User:Guy vandegrift/draft/Ptolemy, Copernicus and Tycho systems

This is a Wikiversity resource
This is page is part of Astronomy college course, and was created by copying and editing some Wikipedia articles for use in Wikiversity. It could be transported over to Wikiversity, but that would require the tedious correction of redlinks and templates not found on Wikiversity. Is Wikipedia OK with this?

If you somehow reached this page through Wikipedia, you are welcome to take this wikiquiz as a pre-reading activity.

Even though this is on my userspace, you may treat it as a true wiki, editable by anybody who is interested in improving open source learning. Be bold!

Geocentric model


The following is from https://en.wikipedia.org/w/index.php?title=Geocentric_model&oldid=613335040

In astronomy, the geocentric model (also known as geocentrism, or the Ptolemaic system) is a description of the cosmos where Earth is at the orbital center of all celestial bodies. This model served as the predominant cosmological system in many ancient civilizations such as ancient Greece including the noteworthy systems of Aristotle (see Aristotelian physics) and Ptolemy. As such, they assumed that the Sun, Moon, stars, and naked eye planets circled Earth.

Two commonly made observations support the idea that Earth was the center of the Universe. The first observation is that the stars, the sun, and planets appear to revolve around Earth each day, making Earth the center of that system. The second observation is that the Earth does not seem to move from the perspective of an Earth bound observer.. In other words, our world seems to be completely at rest.

Ancient Roman and medieval philosophers usually combined the geocentric model with a spherical Earth. It is not the same as the older flat Earth model implied in some mythology, as was the case with the biblical and postbiblical Latin cosmology. The ancient Jewish uranography pictured a flat Earth with a dome-shaped rigid canopy named firmament placed over it. (רקיע- rāqîa').

However, the ancient Greeks believed that the motions of the planets were circular and not elliptical, a view that was not challenged in Western culture until the 17th century through the synthesis of theories by Copernicus and Kepler.

The astronomical predictions of Ptolemy's geocentric model were used to prepare astrological and astronomical charts for over 1500 years. The geocentric model held sway into the early modern age, but from the late 16th century onward was gradually superseded by the heliocentric model of Copernicus, Galileo and Kepler. There was much resistance to the transition between these two theories. Christian theologians were reluctant to reject a theory that agreed with Bible passages (e.g. "Sun, stand you still upon Gibeon", Joshua 10:12 – King James 2000 Bible). Others felt a new, unknown theory could not subvert an accepted consensus for geocentrism.

Copernicican system

 * Animated Copernican and Tychonian orreries; click on "Copernican" or "Tychonian" in the lower right corner -MIGHT BE OFLINE-
 * A Youtube video showing motions from earth -not as good-


 * The following is from https://en.wikipedia.org/w/index.php?title=Copernican_heliocentrism&oldid=612422707

Copernican heliocentrism is the name given to the astronomical model developed by Nicolaus Copernicus and published in 1543. It positioned the Sun near the center of the Universe, motionless, with Earth and the other planets rotating around it in circular paths modified by epicycles and at uniform speeds. The Copernican model departed from the Ptolemaic system that prevailed in Western culture for centuries, placing Earth at the center of the Universe, and is often regarded as the launching point to modern astronomy and the Scientific Revolution.

As a university-trained Catholic priest dedicated to astronomy, Copernicus was acquainted with the Sun-centered cosmos of the ancient Greek Aristarchus. Although he circulated an outline of the heliocentric theory to colleagues decades earlier, the idea was largely forgotten until late in his life he was urged by a pupil to complete and publish a mathematically detailed account of his model.



Tychonic system
The following is from Tychonic_system&oldid=606454264

The Tychonic system (or Tychonian system) was a model of the solar system published by Tycho Brahe in the late 16th century which combined what he saw as the mathematical benefits of the Copernican system with the philosophical and "physical" benefits of the Ptolemaic system.

It is essentially a geocentric model; the Earth is at the center of the universe. The Sun and Moon and the stars revolve around the Earth, and the other five planets revolve around the Sun. The motions of the planets and the Sun relative to the Earth in Brahe's system are mathematically equivalent to the motions in Copernicus' heliocentric system. In other words, the Tychonic system is exactly the same as the Copernicus system except that the planets are measured with respect to a coordinate system that attached to the Earth.


 * See also Relative velocity and Parallax
 * Trombone Silliness

Motivation for the Tychonic system
Tycho admired aspects of Copernicus's heliocentric model of the solar system, but felt that it had problems as concerned physics, astronomical observations of stars, and religion. Regarding the Copernican system Tycho wrote, This innovation expertly and completely circumvents all that is superfluous or discordant in the system of Ptolemy. On no point does it offend the principle of mathematics. Yet it ascribes to the Earth, that hulking, lazy body, unfit for motion, a motion as quick as that of the aethereal torches, and a triple motion at that.

In regard to physics, Tycho held that the Earth was just too sluggish and heavy to be continuously in motion. According to the accepted Aristotelian physics of the time, the heavens (whose motions and cycles were continuous and unending) were made of "Aether" or "Quintessence"; this substance, not found on Earth, was light, strong, and unchanging, and its natural state was circular motion. By contrast, the Earth (where objects seem to have motion only when moved) and things on it were composed of substances that were heavy and whose natural state was rest—thus the Earth was a "lazy" body that was not readily moved. Thus while Tycho acknowledged that the daily rising and setting of the sun and stars could be explained by the Earth's rotation, as Copernicus had said.

Religion played a role in Tycho's geocentrism also – he cited the authority of scripture in portraying the Earth as being at rest. He rarely used Biblical arguments alone (to him they were a secondary objection to the idea of Earth's motion) and over time he came to focus on scientific arguments, but he did take Biblical arguments seriously.



History and development of the Tychonic system
Tycho's system was foreshadowed, in part, by that of Martianus Capella, who described a system in which Mercury and Venus are placed on epicycles around the Sun, which circles the Earth. Copernicus, who cited Capella's theory, even mentioned the possibility of an extension in which the other three of the six known planets would also circle the Sun.

Quiz
Astronomy_college_course/Ptolemy,_Copernicus_and_Tycho_systems/Quiz01