Astronomy - History of Scientists

Key Scientists & Their Contributions to Astronomy

What was Ptolemy known for/main contribution?

Geocentric Model

First name of Ptolemy?

Claudius

Who was Ptolemy?

ancient Greek-Roman astronomer, mathematician, and geographer

Geocentric Model

Where the Earth is the center of the universe and all the celestial bodies orbit around it.

Ptolemy’s Key Work?

Almagest

What was Almagest?

Comprehensive treatise that became the authoritative text on astronomy for over a thousand years.

What was Copernicus know for/main contribution?

Heliocentric Model

Copernicus’ first name?

Nicolaus

Who was Copernicus?

a Renaissance-era mathematician and astronomer

Heliocentric Model

The Sun is the center of the universe, and all celestial objects orbit around that.

Copernicus’ key work?

De revolutionibus orbium coelestium (On the Revolutions of the Heavenly Spheres)

De revolutionibus orbium coelestium (On the Revolutions of the Heavenly Spheres)

published in 1543, the book that outlined his heliocentric theory

What was Tycho known for/main contribution?

Observational Astronomy

Tycho’s last name?

Brahe

Who was Tycho?

Danish nobleman and astronomer

Observational Astronomy

accurate and comprehensive, he meticulously charted the positions of stars and planets over decades, which provided the most precise data available before the telescope

Tycho’s key work?

Tychonic System

Tychonic System

a model of the universe combining aspects of both geocentric and heliocentric models,

Kepler known for/main contribution?

Laws of Planetary Motion

Kepler’s first name?

Johannes

Who was Kepler?

German mathematician, astronomer, and astrologer

Three Laws of Planetary Motion

Law of Ellipses, Law of Equal Areas, Harmonic Law

Law of Ellipses

planets move in elliptical orbits with the Sun at one focus

Law of Equal Areas

line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time

Harmonic Law

square of the orbital period of a planet is proportional to the cube of the semi-major axis of its orbit

Key Works of Kepler?

Astronomia nova (New Astronomy) and Harmonices Mundi (Harmony of the Worlds)

Galileo’s known for/main contribution?

Telescope

Galileo’s last name?

Galilei

Who was Galileo?

Italian astronomer, physicist, and engineer

Telescope

significant improvements to the telescope which helped in making groundbreaking observations like moon of Jupiter, phases of Venus and the Moon’s surface, his observations supported the Copernican heliocentric model

Galileo’s Key Work?

Sidereus Nunicius (Starry Messenger)

Sidereus Nunicius (Starry Messenger)

short treatise where he published his early telescopic observations

What was Newton known for/main contribution?

Law of Universal Gravitation

Newton’s first name?

Issac

Who was Newton?

English mathematician, physicist and astronomer

Law of Universal Gravitation

every mass attracts every other mass in the universe with a force proportional to the product of their masses and inversely proportional to the square of the distance b/w them, explains why planets orbit the sun and why objects fall to Earth

Key Work of Newton

Philosophiæ Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy)

Philosophiæ Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy)

commonly known as the “Principia”, laid the foundation for classical mechanics

Retrograde Motion

on is an optical illusion observed from Earth, where a planet appears to move backward (westward) in the sky relative to the stars. This occurs because of the relative positions and movements of Earth and the other planets.

Epicycles in Celestial Motion

small circular path that a planet follows as it moves along a larger circular path (the deferent) around the Earth. Used to explain the irregularities in planetary motion, including retrograde motion.

Derferent

large circular path that a planet follows in the geocentric mode, with epicycles being smaller orbits on this path