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Objectives

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Title: Objectives


1
Objectives
Section 1 Viewing the Universe
Chapter 26
  • Describe characteristics of the universe in terms
    of time, distance, and organization
  • Identify the visible and nonvisible parts of the
    electromagnetic spectrum
  • Compare refracting telescopes and reflecting
    telescopes
  • Explain how telescopes for nonvisible
    electromagnetic radiation differ from light
    telescopes

2
The Value of Astronomy
Section 1 Viewing the Universe
Chapter 26
  • astronomy the scientific study of the universe
  • Scientists who study the universe are called
    astronomers
  • Astronomers have made exciting discoveries, such
    as new planets, stars, black holes, and nebulas.
  • By studying these objects, astronomers have been
    able to learn more about the origin of Earth and
    the processes involved in the formation of our
    solar system.

3
The Value of Astronomy,
Section 1 Viewing the Universe
Chapter 26
  • Studies of how stars shine may one day lead to
    improved or new energy sources on Earth.
  • Astronomers may also learn how to protect us from
    potential catastrophes, such as collisions
    between asteroids and Earth.

4
Where does the Value of Astronomy come into play?
Section 1 Viewing the Universe
Chapter 26
  • Astronomical research is supported by federal
    agencies, such as the National Science Foundation
    and NASA.
  • Private foundations and industry also fund
    research in astronomy.
  • We can all gain from what they learn.

5
Characteristics of the Universe
Section 1 Viewing the Universe
Chapter 26
  • The evolution of the universe is called
    cosmology.
  • Most astronomers believe the universe began about
    14 billion years ago.
  • We study the stars to see the past and predict
    the future.

6
Organization of the Universe
Section 1 Viewing the Universe
Chapter 26
  • The solar system includes the sun, Earth, the
    other planets, and many smaller objects such as
    asteroids and comets.
  • The solar system is part of a galaxy.
  • galaxy a collection of stars, dust, and gas bound
    together by gravity
  • The galaxy in which the solar system resides is
    called the Milky Way galaxy.
  • The nearest part of the universe to Earth is our
    solar system.

7
A Galaxy
8
The Same Galaxy
9
Measuring Distances
Section 1 Viewing the Universe
Chapter 26
  • What are some ways we measure distances?

10
Measuring Distances in the Universe
Section 1 Viewing the Universe
Chapter 26
  • astronomical unit the average distance between
    the Earth and the sun approximately 150 million
    kilometers (symbol, AU)
  • Astronomers also use the speed of light to
    measure distance.

11
Measuring Distances in the Universe
Section 1 Viewing the Universe
Chapter 26
  • Light travels at 300,000,000 m/s. In one year,
    light travels 9.4607 x 1012 km. This distance is
    known as a light-year.
  • Aside from the sun, the closet star to Earth is
    4.2 light-years away.

12
Observing Space
Section 1 Viewing the Universe
Chapter 26
  • What we see in the universe is light that was
    formed a long time ago.
  • It take light from the sun about 8 min. to reach
    the earth.

13
Electromagnetic Spectrum
Section 1 Viewing the Universe
Chapter 26
  • electromagnetic spectrum all of the frequencies
    or wavelengths of electromagnetic radiation.
  • Light, radio waves, and X rays are all examples
    of electromagnetic radiation.
  • The radiation is composed of traveling waves of
    electric and magnetic fields that oscillate at
    fixed frequencies and wavelengths.

14
Visible Electromagnetic Radiation
Section 1 Viewing the Universe
Chapter 26
  • Though all light travels at the same speed,
    different colors of light have different
    wavelengths. These colors can be seen when
    visible light is passed through a spectrum.
  • The human eye can see only radiation of
    wavelengths in the visible light range of the
    spectrum.

15
Visible Electromagnetic Radiation
Section 1 Viewing the Universe
Chapter 26
  • Electromagnetic radiation shorter or longer than
    wavelengths of violet or red light cannot be seen
    by humans.
  • The shortest visible wavelength of light are blue
    and violet, while the longest visible wavelength
    of light are orange and red.

16
The Electromagnetic Spectrum
17
Reading check
Section 1 Viewing the Universe
  • Which type of electromagnetic radiation can be
    seen by humans?

18
Reading check
Section 1 Viewing the Universe
Chapter 26
  • Which type of electromagnetic radiation can be
    seen by humans?
  • The only kind of electromagnetic radiation the
    human eye can detect is visible light.

19
Invisible Electromagnetic Radiation
Section 1 Viewing the Universe
Chapter 26
  • Invisible wavelengths include infrared waves,
    microwaves, radio waves, ultraviolet rays, X
    rays, and gamma rays, and are detected only by
    instruments.
  • In 1852, a scientist named Sir Frederick William
    Herschel discovered infrared, which means below
    the red.Infrared is radiation that has waves
    longer than waves of visible light.
  • Ultraviolet means beyond the violet and has
    wavelengths shorter than waves of visible light.

20
Telescopes
Section 1 Viewing the Universe
Chapter 26
  • telescope an instrument that collects
    electromagnetic radiation from the sky and
    concentrates it for better observation.
  • In 1609, an Italian scientist, Galileo, heard of
    a device that used two lenses to make distant
    objects appear closer.
  • Telescopes that collect only visible light are
    called optical telescopes.

21
Telescopes
Section 1 Viewing the Universe
Chapter 26
  • The two types of optical telescopes are
    refracting telescopes and reflecting telescopes.

22
Optical Telescopes
  • Refractors
  • Focus light with refraction bend light
    path in transparent medium
  • Use lenses
  • First kind made
  • Kind used by Galileo
  • Reflectors
  • Focus light by reflection bounce light off
    a solid medium
  • Use mirrors
  • First designed and created by Sir Isaac Newton
  • Many different designs

23
Refracting Telescopes
Section 1 Viewing the Universe
Chapter 26
  • refracting telescope a telescope that uses a set
    of lenses to gather and focus light from distant
    objects
  • The bending of light is called refraction.
  • Refracting telescopes have an objective lens that
    bends light that passes through the lens and
    focuses the light to be magnified by an eyepiece.

24
Refracting Telescopes
Section 1 Viewing the Universe
Chapter 26
25
First Optical Telescopes Refractors
26
Refracting Telescopes
Section 1 Viewing the Universe
Chapter 26
  • One problem with refracting telescopes is that
    the lens focuses different colors of light at
    different distances causing the image to distort.
  • Another problem is that objective lenses that are
    too large will sag under their own weight and
    cause images to become distorted.

27
Chromatic Aberration
  • Dispersion of light through optical material
    causes blue component of light passing through
    lens to be focused slightly closer to lens than
    red component.
  • Known as chromatic aberration.

28
Reflecting Telescopes
Section 1 Viewing the Universe
Chapter 26
  • In the mid-1600s Isaac Newton solved the problem
    of color separation that resulted from the use of
    lenses.
  • reflecting telescopes a telescope that uses a
    curved mirror to gather and focus light from
    distant objects

29
Reflecting Telescopes
Section 1 Viewing the Universe
Chapter 26
30
Reflecting Telescopes
31
Reflecting Telescopes
Section 1 Viewing the Universe
Chapter 26
  • When light enters a reflecting telescope, the
    light is reflected by a large curved mirror to a
    second mirror. The second mirror reflects the
    light to the eyepiece, where the image is
    magnified and focused.
  • Unlike refracting telescopes, reflecting
    telescopes can be made very large without
    affecting the quality of the image.

32
Reading check
Section 1 Viewing the Universe
Chapter 26
  • What are the problems with refracting telescopes?

33
Reading check, continued
Section 1 Viewing the Universe
Chapter 26
  • What are the problems with refracting telescopes?
  • Images produced by refracting telescopes are
    subject to distortion because of the way
    different colors of visible light are focused at
    different distances from the lens and because of
    weight limitations on the objective lens.

34
Maps in Action
Maps in Action
Chapter 26
  • Light Sources

35
Telescopes for Invisible Electromagnetic Radiation
Section 1 Viewing the Universe
Chapter 26
  • Scientists have developed telescopes that detect
    invisible radiation, such as a radiotelescope for
    radio waves.
  • Ground-based telescopes work best at high
    elevations, where the air is dry.

36
Telescopes for Invisible Electromagnetic Radiation
Section 1 Viewing the Universe
Chapter 26
  • The only way to study many forms of radiation is
    from space because the Earths atmosphere acts as
    a shield against many forms of electromagnetic
    radiation.

37
Space-Based Astronomy
Section 1 Viewing the Universe
Chapter 26
  • Space telescopes have been launched to
    investigate planets, stars, and other distant
    objects
  • In space, Earths atmosphere cannot interfere
    with the detection of electromagnetic radiation.

38
Reading check
Section 1 Viewing the Universe
Chapter 26
  • Why do scientists launch spacecraft beyond
    Earths atmosphere?

39
Reading check, continued
Section 1 Viewing the Universe
Chapter 26
  • Why do scientists launch spacecraft beyond
    Earths atmosphere?
  • Scientists launch spacecraft into orbit to
    detect radiation screened out by Earths
    atmosphere and to avoid light pollution and other
    atmospheric distortions.

40
Space-Based Astronomy
Section 1 Viewing the Universe
Chapter 26
  • A space telescope does not have to view the stars
    through the earths atmosphere.
  • The same telescope in space will see many times
    further than on earth.

41
Space Telescopes
Section 1 Viewing the Universe
Chapter 26
  • The Hubble Space Telescope collects
    electromagnetic radiation from objects in space.
  • The Chandra X-ray Observatory makes remarkably
    clear images using X rays from objects in space,
    such as remnants of exploded stars.
  • The Compton Gamma Ray Observatory detected gamma
    rays from objects, such as black holes.
  • The James Webb Space Telescope will detect
    infrared radiation from objects in space after it
    is launched in 2011.

42
Hubble Space Telescope
  • Launched from the Space Shuttle in 1990.
  • Largest telescope in space 2.4 meter mirror.
  • Mirror has an optical flaw (spherical
    aberration).
  • Hubble was fixed by astronauts in 1994.
  • Hubble has higher resolution and gathers more
    light than most Earth-based telescopes.

43
Our Sun in Different Wavelengths
Visible (BBSO)
X-Ray (Yohkoh)
Ultraviolet (SOHO)
Infrared (NSO)
Radio (Nobeyama)
44
Crab Nebula at Different Wavelengths
45
Other Spacecraft
Section 1 Viewing the Universe
Chapter 26
  • Since the early 1960s, spacecraft have been sent
    out of Earths orbit to study other planets.
  • The Voyager 1 and Voyager 2 spacecraft
    investigated Jupiter, Saturn, Uranus, and
    Neptune, and collected images of these planets
    and their moons.
  • The Galileo spacecraft orbited Jupiter and its
    moons from 1995 to 2003.
  • The Cassini-Huygens spacecraft will study Titan,
    Saturns largest moon. Like Earth, Titan has an
    atmosphere that is rich in nitrogen. Scientists
    hope to learn more about the origins of Earth by
    studying Titan.

46
Human Space Exploration
Section 1 Viewing the Universe
Chapter 26
  • Spacecraft that carry only instruments and
    computers are described as robotic and can travel
    beyond the solar system.
  • The first humans went into space in the 1960s.
    Between 1969 and 1972, NASA landed 12 people on
    the moon. Humans have never gone beyond Earths
    moon.
  • The loss of two space shuttles and their crews,
    the Challenger in 1986 and the Columbia in 2003,
    have focused public attention on the risks of
    human space exploration.

47
Spinoffs of the Space Program
Section 1 Viewing the Universe
Chapter 26
  • Satellites in orbit provide information about
    weather all over Earth.
  • Other satellites broadcast television signals
    from around the world or allow people to navigate
    cars and airplanes.
  • Even medical equipment, like the heart pump, have
    been improved based on NASAs research on the
    flow of fluids through rockets.

48
Objectives
Section 2 Movements of the Earth
Chapter 26
  • Describe two lines of evidence for Earths
    rotation.
  • Explain how the change in apparent positions of
    constellations provides evidence of Earths
    rotation and revolution around the sun.
  • Summarize how Earths rotation and revolution
    provide a basis for measuring time.
  • Explain how the tilt of Earths axis and Earths
    movement cause seasons.

49
The Rotating Earth
Section 2 Movements of the Earth
Chapter 26
  • rotation the spin of a body on its axis
  • Each complete rotation takes about one day.
  • The Earth rotates from west to east. At any
    given moment, the hemisphere of Earth that faces
    the sun experiences daylight. At the same time,
    the hemisphere of Earth that faces away from the
    sun experiences nighttime.
  • These movements of Earth are also responsible for
    the seasons and changes in weather.

50
The Foucault Pendulum
Section 2 Movements of the Earth
Chapter 26
  • In the 19th century, the scientist
    Jean-Bernard-Leon Foucault, provided evidence of
    Earths rotation by using a pendulum.
  • The path of the pendulum appeared to change over
    time. However, the path does not actually
    change. Instead, the Earth moves the floor as
    Earth rotates on its axis.

51
The Coriollis Effect
Section 2 Movements of the Earth
Chapter 26
  • The rotation of Earth causes ocean currents and
    wind belts to curve to the left or right.
  • This curving is caused by Earths rotation and is
    called the Coriolis effect.

52
The Revolving Earth
Section 2 Movements of the Earth
Chapter 26
  • The Earth is traveling around the sun at an
    average speed of 29.8 km/s.
  • One complete trip along an orbit is called
    revolution.
  • Each complete revolution of Earth around the sun
    takes 365 1/4 days, or about one year.

53
Earths Orbit
Section 2 Movements of the Earth
Chapter 26
  • Earths orbit around the sun is an ellipse.
  • An ellipse is a closed curve whose shape is
    determined by two points, or foci, within the
    ellipse.
  • Earth is not always the same distance from the
    sun.

54
  • perihelion the point in the orbit of a planet at
    which the planet is closet to the sun
  • aphelion the point in the orbit of a planet at
    which the planet is farthest from the sun

55
Evidence of Earths Rotation
Section 2 Movements of the Earth
Chapter 26
  • A constellation is a group of stars that are
    organized in a recognizable pattern.
  • Constellations appear to change positions in the
    sky.
  • The rotation of Earth on its axis causes the
    change in position.

56
Evidence of Earths Revolution
Section 2 Movements of the Earth
Chapter 26
  • Earths revolution around the sun is evidenced by
    the apparent motion of constellations.
  • Thus different constellations will appear in the
    night sky as the seasons change.

57
Constellations and Earths Motion
Section 2 Movements of the Earth
Chapter 26
58
Spot Question
Section 2 Movements of the Earth
Chapter 26
  • How does movement of constellations provide
    evidence of Earths rotation and revolution?

59
Spot Question
Section 2 Movements of the Earth
Chapter 26
  • How does movement of constellations provide
    evidence of Earths rotation and revolution?
  • Constellations provide two kinds of evidence
    of Earths motion. As Earth rotates, the stars
    appear to change position during the night. As
    Earth revolves around the sun, Earths night sky
    faces a different part of the universe. As a
    result, different constellations appear in the
    night sky as the seasons change.

60
Measuring Time
Section 2 Movements of the Earth
Chapter 26
  • Earths motion provides the basis for measuring
    time.
  • A day is determined by Earths rotation on its
    axis. Each complete rotation of Earth on its
    axis takes one day, which is then broken into 24
    hours.
  • The year is determined by Earths revolution
    around the sun. Each complete revolution of
    Earth around the sun takes 365 1/4 days, or one
    year.

61
Formation of the Calendar
Section 2 Movements of the Earth
Chapter 26
  • A calendar is a system created for measuring long
    intervals of time by dividing time into periods
    of days, weeks, months, and years.
  • A year is 365 1/4 days long.
  • Every four years, one day is added to the month
    of February.
  • Any year that contains an extra day is called a
    leap year.

62
The Modern Calendar
Section 2 Movements of the Earth
Chapter 26
  • In the late 1500s, Pope Gregory XIII created a
    calendar that would stay aligned with the
    seasons.
  • In this Gregorian calendar, century years, such
    as 1800 and 1900, are not leap years unless the
    century years are exactly divisible by 400.

63
Time Zone
Section 2 Movements of the Earth
Chapter 26
  • The earth rotates about 15o every hour.
  • Earths surface has been divided into 24 standard
    time zones.
  • Each time zone is about 15o.
  • The time zone is one hour earlier than the time
    in the zone east of each zone.

64
International Date Line
Section 2 Movements of the Earth
Chapter 26
  • The International Date Line was established to
    prevent confusion about the point on Earths
    surface where the date changes.
  • This line runs from north to south through the
    Pacific Ocean. The line is drawn so that it does
    not cut through islands or continents.

65
Spot Question
Section 2 Movements of the Earth
Chapter 26
  • What is the purpose of the International Date
    Line?
  • It is a time zone border, the calendar moves
    ahead one day as you cross it. The purpose of the
    International Date Line is to locate the border
    so that the transition would affect the least
    number of people. So that it will affect the
    least number of people, the International Date
    Line is in the middle of the Pacific Ocean,
    instead of on a continent.

66
Measuring Time
Section 2 Movements of the Earth
Chapter 26
67
Daylight Savings Time
Section 2 Movements of the Earth
Chapter 26
  • Because of the tilt of Earths axis, daylight
    time is shorter in the winter months than in the
    summer months.
  • During the summer months, days are longer so that
    the sun rises earlier in the morning.
  • daylight savings time
  • Under this system, clocks are set one hour ahead
    of standard time in April, and in October, clocks
    are set back one hour to return to standard time.

68
Why is it hot in the tropics?
69
Why is it cold at the poles?
70
The seasons are caused by
  • Changes in the angle at which the suns rays
    strike Earths surface.
  • unequal heating
  • rotation of the earth on its axis
  • revolution of the earth around the sun
  • 23.5O tilt of the earth axis from perpendicular
    to the plane of the ecliptic
  • time exposure

71
Equinoxes
Section 2 Movements of the Earth
Chapter 26
  • equinox the moment when the sun appears to cross
    the celestial equator
  • At an equinox, the suns rays strike Earth at a
    90 angle along the equator.
  • The hours of daylight and darkness are
    approximately equal everywhere on Earth on that
    day. (12 hours)

72
EQUINOXES VERNAL(spring), MARCH
21 AUTUMNAL(Fall), SEPTEMBER 21
73
Summer Solstices
Section 2 Movements of the Earth
Chapter 26
  • solstice the point at which the sun is as far
    north or as far south of the equator as possible
  • The suns rays strike the Earth at a 90 angle
    along the Tropic of Cancer.
  • The summer solstice occurs on June 21 or 22 of
    each year and marks the beginning of summer in
    the Northern Hemisphere.
  • The farther north of the equator you are, the
    longer the period of daylight you have.

74
Winter Solstices
Section 2 Movements of the Earth
Chapter 26
  • The suns rays strike the Earth at a 90 angle
    along the Tropic of Tropic of Capricorn.
  • The winter solstice occurs on December 21 or 22
    of each year and marks the beginning of winter in
    the Northern Hemisphere.
  • Places that are north of the Arctic Circle then
    have 24 hours of darkness.
  • Places that are south of the Antarctic Circle
    have 24 hours of daylight at that time.

75
SOLSTICES SUMMER, JUNE 21 WINTER, DECEMBER 21
Where are the overhead rays of the sun on these
days? Which parts of the earth are in darkness
and light? For how long?
76
The Seasons
Section 2 Movements of the Earth
Chapter 26
  • The earth is tilted 23.5º from perpendicular to
    the plane of the ecliptic.

77
Notice these four important parallels. Where do
they occur? Why?
Tropic of Cancer at 23.5º N Tropic of Capricorn
at 23.5º S Arctic Circle (66.5 º N) Antarctic
Circle (66.5º S)
78
Effects of the Seasons
  • Changes in solar intensity
  • Changes in solar altitude
  • Changes in day length
  • Changes in temperature
  • All of these changes are most extreme at high
    latitudes and minimized at the equator.
  • We will talk more about this in chapter 22.
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