Course Introduction
The Subject Matter of Earth Science
- What causes Volcanic
Eruptions?
- What causes earthquakes?
- What causes hurricanes and
tornadoes?
- How are hurricanes and
tornadoes different?
- What forces are involved in
the making of mountains?
- How has our climate changed?
How is it changing?
- How are different rocks and
minerals produced?
- How did our Moon originate?
A. Earth Science (defn):
all the sciences that collectively seek to understand Earth and its
neighbors in space.
- Geology (defn) - the study (logos) of the Earth (geo)
- Physical Geology -
examines the materials of the Earth and seeks to understand the processes
and forces acting beneath and on the Earth's surface
- Historical Geology -
studies the origin of the Earth and its development through time -
sequence of fossils in rock beds
- Meteorology - the
study of the atmosphere and the processes that produce weather and climate
- Oceanography - the
study of the oceans and oceanic phenomena: e.g., the study of sea water,
coastal processes, seafloor topography, and marine life.
- Astronomy - the study
of the universe; it includes the observation and interpretation of
celestial bodies and phenomena.
B. Earth - our home - is a unique and beautiful
entity. It is also a complex entity because it is not static.
- It is a dynamic place with
many interacting parts that form a complex and continuously interacting
whole - "Earth System".
- a
change in one part of the Earth System can produce changes in one or any
of all of the other parts.
The Earth's Subsystems (Spheres):
Earth's Subsystems (Four Spheres)
- biotic - living; abiotic - nonliving; all four spheres are
interconnected
(1) Atmosphere - a thin layer of gases (below 480 km)
surrounding the Earth, and held to the Earth by gravity; it forms a protective
boundary between outer space and the biosphere
(2) Hydrosphere - an abiotic open system
that includes all of the Earth's waters (surface, atmosphere, & crustal; & gaseous, solid, & liquid)
(3) Lithosphere - the Earth's crust and that portion of the upper
mantle directly below the crust that extends downward to 70 kilometers (km) (45
miles)
(4) Biosphere (ecosphere) - that area where the atmosphere, hydrosphere,
and lithosphere function together to form the context within which life exists.
- it is an interconnected web
that links all organisms with their physical environment
- just as the other three
spheres impact and shape life, life itself impacts and shapes the other
three spheres
C. Scientific Inquiry (The Scientific Method)
(1). The Goal of Science
- The job of the scientist is
to learn about the natural world that surrounds them; to attempt to
discover how and why it works the way it does.
- This task is made easier
because the universe is a regular and predictable place.
- It is the job of the
scientist to discern the predictable patterns, and discover the
"simple laws" that are responsible for them.
- Science thus operates under
the following assumption: natural laws that control our universe exist,
and can be understood by the human mind.
(2). How Our Present Way of Conducting Science Came to Be
- The first science was
astronomy. It came about out of a practical need for a reliable calender that could be used to assist farmers.
- In the early 17th century,
men like Galileo first began to make careful and systematic observations
of natural phenomenon and to try explaining them.
- Galileo made many careful
measurements.
- He and some of his
contemporaries introduced the concept that a theory was valid only
insofar as it predicted and explained the observations on which it was
based.
- They thus established a
close connection between observations and theory, which is
the essence of the scientific method (scientific inquiry).
(3). The Scientific Method
- The term scientific
method refers to the principles and processes that guide scientific
investigation.
- It provides the framework
within which scientists try to discover the laws governing the natural
(observable) world.
Steps Involved in the Scientific Method:
1) Observation
- A scientist begins by
making an observation about some system.
- It can involve the making
of measurements of the properties of the system that is being observed.
- These measurements can
range, for example, from finding the size of some object, to finding the
length of time it takes for some process to occur.
- An important characteristic
of measurement is that its accuracy is always limited: in part from
inaccuracies inherent in any measuring device.
2) The Hypothesis/Theory
- The scientist then comes up
with a hypothesis to answer his/her question and explain his/her
observations.
- After a hypothesis has been
formulated, it must be tested. It must predict the observations; if
it doesn't, it must be discarded and another found.
- In order for a hypothesis
to be considered valid, it must be (experimentally) verified. (One way of
testing a hypothesis is to conduct a controlled experiment).
- If a hypothesis has
survived extensive scrutiny, and competing hypotheses have been
eliminated, a hypothesis is elevated to the status of a scientific theory.
3) The Scientific Law
- After a theory has survived
many years of experimental investigation, it is frequently accorded the
status of a scientific law.
Summary: The Scientific Method
- Observation
- Hypothesis/Theory
- Testing (perhaps via a
controlled experiment)
- Law
D. Our Galaxy (the "Milky Way") and Solar System
- Our sun & solar system
is within the Milky Way Galaxy - just one of millions within the
universe
- Our sun is just one of
billions within the Milky Way Galaxy
- The Milky Way Galaxy is a
"Spiral Galaxy", and we are located far out from the
center of the galaxy on one of the spiral arms - the "Orion Arm"
Structure of the Milky Way Galaxy
(1) Galactic Dimensions
- speed of light: 299,792
km/sec
- at this speed, the distance
that light can travel in one year is more than 9 trillion km
- this distance is called a
"light year"
- we use the "light
year" as a distance unit
- 1 light year = 9,454,000,000,000
km
- our moon = 1.28 seconds
away in light speed
- our solar system's diameter
= 11 hours in light speed
- our entire galaxy ~ 100,000
light years
- the entire known universe ~
12 billion light years
(2) Formation of our Solar System: "nebular
hypothesis"
- our solar system formed from
a rotating, cloud of gas, dust,and ice - a
"nebula" (4.6 billion years ago)
- a proto-Sun formed
at the center of the nebula where the most mass existed
- the rotating cloud of gas
and dust flattened out an assumed a disk shape
- mass accumulated by
"accretion" away from the center of the nebula - protoplanets
- the protoplanets
grew in size - "planetesimals"
as the
proto-Sun grew in size it became hotter due to intense pressures; and
eventually thermonuclear reactions within the sun occurred - fusion -
the conversion of hydrogen to helium - which releases tremendous amounts of
energy
Nebular Hypothesis
Nebular
Hypothesis Power Point Presentation (PPT)
(3) Our Solar System
- Is comprised of nine
planets: Mercury, Venus, Earth, Mars [the terrestrial (Earth-like)
planets]; and Jupiter, Saturn, Uranus, Neptune
[the Jovian (Jupiter-like) planets], and Pluto.
- The terrestrial, or inner
planets, are small, dense (5 times that of water), rocky, and metalic, with minor amounts of gases (i.o.w., a meager atmosphere).
- The Jovian,
or outer planets, are large, not very dense (only 1.5 times that of
water), and contain a large percentage of gases (i.o.w.,
a thick atmosphere -- of mainly hydrogen and
helium).
Orbits and Relative Positions of the
Planets
Relative Sizes of the Planets