Early Heliocentric Model

Philolaus of Craton

He proposed that there is a massive ball of fire at the center of the universe, around which the sun, moon, Earth, five planets, and stars revolve.

Aristotle

He says that Earth is at then center of the universe and every celestial bodies around revolves around it.

Ptolemy

He claims an Earth-centered (geocentric) model of the universe.

Nicolaus Copernicus

He proposes a sun-centered (heliocentric) universe.

Friedrich Bessel

He is the first astronomer to measure a star's distance precisely using a technique called parallax.

Aristarchus of Samos

The first person to propose that the sun, rather than Earth, is at the center of the universe and that Earth revolves around it.

The Sand Reckoner

In this Book, Aristarchus proposed that "the fixed stars and sun stay unmoved" and that "Earth revolves around the sun."

Archimedes

Author of *The Sand Reckoner*

Seleucus of Seleucia

He was the only persuaded of the truth of Aristarchus’ heliocentric view of the universe, during their time.

Heliocentric Model

Earth revolves around the sun on the circumference of a circle.

Geocentric Model

The celestial bodies revolve around the stationary Earth.

Sir Thomas Heath

He said, “*Aristarchus was the real originator of the Copernican hypothesis.”*

430 BCE

Philolaus of Craton proposed that there is a massive ball of fire at the center of the universe, around which the sun, moon, Earth, five planets, and stars revolve.

350 BCE

Aristotle says that Earth is at then center of the universe and every celestial bodies around revolves around it.

150 CE

Ptolemy claims an Earth-centered (geocentric) model of the universe.

1453

Nicolaus Copernicus proposes a sun-centered (heliocentric) universe.

1838

Friedrich Bessel of Germany is the first astronomer to measure a star's distance precisely using a technique called parallax.

Parallax

A technique used by Bessel to measure a star's distance precisely.

15th century

In 150 CE, the geocentric viewpoint was still the prevailing one, and it persisted until Nicolaus Copernicus revived the heliocentric perspective in the _______.

moon

Aristarchus’s calculations for the ______'s distance were largely accurate.