Astronomy, derived from the Greek word meaning "star" and "law" or "culture", has come to be known as "law of the stars" (or "culture of the stars" depending on the translation). Astronomy should not be confused with astrology, the belief system, which claims that human affairs are correlated with the positions of celestial objects. Although the two fields share a common origin, they are now entirely different.
Until the invention of the telescope and seminal discoveries in physics related to motion and gravity, astronomy was primarily concerned with noting and predicting the positions of the sun, moon, and planets, originally for calendrical and astrological purposes and later for navigational uses and scientific interest.
In recent times, the study has branched out to several categories, which are distinguished in order of increasing distance, the solar system, the stars that make up the Milky Way galaxy, and other, more distant galaxies. With the advent of scientific space probes, Earth also has come to be studied as one of the planets, though its more detailed investigation remains the domain of the Earth sciences.
Astronomer
An astronomer is a scientist in the field of astronomy who focuses on the study of a specific question or field outside the scope of Earth. An astronomer will observe astronomical objects such as stars, planets, moons, comets and galaxies – in either observational (by analysing the data) or theoretical astronomy.