• 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.

A. The Earth's Subsystems (Spheres):

                            
        Earth's Subsystems (Four Spheres)
 

• biotic - living; abiotic - nonliving; all four spheres are interconnected

(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.

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.

• 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.

• 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: "nebula 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

(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).

                            
                   Relative Sizes of the Planets