ASTRONOMISTS

ARISTOTLE

• A greek philosopher
• His model placed the moon,sun, planets,and stars on a series of circles that surround the earth.
• He thought that if Earth went around the sun, then the relative position of stars would change as earth moves.
• He lived from 384-322 BCE

ARISTARCHUS

• A greek astronomer and mathmetician
• His model that he created was not widely known and liked.
• He attempted to measure the relative distance from the moon and the sun.
• His ratio of distance was to small but was important in the use of observation and gemoetry to solve a scientific problem.
• Lived from 310-230 BCE

PTOLEMY

• An astronomef, geographer, and mathematician.
• His book, that was named "Almagest" is one of the few books we have from this early in time.
• The book was on the observation of planets going back as much as 800 years ago.
• His theory was that planets moved on larger circles. " wheels on wheels"
• Lived from 100-170 BCE

COPERNICUS

• He thought that Ptolemy's theory was to complicated.
• He used "wheels on wheels" system, he thought that they should travel in perfect circles.
• He also thought that earth circled the sun.
• 1473-1543

KEPLER

• He realized that requiring planetary motion to be exactly circular did not fit.
• He took another path and found that ellipses fit best.
• Lives from 1571-1630

GALILEO

• Scientific method
• He helped improve the telescope.
• Observed the moons Io, Europa, Callisto, and orbiting jupiter.
• Lived from 1564-1642

KEPLERS 1ST LAW

• He carefully plotted the orbit of mars, and it showed a deformed circle.
• After 8 years, he realized that this was an ellipse.
• Kepler placed the sun at one of the foci of the ellipse.

KEPLERS 2ND LAW

• Using the shape of an ellipse, he looked deeper in to the data.
• He found that when planets get closer to the sun, they get faster.

KEPLERS 3RD LAW

• He calculated the orbital period and the distance from the sun for the planets using tycho's data.
• He discovered that the square of the orbital period was proportional to the cube of the planets distance from the sun.