History of astronomy

From ArticleWorld

The history of astronomy is rooted in the ancient art of astrology, which was practiced by priests and oracles across every inhabited continent in the world. Folk legends, petroglyphs, and stone monuments such as Stonehenge demonstrate that the study of the heavens was widespread long before the advent of writing.

Early astronomers, lacking modern equipment, based their studies on purely visible phenomena, such as naked eye planets, the moon, and brighter, easily visible stars. These observations were compiled over time, leading not only to astrology but also to the development of systems to predict planetary orbits.


Ancient astronomy

It was believed by most early priest-astronomers that stars and planets were the embodiments of spirits and deities. Thus, many constellations and planets are named after mythical entities, such as Orion, Cassiopeia, Ursa Minor and Ursa Major, Mars, Venus, Jupiter, Mercury and almost every other planet in our solar system.

Until the 18th century, the spiritual aspect of astronomy was closely linked to the development of prediction systems and calendars. Ancient holy days such as the equinoxes and solstices were pinpointed by carefully analyzing the heavens. The stars and planets were also used to predict the best times for planting crops, performing marriages and hunting.

Asia and early America

Early Indian astronomers made many important developments in astronomy. Most notably, in the 6th century, Aryabhata created mathematical models demonstrating that planets have elliptical orbits around the sun. He also calculated the size of the earth with surprising accuracy and made demonstrated that the earth spins on an axis. This was long before the Copernican Revolution.

In China, often noted for its advanced ancient technology, astronomy was a precise endeavor that tied strongly into mathematics. The first supernova recorded on earth was seen by Chinese astronomers, and sophisticated methods were developed to predict eclipses.

In South America, the Mayans relied heavily on astronomical prediction as an integral part of their religion. Their calendar is said by some to be more accurate than the Gregorian calendar that we use today.

Europe and the Middle East

Western astronomy is strongly linked to that of the Middle East, especially Mesopotamia and Babylonia. The Sumerians of Mesopotamia developed the 360-degree circle, which is still used today to calculate the angular size of stellar or planetary objects. The Babylonians later expanded on early Sumerian knowledge with the development of planetary prediction systems based on past records as well as mathematics.

The ancient Greeks developed methods to mathematically calculate the distance around the earth and to measure physical phenomena such as precession. Classical Greek models of the universe underpinned European astronomy until the middle ages.

Significant developments in European astronomy were not made for several centuries after the fall of the Roman empire. Generally, work to calculate and predict the motion of heavenly bodies was limited to religious functions, such as determining the proper day to celebrate Easter. In general, European astronomers limited their studies to the geocentric model. It was commonly believed that the Earth was the center of the universe as stated by classical philosophers such as Aristotle and Ptolemy.

Copernicus and Galileo

The renaissance brought renewed interest in cosmology in Europe. It was during this time that the study of the sky started to become divorced from religion. By the year 1800, astronomy had become a full-fledged science.

Nicolaus Copernicus was the first European scientist to propose a heliocentric, or sun-centered model of the solar system. His work was further verified by Johannes Keplar and Tycho Brahe.

In the early 1600s, Galileo Galilei, using the world’s first telescope, observed four of Jupiter’s moons. He also observed the phases of Venus, craters on the Earth’s moon, and sunspots. His writings created a controversy with the Roman Catholic Church, his books were banned, and he was forced to live under house arrest until he died. It was not until Isaac Newton integrated physics with the celestial sciences that astronomy started to become a fully scientific, verifiable, and widely accepted discipline.

20th century astronomy and cosmology

In the 19th century, James Clerk Maxwell developed a set of equations linking electricity to magnetism. Maxwell concluded that electromagnetic waves traveled at the speed of light, and that light itself was an electromagnetic disturbance. This idea was elaborated upon by others, among them, Albert Einstein, who developed the theories of Special and General Relativity. Herman Minkowski used Einstein’s theories to develop a model of the universe that included three spatial dimensions and time in four-dimensional “spacetime.”

Relativity opened the doors to new ideas about the universe. Georges Lemaître proposed the big bang theory in the 1930s. Edwin Hubble also made considerable contributions to modern astronomy with his observations showing that we live in an expanding universe populated by multiple receding galaxies.