Summarized much of ancient astronomical knowledge. Ptolemy also used trigonometry toĪccurately measure the distance to the moon. In concentric circles around the Earth, while some planets moved in smaller circles calledĮpicycles around their main orbits. In the Ptolemaic system, the planets moved Hipparchus's idea of how the planets moved was later refined by Ptolemy, and became The planets, to be used by future astronomers. In addition, he intended for many of his observations, especially his observations of Observations extended over centuries, so he used many old observations along with his own. Hipparchus recognized that astronomy requires accurate and systematic With trigonometry, he couldĬalculate distances to planets and stars by knowing the angle from which they were Two hundred years later, Hipparchus developed trigonometry. In the 4 th century B.C., Aristotle summarized GreekĪstronomical knowledge and Aristarchus calculated the sizes of the Sun and Moon relative Mathematician Pythagoras theorized that the planets moved along the surfaces The Greeks introduced geometry into astronomy. The motions of the Sun, the Moon, and the planets. These theories, based on detailed observations, made predictions for Period, Greek philosophers and astronomers began to develop theories of the workings Maps of the universe improved dramatically from 600 B.C. The first known star catalog, containing 800 stars, was created in China in about 350 B.C. Stonehenge that aligned with specific astronomical events. They recorded theirĭata on stone tablets or temple walls, and sometimes they even built giant structures like People in ancient Egypt, China, CentralĪmerica, and Mesopotamia conducted these surveys over 5,000 years ago. The positions and motions of stars and planets. In the sky called the north celestial pole. At night, more than 1000 visible stars followed a similar course,Īppearing to rotate in permanent groups, or constellations, around a fixed point It developed inĪncient times from curiosity about day and night, the sun, the moon, and the 940 A.D.Ĭopyright c 1997, The British Library BoardĪstronomy is the oldest of the physical sciences. The earliest moments after the big bang, more than 12 billion years ago, intoĪn ancient Chinese star chart from ca. Learn something about how microscopic matter and energy variations evolved from The SDSS will map theseĬlusters in greater detail than any survey so far. Was created to study how galaxies cluster on the largest scales. This survey, the Sloan Digital Sky Survey (SDSS), We find enough objects, we can study them to derive the basic physical Technique we have for discovering new objects and interactions of objects. Complete, scientific sky surveys are the best Universe, over ever-larger areas, to ever-greater depths, and over an ever-increasing range of wavelengths. These ideas have guided the many projects in the last century to map the So rare that we must look at millions of objects to find just one example. Many structures cover large areas of sky others are These objects, we must first know where to find them, how they interact, and Stars and planets, but also of galaxies, clusters of galaxies, streams andĬlumps of gas, and a component of unseen (or dark) matter. Today, we understand that the universe consists not only of

(This important aspect of sky surveys survives today, with examples like the With naked-eye observations, became essential tools for navigation and trade. Helping with agriculture and religious observances.

These civilizations used these regular events to mark time, SomeĬivilizations began to realize that certain celestial events repeated at With higher powers beyond their control, such as gods and goddesses. To the ancients, these points of light were often viewed in connection

Sky, have always piqued our curiosity as we have sought to The stars and planets, mere points of light in the night Or browse the many interesting sites on the Internet.įor millennia, humans have wondered about the universe Introduction to their reasons, and outlines the history of astronomical Why do astronomers map the sky? This page gives a brief

Sky and telescope