Chapter 3: The Science of Astronomy
The Ancient Roots of Science:
In what ways do all humans employ scientific thinking?
-scientific thinking is based on everyday ideas from observing and trial and error
How did astronomical observations benefit ancient societies?
-in keeping track of time and seasons.
-this was done for practical purposes, example: for agriculture
-for religious and ceremonial purposes as well
-this aids in navigation
-ancient people of central Africa (6500 BC) could predict seasons from the
orientation of the crescent moon
What did ancient civilizations achieve in
- daily time keeping
-tracking the seasons and calendar
-monitored lunar cycles
-monitored planets and stars
-predicting eclipses and etc
-Egyptian Obelisk- this is how shadows tell time of day
-England had Stonehenge which was erected around 1550 BC
-Mexico had the MOdel of the Templo Mayor
-SW United States: "sun dagger" masks summer Solstice
-Scotland has a 4000 year old stone circle, when moon rises every 18.6 years
-Peru :lines and patterns, which some are aligned with stars
-Machu Picchu, Peru have structures aligned with solstices
- South Pacific:Polynesians were very skilled in the celestial navigational arts
- France: Cave painting from 18,000 BC may suggest lunar phases knowledge
-China: earliest known records of supernova explosions which was around 1400
Ancient Greek Science:
Why does modern science trace its roots to the Greeks?
-Mathematical and scientific heritage originated with the civilization of the Middle
-Artis's reconstruction of The Library of Alexandria
-Greeks were the first known to make models of nature
-they tried to explain patterns in nature without myth or the supernatur to be
Greek geocentric model (400 BC)
Eratosthenes measures the Earth (240 BC)
How did the Greeks explain planetary motion?
--Earth is at Center of universe
-the heavens must be "perfect" because the objects move on a "perfect" spheres
or in circles
-PLato and Aristotle were instrumental in this theory for planetary motion
- Unfortunately this made it quite difficult to explain apparent retrograde motion
of planets...ex: Mars
-over a period of of 10 weeks, Mars appears to stop, back up, then forward once
- The Ptolemaic model is most sophisticated geocentric model by Ptolemy (AD
-sufficiently accurate to remain in use for 1500 years
-Arabic translation of Ptolmey's worked Almagest (The greatest compilation)
Answer is : D
How did Islamic scientists preserve and extend science?
-The muslim world preserved and enhanced the knowledge from Greeks while
Europe was in Dark Ages
-Al-Mamun's House of Wisdom in Baghdad was a wonderful center for learning
approx. AD 800.
-The fall of Constantinople (Istanbul) in 1453, Eastern scholars headed west to
Europe, carrying knowledge that was instrumental in igniting the European
The Copernican Revolution:
How did Copernicus,Tycho and Kepler challenge the Earth-centered idea?
-Corpernicus proposed the sun centered model (pub. 1543)
-He used model to show the layout of the solar system
-Yet the model was no more accurate in predicting planet positions, due to using
perfect circles still in the model
Tycho Brahe (1546-1601)
-He complied the most accurate naked eyes
measurements that were made in planetary positions.
-He still could not see the stellar parallax and thought
Earth must be the center of the solar system (yet he recognized other planets
orbited the Sun).
Brahe hired Kepler, who used Tycho's observations to find the truth about
Johannes Kepler (1571-1630)
-He first tried to match Tycho's oberservations with circular
-yet, an 8 arcminute discrepancy brought him to eveutally to
An ellipse looks like an elongated circle.
What are Kepler's three laws of planetary motion?
- The first law;The orbit of each planet around the Sun i an ellipses with the Sun
at one focus.
-The second law: As a planet moves around its orbit,it sweeps out equal areas in
the third law:
Most distant planets orbit the Sun at slower average speeds, obeying the
p=orbital period in years
a=average distance form sun in AU
How did Galileo solidify the Copernican revolution?
- overcame major objections to the Copernican view. Three key objections
rooted in the Aristotelian view:
Earth could to be moving because the objects 1. in the air would be left behind
2. Noncircular orbits are not "perfect: as heavens should be.
If in fact Earth was really orbiting Sun, we would see stellar parallax
Galileo's experiments showed that objects in air would in fact stay with Earth
-Aristotle concluded that all objects naturally come to rest
-Galileo brought the idea and showed that objects will stay in motion unless a
force acts to slow the objects down. (this was Newton's first Law of motion)
-Tycho's observations of comet and supernova already challenged this idea
-So Galileo used his telescope and saw;
• sunspots on the sun(imperfections)
mountains and valleys on the moon(this proved it is not a perfect sphere)
Tycho thought he had measured stellar distances, so lack of the parallax seemed
to rule out an orbiting Earth
-Galileo showed stars are much farther than Tycho had fist thought--which with
using his telescope to se that the Milky Way is countless individual stars.
-If stars were much farther away, then lack of detectable parallax was no longer
-Galileo also saw four moons orbiting Jupiter proving that
not all objects orbit Earth
-Galileo observations of phases of venus
-in 1633 the Catholic church ordered Galileo to recent his claim that earth orbits
-his book on the subject was removed form the Church's index of banned book
-Galileo was formally vindicated by the Church in 1992
The Nature of Science:
How can we distinguish science from non-science?
-Defining science is difficult
-Science come from Latin Scientia, defined as "knowledge"
-but not all knowledge comes from science
Idealized scientific method:
-based on proposing and testing hypotheses
Science rarely proceeds in this idealized way:
example could be:
-sometimes we start "just looking" then coming up with possible explanations
-sometimes we follow intuition rather than a particular line of evidence
Hallmarks of Science #1
-modern science seeks explanation for observed phenomena that rely on solely
on natural cases
-scientific model cannot include divine intervention
Hallmarks of Science #2
-Science progresses though the creation and testing of models nature that explain
the observations simply as possible.
-Simplicity= Occam's razor
Hallmarks of Science #3
-a scientific model must take testable predictions about natural phenomena that
would force us to revise or abandon the model if the prediction if the do not
agree with the observations.
What is a scientific theory?
-the owrd theory has dfferent meanings in science that in everyday life
-theory is NOT the same as hypithesis
-a scientific theory must:
explain a wide variety of observations • with few simple principles
• be supported by a large body of evdicen
• NOT have failed any crucial test its validity