Astronomy

Introduction and History

Acknowldegements

• Ptolemy (367 BC – 283 BC)• Aristotle (384 BC - 322 BC)• Copernicus (1473 – 1543) • Brahe (1546 – 1601) • Galileo (1564 – 1642) • Kepler (1571 –1630)• Newton (1643 – 1727)

Who were these people and what did they do?

Ptolemy: Best known for GEOCENTRIC model of universe. Theorized that planets orbited around the earth in EPICYCLES (circles within circles.) Each planet’s path was called a DEFERENT. The sun then orbited around all the other celestial bodies. http://astro.unl.edu/naap/ssm/animations/ptolemaic.swf

epicycle

deferent

Aristotle: Known as a philosopher. He wrote a book called “On the Heavens.” In this book he said the Earth was spherical in shape because of the circular shadow of eclipses, seeing the sailBefore the ship, and the height of the stars is changing as we move.

Christopher Columbus was motivated because of Aristotle.

Copernicus: First to propose the universe was HELIOCENTRIC.

Copernicus: Priest proofread his book and inserted a preface which stated Copernicus did not believe his own hypothesis. Copernicus never saw this because he died the same day he got a copy of the book.

He observed apparent PROGRADE (orbit in same direction) and (orbit in opposite direction) RETROGRADE motion of celestial bodies.

What Copernicus observed about Mars:

This led to the word planet which means wanderer.

Tycho Brahe: He devoted his life to Astronomy starting at age 14 when he observed an eclipse. He was the first scientist to observe and document a SUPERNOVA (exploding star.) He worked to combine the geometrical aspectsof the Copernican system and the Ptolemaic system into his own model of the universe, the Tychonic system.

The sun and all the other planets orbit as a system around the earth. All of this is contained in a sphere of stars.

Tycho Brahe fun fact or fiction?

He owned a pet elk that diedwhen it fell down some stairsafter drinking too much beer.

At the age of twenty he arguedwith a friend about a mathformula and they decided tosettle it with a sword duel since there was no authority onthe math to check with. Tycho lost part of hisnose. He wore a metal prosthetic by gluingit on.

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Galileo: Invented a telescope (*not the first) that enabled him to discover four of Jupiter’s satellites. He basically Proved the Copernican system.

He was in and out of trouble with the church for his views on heliocentrism. The church requested he putboth views in a book. He made the church’s view look foolish.

He was inquisitioned and imprisoned for heresy. The church made him recant heliocentrism. But he wrotethe words “The Earth moves” on his prison walls.

Galileo’s writings:

Galileo's main written works are as follows:The Little Balance (1586)On Motion (1590)[145]

Mechanics (ca. 1600)The Starry Messenger (1610; in Latin, Sidereus Nuncius)Discourse on Floating Bodies (1612)Letters on Sunspots (1613)Letter to the Grand Duchess Christina (1615; published in 1636)Discourse on the Tides (1616; in Italian, Discorso del flusso e reflusso del mare)Discourse on the Comets (1619; in Italian, Discorso Delle Comete)The Assayer (1623; in Italian, Il Saggiatore)Dialogue Concerning the Two Chief World Systems (1632; in Italian Dialogo dei due massimi sistemi del mondo)Discourses and Mathematical Demonstrations Relating to Two New Sciences (1638; in Italian, Discorsi e Dimostrazioni Matematiche, intorno a due nuove scienze)

*Thomas Harriot had already invented a telescope four months before Galileo.

STAR PARALLAX: The apparent shift of stars as the earth moves in its orbit around the sun.

Since Galileo’s telescope couldnot account for this most men of science of the time argued against heliocentrism.

Johannes Kepler: Most known for 3 Laws of Planetary Motion.

He was Tycho Brahe’s assistant and they often arguedabout Kepler getting access to Tycho’s data regarding his observations of Mars.

When Brahe died Kepler was suspected of poisoninghim with mercury. He did finally get access to the Mars data.

Kepler wrote a manuscript Sominium which is considered to be the first science fiction story. It was used against his mother and she was tried for witchcraft.

Kepler was a brilliant mathematician and had a fascination with geometric shapes.

This led to his first law which says planets orbitthe sun in elliptical paths.

Isaac Newton: Devised the Law of Universal Gravitation based on Kepler’s work.

Also known for his experiments with light. Again based on Kepler’s work with lenses and spherical mirrors.

Newton invented calculus and wrote Prinicpia Mathematica which was about his three laws of motion and his derivation of the Law ofUniversal Gravitation.

It was more than 200 years before anyone in scienceor math could go beyond Isaac Newton’s work.

On the story of the apple: Stems from a conversationin an orchard with an associate in which Newton asked: Why should that apple always descendperpendicularly to the ground, why should it notgo sideways, or upwards? It is constantly drawn to theEarth’s center. There must be a drawing power in the earth and in matter. It has to be in the centerbecause the apple falls perpendicularly. And, if the earthdraws the apple then the apple draws the earth.

Newton said of his work:“If I have seen further it is becauseI stand on the shoulders of giants.”

http://micro.magnet.fsu.edu/primer/java/scienceopticsu/powersof10/index.html