In the 1500's, there was considerable dissatisfaction with the Ptolemaic Model due to the repeated updates needed to be able to predict the postions of <1> accurately. The sizes and speeds of deferents and epicycles were adjusted, but errors would still accumulate which created the need for more alterations. Dissatisfaction with the Ptolemaic Model was also increasing due to its complexity. Scientists had begun using the concept of Occam's Razor to guide their thinking. Occam's Razor is the belief that <2> explanations are more likely to be correct than complicated ones.
Copernicus was the first astronomer to successfully promote <3>. It had the sun at the center of the solar system and 6 planets revolving around the sun. The orbits of the planets were exactly <4>, circular, and the planets moved at constant velocity. Because these assumptions are not exactly correct, the Copernican Model didn't do any better at predicting planetary position than the Ptolemaic Model.
Copernicus specified planetary positions using <5> (the angular separation of a planet from the sun) which ranges from 0 degrees to <6>. The inferior planets (Mercury and <7>) have 3 special elongation configurations known as superior conjunction, inferior conjunction, and <8>. The Superior planets also have 3 special elongation configurations. An elongation of $elongation is known as <9>.
Copernicus used elongation to learn about the periods (and sizes) of the planetary orbits. The time interval between successive $periodPhrase is known as the <10> period. $closingPhrase in which astronomers are really interested.
@ qu.1.1.algorithm= $num1 = rint(2); $elongation=switch($num1,"180 degrees","90 degrees"); $rightAnswer=switch($num1,"opposition","quadrature"); $wrongAnswer=switch($num1,"quadrature","opposition"); $num2 = rint(2); $periodPhrase=switch($num2,"alignments of the sun, planet, and a distant star","occurrences of the same elongation configuration"); $rightAnswer2=switch($num2,"sidereal","synodic"); $wrongAnswer2=switch($num2,"synodic","sidereal"); $closingPhrase=switch($num2,"These are the true orbital periods", "These periods are easy for astronomers to observe. They can then be used to calculate the true orbital periods"); @ qu.1.1.blank.1=planets,the moon,the sun,stars@ qu.1.1.blank.2=simple,mathematical,thorough,precise@ qu.1.1.blank.3=the heliocentric model,the geocentric model,retrograde motion,star magnitudes@ qu.1.1.blank.4=coplanar,aligned,perpendicular,parallel@ qu.1.1.blank.5=elongation,conjunction,azimuth,retrogration@ qu.1.1.blank.6=180 degrees,270 degrees,90 degrees,360 degrees@ qu.1.1.blank.7=Venus,Mars,Jupiter,Saturn@ qu.1.1.blank.8=greatest elongation,quadrature,opposition,retrogration@ qu.1.1.blank.9=$rightAnswer,$wrongAnswer,greatest elongation,conjunction@ qu.1.1.blank.10=$rightAnswer2,$wrongAnswer2,diurnal,longitudinal@ qu.1.1.grader.1=menu@ qu.1.1.grader.2=menu@ qu.1.1.grader.3=menu@ qu.1.1.grader.4=menu@ qu.1.1.grader.5=menu@ qu.1.1.grader.6=menu@ qu.1.1.grader.7=menu@ qu.1.1.grader.8=menu@ qu.1.1.grader.9=menu@ qu.1.1.grader.10=menu@