astronomy 101.ppt 0

8/6/2019 Astronomy 101.Ppt 0

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ASTRONOMY


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COPERNICUSand theHELIOCENTRIC

HYPOTHESIS


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Nicholas Copernicus(1473-1543)

In Polish, Mikolaj Kopernikwas born in Torun on theVistula in modern-day Poland.

His training was in law andmedicine but his main interestwas astronomy andmathematics.

His unorthodox idea is calledHeliocentic model ofcosmology.


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His ideas is presented in his book DeRevolutionibus.

Copernicus made the Earth anastronomical body, which brought a kindof unity to the universe. His newcosmology had the revolutionaryimplication that the Earth was small, whilethe universe was large.


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Heliocentric plan of the

solar system in first editionof Copernicus' DeRevolutionibus.

The most importanthypothesis Copernicusadopted in DeRevolutionibus is that Earthis but one of six (then

known) planets that revolveabout the Sun.


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DISTANCES OF PLANETSFROM THE SUN IN AU

Planets Copernicus Modern

Mercury 0.38 0.39

Venus 0.72 0.72

Earth 1.00 1.00

Mars 1.52 1.52

Jupiter 5.22 5.20

Saturn 9.18 9.54

This table shows the values obtained byCopernicus for the distances of the

various planets from the sun, in units ofEarth's distance. Also given are thevalues determined by modern

measurement.


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Tycho Brahe(1546-1601)

He came from a nobleDanish family.

He developed an earlyinterest in astronomy and asa young man madesignificant astronomicalobservations.


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In 1597 he left Denmark and worked at

Prague for Emperor Rudolph II of Bohemia.

In 1600, he secured the assistance ofJohannes Kepler who like Tycho, was an exile

from his native land.

His work gained patronage of the Danish

king Frederick II and in 1576 he made accuratepretelescopic observations for 20 years.


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With instruments of his own design, he wasable to make observation accurate to the limitvision with the naked eye.

Sextant from Tycho BrahesAstronomiae instauratae

mechanica

Tycho armillary SphereReplica

(a) Tycho's Observation


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(b) Tycho's Cosmology

Tycho rejected the Copernican heliocentrichypothesis an what seemed at the time to be verysound grounds.

His ideas were debated among the astronomers ofhis time, but later diserted as the Copernican sytemgained favor.

It is his superb observation, not his cosmological

ideas that we remember Tycho today.


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Johannes Kepler(1571-1630)


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Born in Wurttemberg inSouthern Germany

Famous for his 3 laws ofPlanetary motion.

Attended the University

of Tubingen and studiedfor a theological career.


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1. The orbit of every planet is an ellipsewith the sun at the focus.

KEPLER'S 3 LAWS of

PLANETARY MOTION

2. A line joining a planet and the sunsweeps out equal areas during equalintervals of time.

3. The square of the orbital period of aplanet is directly proportional to thecube of the semi major axis of its orbit.


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1.) KEPLER'S FIRST LAW: The orbit of everyplanet is ellipse with the sun at one focus

1609

- Kepler published the first results of his workin the The New Atronomy or theCommentaries on the Motion of Mars.

Ellipse- is the simplest kind of closed curve- belongs to a family of curves known as conic sections.

Conic Section- is the curve of intersection between a hallow coneand a plane that cuts through it.

Foci (singular; focus)- is the sum of the distances to two points inside the

ellipse.Major axis- is the maximum diameter of the ellipse


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2.) KEPLER'S SECOND LAW:

A line jointing a planet andthe sun sweeps out equalareas during equal intervalsof time, also called the Law of

Equal Areas.This explains how the speed of

Mars varied at different parts of itsorbit. The planet speeds up as it

come closer to the sun and slowsdown as it pulls away.


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3.) KEPLER'S THIRD LAW: The square of theorbital period of a planet is directly

proportional to the cube of the semi majoraxis of its orbit, also known as harmoniclaw.

1619- Kepler published his discovery about theharmony of the worlds through a simple

algebraic equation.

P2 = Ka3

- is the algebraic equation of Kepler's Third Law ofPlanetary Motion where P represents the siderealperiod of the planet, a is the semi major axis of its

orbit, and K is the numerical constant whose valuedepends on the kinds of units chosen to measuretime and distance.


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The Astronomical Unit (AU)

- is the unit of time the Earth's periodand for the unit of distance thesemimajor axis of the Earth's orbit.

P2 = a3

-is the derived algebraic equation ofKepler's Third Law.

Harmony of the worlds- a book of Kepler which deals with Kepler'sattempts to associate numerial relations in

the solar system with the music.


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OBSERVATIONAL TEST OF KEPLER'S THIRD LAW

Semimajor PeriodPlanet Axis(AU) (Years) a3 P2

Mercury 0.387 0.241 0.053 0.058

Venus 0.723 0.615 0.378 0.378

Earth 1.000 1.000 1.000 1.000

Mars 1.524 1.881 3.537 3.537

Jupiter 5.203 11.862 140.8 140.7

Saturn 9.534 29.456 867.9 867.7


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Whois Galileo?

In 1589, he became aprofessorof mathematics andastronomy at the University ofPisa.

In 1592, he obtained betterposition at the University ofPadua until 1960.

After 1960 he left tobecome mathematicianto the grand Duke ofTuscany.

Galileo Galilei

(1564-1642), the Italiancontemporary of Kepler,was born in Pisa.


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a) Galileo's Experiments in Mechanics

- the study of motion and actions of forces on bodies.* inertia - the property of the body that resists any of motion.

-Galileo argued the theory of Aristotle that heavy objects fallfaster than lighter ones.

b) Galileo and the Heliocentric Cosmmology

1590- Galileo accepted the Copernican hypothesis ofsolar system.

* Heliocentric Cosmmology introduced by Nicholas

Copernicus.- earth is a planet and that the

planets all circle about theSun.


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c) Galileo's Astronomical Observations

1608 Dutch spectacle maker

Hans Lipershey made first telescopesto attract much notice in Europe.

1609 Galileo heard the discovery

and assembled his own telescope..

1610 he started the world bypublishing a list of his remarkabledicoveries in a small book, Thesidereal Messenger.

d) Dialogue on the two GreatWorld System -the book written in Italian byGalileo which appeared in1632.


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Thank You for Listening!!(^-^)!!

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