Lecture 2 Quiz 1

Lecture 2 Quiz 1 - Astronomy 100 - Dr. Wilson Lecture # 2 -...

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Astronomy 100 - Dr. Wilson Lecture # 2 - 8/26/2010
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http://www.bbc.co.uk/news/science-environment-11070991
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What is a Moon? Traditionally, moons were defined as objects that revolved around planets However, the discovery of more and more objects in our Solar System have led some to reconsider this definition At last count, Jupiter as 63(!) moons.
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The Moon’s Phases The phases of the Moon—the changing appearance of the Moon during its cycle— are caused by the relative positions of the Earth, Moon, and Sun. The phases follow the sequence of: new, waxing crescent, first quarter, waxing gibbous, full Moon, waning gibbous, third (or last) quarter, waning crescent, and once again new Moon.
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The Moon’s Phases (continued) The changing appearance of the moon on each successive day during the month of December, 1998, is shown in the following chart.
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The Moon’s Phases (continued) Whenever two full moons occur within one calendar month, the second of the two full moons is called a “blue moon” as in the following chart of lunar phases for January,1999.
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The Moon’s Phases A synodic period is the time interval between successive similar alignments of a celestial object with respect to the Sun. In the case of the Moon one synodic period is the time between two successive new moons. A synodic revolution of the Moon takes about 29 1/2 days, a time interval which is also known as one lunar month .
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Criteria for Scientific Models The modern criteria of scientific models are 1. The model must fit the data. 2. The model must make new predictions which can be tested with later observations. 3. A new model must be found if the old model’s predictions are found to be wrong. 4. The model should be the simplest possible model; it should not be overly complicated. This last point is called Ockham’s Razor.
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Criteria for Scientific Models Ptolemy’s model matched the observations to the accuracy available in his time. Ptolemy’s model was not as simple as Aristarchus’s heliocentric model, but nevertheless Ptolemy made incorrect arguments to refute the heliocentric model. Only with more accurate observations which were not made until more than 1000 years later was the Ptolemaic model shown to be inaccurate as well as overly complicated.
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Model, Theory, and Hypothesis An hypothesis is a tentative explanation awaiting further development and testing. A model is an hypothesis. A theory is an hypothesis or a set of hypotheses that have been tested and verified to the accuracy of the available data. The geocentric model could just as well have been labeled a theory during Greek times even though today we know that it is not a correct model.
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Evidence for a Pre-Modern Observer Stars move through the night sky but return to same position each night
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Evidence for a Pre-Modern Observer Noting where the Sun sets and rises shows apparent motion along the ecliptic
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Evidence for a Pre-Modern Observer Moon undergoes phases within a cycle of about 29.5 days
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This note was uploaded on 02/06/2011 for the course ASTR 100Lxg at USC.

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Lecture 2 Quiz 1 - Astronomy 100 - Dr. Wilson Lecture # 2 -...

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