THE UNIVERSEAs the totality of everythingthat exists, includingall matter and energy, the planets, stars, galaxies, andthe contents of intergalacticspace.
PTOLEMY ARISTARCHUS COPERNICUS BRAHE SELECT AN ASTRONOMER TO BEGINGALILEI KEPLER NEWTON
CLAUDIUS PTOLEMY Ptolemy is most famous for his contribution to astronomy, which is in his 13-book work called the Almagest. The Ptolemaic system of astronomy placed the Earth at the center of the universe and explained all the observed motions of the Sun, Moon, planets, and stars with a system of uniform circular motions. Ptolemy borrowed heavily from the previous work of Hipparchus. The Ptolemaic astronomical system was wrong, but it was a good enough scientific model to last over 1400 years until the time of Copernicus.
ARISTARCHUS OFSAMOS Aristarchus (310 BC -230 BC) was a famous Greek mathematician and astronomer, popular for his theories regarding the heliocentricity of our solar system. He was the first to say that the Sun, and not the Earth, was the center of our universe. This theory brought him ridicule during his lifetime. Aristarchus was one of the first astronomers to calculate the relative sizes of the Sun, the Moon and the Earth.
NICOLAS COPERNICUS The Universe was Earth centered. His theory answered the fact that the planet’s sizes were different throughout the year and the fact that the orbits of the planets were irregular now and then would be explained. He wrote his theory in a book, De Revolutionibus Orbium Coelestium (On the Revolutions of the Heavenly Spheres)
TYCHO Tychos major works include De Nova et Nullius Aevi Memoria Prius Visa Stella ("On the NewBRAHE and Never Previously Seen Star) (Copenhagen, 1573); De Mundi Aetherei Recentioribus Phaenomenis ("Concerning the New Phenomena in the Ethereal World) (Uraniburg, 1588); Astronomiae Instauratae Mechanica ("Instruments for the Restored Astronomy") (Wandsbeck, 1598; English tr. Copenhagen, 1946); Astronomiae Instauratae Progymnasmata ("Introductory Exercises Toward a Restored Astronomy") (Prague 1602). His observations were not published during his lifetime. Johannes Kepler used them but they remained the property of his heirs. Several copies in manuscript circulated in Europe for many years, and a very faulty version was printed in 1666. At Prague, Tycho hired Johannes Kepler as an assistant to calculate planetary orbits from his observations. Kepler published the Tabulae Rudolphina in 1627. Because of Tychos accurate observations and Keplers elliptical astronomy, these tables were much more accurate than any previous tables.
GALILEO in 1609, instrument put together by aGALILEI lens-grinder in Holland, he constructed the first complete astronomical telescope. Galileo discovered that the moon, shining with reflected light, had an uneven, mountainous surface and that the Milky Way was made up of numerous separate stars. In 1610 he discovered the four largest satellites of Jupiter, the first satellites of a planet other than Earth to be detected. He observed and studied the oval shape of Saturn (the limitations of his telescope prevented the resolving of Saturns rings), the phases of Venus, and the spots on the sun. His investigations confirmed his acceptance of the Copernican theory of the solar system; but he did not openly declare a doctrine so opposed to accepted beliefs until 1613, when he issued a work on sunspots.
JOHANNES KEPLER Johannes Kepler 1571- 1630 Worked for Tycho Brahe, inherited his data Heliocentric model (29 years!) Found orbit shapes by observation from different points in Earth’s orbit
KEPLERS 3 LAWS: Orbit of every planet is an ellipse with the sun at one of the foci. Thus, Kepler rejected the ancient Aristotelean and Ptolemaic and Copernican belief in circular motion. A line joining a planet and the sun sweeps out equal areas during equal intervals of time as the planet travels along its orbit. This means that the planet travels faster while close to the sun and slows down when it is farther from the sun. The squares of the orbital periods of planets are directly proportional to the cubes of the semi-major axes (the "half-length" of the ellipse) of their orbits. This means not only that larger orbits have longer periods, but also that the speed of a planet in a larger orbit is lower than in a smaller orbit.
ISAAC NEWTON Gravity, Newton’s other great contribution, is one of the four fundamental forces in the universe.
Because of Galileo’s work, Newton knew that an object fell to the Earth at a rate of about 9.8 meters (32 feet) per Newton’s Third Law of second. Thus “the Motion : every force exerted apple [that] fell from by one object on another is the tree” fell to the equal to a force, but Earth at about this opposite in direction, rate. exerted by the second object on the first (every reaction has an equal but opposite reaction).
GEORGEGAMOW During the War, when all the American nuclear physicists were involved in the Manhattan project, Gamow worked on the problem of the cosmic origin of the elements, which he proposed to solve, in 1948, by what is now called the Big Bang theory. He wrote books on atomic physics for the general public, such as The Creation of the Universe (1952), and for young people, such as Mr. Tompkins Explores the Atom (1944)
EDWIN HUBBLE • American astronomer who profoundly changed the understanding of the universe by confirming the existence of galaxies other than the Milky Way. He also considered the idea that the loss in frequency—the redshift— observed in the spectra of light from other galaxies increased in proportion to a particular galaxys distance from Earth. This relationship became known as Hubbles law.
Bondi, Gold, Hoyle The steady state theory of Bondi and Gold was inspired by the circular plot of the film Dead of Night, which they had watched together. Theoretical calculations showed that a static universe was impossible under general relativity, and observations by Edwin Hubble had shown that the universe was expanding. The steady state theory asserts that although the universe is expanding, it nevertheless does not change its appearance over time; it has no beginning and no end.
CREATION THEORYOld Earth creation theory asserts that Goddid create the universe, but includes the ideathat Genesis is not a literal descriptionof creation. This branchof creation theory accepts scientific dating ofthe Earth and the physical universe, butquestions evolution theory. Old Earthcreationism can be separated into threedifferent categories, including gap, day age,and progressive creationism. Each categoryaccepts God as the creator of the physicaluniverse, but supports different viewsconcerning the processes involved increating the world as we know it.