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
of the earth—are more important and these will be emphasized in
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 already 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
200 billion stars.
consisting of diffuse dust and gas within the
galaxy, begins to collapse.
This 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.
represents an 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.
condensed from the solar disk, and the sun condensed from the central bulge.
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 quantities of
(liquids, gases at room temperature).
Beyond the orbit of Mars there is a large gap populated by thousands of small objects, the
, and beyond the asteroids come the orbits of the
Uranus, and Neptune.
(Outermost Pluto, formerly regarded 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.
postulate 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 metal. Outer planets survived with less loss of
material, and therefore they have a more sun-like composition today.
The earth consists of a metallic
16% of its volume) overlain by a
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.
Initially the earth must have been composed of a mixture of metal and rocky material.
Sources of heat, such as radioactive decay, caused early melting of material with the