Astronomy
Astronomy is the science that explores the wonders of the universe. It studies celestial objects and cosmic events - from planets and stars to galaxies, comets, and spectacular phenomena like supernova explosions. To understand how these objects are born and how they change over time, astronomers draw on tools from mathematics, physics, and chemistry. In the past, astronomy also included areas like celestial navigation, astrometry, and calendar-making. Today, the line between astronomer and astrophysicist is often blurred. What’s especially fascinating is that astronomy remains one of the few sciences where dedicated amateurs can still make significant contributions - for example, by spotting new astronomical events.
The word “astronomy” comes from Greek, meaning “law of the stars.” It’s important not to confuse astronomy with astrology. Astrology is a belief system claiming that the positions of celestial bodies influence human affairs - a notion without scientific basis - even though both fields share historical roots.
Modern astronomy is usually divided into two main branches:
- Observational astronomy
This branch focuses on gathering data by observing celestial objects using telescopes and other instruments. - Theoretical astronomy
Theoretical astronomers use math and computer models to explain how cosmic objects and phenomena behave.
The History of Astronomy
Ancient Era
Thousands of years ago, astronomy was mainly about watching the skies and predicting the movements of objects visible to the naked eye. Ancient cultures built observatories to track the seasons, crucial for farming, and to measure the length of the year. Before telescopes existed, stargazing depended entirely on human eyesight. Across history, different civilizations expanded our cosmic knowledge. The Babylonians were early pioneers in using math for astronomy, while the Greeks were the first to seek rational, physical explanations for celestial events. The Greeks also introduced the heliocentric idea - that planets orbit the Sun.
Medieval Era
During the Middle Ages, Europe produced brilliant astronomers like Richard of Wallingford, who built the first astronomical clock and the Albion equatorium, an instrument for astronomical calculations. Scholars such as Nicole Oresme and Jean Buridan explored Earth’s rotation and theories like impetus. Georg von Peuerbach and Regiomontanus were key in developing the heliocentric model further. For centuries, the Roman Catholic Church supported astronomical research, partly to help calculate the date of Easter. Meanwhile, astronomy thrived in the Islamic world, driven by astronomers like Al-Battani and Biruni, who used advanced algebra to tackle complex astronomical problems. Significant observatories were built in places like Maragheh and Samarkand as early as the 9th century.
Modern Era
In the modern age, Nicolaus Copernicus proposed a Sun-centered model of the solar system. His revolutionary ideas were championed by Galileo Galilei and refined by Johannes Kepler, who accurately described how planets move around the Sun - even if he couldn’t fully explain why. Isaac Newton provided the answer with his laws of motion and universal gravitation, transforming our understanding of celestial mechanics. Newton also invented the reflecting telescope. As telescopes grew bigger and better, astronomers made new discoveries. John Flamsteed, an English astronomer, cataloged over 3,000 stars. Nicolas Louis de Lacaille expanded star catalogs even further. William Herschel meticulously mapped nebulae and star clusters, and in 1781, discovered Uranus - the first new planet found in modern times.
Contemporary Era
In the 18th and 19th centuries, scientists like Euler, Clairaut, and d’Alembert tackled the difficult three-body problem, leading to better predictions of how the Moon and planets move. Lagrange and Laplace refined their work and used gravitational effects to estimate the masses of planets and their moons. New technologies such as spectroscopy and photography revolutionized astronomy. Scientists discovered that stars are similar to our Sun, yet vary enormously in temperature, size, and mass.
20th and 21st Century
In the 20th century, astronomers confirmed that the Milky Way is our home galaxy - and that countless other galaxies exist far beyond it. Observations of galaxies moving away from us revealed that the universe is expanding. Meanwhile, theoretical astronomy unlocked new insights into exotic objects like black holes and neutron stars, which help explain phenomena such as quasars, pulsars, blazars, and radio galaxies. The 20th century also saw major breakthroughs in cosmology, especially the development of the Big Bang theory. This model is strongly supported by evidence like the cosmic microwave background, Hubble’s law, and the cosmic abundance of elements. In the 1990s, astronomers confirmed the existence of exoplanets - worlds orbiting stars beyond our Sun. Launching the first space-based telescopes and observatories allowed astronomers to study parts of the electromagnetic spectrum normally blocked or blurred by Earth’s atmosphere. Finally, in February 2016, scientists announced that the LIGO project had made the first direct detection of gravitational waves, opening a brand-new way to explore the universe.
