From Perfect Circles to Ellipses

From Perfect Circles to Ellipses - From Perfect Circles to...

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From Perfect Circles to Ellipses Introduction: Welcome to the wonderful world of Astronomy. In the next five weeks, you will be hearing a wonderful story, comparable to the great creation myths. You will learn about where you are in the universe, what is out there in places you have never been, what happened before you were born (long before!), and what will happen after you die (not to you!). The details of this story are changing daily as new telescopes and new spacecraft add to our knowledge. These are exciting times for Astronomy and I hope to share with you some of the excitement, joy, and wonder of the science of Astronomy. This week the course will cover: 1. The celestial sphere. 2. The science of astronomy and its demented cousin astrology. 3. The birth of modern astronomy. 4. The motions of the earth and moon. The lecture will attempt to tie more closely together the second and third objectives. I strongly recommend that you read the assigned sections of the textbook before reading the lecture. Lecture: The advances in our knowledge of how the universe 'works' is usually ascribed to the 'Scientific Method'. This is a process which is often described by an initial Hypothesis which is tested by an Experiment and the results of which are used to create a more accurate Hypothesis. The history of Astronomy shows that factors other than the 'Scientific Method' were involved in the advances. In particular, technological or engineering improvements, advances in related areas of knowledge, and improved abilities to perform calculations were critical to the advancement of Astronomy. The evolution of our theories of the motions of Solar System bodies is a good example of how technological improvements and improved theories in Physics were critical to the application of the 'Scientific Method'. The earliest observations of planetary positions were rather crude and were made relative to the positions of the stars. The earliest models described the planets as moving at a uniform rate across the sky. By closely observing the positions of Mars, Jupiter, and Saturn when these planets were opposite to the sun, the early astronomers were forces to add extra circular motions or epicycles in order to produce the retrograde motion of Mars, Jupiter, and Saturn. An example of the retrograde motion of Mars is shown on page 51 of the textbook. By the time of the Middle Ages, angular positions of planets were measured with instruments
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This note was uploaded on 04/07/2010 for the course SCI 151 taught by Professor Jackson during the Fall '09 term at University of Phoenix.

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From Perfect Circles to Ellipses - From Perfect Circles to...

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