5.8D Earth, Sun & Moon
Key Concept 1: We can identify and compare the physical
characteristics of the Sun, Earth, and Moon, such as surface,
temperature, geological features, composition, and size.
Alert students to look for data that shows what these celestial bodies
have in common, and how they are different. Using library books, the
Internet, and other research resources, students will need to sort
information into agreed-on categories as individuals, partners, or teams.
Be careful that book copyrights are recent and that websites are authentic
science resources so that students acquire valid and up-to-date
information.
The Sun is an average yellow star at the center of our Solar System
composed of glowing hydrogen and helium gases. About 109 Earths
could fit across the diameter of the Sun, while the volume of the Sun
could hold 1,000,000 Earths inside. The Sun’s enormous mass creates
enough gravity to pull in orbit the classic and dwarf planets, their assorted
moons and rings, asteroids, meteoroids, and thousands of tiny frozen
worlds. The Sun’s mass also creates tremendous heat and pressure in its
core causing the hydrogen to fuse into helium which gives off heat and
light energy (which only stars can do). The Sun also has a huge magnetic
field which gets twisted in places on the surface where the gases are not
as hot causing temporary large marks called sunspots. Often these twisted
magnetic lines snap releasing huge amounts of gas and energy called
solar prominences or flares. The temperature of the Sun’s surface is 6,000°
C (Celsius) or 11,000° F (Fahrenheit). The Sun has six layers: Core,
Radiative Zone, Convective Zone, Photosphere, Chromosphere, and
Corona.
The Earth is a planet that orbits third from the Sun. The size of the Earth
is about 1/109 the diameter of the Sun, but four times the diameter of
the Moon. Unlike the Sun, whose gravity pulls the entire Solar System
around it, only one moon revolves around Earth. Unlike the Sun, the Earth
and Moon do not give off their own heat and light, but reflect sunlight.
The Earth is 93,000,000 miles from the Sun, which is just the right distance
where water can exist naturally in three forms: solid ice mainly at polar
regions; liquid water in streams, rivers, ponds, lakes and oceans that cover
¾ of the Earth’s surface; and gas (water vapor) in our atmosphere. Unlike
the Sun and Moon, Earth has life and water in all three states. Unlike the
Sun which is a glowing ball of gas, Earth is rocky and made of three
major layers: core, mantle and crust. The rigid outer mantle and the crust
make up a layer that is broken into massive plates that move very slowly
causing the surface of our Earth to form a diverse assortment of
landforms such as continents, mountains, volcanoes, etc. New surface is
created on the ocean floor, while old surface plates get pushed down
elsewhere. Erosion constantly sculptures old landforms and creates new
ones. Unlike the Moon, which has no measurable atmosphere, the Earth
has a thin atmosphere made of a thin mixture of nitrogen and oxygen
(produced by plants), whereas the Sun is made entirely of hot gas. The
temperature range on Earth varies from -89° C to 57° C (-128.2° F to
134.6° F).
The Moon is the Earth’s only natural satellite. Planet Earth is the first inner
planet to have a moon (Mercury and Venus have no moons). Earth is the
only planet to have just one moon; Mars has two moons and the gas
giants have huge numbers of moons. The Moon is ¼ the diameter of
Earth, has 1/6 the gravity of Earth, and orbits the Earth once a month
(about every 29 days). The surface of the Moon shines by reflected
sunlight as does the Earth. However, because the Moon revolves around
the Earth and changes its angular position between the Earth and the Sun,
different amounts of sunlight illuminate the Moon during the month
creating different phases of the moon (studied in 4th grade). The Moon’s
surface is covered in dusty soil, craters, and lava flows (Mare) caused by
ancient meteorite impacts because there is no atmosphere to weather or
erode the surface. The Earth, in contrast, has few impact craters that
remain due to erosion and movement of the crust. The Moon has small
hills and numerous mountains.
Key Concept 2: The Sun is made of gases, while the Earth and Moon
are made largely from rock.
Because the Sun is a star, it is composed entirely of glowing gases. The
Earth and Moon’s rocky composition is similar with iron cores, rocky
mantles, and surface rocks made of silicates and other minerals. Both the
Earth and the Moon have magma that escapes into the surface as lava;
although the Moon no longer has active volcanoes. The Earth’s large iron
core spins creating a magnetic field, while the small Moon core does not
spin and creates no magnetic field.
Key Concept 3: The Sun and Earth have very different atmospheres,
while the Moon does not have an atmosphere, and only the Earth has
liquid water.
Unlike the Moon, which has no atmosphere, the Earth has a thin
atmosphere made of a mixture of oxygen (produced by plants) and
nitrogen, whereas the Sun’s is made entirely hot gas. Earth is 93,000,000
miles from the Sun, which is just the right distance to make Earth the only
body in the Solar System that has water in three forms: as solid ice mainly
at polar regions; as liquid water in streams, rivers, ponds, lakes and
oceans that cover ¾ of the Earth’s surface; and as a gas (water vapor) in
our atmosphere. The Moon has a small amount of frozen water detected
at the poles, but the Sun is too hot for water to exist.