AST 115 1st Edition Lecture 6Outline of Last Lecture I. Eclipses continueda. Solar eclipsesb. Lunar eclipsesII. Measuring anglesa. Small angle equationOutline of Current Lecture I. What is science?a. “Laws”b. Important aspectsII. The Scientific Methoda. StepsIII. The 5th illusion in the night skyIV. Ptolemy’s Geocentric Theorya. Was it a successful theory?V. Introduction to astrologyCurrent Lecture What is science?o Science is a rational method of investigation used to discover how nature works.- “Laws” of science: The laws of science are not absolute The laws of science are the current best descriptions of nature- Two important aspects of science: It is a method of successive approximation It is self-correcting The Scientific Methodo Steps:- State the problem- Perform a relevant experiment *(in astronomy, you would obtain relevant observations)*- Develop a logical way of explaining the results: Hypothesis, theory, model.- Test the theory = predict future results; perform new experimentsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute. *(in astronomy, instead of performing new experiments, you would obtain new observations)*- If the results of the new experiment (observations) agree with the prediction, keep it and predict again. If the results of the new experiment (observations) disagree with the prediction, modify the theory or start over.o Example: What paths do the planets follow around the Sun?- First, measure the angle between the Sun and Venus for several years.- If you were to graph the data obtained by measuring the angle, it would show that Venus appears to move in a circle around the Sun.- Next, you would need to predict another planet. Prediction #2: Mercury should move in a circle around the Sun too. Measure the angle between the Sun and Mercury for several years.- New observations would show that Mercury does not move in a circle around the Sun. Then modify your theory: Mercury, thus all planets move in elliptical paths around the Sun. 5th Illusion in the night sky: Retrograde Motiono Usually the planets move slowly eastward in the sky with respect to the stars (not daily motion carrying objects on the CS toward the west)o However, when a planet is closest to Earth, it will appear to stop, reverse its motion in the sky, stop, and then resume its normal eastward motion.o The westward motion is called retrograde motion.o Explanation:- As an inner planet catches up to and passes an outer planet, the outer planet appears to move westward for a time.- This effect is seen on both planets.- The inner planet is moving faster.- Inferior planets retrograde when they are near inferior conjunction.- Superior planets retrograde when near opposition. Ptolemy’s Geocentric Theoryo Greece (circa 140 AC)o Ptolemy was one of the last great ancient Greek astronomers who compiled the 13 volume Almagest (a work that included summaries of others).o He devised a scheme for explaining retrograde motions of planets.o Proposed the existence of epicycles and deferens. Only the Moon and Sun did not require epicycles. Each of the other planets moved in these circles around the Earth.o Was this a successful theory?- Simplicity test: “Occam’s Razor” or the “Law of Parismony”; and what is the center of the epicycle. Did not pass the simplicity test.- Longevity test: Ptolemy’s theory lasted uncontested for about 1400 years. Passed the longevity test- Scientific test: do the predictions of the theory math the observations? Did not pass the scientific test because Ptolemy was not accurate enough because his observations were done with the naked eye instead of a telescope. Astrologyo Codified by Ptolemy in his book “Tetrabiblos”.o Rigid rules were established to be used to interpret a person’s fate.o The concepts and explanations in astrology are not subjected to testing by prediction and further observations.o “Pseudoscience” = not a real scienceo Astronomy developed into a science due to the use of the scientific method, which requires the testing of a hypothesis. Because the concepts and explanations in astrology are not subjected to testing by prediction and further observations, it is not considered a real
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