1.0 STS Topic 6 Copernican Revolution

Cosmology

Kosmos

________is the study of the nature of the universe as a whole entity. The word ______is derived from the Greek ________meaning harmony or order.

Cosmologist

_________are interested in the formation, evolution and future of the universe and its constituents.

Magic Cosmology

Early cosmology, from Neolithic times of 20,000 to 100,000 years ago, was extremely local.

The Universe was what was immediately interacted with.

Cosmological things were weather, earthquakes, and cataclysms. Things outside daily experience were considered supernatural.

Mythical Cosmology

About 20,000 years ago, humankind began to organize itself and develop cultures. This led to the development of creation myths to explain the origin of the Universe. Many of the myths still maintained supernatural themes, but there was an internal logical consistency to many of the stories. In some sense, the creation myths are the first scientific theories.

Geometric Cosmology

The third stage, considered the core of modern cosmology, grew out of ancient Greece, later adopted by the Church. The underlying theme in Greek science is the use of observation and experimentation to search for simple, universal laws.

Plato

believed that concepts had a universal form, an ideal form, which leads to Platonic Idealism.

Aristotle

________ believed that universal forms were not necessarily attached to each object or concept, and that each instance of an object or a concept had to be analyzed on its own. This is Aristotelian Empiricism.

Plato

________, thought experiments and reasoning would be enough to "prove" a concept or establish the qualities of an object

Aristotle

________ dismissed this in favor of direct observation and experience.

Homer and Hesoid

postulated a flat or cylindrical earth located in a hemispherical cosmos

Pythagoras

held the view that the earth was a sphere in a universe which was itself also fully spherical

Round Earth

• The belief that the circle or sphere was the most perfect of geometric shapes, and therefore appropriate for the earth and the cosmos

• The observations of a ship and its mast as the vessel receded beyond the horizon.

trigonometric considerations

Through ______________, ancient Greeks were able to determine the Earth’s circumference.

Eratosthenes

Circumference of the earth?

Alexandria to Syene

40,075 kms

The distance from_________ was 4900 stadia, so the ratio of that circumference of the Earth, C, is given by:

Present estimate of the Earth’s circumference is about _____

Demiurge

Demos

Ourgos

PLATO

The world was the creation of a ______ (from the Greek "_____" or people and "____" or work) out of materials provided by a pre-existing "chaos" , or jumble of matter

Demiurge; Plato

The ________ organized the world out of the elements-- Earth, Water, Air and Fire. These formed the "body" of the cosmos, which was also endowed with a "soul".

Soul of the cosmos

The________, which Plato considered as the more important part, was its principle of eternal and recurring circular motion, as done by the moon, planets, sun and stars.

center of the cosmos

It is presumed, though not explicitly stated by Plato, that the Earth is the __________, with the other heavenly bodies rotating about it

Aristotle

based himself on various observations evident to the unaided eye:

– We see the sun "rise" and "set" each day

– We don't feel that the earth moves under our feet

– We see the stars describe a semi-circle about the horizon each night

All of these seem to imply that the earth is fixed at the center and the sun moves around it.

Aether

Acceptance of the four Platonic elements of Earth, Water, Air and Fire as the basis for phenomena on both the Earth (the planet) and in the atmosphere.

The addition of a fifth element-- known as "____" -- as the matter of the heavenly bodies (moon, planets, sun, and stars)

Geocentrism

Heliodynamism

The earth as the center of the cosmos – _______.

The sun moves around the earth – __________.

Circular

All heavenly motions are _______(or spherical, in three dimensions).

• Geocentric Model

• Heliocentric Model

MODELS OF THE SOLAR SYSTEM

• There are two main divisions among the models:

Eudoxus of Cnidos

• was the most renown astronomer and mathematician of his day.

• He developed a geocentric solar system model composed of concentric spheres, incorporating Platonic ideal of uniform circular motion

Eudoxus of Cnidos

• The spherical earth is at rest at the center.

• Around this center, 27 concentric spheres rotate.

• The exterior one caries the fixed stars,

• The others account for the sun, moon, and five planets.

• Each planet requires four spheres, the sun and moon, three each.

Eudoxus of Cnidos

This model doesn’t work well with planets, doesn’t explain retrograde motions and doesn’t explain different brightness levels.

Aristotelian-Ptolemaic Model

Domain of the Prime Mover

• Aristotle proposed 55 concentric, crystalline spheres to which the celestial objects were attached, and which rotated at different velocities with the Earth at the center

• Additional "buffering" spheres that lay between the spheres illustrated.

• The outermost sphere was the __________ which caused the outermost sphere to rotate at constant angular velocity, and this motion was imparted from sphere to sphere, thus causing the whole thing to rotate.

His model could not explain varying planetary brightness and the retrograde in their motions

Epicycles

Ptolemy; idea of the equant

ARISTOTELIAN-PTOLEMAIC MODEL

The solution to the deficiency in Aristotle’s model was to add ____.

______made the most sophisticated version of this model by introducing epicycles in epicycles it also introduced the________ , an observation point slightly off from where the earth is

Prime Mover of Aristotle's universe

The _____________ became the God of Christian theology, the outermost sphere of the _______ became identified with the Christian Heaven, and the position of the Earth at the center of it all was understood in terms of the concern that the Christian God had for the affairs of mankind.

Nicolaus Copernicus

_________, a Polish priest, proposed (in 1515) that the Earth was a planet like Venus and Saturn, and all these circled the Sun, but did not publish his work until 1543.

His theory gained followers and some of them faced charges of heresy.

Copernican Model

Heliocentric Model

Copernican heliocentrism

positioned the Sun near the center of the Universe, motionless, with Earth and the other planets rotating around it in circular paths modified by (fewer) epicycles and at uniform speeds.

The shortcoming of this model is the use of circular instead of elliptical orbits.

Copernicus System

• Daily Rotation

• Annual Revolution around the Sun

• 3rd Motion

• Earth a planet, like others, all circling the sun (no longer a planet)

• Moon circling earth (no longer a planet)

• Earth has three motions:

  • a. _______ - replacing the movement of the sphere of the fixed start

  • b.________ - accounting for retrograde motion

  • c. ________ - an annual rotation about an axis perpendicular to the ecliptic

• Fixed stars truly fixed now. Sphere of the fixed stars motionless.

• No equant.

Daily Rotation

• replacing the movement of the sphere of the fixed start

Annual Revolution around the Sun

• accounting for retrograde motion

3rd Motion

• an annual rotation about an axis perpendicular to the ecliptic

Copernican Revolution

• It is believed by many that Copernicus’ book was only published at the end of his life because he feared ridicule and oppression by his peers and by the Church.

• His ideas remained rather obscure for about 100 years after his death. In the 17th century, the work of Kepler, Galileo, and Newton would build on the heliocentric universe of Copernicus and produce the revolution that would sweep away completely the ideas of Aristotle and replace them with the modern view of astronomy and natural science. This sequence is commonly called the _________.

• His book was eventually included in the list of forbidden books by the Church.