(ASN) Explorations - Introduction to Astronomy (Arny), 6th Edition

(ASN) Explorations - Introduction to Astronomy (Arny), 6th Edition

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Explorations: Introduction to Astronomy (Arny), 6th Edition Chapter 1: The Cycles of the Sky We see the Sun, Moon, and stars rise along the eastern horizon, move across the sky, and set along the western horizon. The stars form patterns (constellations) whose shapes do not change. We see different constellations at different times of the year—Orion in January, Scorpius in August, for example. The shape of the lit portion of the Moon changes during the month. Cycles of the Moon, Sun, and stars are the basis for keeping time and our calendar. o The day is based on the Earth’s spin (rotation about its own axis). o The month is based on the Moon’s orbital motion around the Earth. o The year is based on the Earth’s orbital motion around the Sun. These motions also lead to seasons and eclipses. Astronomers of antiquity deduced the shape and size of the Earth. Starting around a.d. 1500, scientists such as Copernicus, Galileo, Kepler, and Newton deduced laws to describe and explain planetary motion. Chapter 2: The Rise of Astronomy Gravity controls the motion of most astronomical objects. If no forces act on an object, inertia keeps it moving in a straight line at a constant speed. If an object is not moving along a straight line at a constant speed, a force must be acting on it. Newton’s laws of motion allow us to describe and predict an object's motion if we know the forces acting on it. The force of gravity between two objects depends on their mass and the distance between them: o The greater their separation, the weaker the force. o The greater their mass, the greater the force. Orbital motion allows us to determine the mass of (“weight”) astronomical objects. Chapter 3: Gravity and Motion Light can be thought of either as a wave of energy or a stream of particles called photons. White light is a mix of all colors. The color of light is determined by its wavelength. Atoms can emit light when their electrons shift orbits. Each kind of atom emits light at a unique set of wavelengths (colors). For many kinds of objects, the color and intensity of their light are set by their 1
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Explorations: Introduction to Astronomy (Arny), 6th Edition temperature: o The hotter the object, the bluer the light it emits. o The hotter the object, the more light it emits. These properties allow us to deduce an object’s temperature from its color. The wavelengths of the radiation emitted by a moving object are shifted. Chapter 4: Light and Atoms Astronomers use telescopes to gather light and thereby make dim objects observable. The larger the diameter of the lens or mirror used in a telescope: o The greater its ability to gather light o The finer the detail that the instrument will show The Earth’s atmosphere interferes seriously with observing. o
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(ASN) Explorations - Introduction to Astronomy (Arny), 6th Edition

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