* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Kepler`s Laws and Galileo 8/31/2016
Patronage in astronomy wikipedia , lookup
Discovery of Neptune wikipedia , lookup
Rare Earth hypothesis wikipedia , lookup
Kepler (spacecraft) wikipedia , lookup
History of Mars observation wikipedia , lookup
International Ultraviolet Explorer wikipedia , lookup
Copernican heliocentrism wikipedia , lookup
IAU definition of planet wikipedia , lookup
Tropical year wikipedia , lookup
Planets beyond Neptune wikipedia , lookup
Aquarius (constellation) wikipedia , lookup
Exploration of Io wikipedia , lookup
Observational astronomy wikipedia , lookup
Astrobiology wikipedia , lookup
History of astronomy wikipedia , lookup
History of Solar System formation and evolution hypotheses wikipedia , lookup
Exploration of Jupiter wikipedia , lookup
Solar System wikipedia , lookup
Planetary habitability wikipedia , lookup
Definition of planet wikipedia , lookup
Naming of moons wikipedia , lookup
Formation and evolution of the Solar System wikipedia , lookup
Extraterrestrial skies wikipedia , lookup
Comparative planetary science wikipedia , lookup
Astronomical unit wikipedia , lookup
Extraterrestrial life wikipedia , lookup
Geocentric model wikipedia , lookup
Dialogue Concerning the Two Chief World Systems wikipedia , lookup
Brahe and Kepler 1580-1630 • Brahe discovered a supernova, determined it was “far away”, became famous, and was given an island for an observatory 20 year od data on planet angular positions, and planet geocentric parallax • Kepler (mathematician, astrologer) hired by/succeeded Brahe to analyze data. He also discovered a supernova and analyzed it, and became famous. Last two supernovas observed in Milky Way Galazy. Determined 3 Laws of planetary motion (1600-1630) • Few “modern” tools (no calculus, no graph paper, no log tables) PHYS 162 Class 5 1 Observations of Brahe 1580-1600 • No telescopes, just “long sticks” where one could easily measure both angular coordinates at once by “flipping” the device • Measure relative location of planets to stars (and moon). If do at dusk and dawn for saw Mars have a distance measurement using parallax • As far as I can tell Brahe was mostly in Vienna and Prague and not on his island PHYS 162 Class 5 2 Kepler’s Data Analysis • Kepler figured out correct orbital shape (circle vs ellipse vs circle with circle, etc) • Mercury and Venus relatively easy. Will be PHYS 162H activity 2. Looks like an ellipse • Mars, Jupiter and Saturn tougher, especially as Jupiter has 12 year orbit and Saturn 30 years Kepler mostly did Mars as about 2 years and so Brahe’s data had 10 orbits of Mars around the Sun • Orbital period for all planets easy • Distance better measured for closer. Ratio easier PHYS 162 Class 5 3 Kepler’s Laws of Motion • A big step was realizing that Earth’s orbit about the Sun also wasn’t a circle – mostly he used relative location of Mars after repeated orbits around the Sun (Mars is close and so most accurate measurements) PHYS 162 Class 5 4 Apparent Shift = Parallax • A moving observer sees fixed objects move. • Near objects appear to move more than far objects • The effect is due to the change in observation point, and is used by our eyes for depth perception. Geocentric parallaxEarth as base Heliocentric parallax-use orbit about Sun as base. Use for stars as need telescope angle A Earth angle B PHYS 162 Class 5 5 Kepler’s Laws of Planetary Motion (1630) FIRST LAW: The orbit of a planet is an ellipse with the sun at one focus. A line connecting the two foci in the ellipse always has the same length. PHYS 162 Class 5 6 Kepler’s Second Law • The line joining a planet and the sun sweeps equal areas in equal time. The planet moves slowly here. The planet moves quickly here. PHYS 162 Class 5 7 Kepler’s Third Law • The square of a planet’s period is proportional to the cube of the length of the orbit’s semimajor axis. • Mathematically, T2/a3 = constant (=1 if use 1 Earth year and 1 AU as units) • The constant is the same for all objects orbiting the Sun same process determines all planets’ motions direction of orbit semimajor axis: a The time for one orbit is one period: T PHYS 162 Class 5 8 Mean Distance Sidereal from Sun Orbital Period AU Mercury 0.387 Venus 0.723 Pe 0.241 0.615 Earth Mars Jupiter 1.000 1.881 11.857 1.000 1.524 5.203 Saturn 9.537 Uranus 19.191 Neptune 30.069 29.424 83.749 163.727 PHYS 162 Class 5 9 Third Law Example • Jupiter compared to Earth • If we measure that it takes Jupiter 11.9 years to orbit the Sun then: distance 3(Jupiter-Sun) = period(Jupiter)2 distance = period2/3 distance = (11.9*11.9)1/3 distance = (142)1/3 = 5.2 AU PHYS 162 Class 5 10 Mean Distance Sidereal from Sun Orbital Period AU Mercury 0.387 Venus 0.723 Pe 0.241 0.615 Earth Mars Jupiter Saturn 1.000 1.881 11.857 29.424 1.000 1.524 5.203 9.537 Uranus 19.191 Neptune 30.069 D3 .05 0.4 1 3.5 140 866 P2 .05 0.4 1 3.5 140 866 83.749 163.727 PHYS 162 Class 5 . 11 • All other orbits obey Kepler’s law (with different constant related to mass of system) • Moons of Jupiter, satellites about Earth, two stars about each, material in Milky Way Galaxy • Due to same underlying physics • They needed to develop Physics as a science: understand motion, forces, and gravity PHYS 162 Class 5 12 • Kepler correctly determined the motion of the planets. • Did not address WHY. Simply what curve best matched orbits and some arithmetical relationships • The WHY was determined by physicists like Galileo and Newton. • They needed to develop Physics as a science: understand motion, forces, and gravity PHYS 162 Class 5 13 Galileo 1564-1642 • Professor of art, mathematics, natural philosophy, astronomy in Florence, Pisa, Padua with occasional “contract” work for various Dukes, etc • Very strong proponent of the scientific method – use of observations to test theories • Early work:motion, and practical elements like hydrostatics • 1609: first person to use a telescope for astronomy became the most famous scientist/celebrity in Europe • Last 25 years of life was often in trouble with the Catholic Church. His celebrity helped to save him PHYS 162 Class 5 14 Galileo – Telescope - 1610 • Jupiter had at least 4 moons which circled it (something besides Earth could be the center of motion); there were many more stars, mountains on moon Book Starry Messenger • Venus had definite phases and clearly orbiting Sun • Observed sunspots (patches on Sun). Sun revolved on own axis. Wasn’t “perfect” and changes in unpredictable manner • Observed Saturn’s rings but was confused as to what they were • Wrote book on Copernican vs Ptolemaic models in 1632, nominally with Church’s permission. But it offended Church. Dialogue Concerning the Two Chief World Systems. In Italian. Character in book Simplicio defended Church’s position spent last 10 years of his life in house arrest. Catholic church said contrary to scriptures……Church admits in error in 1992 162 Class 4 15 Jupiter’s Moons (1610) 4 moons can be seen with a small telescope. Change position with time how long it takes to go around vs distance from Jupiter More discovered: Pluto now has 4 moons 162 Class 4 16 Phases of Venus (1610) Venus has phases like the Moon which are easily explained by having it orbit the Sun and impossible to explain if the Earth was at the center of the Solar System 162 Class 4 17 Sunspots Sunspots are now known to be magnetic storms. Allows the rotation of the Sun to be readily observed. Seen without telescopes before Galileo but his observations were of higher quality and showed Sun’s 25 day rotation Sun isn’t “perfect” and rotates like Earth 162 Class 4 18