ASTROLOGY CHAP 3
250 BC
- Helio-centric model was suggested and Earth's circumference was calculated with 2% error
Arguments people made against Galileo
1. Earth cannot be moving or we would leave behind clouds, birds, ect. 2. Heavens should be perfect and unchanging. 3. Stellar parallax has not been detected.
Kepler's Laws
1. All planets orbit an ellipse, with the sun at one focus. 2. A planet moves faster when it's near the sun, sweeping out equal areas in equal times. 3. More distant planets orbit the sun at slower average speeds.
Galileo's Counter Arguments
1. An object in motion stays in motion 2. Used a telescope to show imperfections in the heavens 3. Argued we are too far away to detect parallax.
How can we distinguish science from nonscience?
1. Modern science seeks explanations for observed phenomena that rely solely on natural causes. 2. Science progresses through the creation and testing of models of nature that explain the observations as simply as possible. 3. A scientific model must take testable predictions about natural phenomena that would force us to revise or abandon the model if the predictions did not agree with observations
How did the innovations of Greek Philosophers influence modern day science?
1. Philosophy of trying to explain what they saw without invoking supernatural causes. 2. Using mathematics to give precision to their ideas. 3. Power of reasoning from observations.
What is at each foci of an ellipse?
A sun.
What traits are needed for something to be called "science"?
A hypothesis, Fact, Law, and Theory.
What is a scientific theory?
A scientific theory explains stuff by using general principles and survived repeated testing.
Ptolemaic model (150 AD)
Best and most accurate geo-centric model. Added Epicycles (circles on circles) Each planet moves on a small circle whose center moves around the Earth on a larger circle. The model was complex and explained retrograde motion
How did Copernicus, Tycho, and Kepler challenge the Earth centered model?
Copernicus created a sun-centered model of the solar system designed to replace the Ptolemaic model, but it was no more accurate than Ptolemy's because Copernicus still used perfect circles. Tycho's accurate, naked eye observations provided the data needed to improve on the Copernicus model. Kepler developed a model of planetary motion that fits Tycho's data.
Geocentric Model
Earth is the center of the Universe
What explained retrograde motion in the Ptolemaic Model?
Epicycles
Galileo's final nail in the coffin of the Earth centered model
Galileo discovered four moons orbiting Jupiter and showing Venus goes through phases in a way it orbits the Sun and not Earth
How did Galileo solidify the Copernican Revolution?
Galileo's experiments and telescopic observations overcame remaining objections to the Copernician idea of Earth as a planet orbiting the Sun. Galileo solidified the sun-centered solar system.
Why didn't Copernicus method work as well as Ptolemaic's?
His method didn't work that well because of his belief that heavenly motion must occur in perfect circles that caused him to add complexities into his system, so it was no more as accurate than the Ptolemaic model.
The Greek geocentric model reached its culmination with the Ptolemaic Model, which explained apparent retrograde motion by having each planet moves on a small circle whose center moves around Earth on a larger circle.
How did the Greeks explain planetary motion?
Did Copernicus' model make better predictions than the Ptolemaic model?
No. His ideas were based on the right general ideas (like Earth orbits around the sun), but his model was still too complex. A big problem was his belief that heavenly motion must occur in perfect circles, causing him to add numerous complexities in the end to get decent predictions.
Copernicus
Noticed the Ptolemaic Model can be improved. First mentioned the sun-centered idea. Put planets around the sun on perfect circles that allowed him to calculate each planet's orbital period and relative distance from the sun.
How did the Greeks explain planetary motion?
The Greek geocentric model reached its culmination with the Ptolemaic model, which explained apparent retrograde motion by having each planet move on a small circle whose center moves around Earth on a larger circle.
Why does modern science trace it's roots to the Greeks?
The Greeks developed models of nature, and emphasized the importance of agreement between the predictions of those models and observations of nature.
Ptolemaic Model
The geocentric model of the universe developed by Ptolemy in about 150 A.D. Each planet moves on a small circle whose center moves around Earth on a larger circle called an epicycle. Can explain retrograde motion.
Galileo
Tried to dispel arguments against a helio-centric system
Tycho
Wanted to improve on Copernicus work. Made naked eye observations that improved his model. However, due to his inability to detect stellar parallax, he thought Earth must be stationary. Also thought the Sun orbits the Earth, while planets orbit the Sun.
Kepler
Worked with Tycho. Used his data, used a special oval called ellipses instead of perfect circles. By using elliptical orbits, Kepler created a sun-centered model that predicted planetary positions with outstanding accuracy, better than Ptolemy's
Perihelion
orbital point nearest the sun
Aphelion
point in a planet's orbit that is farthest from the sun
