terms below that are printed in
are meant to catch your attention, and you will note
that most of them are nouns.
In science nouns are necessary, but verbs—the
of the earth—are
more important and these will be emphasized in Quiz 1.
The quiz will be a mixture of very easy, to a
few quite challenging questions.
The more difficult questions will ask you to take something you al-
ready know and put the pieces of information together to come up with a conclusion.
ORIGIN OF THE SOLAR SYSTEM
Our own sun is a typical star within the Milky Way, a
2 x 10
consisting of diffuse dust and gas within the galaxy, begins to collapse.
is due to the force of gravity, which causes all particles that have mass to be mutually attracted to one
another, and collapse is assisted slightly by the pressure of starlight. As shrinkage continues, the cloud
breaks up into a swarm of smaller clouds, each destined to become a star.
early stage of star formation; it consisted of a central "bulge" surrounded by a rotating flattened disk,
which itself sustains complex internal motions of dust and gas.
Planets, their moons, etc.
from the solar disk, and the sun condensed from the central bulge.
Thus the sun and planets, their
moons, asteroids, comets, meteorites, etc.—the entire
—formed together, at the same time
from the same material.
—Mercury, Venus, Earth, and Mars—are relatively small, dense bodies with small quanti-
(liquids, gases at room temperature). Beyond the orbit of Mars there is a
large gap populated by tens of thousands of small objects, the
, and beyond the asteroids come
the orbits of the
Jupiter, Saturn, Uranus, and Neptune.
(Outermost Pluto, formerly re-
garded as a planet, has been demoted to “dwarf planet” status.)
Outer planets, known as “gas giants,”
are of low density; they consist mostly of volatile substances and are relatively large bodies.
late that early in the development of the solar system, the proto-sun heated up and drove away a large
amount of gas in its near vicinity, leaving inner planets as small bodies consisting chiefly of rock and
Outer planets survived with less loss of material, and therefore they have a more sun-like compo-
The earth consists of a metallic
16% of its volume) overlain by a
83%) consisting of
dark, dense rock.
At the surface, the earth’s
(<1%) consists of a great variety of rock types, and it
conceals the mantle almost everywhere.
If the early earth had been stripped of much of its volatile substance, then there are two logical possibili-