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GE 150 Astronomy. Week #6 February 19,21 2013. The Beginnings of Modern Astronomy. The use of Precision measurements and Telescopic Observations. Astronomers of 16 th century. Astronomy was often a pursuit of rich noblemen No gov’t funding
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GE 150 Astronomy Week #6 February 19,21 2013
The Beginnings of Modern Astronomy The use of Precision measurements and Telescopic Observations
Astronomers of 16th century • Astronomy was often a pursuit of rich noblemen • No gov’t funding • Though interested in science, they still held on to beliefs we would call pseudoscience • Alchemy • Numerology • Astrology
Polish Danish Italian German Greek Tycho Brahe (1546-1601) was
Tycho Brahe (1546-1601) Probably died a virgin Had artificial wooden and silver noses Probably died of Mercury poising Rumored to have died of a bladder burst Was labeled a heretic by the church
Tycho Brahe (1546-1601) is known for: First telescope observations of the sun First sun centered scientific model of the solar system or universe Being the world’s best naked-eye astronomer Creating first a theoretical model to explain planetary motions Creating first a theoretical model for explaining gravity
Tycho Brahe (1546-1601 C.E.) • Built “meridian circle” to measure the positions of planets very accurately (~1 arc minute) Major Accomplishments: • Made the most continual and accurate observations of stars and planets (Mars) for his time
Tycho Brahe (1546-1601 C.E.) Major Accomplishments: • Found that comets moved outside of the Earth’s atmosphere • Witnessed a supernova (1572) and concluded that it was much farther away than any celestial object • Couldn’t detect parallax motion in the stars
Why were Tycho’s parallax distances important? Disproved ancient ideas about the heavens: The supernova in 1572 showed that the heavens were both changing and had a dimension of distance Comets were thought to be atmospheric occurrences, not objects in the region of the planets This troubled scholars who previously thought the heavens were unchanging.
Tycho Brahe (1546-1601 C.E.) • Created his own hybrid geo-heliocentric model of the solar system - planets go around the Sun, but the Sun, in turn, orbits around the Earth
Brilliant Geometer and MathematicianJohannes Kepler1571 - 1630
Johannes Kepler 1571 - 1630 was : Polish Danish Italian German Greek
Johannes Kepler 1571 - 1630 - Probably died a virgin Was a priest and Lawyer Probably died of Mercury poising Was blind at the time of his death Was labeled a heretic by the church
Johannes Kepler 1571 - 1630 - None of these. He was a deeply religious man and a family man. Tycho Brahe’s assistant but rumored to have hated Tycho. Inherited Tycho’s data after his death. With that data he changed the understanding of motion of heavenly bodies forever. He was also a writer, who wrote children stories about the heavens.
Johannes Kepler 1571 - 1630is known for - First telescope observations of the sun First sun centered scientific model of the solar system or universe Being the world’s best naked-eye astronomer Creating first a theoretical model to explain planetary motions Creating first a theoretical model for explaining gravity
Johannes Kepler1571 – 1630Kepler’s Three Laws of Planetary Motion
Kepler’s First Law: The orbit of a planet about the Sun is an ellipse with the Sun at one focus.
Eccentricity:e • how squashed or “out of round” the ellipse is • a number ranging from 0 for a circle to 1 for a straight line e = 0.02 e = 0.7 e = 0.9
What is the shape of Earth’s orbit around the Sun?Earth, e = 0.017
Kepler’s Second Law: A line joining a planet and the Sun sweeps out equal areas in equal intervals of time.
SECOND LAW • A line drawn from the planet to the Sun sweeps out equal areas in equal times • Consequences: • orbital speed is not constant for an ellipse only for a circle • planets move faster when near the Sun (perihelion) • planets move slower when they are far from the Sun (aphelion)
THIRD LAW The size of the orbit determines the orbital period Planets that orbit near the Sun orbit with shorter periods than planets that are far from the Sun a3AU= P2years
THIRD LAW The size of the orbit determines the orbital period Planets that orbit near the Sun orbit with shorter periods than planets that are far from the Sun
SECOND LAW • The speed a planet travels during its orbit is related to the distance from the star • When the planet is near the sun the planet goes faster than when the planet is farther from the sun Planet travels slow here Planet travels fast here
THIRD LAW • The size of the orbit determines the orbital period • planets that orbit near the Sun orbit with shorter periods than planets that are far from the Sun p = ~ 12 years p = 1 year
THIRD LAW • The size of the orbit determines the orbital period • planets that orbit near the Sun orbit with shorter periods than planets that are far from the Sun • SIZE & MASS OF THE PLANET DOES NOT MATTER Both have p = 1 year
The 2nd Law tells us what a particular planet does when it orbits a Star The planet will move faster when it is close to the Sun and slower when it is farther from the Sun The 3rd Law relates orbital periods to the orbital distances for all the planets in the Solar System planets orbiting nearer the Sun have short orbital periods Planets orbiting farther from the Sun have long orbital periods The Second and Third Laws
The great scientist Galileo made discoveries that strongly supported a heliocentric cosmogony One of the principal founders of the experimental method for studying scientific problems. • Using a Dutch-designed telescope that he built himself, he made several observations that disproved ancient thinking about the Universe (1610)
Galileo - 1564-1642 was - • Polish • Danish • Italian • German • Greek
Galileo - 1564-1642 - • Probably died a virgin • Was a priest and Lawyer • Probably died of Mercury poisoning • Was blind at the time of his death • Was labeled a heretic by the church
Galileo - 1564-1642 is known for - • First telescopic observations of the sun • First sun centered scientific model of the solar system or universe • Being the world’s best naked-eye astronomer • Creating first a theoretical model to explain planetary motions • Creating first a theoretical model for explaining gravity
Saturn: A Being with Ears • Saturn is not a sphere. • Circles and spheres do not dominate the heavens.
Milky Way • With a telescope, Milky Way resolves into thousands (billions) stars • Implication: the Universe is bigger than imagined.
The Moon • The moon has craters and mountains. • The moon is not a “perfect” heavenly body.
Sunspots • The Sun is not a perfect heavenly body. • The Sun rotates about its own axis. • More observations showed Sun’s axis is tilted, which varied with seasons and repeated annually: clue Earth was orbiting the Sun!
Galileo discovered Venus went through phases like the Moon (new thru full) which showed that Venus must orbit the Sun and strongly supported a heliocentric model “Venus is clearly smallest when it in the full phase and largest when it is in the new phase. Then Venus must be very far from Earth when it is in the full phase and quite closes to Earth when in the new phase – which supports the argument that Venus is orbiting the Sun not Earth.”
The Ptolemaic view of the phases of VenusNote the phases which are missing
Heliocentric view of phases of VenusNote the full array of phases and varying size
Galileo’s telescope revealed phases of Venus which could only occur IF Venus orbits the Sun.
Galileo observed “stars” going around Jupiter on successive nights • Today – 4 largest moon’s of Jupiter are known as the Galilean Moons
Galileo’s log showing observations of moons orbiting Jupiter instead of Earth.
The many contributions of Galileo (too many to discuss here) http://brunelleschi.imss.fi.it/itineraries/indexgal.html IN MEMORY OF GALILEO
ExplainingAstronomical Motion Introduction To Gravity
Sir Isaac Newton (1642-1727) • Described the fundamental laws covering the motion of bodies • Had to invent his own mathematics (Calculus) to do it! • And he did most of it before his 24th birthday…
Isaac Newton (1642 – 1727)was - Polish Danish Italian German British