History of Cosmology Timeline

In the 16th century, Nicolaus Copernicus proposed a heliocentric system in which the Sun, rather than Earth, occupied the center of the cosmos. His revolutionary idea overturned the long-dominant Ptolemaic geocentric model and launched the Scientific Revolution.

Image source: Nicolaus Copernicus

Following Copernicus, Johannes Kepler subsequently developed the heliocentric system further, formulating his laws of planetary motion that described the elliptical orbits of planets and strengthened the case against the geocentric Ptolemaic system.

Image source: Johannes Kepler

Subsequent to Copernicus and Kepler, Galileo Galilei used his telescope to gather observational evidence supporting the heliocentric system, including observations of Jupiter's moons and the phases of Venus, further undermining the Ptolemaic worldview.

Image source: Galileo Galilei

Isaac Newton's Principia Mathematica, published in 1687, was the first description of the law of universal gravitation. It provided a unified physical framework that could explain both terrestrial and celestial phenomena, laying the foundation for Newtonian cosmology.

Image source: Philosophiæ Naturalis Principia Mathematica

Among the 19th-century cosmological paradoxes related to Newtonian gravity was the Bentley–Seeliger paradox, which questioned why gravitation does not make the universe collapse under its own attraction, exposing weaknesses in static Newtonian models of the cosmos.

Image source: Olbers' paradox

In the 19th century, various cosmological paradoxes appeared related to Newtonian gravity. Olbers' paradox asked why the sky is dark if the universe were infinite, static, and filled with stars — a puzzle that challenged simple Newtonian models of an eternal universe.

Image source: Olbers's paradox

The heat death paradox, one of the 19th-century cosmological paradoxes tied to Newtonian physics, asked why the universe has not yet reached thermal equilibrium if it has existed forever, challenging the notion of an infinitely old, static universe.

The term cosmology was first used in English in 1656 in Thomas Blount's Glossographia, where it carried the meaning of 'a speaking of the world'. This marked the earliest recorded English usage of the word that would later come to define the scientific study of the universe as a whole.

Image source: Cosmology

In 1731, German philosopher Christian Wolff used the term cosmology in Latin (cosmologia) to denote a branch of metaphysics that deals with the general nature of the physical world. This helped establish cosmology as a distinct field of philosophical inquiry.

Image source: Christian Wolff (philosopher)

During the Great Debate era, early cosmologists such as Heber Curtis and Ernst Öpik determined that some nebulae seen in telescopes were separate galaxies far distant from our own, reshaping humanity's understanding of the scale of the universe.

Image source: Heber Doust Curtis