Astronomy - An Introduction

Introduction

People have a few different definitions of Astronomy, beginning with a definition describing it as a study of matter and objects which are outside of Earth's atmosphere, and their chemical and physical properties. Another definition describes Astronomy as a science that is dedicated to studying both the nature and motion of celestial bodies; such as stars, galaxies and planets.

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Astronomy - An Introduction

People have a few different definitions of Astronomy, beginning with a definition describing it as a study of matter and objects which are outside of Earth's atmosphere, and their chemical and physical properties. Another definition describes Astronomy as a science that is dedicated to studying both the nature and motion of celestial bodies; such as stars, galaxies and planets. A third definition of Astronomy declares it to be the study of everything because it involves a study of all things in the universe. Each of these definitions is correct, and there are several different areas of study within the science of Astronomy. These areas include:

Cosmology:

Cosmology is a study of the Universe in its entirety, as well as its beginning. Cosmology is an astrophysical study of the organization, structure, history and the dynamics involved in the universe. The field of cosmology pursues studies involving the evolution of the universe we are a part of; scientists who are a part of this field are referred to as, "Cosmologists."

There are some different areas that Cosmologists focus on in their search for knowledge of the universe. They would like to understand what the universe was like many billions of years ago, as well as what it is like today. Cosmologists would also like to understand what the universe will be like billions of years from now. In order for them to understand these things, they need to understand our place in the universe too.

For the universe, four-hundred years is not too long of a time; yet only four-hundred years ago, most of the people on Earth thought that it was the center of the entire universe! People on Earth at the time believed that the sun, moon, and the other planets traveled around Earth. Scientists such as Galileo Galilei, Nicholas Copernicus, and Isaac Newton completed observations and studies that changed the perspectives of humanity, helping us to understand that the moon, sun, and planets travel around the sun.

A mere one-hundred years ago, Edwin Hubble completed several different observations that show the universe is expanding, or growing larger. His observations helped many Cosmologists to agree with the, 'Big Bang,' theory which suggests that a massive explosion about ten to twenty billion years ago started the universe. Some Cosmologists believe that the universe did not exist prior to the Big Bang, and that it will continue to expand forever now that it has happened. Other Cosmologists believe the universe will contract, or shrink in size again, until it doesn't exist anymore someday. Cosmologists use tools like telescopes and astronomy satellites in their efforts to understand the universe, as well as computers to model ideas.

Astrometry:

Astrometry is a science that measures the position of different objects in space and their motion. Astrometrists are involved in measuring incredible distances between objects in space. They make observations of stars that are close by in order to measure the, 'wobble,' the star may have, caused by planets in orbit around them.
Astronomy is perhaps the oldest field of science, Astrometry is probably the oldest sub-field. Sailors used to figure out their positions on Earth through their observations of the stars above them. Astrometry today is used in the measurement of time. Atomic time is synchronized to Earth's rotation through Astrometry.

Planetology:

Planetology is a branch of the field of Astronomy dealing with actual, physical features of planets and their origins and composition. The field also deals with other bodies in the solar system, like meteors or comets. Planetologists study planets orbiting nearby stars as well.

Radio Astronomy:

Radio Astronomy involves the use of radio telescopes in order to study the universe. Radio Astronomers study electromagnetic radiation from objects that are outside of the Earth's atmosphere using telescopes that gather rays which are reflected or given off by space objects or stars.

A Scottish Mathematician and Theoretical Physicist named James Clerk Maxwell, in the 1860's, produced equations showing that electromagnetic radiation from stellar sources could exist with any wavelength; not just optical ones alone. In 1931, Karl Jansky - an American Physicist and Radio Engineer, confirmed Maxwell's theory. Jansky was investigating static which was interfering with short wave transatlantic voice transmissions while working for Bell Telephone Laboratories. He used a large, directional antenna to track the interference, and noticed a repetitive signal from an unknown source. Jansky noticed that the signal peaked once each day, and thought that it came from the sun, but he continued his analysis. The signal, he found, was repeating on a cycle of 23 hours and 56 minutes; something that was usual for an astronomical source. He compared his observations with astronomical maps and finally concluded that the signal was coming from the direction of the constellation Sagittarius. He announced his discovery in 1933, asking to continue his research; Bell Laboratories reassigned him.

Mathematical Astronomy:

Mathematical Astronomy involves the use of statistics, calculation, and numbers in efforts to explain the universe. It is a science that attempts to predict different aspects of the universe through mathematical calculations. Early civilizations, such as Babylonian and Mesopotamian, created methods for predicting the positions of heavenly bodies and eclipses and tables to refer to. Greek society adopted the mathematical approaches of the Babylonians. The methods these civilizations used remained unchanged for centuries.

By the 1700's a woman named Caroline Herschel and her brother William created a mathematical approach to astronomy that helped them to discover the planet Uranus. By the 1800's, Urbain Jean Joseph Le Verrier had used mathematical calculations in order to find Neptune, and given his calculations to an astronomer named Johann Gottried Galle of the Berlin Observatory. Using Le Verrier's calculations, Johann Galle observed Neptune within an hour of starting! An English mathematician had completed the same calculations, and credit for the discovery of Neptune is given to both Le Verrier and the English mathematician; Adams.

The field of Astronomy is actually a combination of several fields involving mathematics, chemistry, geology, physics and biology. Physics has become such an ingrained part of Astronomy that a number of Astronomers are known as, 'Astrophysicists,' as well. Many of the earliest people who might have been considered Astronomers were actually priests. They studied the movement of the stars and other bodies in space in order to determine planting cycles and celebrations. Ancient Greeks were the first ones to develop theories concerning the design of the universe, but there have been many astronomers throughout history that have contributed important parts to the field. Some of the more notable scientists who have contributed to the field of Astronomy include:

Ptolemy
Copernicus
Tycho Brahe
Galileo Galilei
Johannes Kepler
Isaac Newton
Edmond Halley
William Herschel
Albert Einstein
Willem de Sitter
Georges-Henri Lemaitre
Edwin P. Hubble
Thomas Gold
Carl Sagan
Stephen Hawking

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