leading astronomers to surmise that its surface consists of...

Test Part Three

Do not refer to the text when taking this test. A good score is at least 30 correct. Answers are in the back of the book. It is best to have a friend check your score the first time so that you won't memorize the answers if you want to take the test again. (a) the motion of a planet with respect to the stars. (b) the variation in the Moon's orientation with respect to Earth. (c) the speed of a planet's revolution around the Sun. (d) the wobbling of Earth on its axis. (e) a component of a...

Challenges

Operating a telescope in space presents certain problems that users of Earth-based telescopes don't have to deal with. The most obvious constraint, at least with the HST, is the fact that the observer is not physically present to attend to the apparatus. The telescope must be aimed and the instruments operated by remote control. Pointing and tracking of the HST are somewhat more complicated than is the case with an Earth-based telescope. This is so because the instrument is not fixed with...

Final Exam

Do not refer to the text when taking this exam. A good score is at least 75 correct. Answers are in the back of the book. It is best to have a friend check your score the first time so that you won't memorize the answers if you want to take the test again. 1. As seen from temperate or tropical latitudes, the positions of the constellations shift gradually westward in the sky from night to night because (a) the Earth rotates on its axis. (b) the Earth revolves around the Sun. (c) the tilt of the...

Part Five Space Observation and Travel

CHAPTER 18 Observing the Invisible 447 CHAPTER 19 Traveling and Living in Space 477 CHAPTER 20 Your Home Observatory 501 Suggested Additional Reference 567 This book is for people who want to learn basic astronomy without taking a formal course. It also can serve as a supplemental text in a classroom, tutored, or home-schooling environment. I recommend that you start at the beginning of this book and go straight through. In this book, we'll go on a few mind journeys. For example, we'll take a...

Why Does This Matter

We have conducted mind experiments in this chapter, many of which require us to suspend reality. In real life, scenarios such as these would kill anyone attempting to make the observations. So why is relativity theory important If space is bent and time is slowed by incredibly powerful gravitational fields, so what The theory of general relativity plays an important role in astronomers' quests to unravel the mysteries of the structure and evolution of the Universe. On a cosmic scale,...

Charon

Charon, with a diameter of 1,190 km (740 mi), is the only known satellite of Pluto. Charon is small in absolute terms, but it is significant compared with Pluto. Figure 7-11 (in Chap. 7) compares Charon for size with Earth and Pluto. Charon orbits Pluto at an average distance of approximately 20,000 km (12,500 mi). Charon is unique not only in that it is the largest moon in size relative to its parent planet, but it is also extremely low in its orbit. In fact, the two bodies tidally affect each...

Degrees Minutes Seconds

Degree Minute Second

There are 360 degrees in a complete circle. Why 360 and not 100 or 1000, which are rounder numbers, or 256 or 512, which can be divided repeatedly in half all the way down to 1 No doubt ancient people noticed that there are about 360 days in a year and that the stellar patterns in the sky are repeated every year. A year is like a circle. Various familiar patterns repeat from year to year the general nature of the weather, the Sun's way of moving across the sky, the lengths of the days, the...