CONDENSED LECTURE NOTES 1-9
Comment: 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 already
know and put the pieces of information together to come up with a conclusion.
LECTURE 1: ORIGIN OF THE SOLAR SYSTEM
Our sun is one of about 200 billion stars in the Milky Way galaxy.
Based on a number of lines of
evidence, we believe the sun and its solar system, including Earth, to have originated about 4.5 billion
From telescope observations we infer that the majority of star formation takes place in
nebulae, clouds of gas and dust in space.
Over time clouds with sufficient density slowly collapse, with
clumps of matter shrinking under the influence of their own
This process is aided by
, in which light and particles from nearby stars hit individual particles in the cloud,
accelerating them inward.
Eventually larger clumps separate into smaller ones, and one of these may
eventually condense into a spinning, bulging
, the center of which becomes a star and the
outer material possibly becoming a series of planets.
provide us with a lot of information about the history of our solar system.
There are many
different types of meteorites.
Some contain clumps of the very first matter to condense, but never joined
the sun or a planet and thus stayed pristine for over 4 billion years.
Other meteorites are from small
planetoids that began to form but then were destroyed during early, violent collisions; these give us
snapshots of what happens deep inside a planetary body, much deeper than we can dig or drill here on
Others are blasted-off pieces of other planets.
Eventually the matter in our solar system condensed into the arrangement of planets and other bodies we
Based on the physics of a rotating disk of dust we would expect the inner planets to be larger
and denser than the outer ones, but we find that this is only partially the case.
(Mercury, Venus, Earth, and Mars) are small but dense, containing rock and metal but relatively little
(gaseous or liquid) material. Beyond the inner planets lies the
, a zone of dispersed
rocky material without enough mass to create a planet of its own.
Uranus and Neptune) are much larger
, consisting largely of light atoms and molecules
(hydrogen, helium, methane, ammonia) in their gaseous or liquid form, though possibly with rocky
We postulate that when the sun condensed enough to start the fusion reaction that provides its
energy, the early, violent solar wind drove volatiles away from the inner planets, a closer-to-home