Upload
bhsearthscience
View
1.687
Download
2
Embed Size (px)
Citation preview
Pioneers in AstronomyPioneers in Astronomy
PtolemyPtolemy CopernicusCopernicus Tycho BraheTycho Brahe KeplerKepler GalileoGalileo NewtonNewton HalleyHalley Le Verrier & AdamsLe Verrier & Adams
Uraniborg, Tycho Brahe’s Observatory
PtolemyPtolemy
Almagest Almagest (150 AD), (150 AD), Ptolemy described Ptolemy described the Greek geocentric the Greek geocentric (earth-centered) (earth-centered) model of the universemodel of the universe
Order outward from Order outward from the earth based on the earth based on their apparent speeds their apparent speeds of motion of motion
Orbits were Orbits were considered circlesconsidered circles
Ptolemaic SystemPtolemaic System
http://www.thebigview.com/spacetime
Retrograde Mars, 1995Retrograde Mars, 1995
Retrograde Mars (2003)Retrograde Mars (2003)
http://zuserver2.star.ucl.ac.uk/~apod/apod/ap031216.html
Ptolemy’s EpicyclePtolemy’s Epicycle
Retrograde Planetary MotionRetrograde Planetary Motion
Animation 2.1: Retrograde MotionAnimation 2.1: Retrograde MotionAnimation 2.2: The Path of MarsAnimation 2.2: The Path of Mars
““It is most retrograde to our desire…”It is most retrograde to our desire…”
——HamletHamlet
Nicholas CopernicusNicholas Copernicus Copernicus (1473-1543)
developed heliocentric (sun-centered) model of the solar system
His book, De revolutionibus orbium coelestium (On the Revolutions of the Celestial Spheres, 1543), is considered the starting point of modern astronomy
Copernican SystemCopernican System
Copernican RevolutionCopernican Revolution
• In the Copernican solar system, the retrograde motion of Mars is seen when the Earth passes Mars in its orbit around the Sun
Retrograde Mars (June 2007)Retrograde Mars (June 2007)
Heliocentric ExplanationHeliocentric Explanation
Animation 2.3: A Heliocentric Explanation Animation 2.3: A Heliocentric Explanation of Retrograde Motionof Retrograde Motion
Tycho BraheTycho Brahe
Tycho Brahe (1546-Tycho Brahe (1546-1601) recorded 1601) recorded precise observations precise observations of the positions of the of the positions of the planets and starsplanets and stars
Tycho’s data was Tycho’s data was used by Kepler to used by Kepler to formulate the laws of formulate the laws of planetary motionplanetary motion
Tycho’s SystemTycho’s System
Tycho created a compromise between the universes of Ptolemy and Copernicus
Planets orbit sun, sun orbits earth
http://media4.obspm.fr/public/IUFM/images/13Kepler/images/ticho_brahe.png
Johannes KeplerJohannes Kepler
• Using Tycho’s observations, Johannes Kepler (1571-1630) deduced three laws of planetary motion
Kepler’s First LawKepler’s First Law
K1: The orbit of a K1: The orbit of a planet around the Sun planet around the Sun is an ellipse with the is an ellipse with the Sun at one focusSun at one focus
Elliptical OrbitsElliptical Orbits
Close and FarClose and Far
• Perihelion:Perihelion: The point in a planet’s orbit The point in a planet’s orbit closest to the Sunclosest to the Sun
• Aphelion:Aphelion: Point farthest from sun Point farthest from sun
Earth, 2007Earth, 2007
Perihelion: Jan 03Perihelion: Jan 03
Aphelion: July 07Aphelion: July 07
Kepler’s Second LawKepler’s Second Law
K2: A line joining the planet and the Sun K2: A line joining the planet and the Sun sweeps out equal areas in equal intervals sweeps out equal areas in equal intervals of timeof time
Planets speed up as they approach the Planets speed up as they approach the sun, slow down when the move away from sun, slow down when the move away from the sunthe sun
K1, K2 published in 1609, K1, K2 published in 1609, Astronomia Astronomia NovaNova
Planet moves Planet moves faster in its orbit faster in its orbit when closer to the when closer to the Sun.Sun.
Planet moves Planet moves slower in its orbit slower in its orbit when farther away when farther away from the Sun.from the Sun.
Equal AreasEqual Areas
Kepler’s First & Second LawsKepler’s First & Second Laws
Animation 2.4: Kepler’s First and Second Animation 2.4: Kepler’s First and Second LawsLaws
Kepler’s Third Law (Harmonic, Kepler’s Third Law (Harmonic, 1619)1619)
K3: The square of a planet’s sidereal K3: The square of a planet’s sidereal period (P) around the Sun is directly period (P) around the Sun is directly proportional to the cube of its semi-major proportional to the cube of its semi-major axis (a)axis (a)
P2 = a3
The results are in astronomical units (AU) The results are in astronomical units (AU) with earth = 1with earth = 1
1 AU = 93,000,000 miles1 AU = 93,000,000 milesDemo: ClickDemo: Click
GalileoGalileo
• Galileo (1564-1642), first scientist to use a telescope to examine the night sky
• Discoveries supported the Copernican system
Phases of VenusPhases of Venus
Moons of Jupiter (Galileo, 1610)Moons of Jupiter (Galileo, 1610)
Isaac NewtonIsaac Newton
Isaac Newton (1643-Isaac Newton (1643-1727) 1727)
Laws of motionLaws of motion Law of gravityLaw of gravity Invented calculusInvented calculus Newton’s laws were first Newton’s laws were first
published in the published in the Philosophiae Naturalis Philosophiae Naturalis Principia MathematicaPrincipia Mathematica, or , or PrincipiaPrincipia, 1687, 1687
Newton’s First LawNewton’s First Law
N1: A body remains at rest or moves in a N1: A body remains at rest or moves in a straight line at constant speed unless straight line at constant speed unless acted upon by a net outside forceacted upon by a net outside force
Spaceship moving in spaceSpaceship moving in space
Newton’s Second LawNewton’s Second Law
N2: The acceleration (a) of an object is N2: The acceleration (a) of an object is proportional to the force (F) acting on itproportional to the force (F) acting on it
F = maF = mam = mass of objectm = mass of objectSpin ball on a stringSpin ball on a string
Newton’s Third LawNewton’s Third Law
Whenever one body exerts a force on a Whenever one body exerts a force on a second body, the second body exerts an second body, the second body exerts an equal and opposite force on the first bodyequal and opposite force on the first body
Or, every action has an equal and Or, every action has an equal and opposite reactionopposite reaction
Rocket liftoffRocket liftoff
Law of GravityLaw of Gravity
Law of Universal GravitationLaw of Universal GravitationTwo objects attract each other with a force
that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.
Newtonian OrbitsNewtonian Orbits
Conic SectionsConic Sections
Slice a cone at Slice a cone at various anglesvarious angles
Resulting shapes Resulting shapes same as planetary same as planetary orbitsorbits
Practical math, Practical math, Greece, 200 BCGreece, 200 BC
Comet & Planetary OrbitsComet & Planetary Orbits
Animation 2.5: Planetary OrbitsAnimation 2.5: Planetary OrbitsAnimation 2.6: Orbit & Tail of a CometAnimation 2.6: Orbit & Tail of a Comet
Newton’s CannonNewton’s Cannon
““Cannon” OrbitsCannon” Orbits
Edmond HalleyEdmond Halley Edmond Halley (1656-Edmond Halley (1656-
1742) used Newton’s 1742) used Newton’s methods to describe a methods to describe a comet’s orbit and predict comet’s orbit and predict its returnits return
Halley explained comet Halley explained comet sightings of 1456, 1531, sightings of 1456, 1531, 1607, and 1682 to be the 1607, and 1682 to be the same cometsame comet
Predicted return in 1758 Predicted return in 1758 Comet Halley was last Comet Halley was last
visible in 1986 and will visible in 1986 and will return in 2061return in 2061
Comet HalleyComet Halley
Portion of Bayeux Tapestry, 1066 Comet Halley in 1986,
Milky Way in upper right
Le Verrier and AdamsLe Verrier and Adams English astronomer John
Couch Adams (1819-1892) and French astronomer Urbain Jean Joseph Le Verrier (1811-1877) independently predicted the existence of Neptune
Predictions based upon Neptune’s gravitational effect upon Uranus
Neptune was discovered at the Berlin Observatory on Sept 23, 1846
Le Verrier (left) & Adams
Neptune’s PositionsNeptune’s Positions
1-degree equals the width of an oustretched fingertip
Inferior & SuperiorInferior & Superior
Planet positions compared to earthPlanet positions compared to earth Inferior PlanetsInferior Planets: Between sun and earth: Between sun and earth
Mercury, VenusMercury, VenusSuperior PlanetsSuperior Planets: Farther from the sun : Farther from the sun
than earththan earthMars, Jupiter, Saturn, Uranus, Neptune, Mars, Jupiter, Saturn, Uranus, Neptune,
(Pluto)(Pluto)
Inferior PlanetsInferior Planets
Eastern and western Eastern and western elongationelongation
Inferior conjunction Inferior conjunction Superior conjunctionSuperior conjunction
Superior PlanetsSuperior Planets
Opposition Opposition ConjunctionConjunction
Close & FarClose & Far
SummarySummary