Chapter 3 Notes Jessica Brandon

Chapter 3 the science of astronomy

1.     In what ways do all humans employ scientific thinking?

·      Scientific thinking is based on everyday ideas of observation and trial and error experiences.

·       in keeping track of time and season

·      For practical purposes include agriculture

·      For religious and ceremonial purpose

·      In aiding navigation

·      ancient people of central Africa (6500 BC) could predict seasons from the orientation of the crescent moon. (Picture)

·      table 3.1 in book: days of the week were named for the sun, moon, and visible planets.

2.     What did ancient civilization achieve in astronomy?

·      Daily timekeeping

·      Tracking the seasons and calendar

·      Monitoring planets and stars

·      Predicting eclipses

·      And more....

3.     Ways others tell time

·      Egyptian obelisk: shadows tell time of day figure 3.2

·      England: Stone Age completed around 1550 B.C figure 3.3

·      Mexico: model of the templo mayor figure 3.4

·      New Mexico: Anasazi Kiva aligned north-south

·      SW United States: sun dagger marks summer solstice figure 3.5

·      Scotland: 4000 years old stone circle moon rises as shown here every 18.6 years

·      Peru: lines and patterns, some aligned with stars

·      Manchu pic chi, Peru: structure aligned with solstices

·      South Pacific: Polynesians were very skilled in the arts of celestial navigation

·      France: cave painting from 18,000 B.C. May suggest knowledge of luner phase (29 dots).

    China: earliest know records of supernova explosions (1400 B.C)

Section 3.2 Ancient Greek science

·      Our mathematical and scientific heritage originated with the civil action of the Middle East picture map

·      Artists reconstruction of the library of Alexandria

·      Why does modern science trace its roots to the Greeks?

·      *greeks were the first people known to make models of nature

·      they tired to explain patterns in nature without resorting to myths or the supernatural

·      greek geocentric

·      Special topic: Eratosthenes measure the earth

·      *Measurements syene to Alexandria distance about 5000 stadia angle is 7 degree

·      *Calculate circumference of earth7/360 X ( circum. Earth) =5000 stasis

How did the Greeks explain planetary motion?

·      *Earth at the center of the universe

·      *Heavens must be perfect objects move on perfect sphere or in perfect circle

·      Plato and Aristotle (people)

·      but this made it difficult to explain the apparent retrograde motion of planets...

·      Review: over a period of 10 weeks, mars appears to stop back up then go forward again.

·      How did Islamic scientists preserve and extend Greek science?

3.3 the coperican revolution

How did Copernicus tycoon and Kepler challenge the earth centered idea

·      *copernicus proposed the sum centered model published in 1543

·      he used the model to determine the layout of the solar system planetary distance in AU

·      *the model was no more accurate than the Ptolemaic model in predicting planetary position because it still used perfect circles.

·      *tycho Brahe 1546-1601 Brahe compiled the most accurat naked eye measurement ever made of planetary position

·      *He still could not detect stellar parallax and thus still thought earth must be ar the center of the solar system but recognized that other planets go around the sun

·      *He hired Kepler who used tychos observation to discover the truth about planetary motion

·      *Johannases Kepler 1571-1630 Kepler first tried to match tychos observation with circular orbits

·      *But an 8 arcmintue  discrepancy led him eventually to ellipses

·      *What is a ellipse? An ellipse looks like an elongated circle

What are keplers three laws of planetary motion?

·      *Keplers first law: the orbit of each planet around the sun is an ellipse with the sun at one focus

·      *Second law: as a planet moves around it orbit it sweeps out equal times

·      This means that a planet travels faster when it is nearer to the sun and slower when it is farther from the sun.

·      *Third law: more distant planets orbit the sum at slower average speeds obeying the relationship

·      *P squared = a to the third

·      P= orbital period in years

·      A= average distance from sun in AU

·      Question: an asteroid orbits the sun at an average distance a= 4 AU. How long does it take to orbit the sun?

·      Answer: 8 years

How did Galileo solidify the coperican revolution?

·      *Galileo 1564-1642 overcame major objections to the coperican view. Three key objections rooted in the Aristotelian

·      Earth could not be moving because objects in air would be left behind

·      No circular orbits are not perfect as heaven should be

·      If earth were really orbiting sun we'd detect stellar parallax

·      *Overcoming first objection Galileo experiments showed hat objects in air would stay with a moving earth

·      *Aristotle thought that all objects would come to rest

·      *Galileo showered that objects will stay in motion unless a force acts to slow them down (newtons first law)

·      Overcoming second law

·      tycho observation of comet and supernova already challenged his idea.

·      Using his telescope Galileo saw.

·      *Sunspots on the sun (imperfections)

·      *Mountains and valleys on the moon (proving it is not a perfect sphere)

·      Over coming third observation

·      *tycho thought he had measured steller distance so lack of parallax seemed to rule out orbiting earth.

·      *Galileo showed stars must be much farther then tycho thought in part by using his telescope to see that the Milky Way is countless individual stars

·      *If stars were much farther away then lack of detectable parallax was no longer so troubling

·      *Galileo also saw four moons orbiting Jupiter proving that not all objects orbit earth.

·      *Galileo observations of phases of Venus proved that is orbits the sun not earth

·      *In 1633 the Catholic Church ordered Galileo to recant his claim that earth orbits the sun

·      *His book on the subject was removed from the church index of banned books on 1824

·      *Galileo was formally vindicated by the church in 1992

Section 3.4 nature of science

How can we distinguish science from no science ?

·      *defining science can be surprisingly difficult.

·      *Science comes from the Latin scientia meaning knowledge

·      But not all knowledge comes from science.

·      *The idealized scientific method based on proposing and testing hypotheses

·      *Hypothesis= educated guess

·      *But science rarely proceeds in this idealized way for example...

·      *Sometimes we start by just looking then coming up with possible explanation

·      *Sometimes we follow our intuition rather than a particular line of evidence.

·      Hallmarks of science 1

·      Modem science seeks explanations for observed phenomena that rely on nat

·      Hallmark 2

·      Science progresses thought the creations and testing off models of nature that explain the observation as simple as possible simplicity occam razor

·      Hallmark 3

·      A scientific model must make testable prediction about natural phenomena that would focus us to revise or abandon the model if the predictions do not agree with observations

What is a scientific theory?

·      *The word theory has a different meaning in science than in everyday life.

·      *In science a theory is NOT the same as a hypothesis

·      *A scientific  theory must....

·      Explain a wide variety of observation with a simple principles

·      Be supported by a large compelling body of evidence

·      Not have failed ny crucial test of its validity

·      question: Darwin's theory of evolution meets all the criteria of a scientific theory this means....

·      Answer: after more than 100 years of testing Darwin's theory stands stronger than ever having