Astronomy Chapter 3

Scientific Thinking
based on everyday ideas of observation and trial and error experiments
Ways people used science in the past
keeping track of time/seasons
agriculture
religious purposes
aiding navigation
What did ancient civilizations achieve in astronomy?
daily timekeeping
seasons and calendars
lunar cycles
planets and stars
predicting eclipses
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Ancient greek science
math and science originated in middle East
Babylonia-time and circles

Greeks first known to make scientific models of nature.. geocentric model

Pluto and Aristotle
Earth-center of the universe
Heavens must be “perfect”
Perfect spheres in perfect circles

difficult to explain retrograde motino

Ptolemy (AD 100-700)
Ptolemaic model… sufficiently accurate

Planets go backward in the model circle on a circle

How did Islamic scientists preserve/extend Greek science?
Baghdad- holds Astronomy info
Europe- middle/Dark ages…

Knowledge went back to Europe in the renaissance.

Renaissance: rediscovered what Greeks had learned

Copernicus (1473-1543)
proposed sun centered model
something going around something else
determine layout of the solar system
correct planetary distances in AU
incorrect-still used perfect circles
Tycho Brahe (1546-1601)
complied the most accurate naked eye measurements
couldn’t detect stellar parallax
geocentric
other planets go around the sun
Johannes Kepler (1571-1630)
tried to match Tycho’s observation with circular orbits
eventually led to ellipses

ellipse: elongated circle.. focus points

Kepler’s 1st law of planetary motion
the orbit of every planet around the sun is an ellipse with the sun at one focus
Kepler’s 2nd law of planetary motino
as a planet moves around its orbit, it sweeps out equal areas in equal times
Kepler’s third law of planetary motino
more distant planets orbit the sun at slower average speeds
Galileo’s object to Copernican view
1. Earth could not be moving because objects in air would be left behind
2. Noncircular orbits are not “perfect” as heavens should be
3. If Earth were really orbiting the Sun, we’d detect stellar paralax
Overcoming the first objection
Aristotle- all objects naturally come to rest

Galileo- an object that will stay in motion unless a force acts to slow them down
Newton’s 1st law of motion

Overcoming the second objection
Tycho- comet and supernova
challenged idea of perfection

Using telescopes, Galileo saw: sunspots on sun
mountains an valleys on the moon, not a perfect sphere

Overcoming the third objection
Galileo looked at Milky Way with telescope made out of stars.. considered that stars are really far

Galileo didn’t measure parallax with telescope

Galileo saw four moons orbiting Jupiter
shocking… moons move around moving planet
Phases of Venus
prove that it orbits Sun not Earth
What practical value did astronomy offer to ancient civilizations?
It helped them keep track of time and seasons, and it was used by some cultures for navigation
Scientific Thinking is _________.
based on everyday ideas of observation and trial and error experiments
The names of the seven days of the week are based on __________.
the seven naked eye objects that appear to move along the constellations
The metonic cycle is _________.
used to keep lunar calendars approximately synchronized with solar calendars
Ptolemy was important to the history of astronomy because he __________.
developed a model of the solar system that made sufficiently accurate predictions of planetary positions to remain in use for many centuries.
The ancient Greeks get a lot of attention for their contribution to science because ________.
they were the first people known to try to explain nature with models based on reason and mathematics, without resort to supernatural
What do we mean by a geocentric model of the universe?
a model designed to explain why we see in the sky while having Earth at the center of the universe
What was the Ptolemaic model?
An Earth centered model of planetary motion published by Ptolemy
The great contribution of Nicholas Copernicus was to _________.
create a detailed model of our solar system with the Sun rather than the Earth at the center
The great contribution of Tycho Brahe was to ___________.
observe planetary positions with sufficient accuracy so that Kepler could later use the data to discover the laws of planetary motion
Stellar paralax was ____ observed by Galileo
NOT
The focus of an ellipse is ______ located precisely at the center of the ellipse
NOT
Not one of direct consequence of Kepler’s laws
the force of attraction between only 2 objects decreases with the square of the distance between their centers
Scientific models are used to ________.
make specific predictions that can be tested through observations or experiments
In science, a broad idea that has been repeatedly verified so as to give scientists great confidence that it represents reality is called a __________.
theory
Suppose the planet uranus were much brighter in the sky, so that it was easily visible to the naked eye what would most likely be true in this case?
A week would eight days instead of 7.
How does a 12 month lunar calendar differ from our 12 month solar calendar?
It was 11 fewer days
What best describes a set of conditions under which archaeoastronomers would conclude that an ancient structure was used for astronomical purposes?
the structure has holes in the ceiling that allow viewing the passage of constellations that figure prominently in the cultures folklore
How did the Ptolemaic model explain apparent retrograde motion?
the planets moved along small circles that moved on larger circles around the Earth
When Copernicus first created his sun-centered model of the universe, it did not lead to substantially better predictions of planetary positions than the ptolemaic model..why not?
Copernicus used perfect circles for orbits of the planets
Earth is farthest from the Sun in July and closest to the sun in January. During which season is Earth moving fastest in its orbit?
Winter
According to Kepler’s 3rd law, how does a planet’s mass affect its orbit around the Sun?
mass has no effect on orbit around the Sun
All statements are true.. which deals with Kepler’s 3rd law?
Venus orbits the Sun at a slower average speed than Mercury
Suppose a comet orbits the Sun on a highly eccentric orbit with an average (semimajor axis) distance of 1 AU. How long does it take to complete each orbit?
1 year which we know from Kepler’s 3rd law
Galileo challenged the idea that objects in heaven were perfect by__________.
observing sunspots on the sun/and mountains on the moon
Galileo observed all of the following… which observation offered direct proof of a planet orbiting the sun?
phases of Venus
Which of the following is not with the major hallmarks of science?
Science consists of proven theories that are understood to be true explanations of reality
Which of the following is not a good scientific theory?
A scientific theory cannot be accepted until it has been proven true beyond all doubt
Which one uses the word “theory” correctly?
Einstein’s theory of relativity has been tested and verified thousands of times
Imagine that despite all the evidence, Earth actually is not rotating and orbiting the Sun. Which hypothetical observation would be inconsistent with Sun centered view of the Solar System?
We discover a small planet beyond Saturn that rises in the west and sets in the East each day.

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