Motions of Earth, Moon, and Sun - PowerPoint PPT Presentation

Loading...

PPT – Motions of Earth, Moon, and Sun PowerPoint presentation | free to view - id: 7570aa-NWYxM



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

Motions of Earth, Moon, and Sun

Description:

Unit 4 Motions of Earth, Moon, and Sun – PowerPoint PPT presentation

Number of Views:64
Avg rating:3.0/5.0
Slides: 27
Provided by: Joan3180
Category:
Tags: earth | moon | motions | sun

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: Motions of Earth, Moon, and Sun


1
Unit 4
  • Motions of Earth, Moon, and Sun

2
Apparent Motions of Celestial Objects
  • Apparent motion is the motion an object appears
    to make. Can be real or an illusion.
  • Stars appear to move across the sky from east to
    west, however this is a result of the Earths
    rotation.

3
Daily Motion and Stars
  • Most celestial objects appear to move across the
    sky from east to west.
  • Vast majority are stars.
  • The paths of these celestial objects are
    circular, the polar constellations, or an arc.
  • All motion is at a constant rate of 15 degrees
    per hour for a total of 360 degrees in 24 hours.

4
Apparent Motions of the Planets
  • Planets daily motion is similar to that of
    stars, however over a period of weeks or months
    the planets appear to change position with
    respect to the stars.
  • This motion is not uniform. The planet will
    undergo the same motion from year to year but in
    different locations in the sky.
  • The complicated motion is explained by the fact
    that all the planets rotate and revolve around
    the sun at different rates.

5
Apparent Motions of Earths Moon
  • Follows daily east to west motion
  • Rises 50 minutes later each day
  • Shifts eastward each day compared to the
    background of the stars.

6
Apparent motions of the Sun
  • The sun also seems to move across the sky
  • The path is in the shape of an arc
  • The path changes with the seasons
  • In the summer the days are the longest, the sun
    rises north of east and sets north of west,
    resulting in a longer arc
  • In the winter the days are shortest, the sun
    rises south of east and south of west, resulting
    in a shorter arc
  • In the spring and fall days are almost equal, the
    sun rises due east and sets due west

7
Changes in the Suns Altitude
  • Sun is always at its highest position at local
    solar noon
  • Altitude depends on time of year and location of
    observer
  • Only between latitudes 23 ½ degrees N and S can
    the sun be observed directly overhead

8
Models that Explain Apparent Motions
  • Geocentric Models- Earth is the center of the
    solar system, Earth is stationary and everything
    revolves around it. (early cultures accepted
    this)
  • Explained the motions of the stars, sun, and
    moon, but not the planets.
  • Planets had orbits while they orbited
  • Heliocentric Models- sun centered model
  • Earth rotates on its axis and orbits the sun
  • Daily motion of stars is explained by Earths
    rotation
  • Motions of the sun are explained by Earths tilt
    and revolution

9
Actual Earth Motions
  • Moves with the Milky Way as it expands
  • Around the center of the galaxy once every 225
    million years
  • Rotates and revolves around the sun in an orbit

10
Rotation of Earth
  • Tilted 23 ½ degrees from a line perpendicular to
    the plane of its orbit to the sun
  • Axis remains at the same tilt the entire time it
    orbits the sun.
  • Rotates counterclockwise, from west to east
  • Satellites have proven Earths rotation

11
Other Evidence of Earths Rotation
  • Foucault pendulum- if allowed to swing freely the
    path will appear to change in a predictable way.
    If the Earth did not rotate the pendulum would
    maintain its original path.
  • Coriolis effect- merry-go-round example

12
Evidence of Earths Revolution Around the Sun
  • Earths change in distance does NOT cause the
    change in seasons
  • If Earth didnt rotate around the sun the same
    part of the Earth would receive the more direct
    rays of sunlight
  • See different constellations at different times
    of the year
  • Sun appears to change slightly in size
  • Slight changes in the Doppler effect

13
Earth and Moon Motions and Time
  • Throughout time people have used the motions of
    the Earth and moon as a frame of reference for
    time.
  • A month is determined by one cycle of the moons
    phases
  • One day is determined by the rotation of the
    Earth
  • What determines the length of a year?

14
Local Time
  • Time based on the rotation of Earth as reflected
    in motions of the sun
  • All places on the same longitude have the same
    local time
  • If you move slightly east or west there will be
    different local times due to Earths rotation

15
Local Solar Time
  • For any location the sun reaches its highest
    point once each day, solar noon.
  • The time it takes the Earth to rotate from solar
    noon to solar noon on two consecutive days is
    known as the solar day.
  • This type of time is known as solar time.
  • Does a solar day have a constant length?
  • A mean solar day has been established, divided
    into exactly 24 hrs.

16
Time Zones
  • There is no limit to the amount of longitude
    lines that could exist.
  • 24 time zones in 15 degree bands have been drawn
  • Each 15 degree segment has the same time
  • From one band to another is an increase or
    decrease of one hour

17
Actual Motions of Earths Moon
  • Revolves around the Earth in an elliptical orbit
    with a period of about 27 1/3 days
  • Half of the moon receives light at all times from
    the sun.
  • Phases of the moon are cyclic. It takes 29 ½
    days from full moon to full moon

18
Moon Phases
  • New Moon - The Moon's unilluminated side is
    facing the Earth. The Moon is not visible (except
    during a solar eclipse).
  • Waxing Crescent - The Moon appears to be partly
    but less than one-half illuminated by direct
    sunlight. The fraction of the Moon's disk that is
    illuminated is increasing.
  • First Quarter - One-half of the Moon appears to
    be illuminated by direct sunlight. The fraction
    of the Moon's disk that is illuminated is
    increasing.
  • Waxing Gibbous - The Moon appears to be more than
    one-half but not fully illuminated by direct
    sunlight. The fraction of the Moon's disk that is
    illuminated is increasing.
  • Full Moon - The Moon's illuminated side is facing
    the Earth. The Moon appears to be completely
    illuminated by direct sunlight.

19
More Moon Phases
  • Waning Gibbous - The Moon appears to be more than
    one-half but not fully illuminated by direct
    sunlight. The fraction of the Moon's disk that is
    illuminated is decreasing.
  • Last Quarter - One-half of the Moon appears to be
    illuminated by direct sunlight. The fraction of
    the Moon's disk that is illuminated is
    decreasing.
  • Waning Crescent - The Moon appears to be partly
    but less than one-half illuminated by direct
    sunlight. The fraction of the Moon's disk that is
    illuminated is decreasing.

20
(No Transcript)
21
http//aa.usno.navy.mil/graphics/Moon_movie.gif
22
(No Transcript)
23
Tides
  • Cyclic rise and fall of the oceans
  • Caused by the gravitation between the Earth,
    moon, and sun.
  • There is a bulge of water directly under the
    moons position.
  • When the sun, moon, and Earth are in a straight
    line, the sun enhances the tidal effect, and high
    tides are lower and low tides are higher.

24
Eclipses
  • All opaque objects that do not give off their own
    light cast shadows in space.
  • When another celestial object moves into a shadow
    of another object, there is an event called an
    eclipse.

25
Lunar Eclipse
  • Occurs when the moon revolves into the shadow of
    Earth, at the full moon phase.
  • Averages to about 2 total lunar eclipses a year.
  • Partial eclipse occurs when only part of the
    Earths shadow covers the moon.

26
Solar Eclipse
  • Rare
  • The new moon can barely block out the sun. When
    this happens a shadow is cast on the Earth. The
    moons shadow can barely reach the Earth.
  • A total eclipse can only be seen at any one
    location on Earth for up to 7 ½ minutes and once
    every 200 years.
About PowerShow.com