# Chapter 0 Lecture Astronomy: A Beginners Guide to

Chapter 0 Lecture Astronomy: A Beginners Guide to the Universe Seventh Edition Charting the Heavens 2013 Pearson Education, Inc. Chapter 0 Charting the Heavens

2013 Pearson Education, Inc. Units of Chapter 0 The Obvious View Earths Orbital Motion The Motion of the Moon The Measurement of Distance Science and the Scientific Method Summary of Chapter 0

2013 Pearson Education, Inc. 0.1 The Obvious View Earth is average we dont occupy any special place in the universe Universe: Totality of all space, time, matter, and energy Astronomy: Study of the universe Scales are very large, measured in light-years, the distance light travels in a year about 10 trillion miles

2013 Pearson Education, Inc. 0.1 The Obvious View Stars that appear close in the sky may not actually be close in space. 2013 Pearson Education, Inc. 0.1 The Obvious View The celestial sphere:

Stars seem to be on the inner surface of a sphere surrounding the Earth. They arent, but we can use two-dimensional spherical coordinates (similar to latitude and longitude) to locate sky objects. 2013 Pearson Education, Inc.

More Precisely 0-1: Angular Measure Full circle contains 360 (degrees). Each degree contains 60 (arc-minutes). Each arc-minute contains 60 (arcseconds). Angular size of an object depends on actual size and distance away.

2013 Pearson Education, Inc. 0.1 The Obvious View Declination: Degrees north or south of celestial equator Right ascension: Measured in hours, minutes, and seconds eastward from position of the Sun at vernal equinox 2013 Pearson Education, Inc.

0.2 Earths Orbital Motion Daily cycle, noon to noon, is diurnal motion solar day. Stars arent in quite the same place 24 hours later, though, due to Earths rotation around the Sun; when they are in the same place again, one sidereal day has passed.

2013 Pearson Education, Inc. 0.2 Earths Orbital Motion The 12 constellations the Sun moves through during the year are called the zodiac; path is ecliptic. 2013 Pearson Education, Inc. 0.2 Earths Orbital Motion Ecliptic is plane of Earths path around the Sun; at 23.5

to celestial equator. Northernmost point (above celestial equator) is summer solstice; southernmost is winter solstice; points where path crosses celestial equator are vernal and autumnal equinoxes. Combination of day length and sunlight angle gives seasons. Time from one vernal equinox to

next is tropical year. 2013 Pearson Education, Inc. 0.2 Earths Orbital Motion Precession: Rotation of Earths axis itself; makes one complete circle in about 26,000 years 2013 Pearson Education, Inc. 0.2 Earths Orbital Motion

Time for Earth to orbit once around the Sun, relative to fixed stars, is sidereal year. Tropical year follows seasons; sidereal year follows constellations in 13,000 years July and August will still be summer, but Orion will be a summer constellation. 2013 Pearson Education, Inc. 0.3 The Motion of the Moon

The Moon takes about 29.5 days to go through whole cycle of phases synodic month. Phases are due to different amounts of sunlit portion being visible from Earth. Time to make full 360 around Earth,

sidereal month, is about 2 days shorter than synodic month. 2013 Pearson Education, Inc. 0.3 The Motion of the Moon Lunar eclipse: Earth is between the Moon and Sun Partial when only part of the Moon is in shadow Total when all is in shadow

2013 Pearson Education, Inc. 0.3 The Motion of the Moon Solar eclipse: the Moon is between Earth and Sun 2013 Pearson Education, Inc. 0.3 The Motion of the Moon Solar eclipse is partial when only part of the

Sun is blocked, total when all is blocked, and annular when the Moon is too far from Earth for total. 2013 Pearson Education, Inc. 0.3 The Motion of the Moon

Eclipses dont occur every month because Earths and the Moons orbits are not in the same plane. 2013 Pearson Education, Inc. 0.3 The Motion of the Moon Eclipse tracks, 2010 - 2030 2013 Pearson Education, Inc.

0.4 The Measurement of Distance Triangulation: Measure baseline and angles, and you can calculate distance. 2013 Pearson Education, Inc. 0.4 The Measurement of Distance Parallax: Similar to

triangulation, but looking at apparent motion of object against distant background from two vantage points 2013 Pearson Education, Inc. 0.5 Science and the Scientific Method Scientific theories: Must be testable

Must be continually tested Should be simple Should be elegant Scientific theories can be proven wrong, but they can never be proven right with 100% certainty. 2013 Pearson Education, Inc. 0.5 Science and the Scientific Method Observation leads to theory explaining it. Theory leads to predictions consistent with previous

observations. Predictions of new phenomena are observed. If the observations agree with the prediction, more predictions can be made. If not, a new theory can be made. 2013 Pearson Education, Inc.

Summary of Chapter 0 Astronomy: Study of the universe Stars can be imagined to be on inside of celestial sphere; useful for describing location. Plane of Earths orbit around Sun is ecliptic; at 23.5 to celestial equator. Angle of Earths axis causes seasons. Moon shines by reflected light, has phases. Solar day sidereal day, due to Earths rotation around Sun. 2013 Pearson Education, Inc.

Summary of Chapter 0, cont. Synodic month sidereal month, also due to Earths rotation around Sun Tropical year sidereal year, due to precession of Earths axis Distances can be measured through triangulation and parallax. Eclipses of Sun and Moon occur due to alignment; only occur occasionally as orbits are not in same plane.

Scientific method: Observation, theory, prediction, observation 2013 Pearson Education, Inc.

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