Astronomers

Question 1

Aristarchus

Answer 1

A SUN CENTERED UNIVERSE. The first Greek to profess a heliocentric universe. Suggested a sun centered universe dominated western thought for 2000 years.

Question 2

Hipparchus

Answer 2

Famous star catalogue. Determined the location of almost 850 stars, which he divided into six groups according to their brightness. Measured the length of the year to within minutes of the modern value and developed a method for predicting the times of lunar eclipses within a few hours.

Question 3

Ptolemy

Answer 3

Created the Ptolemaic System, which created a geocentric outlook (earth centered) and had planets moving in perfect circular orbits around a motionless earth - had retrograde motion. Compiled a 13 volume treatise called Almagest (the great work). Credited with developing a model of the universe that accounted for observable motions of the celestial bodies. Proposed that planets orbited on small circles (epicycles), revolving along larger circles (deferents).

Question 4

Copernicus

Answer 4

Concluded that earth is a planet. Reasoned that the daily motions of the heavens could be more simply explained by a rotating earth. Constructed a heliocentric model for the system with the sun at the center and the planets orbiting it. Wrote “on revolution of the heavenly spheres” which set forth his controversial sun centered solar system

Question 5

Brahe

Answer 5

Did not believe in the Copernican model because he was unable to observe an apparent shift in the position of the stars that should result if earth traveled around the sun. If earth orbits the sun, the position of a nearby star, when observed from two locations in earth’s orbit six months apart, should shift with respect to the more distant stars. (He was correct) the apparent shift of the stars is called stellar parallax.

Question 6

Kepler

Answer 6

Derived three basic laws of planetary motion.

1. The path of the planet around the sun, while almost circular, is actually an ellipse, with the sun at one focus
2. Each planet revolves so that an imaginary line connecting it to the sun weeps over equal areas of equal intervals of time (law of equal areas)
3. The orbital periods of the planets and their distances to the sun are proportional; astronomical unit is equal to about 150 million kilometers the planet’s orbit period squared it equal to its mean solar distance cubed

Question 7

Galileo

Answer 7

Descriptions of the behavior of moving objects through the telescope he constructed. Supported the Copernicus view of the universe. Discovered Jupiter’s 4 largest satellites which dispelled the old idea that the earth was the sole center of motion in the universe. Planets are circular disks rather than just points of light. Discovery that Venus exhibits phases just as the moon does. Discovery that the moon’s surface is not a smooth glass sphere. Discovery hat the sun has sun spots - dark regions caused by slightly lower temperatures.

Question 8

Newton

Answer 8

Inertia was Newton’s first law of motion. First to formulate and test the law of universal gravitation, which states everybody in the universe attracts every other body with a force that is directly proportional to their masses ab inversely proportional to the square distance between them. The greater the mass of an object, the greater it’s gravitational force. Proved that the force of gravity would result in a planet having an elliptical orbit as established by Kepler

Question 9

Eratosthenes

Answer 9

MEASURING THE EARTH’S CIRCUMFERENCE. First successful attempt to establish size of earth. Observed the angles of the noonday sun in two Egyptian cities calculated earth’s circumference to be about 39,300 kilometers (40,075 km).

Question 10

Aristotle

Answer 10

Earth is spherical because it always casts a curved shadow when it eclipses the moon.