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Astronomy in the Renaissance

Astronomy in the Renaissance. Tycho Brahe Made observations (supernova and comet) that suggested that the heavens were both changeable and more complex than previously believed Proposed compromise geocentric model, as he observed no parallax motion!. Johannes Kepler - German.

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Astronomy in the Renaissance

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  1. Astronomy in the Renaissance • Tycho Brahe • Made observations (supernova and comet) that suggested that the heavens were both changeable and more complex than previously believed • Proposed compromise geocentric model, as he observed no parallax motion!

  2. Johannes Kepler - German Supported heliocentric model Wanted to find a unifying principle to explain planetary motion without using epicycles 9 years after Tycho’s death discovered the problem with prior models – the shape of the orbit was not a circle but an ellipse Using Tycho’s very precise Mars data, Kepler showed the orbit to be an ellipse Did this using triangulation (1571-1630)

  3. Kepler’s 1st Law • Planets move in elliptical orbits with the Sun at one focus of the ellipse • The long axis of the ellipse is the major axis. • Semimajor axis, ½ the major axis, is a measure of the ellipse’s size

  4. Astronomers use the term eccentricityto describe how round or “stretched out” an ellipse is It’s the ratio of the distance between the 2-foci to the length of the major axis Eccentricity of zero  perfect circle Eccentricity of one  straight line Johannes Kepler

  5. Examples of Ellipse Eccentricity • Most planets have eccentricities that look more like perfect circles (which is why Ptolemy and Copernicus’ models came close to working) • Mercury and Pluto have the greatest eccentricity • Comets have very eccentricity orbits between .5 and 1, coming very close to the Sun at perihelion but spending the majority of time far away.

  6. Kepler’s 2nd Law • The orbital speed of a planet varies so that a line joining the Sun and the planet will sweep out equal areas in equal time intervals • The closer a planet is to the Sun, the faster it moves aphelion perihelion

  7. Kepler’s 1st & 2ndLaws Explained why a planets brightness would change (no more epicycles) Apply to any orbiting object Published in 1609; only proven for Mars at this point.

  8. Kepler’s 3rd Law • The amount of time a planet takes to orbit the Sun is related to its orbit’s size • The square of the orbital period(P) is proportional to the cube of the semimajor axis (a) (average distance from the Sun)

  9. Kepler’s 3rd Law • This law implies that a planet with a larger average distance from the Sun, which is the semimajor axis distance, will take longer to circle the Sun • Third law hints at the nature of the force holding the planets in orbit

  10. Galileo (1564-1642) • Italian mathematician & philosopher • Same time as Kepler • Believed in the Copernican System • Revolutionized science by: • Performing experiments • Use of technology

  11. Discoveries 1st astronomer to use a telescope-1609 Discovered/Found: Mts. & valleys on the Moon Sunspots moving across the Sun More stars 4 moons of Jupiter Documented Venus’ complete cycle of phases Supported Copernicus’ heliocentric model

  12. Starry Messenger • Published in 1610 • It supported the Copernican Model • By doing this he directly challenged: • the current scientific establishment. • religious dogma.

  13. Church Reacts • This led to a trial where in 1616 his ideas were judged heretical and banned by the Church. • Galileo was instructed to abandon his astronomical pursuits. He did not…

  14. A Dialogue Concerning the Two Chief World Systems • Published in 1632, comparing the Ptolemy and Copernican models.

  15. Isaac Newton • Isaac Newton (1642-1727) was born the year Galileo died • He made major advances in mathematics, physics, and astronomy

  16. Isaac Newton • He pioneered the modern studies of motion, optics, and gravity and discovered the mathematical methods of calculus • It was not until the 20th century that Newton’s laws of motion and gravity were modified by the theories of relativity

  17. The Growth of Astrophysics • New Discoveries • In 1781, Sir William Herschel discovered Uranus; he also discovered that stars can have companions • Irregularities in Uranus’s orbit together with law of gravity led to discovery of Neptune • New Technologies • Improved optics led to bigger telescopes and the discovery of nebulas and galaxies • Photography allowed the detection of very faint objects

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