Chapter 2, Lesson 1 The Sun-Earth-Moon System

1
Chapter 2, Lesson 1The Sun-Earth-Moon System

• Grade 6 Science
• Ms. Amanda and Ms. Diana

2
Earth and the Universe

• Earth is one of eight planets that orbit the Sun.
• The Sun is one of billions of stars that make up
  the Milky Way galaxy.
• The Milky Way is one of billions of galaxies in
  the universe.

3
The Scale of the Solar System

• The Sun is 100 times wider than Earth and 10
  times wider than the planet Jupiter. The Sun and
  Jupiter are the two largest objects in the solar
  system.

4
Motions of the Earth

• Without the Suns pull, Earth would move off into
  space in a straight line.
• Earths orbit is nearly round, or elliptical.
• The orbit of an object around another object is
  revolution.
• It takes Earth 365.25 days, or one year, to
  revolve around the Sun once.

5
Measuring Distance

• An astronomical unit (AU) can be used to measure
  distances to objects in the solar system.
• An AU is the average distance between Earth and
  the Sun, approximately 150 million km.

6
Day and Night

• Rotation is the spin of an object around its
  axis.
• Earth spins, or rotates, on its axis like a top.
• Earths rotation causes day and night.
• The side of Earth facing the Sun is in daylight.
  The side of Earth away from the Sun is in
  darkness.
• Earth makes one full rotation every 24 hours.

7
Earths Tilt and Seasons

• Seasons occur because Earths tilt does not
  change as Earth orbits the Sun.

8
Equinox

• An equinox occurs when Earths rotation axis is
  tilted neither toward nor away from the Sun.
• An equinox occurs twice each year. These two days
  signify the beginning of spring and fall.

9
Solstice

• When the Earths rotation axis is tilted directly
  toward or away from the Sun a solstice occurs.
• When the North Pole is toward the Sun, it is
  summer in the northern hemisphere.
• When the South Pole is toward the Sun, it is
  winter in the northern hemisphere.

10
The Moon

• Gravity holds the Moon in orbit around Earth.
• The Moon is about one-fourth the size of Earth,
  is dry, airless, and made mostly of rock.
• The Moon rotates on its axis, and revolves around
  Earth, orbiting Earth once every 27.3 days.
• Because the Moon revolves and rotates in the
  same amount of time, the same side of the Moon
  always faces Earth.

11
The Moon

• The Moon is visible because it reflects sunlight.
• The Moon completes a cycle of phases every 29.5
  days.

12
Tides

• Tides are the periodic rise and fall of the
  oceans surfaces caused by the gravitational
  force between Earth and the Moon and the Sun.
• The Moon has more influence on tides than the Sun
  because it is closer to Earth than the Sun.
• High tides on Earth occur at locations closest to
  and farthest from the Moon.
• Most coastlines have two high tides and two low
  tides each day.

13
Spring Tides

• When Earth and the Moon are in line with the Sun,
  the Suns gravitational pull adds to the Moons
  gravitational pull.
• As a result, high tides are higher than usual.
• Tides at this time are called spring tides.
  Spring tides occur during full moon and new moon
  phases.

14
Neap Tides

• During the first and third quarter moons, the
  gravitational pull of the Moon is perpendicular
  to the gravitational pull of the Sun.
• High tides are lower than usual. Tides at these
  times are called neap tides.

15
Eclipses

• An eclipse is the movement of one solar system
  object into the shadow of another object.
• During a solar eclipse, a small part of Earth is
  in the Moons shadow.
• The Moon appears to completely or partially cover
  the Sun.

16
Lunar Eclipse

• During a lunar eclipse, Earths shadow completely
  or partially covers the Moon.
• The Moon is visible during a total lunar eclipse
  because light changes direction as it passes
  through Earths atmosphere.