CHAPTER 3 (3.1-3.4)
Overcoming the second objection:`
- Brahe's observations of comet and supernova already challenged this idea. - Using his telescope, Galileo saw: - Sunspots on the Sun ("imperfections") - Mountains and valleys on the Moon (proving it is not a perfect sphere)
Consequences of Newton's law of gravity:
- Kepler's first two laws apply to all orbiting objects, not just planets. - Ellipses are not the only orbital paths. Orbits can be: - bound (ellipses) - unbound ₀ parabola ₀ hyperbola
Newton 1687: Explanation of Kepler's laws:
- Realized that the same physical laws that operate on Earth also operate in the heavens one universe - Discovered laws of motion and gravity Force = mass x acceleration (if mass is constant)
In what ways do all humans use scientific thinking?
Scientific thinking is based on everyday ideas of observation and trial-and-error experiments.
Overcoming the third objection (parallax):
- Tycho thought he had measured stellar distances, so lack of parallax seemed to rule out an orbiting Earth. - Galileo showed stars must be much farther than Tycho thought — in part by using his telescope to see the Milky Way is countless individual stars. - If stars were much farther away, then lack of detectable parallax was no longer so troubling.
How did Johannes Kepler contribute to Astronomy? A. He determined that planets move in ellipses, and proposed Kepler's Laws of Planetary Motion. B. He discovered the first 4 moons around Jupiter. C. He proved that Brahe's measurements of the heavenly bodies were wrong. D. He showed that comets also move in perfect circles around the Sun.
A
What are Kepler's three laws of planetary motion?
1. The orbit of each planet is an ellipse with the Sun at one focus. 2. As a planet moves around its orbit it sweeps out equal areas in equal times. 3. More distant planets orbit the Sun at slower average speeds: p2 = a3.
What are three kepler's three laws of planetary motions:
1. The orbit of each planet is an ellipse with the Sun at one focus. 2. As a planet moves around its orbit it sweeps out equal areas in equal times. 3. More distant planets orbit the Sun at slower average speeds: p2 = a3.
How did an ancient Egyptian "hour" compare to the one we use today? A. It varied in length depending on the seasons. B. It was shorter (about 45 minutes long). C. It divided the day into 24 equal parts. D. It was defined by whoever was Pharaoh at the time.
A
Ptolemy created an astronomical model that allowed for very accurate predictions of the positions of the stars and planets. Why is his model no longer favoured today? A. His model had the Earth as the center of the solar system. B. It was not able to account for retrograde motion of the planets . C. He assumed that all planets would follow elliptical orbits. D. It relied heavily on supernatural explanations for the motions of the planets.
A
What was Nicolaus Copernicus' most notable contribution to modern day Astronomy? A. He proposed a Heliocentric model of the solar system. B. He proposed Copernicus' Three Laws of Planetary Motion. C. He drastically improved upon the telescope and was the first to observe Jupiter's moons. D. He was able to improve on Ptolemy's model by adding extra epicycles to planetary motion while keeping the Earth at the centre.
A
Hallmark of Science: #3
A scientific model must make testable predictions about natural phenomena that would force us to revise or abandon the model if the predictions do not agree with observations.
Stonehedge
Also winter solstice (Dec. 21, shortest day), sun sets opposite to heel stone but next full moon will rise near the heel stone. At summer solstice (longest day, June 21) sun rises at heel stone. Tradition started around 2950 B.C.
What is an ellipse?
An ellipse looks like an elongated circle.
How did Ancient people of central Africa (6500 BC) predict seasons?
Ancient people of central Africa (6500 BC) could predict seasons from the orientation of the crescent Moon.
Kepler's second Law:
As a planet moves around its orbit, it sweeps out equal areas in 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.
Overcoming the second objection (heavenly perfection):
Brahe's observations of comet and supernova already challenged this idea. Using his telescope, Galileo saw: Sunspots on the Sun ("imperfections") Mountains and valleys on the Moon (proving it is not a perfect sphere)
Kepler's Second Law tells us that a planet with an elliptical orbit will: a. move at a constant speed around the Sun, regardless of its orbit. b. move faster when it is further from the Sun. c. move more slowly when it is further from the Sun. D. slowly spiral into the sun.
C
Kepler's Third Law relates the following characteristics of a planet: a. period and rotational speed. b. average distance and size. c. average distance and period. D. rotational speed and size.
C
Which of the following generally is not a possible orbit in the context of Kepler's First Law? A planet moves in an ellipse with the Sun at one focus. A planet moves in a circle with the Sun at the centre. A planet moves in an ellipse with the Sun at the centre. D. All are possible.
C
Tycho Brahe (1546-1601)
Compiled the most accurate (one arcminute) naked eye measurements ever made of planetary positions. Still could not detect stellar parallax, and thus still thought Earth must be at center of solar system (but recognized that other planets go around Sun). Hired Kepler, who used Tycho's observations to discover the truth about planetary motion.
Hallmark of Science: #1
Modern science seeks explanations for observed phenomena that rely solely on natural causes.
How did Copernicus, Tycho and Kepler challenge the Earth-centered idea? (summary q)
Copernicus created a sun-centered model; Tycho provided the data needed to improve this model; Kepler found a model that fit Tycho's data.
During the Dark Ages, a time when scientific thinking was rapidly regressing in Europe, where did the majority of scientific advancement take place? A. The Americas. B. Australia. C. Middle Earth. D. The Middle East.
D
How did Eratosthenes determine the size of the Earth? A. Measuring the curvature of Earth's shadow during lunar eclipses. B. Google. C. Careful observation of the stars and planets, and how their positions change throughout the seasons with respect to manmade structures. D. Measuring the distance between two cities and considering the position of the sun at noon on the summer solstice in both places.
D
How did Galileo contribute to modern Astronomy? a. He refined the telescope for use as a scientific instrument. b. He discovered the largest 4 moons around Jupiter. c. He showed that Venus actually rotated around the Sun, not the Earth. d. all of the above.
D
How did Tycho Brahe contribute to the field of Astronomy? A. He recruited Kepler as his assistant for analyzing his observational data. B. He determined that comets and novae occur much further away than the moon. C. He took extremely detailed and accurate measurements of the positions of heavenly bodies. D. all of the above.
D
Mexico: Model of the Templo Mayor
Dominant building in the sacred precinct of Tenochtitlan (now Mexico City), ~1325-1521. 80mx100m platform, (31-45)m+30m heights. Dedicated to the Aztec Gods of war and of water. Religious festivals at equinoxes, when sun would rise between the two temples. Destroyed by Spanish Conquistadores and their allies (led by Hernan Cortes) in 1521.
How did Galileo solidify the Copernican revolution?
Galileo overcame major objections to the Copernican view. Three key objections rooted in Aristotelian view were: 1 Non-circular orbits are not "perfect" as heavens should be. 2. Earth could not be moving because objects in air would be left behind. 3. If Earth were really orbiting Sun, we'd detect stellar parallax.
What was Galileo's role in solidifying the Copernican revolution?
Galileo overcame major objections to the Copernican view. Three key objections rooted in Aristotelian view were: 1. not "perfect" as heavens should be. 2. Earth could not be moving because objects in air would be left behind. 3. If Earth were really orbiting Sun, we'd detect stellar parallax.
Overcoming the first objection (nature of motion):
Galileo's experiments showed that objects in air would stay with Earth as it moves. 1. Aristotle thought that all objects naturally come to rest. 2. Galileo showed that objects will stay in motion unless a force acts to slow them down (Newton's first law of motion).
Overcoming the first objection (nature of motion):
Galileo's experiments showed that objects in air would stay with Earth as it moves. Aristotle thought that all objects naturally come to rest. Galileo showed that objects will stay in motion unless a force acts to slow them down (Newton's first law of motion).
Galileo's observations of phases of Venus proved ________?
Galileo's observations of phases of Venus proved that it orbits the Sun and not Earth.
What did Galileo's observation of phases of Venus prove?
Galileo's observations of phases of Venus proved that it orbits the Sun and not Earth.
Why does modern science trace its roots to the Greek
Greeks were the first people known to make models (or theories) of nature. They tried to find rational explanations for patterns in nature. Greek geocentric model (c. 400 B.C)
What was Galileo's role in solidifying the Copernican revolution? (conclusion q)
His experiments and observations overcame the remaining objections to the Sun-centered solar system model.
Hallmark of Science: #2
Science progresses through the creation and testing of models of nature that explain the observations with the fewest assumptions.
How did astronomical observations benefit ancient societies?
Keeping track of time and seasons for practical purposes, including agriculture for religious and ceremonial purposes Aid to navigation
Special Topic: Eratosthenes Measures Earth (c. 240 B.C.)
Measurements: Syene to Alexandria distance ≈ 5000 stadia, angle = 7 Calculate circumference of Earth: 7/360 (circum. Earth) = 5000 stadia circum. Earth = 5000 360/7 stadia ≈ 250,000 stadia Compare to modern value (≈ 40,100 km): Greek stadium ≈ 1/6 km 250,000 stadia ≈ 42,000 km
Kepler's third law:
More distant planets orbit the sun at slower average speeds, obeying the relationship. p2 = a3 p = orbital period in years a = avg. distance from Sun in AU innermost planets are the fastest.
Where did most of our mathematical and scientific heritage originated from?
Most of our mathematical and scientific heritage originated with the civilizations of the Middle East.
How did Copernicus, Brahe, and Kepler challenge the Earth-centered model?
Proposed a Sun-centered model (published 1543) Used model to determine layout of solar system (planetary distances in AU) But, the model was no more accurate than the Ptolemaic model in predicting planetary positions, because it still used perfect circles. Model was also nearly as complex as the Ptolemaic model because he still used circles upon circles (epicycles) to try to get better matches to data.
So how does the Ptolemaic model explain retrograde motion? Planets really do go backward in this model..
Ptolemy used epicycles to explain the retrograde motions of planets. However, Aristarchus of Samos (~ 310-230 B.C) had already proposed a heliocentric model of the Solar System. He also made estimates for the sizes and distances of the Sun and the Moon.
REVIEW QUESTIONS:
REVIEW QUESTIONS:
crab nebula
SW United States: Anasazi "Sun Dagger" marks summer solstice
what doēs the Sun dagger mark?
SW United States: Anasazi "Sun Dagger" marks summer solstice
Galileo and the catholic church:
The Catholic Church ordered Galileo to recant his claim that Earth orbits the Sun in 1633. His book on the subject was removed from the Vatican's index of banned books in 1824. Galileo was formally vindicated by the Vatican in 1992.
Galileo and the church?
The Catholic Church ordered Galileo to recant his claim that Earth orbits the Sun in 1633. His book on the subject was removed from the Vatican's index of banned books in 1824. Galileo was formally vindicated by the Vatican in 1992.
How has the study of astronomy affected human history?
The Copernican revolution showed that Earth was not the center of the universe (Chapter 3). Study of planetary motion led to Newton's laws of motion and gravity. Newton's laws laid the foundation of the industrial revolution. Modern discoveries are continuing to expand our "cosmic perspective."
The formation of hypotheses is usually informed by _________________ ?
The formation of hypotheses is usually informed by The assumptions cannot contradict existing observations. What has worked in other scientific problems? Simplicity Beauty (every science has its own sense of appeal and beauty of an explanation) However, if the hypothesis cannot successfully predict the outcomes of new observations, it will never be promoted to a scientific theory.
3.4 The Nature of Science
The idealized scientific method Based on proposing and testing hypotheses hypothesis = educated guess
Ptolemy
The most sophisticated geocentric model was that of Ptolemy (A.D. 100-170) — the Ptolemaic model: Sufficiently accurate to remain in use for 1,500 years. Arabic translation of Ptolemy's work named Almagest ("the greatest compilation")
Kepler's First Law of planetary motion?
The orbit of each planet around the Sun is an ellipse with the Sun at one focus.
What determines the strength of gravity?
The universal law of gravitation: 1 - Every mass attracts every other mass. 2 - Attraction is directly proportional to the product of their masses. 3 - Attraction is inversely proportional to the square of the distance between their centers
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, rather: A scientific theory must: - Explain a wide variety of observations with a few simple principles, AND - Must be supported by a large, compelling body of evidence, AND - Must NOT have failed any crucial test of its validity.
What did ancient civilizations achieve in astronomy?
To tell the time of day and year, to track cycles of the Moon, to observe planets and stars. Ancient structures aided in astronomical observations
What did ancient civilizations achieve in astronomy
Tracking the seasons Daily timekeeping Calendar Monitoring lunar cycles Monitoring planets and stars Predicting eclipses, etc.
Overcoming the third objection (parallax):
Tycho thought he had measured stellar distances, so lack of parallax seemed to rule out an orbiting Earth. Galileo showed stars must be much farther than Tycho thought — in part by using his telescope to see 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.
How did the Greeks explain planetary motion?
Underpinnings of the Greek geocentric model: Earth at the center of the universe Heavens must be "perfect": Objects moving on perfect spheres or in perfect circles.