FAMOUS ASTRONOMERS

Aristotle
384-322 BCE
Ancient Greece

ARISTOTLE

• He believed everything rotated around Earth, his models showed so
• He also though the stars position would change if the earth moved.
• This apparent shift, is called a parallax
• He believed earth, was the only planet that wasn't perfect. That had death
• He also though the solar system was round

Aristarchus
310-230 BCE
He was a Greek astronomer and mathematician

ARISTARCHUS

• He was reported to have a heliocentric model if the solar system
• Attempted to measure the distances between the moon & sun
• This was his main contribution to science
• Heliocentric means that sun was the centric.
• Though his distances were too small, they were very helpful

PTOLEMY
HE WAS AN GEOGRAPHER, AND MATHEMATICIAN IN ALEXANDRIA EGYPT, WHICH WAS PART OF ANCIENT ROME
100-170 BCE

PTOLEMY

• He believed retro grade motion, the first to observe it
• He developed geocentric models used for 1400 yrs
• He believed a celestial body traveled a t a constant speed
• His models showed planets moved in smaller circles on larger circles
• This "wheels on wheels" system fit differently due to retro grade motion

Copernicus
A polish astronomer, Nicolaus Copernicus lived in 1473-1543

COPERNICUS

• He adopted Ptolemy's idea of wheels on wheels
• But added the heliocentric idea of Aristarchus
• He believed Ptolemy's idea was too complicated
• And perfected it
• It is seen as the first step in the development of models

Kepler
Johannes Kepler was a German mathematician and astronomer
1571-1630

KEPLEr

• He noticed what was wrong about the pervious models
• He did a lot of analyzing until he found which fit best.
• Kepler formulated 3 principles. One, planetary orbits are ellipses...
• ...with the sun at one focus. 2, planets move faster in their orbits when they are closer to the sun
• The third law related to the distance of a planet from the sun to the time it takes to orbit

GALILEO GALIEI
Was a scientist who used the scientific method. In Pisa, Italy
1564-1642

GAILIEO

• He made significant improvements to the telescope
• He observed the moons of Jupiter, Io, Europa, Callisto and Ganymede
• His observations showed that earth wasn't the only planet with moons
• This gave more support to the heliocentric model
• He also observed how Venus goes through phases like the moon

Isaac Newton
1642-1721
A British physicist and mathematician.

ISAAC NEWTON

• He learned about gravity, deriving it from Kepler's laws of motion
• 1: when viewed in a inertial reference frame, an object either remains at rest or...
• ..continues to move at the same velocity.
• 2: F=ma forces are equal to the mass times acceleration to the object
• 3: when one body exerts force on a 2nd body, the 2nd body continues to force

Edwin Hubble
An american astronomer
1889-1953

EDWIN HUBBLE

• He played a crucial role in establishing the field of extragalactic astronomy
• Is known as one of the most important observational cosmetologist of the 20th century
• He created "Hubble's law" which is:
• The law that velocity of recession of distant galaxies is from our own is proportional to...
• ...their distance from us,

GEOCENTRIC

• Aristotle created the idea
• It meant that the earth was the center of our solar system
• and was used for ~2000 years
• Was also used by Ptolemy
• Until Copernicus' correction was used for ever

HELIOCENTRIC

• Created Aristarchus
• It meant that the sun was the center of the solar system
• Used also by Copernicus and modern scientists
• but was only used ~2000 years later
• When Copernicus corrected them