History of Astronomy Jay Pasachoff, Magda Stavinschi, Mary Kay Hemenway International Astronomical Union, Williams College (Massachusetts, USA), Astronomical Insti- tute of the Romanian Academy (Bucarest, Rumania), University of Texas (Austin, USA). ttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttt Summary from the others. ese came to be called wanderers or is short survey of the History of Astronomy provides planets by the Greeks. Virtually every civilization on a brief overview of the ubiquitous nature of astronomy Earth noticed, and named, these objects. at its origins, followed by a summary of the key events Some ancient people built monuments such as stand- in the development of astronomy in Western Europe ing circles, like Stonehenge in England, or tombs such to the time of Isaac Newton. as the ones in Menorca in Spain that aligned with the Goals Southern Cross in 1000 BCE. e Babylonians were t(JWFBTDIFNBUJDPWFSWJFXPGUIFIJTUPSZPGBTUSPO - great recorders of astronomical phenomena, but the omy in different areas throughout the world, in order Greeks built on that knowledge to try to “explain” the to show that astronomy has always been of interest to sky. all the people. The Greeks t -JTU UIF NBJO mHVSFT JO UIF IJTUPSZ PG BTUSPOPNZ Most ancient Greeks, including Aristotle (384 BCE – who contributed to major changes in approaching this 322 BCE), thought that Earth was in the center of the discipline up to Newton: Tycho Brahe, Copernicus, universe, and it was made of four elements: Earth, Air, Kepler and Galileo. Fire, and Water. Beyond the Earth was a fifth element, t$POGFSFODFUJNFDPOTUSBJOUTQSFWFOUVTGSPNEFWFM - the aether (or quintessence), that made up the points oping the history of astronomy in our days, but more of light in the sky. details can be found in other chapters of this book. How did these wanderers move among the stars? ttttttttttttttttttttttttttttttttttttttttttt Mostly, they went in the same direction that the stars Pre-History went: rising in the east and moving toward the west. With dark skies, ancient peoples could see the stars But sometimes, they seemed to pause and go back- rise in the eastern part of the sky, move upward, and wards with respect to the stars. is backward motion set in the west. In one direction, the stars moved in is called “retrograde” motion, to tell it apart from the tiny circles. Today, when we look north, we see a star forward motion, called “prograde.” at that position – the North Star, or Polaris. It isn’t a e Greek astronomer Claudius Ptolemy (c. CE 90 – very bright star: 48 stars in the sky are brighter than c. CE 168) worked in Alexandria in North Africa in it, but it happens to be in an interesting place. In an- the second century AD. Ptolemy wanted to be able to cient times, other stars were aligned with Earth’s north predict the positions of planets and came up with a pole, or sometimes, there were no stars in the vicinity mathematical solution. Following Aristotle, he placed of the pole. the Earth at the center of the universe. e Moon and Since people viewed the sky so often, they noticed that the planets go around it in nested circles that got big- a few of the brighter objects didn’t rise and set exactly ger with distance from Earth. What if the planets re- with the stars. Of course, the Moon was by far the ally move on small circles whose centers are on the brightest object in the night sky. It rose almost an hour big circles? en, on some of the motion on the small later each night, and appeared against a different back- circles, they’d be moving faster backwards than the ground of stars. Its shape also changed; this is what we centers of these circles move forward. For those of us now call phases. on Earth, we’d see the planets move backwards. But some of these lights in the sky moved differently ose small circles are called “epicycles,” and the big circles are called “deferents.” Ptolemy’s idea of circles 22 moving on circles held sway over western science for over a thousand years. Going from observation to the- ory using mathematics was a unique and important step in the development of western science. Although they didn’t have the same names for the ob- jects they observed, virtually every culture on Earth watched the skies. ey used the information to set up calendars and predict the seasonal cycles for plant- ing, harvesting, or hunting as well as religious ceremo- nies. Like the Greeks, some of them developed very sophisticated mathematics to predict the motions of the planets or eclipses, but this does not mean that they attempted what we would call a scientific theory. Fig. 1: Arabic astrolabe. Here are some examples: The Americas Africa North America e standing stones at Nabta in the Nubian Desert Native peoples of North America also named their pre-date Stonehenge by 1000 years. Egyptians used constellations and told sky stories which were passed astronomy to align their pyramids as well as extend down through oral tradition. Some artifacts, such as their religious beliefs to include star lore. Petroglyphs stone wheels or building alignments, remain as evi- at Namoratunga (Kenya) share aspects of modern cat- dence of their use of astronomy in every-day life. tle brands. Star lore comes from all areas of Africa, from the Dogon region of Mali, to West Africa, to Mayan Astronomy Ethiopia, to South Africa. e Maya were a Mesoamerican civilization, noted for the only known fully developed written language Islamic Astronomy of the pre-Columbian Americas, as well as for its art, Many astronomical developments were made in the architecture, mathematical and astronomical systems. Islamic world, particularly during the Islamic Golden Initially established during the Pre-Classic period (c. Age (8th-15th centuries), and mostly written in the 2000 BCE to 250 CE), Mayan cities reached their Arabic language. It was developed most in the Mid- highest state of development during the Classic period dle East, Central Asia, Al-Andalus, North Africa, and (c. 250 CE to 900 CE), and continued throughout later in the Far East and India. A significant number the Post-Classic period until the arrival of the Span- of stars in the sky, such as Aldebaran and Altair, and ish. e Mayan peoples never disappeared, neither at astronomical terms such as alidade, azimuth, al- the time of the Classic period decline nor with the ar- mucantar, are still referred to by their Arabic names. rival of the Spanish conquistadors and the subsequent Arabs invented Arabic numbers, including the use of Spanish colonization of the Americas. zero. ey were interested in finding positions and time of day (since it was useful for prayer services). Mayan astronomy is one of the most known ancient ey made many discoveries in optics as well. Many astronomies in the world, especially due to its famous works in Greek were preserved for posterity through calendar, wrongly interpreted now as predicting the their translations to Arabic. end of the world. Maya appear to be the only pre- telescopic civilization to demonstrate knowledge of e first systematic observations in Islam are reported the Orion Nebula as being fuzzy, i.e. not a stellar pin- to have taken place under the patronage of Al-Maâ- point. mun (786-833 CE). Here, and in many other private observatories from Damascus to Baghdad, meridian e Maya were very interested in zenithal passages, degrees were measured, solar parameters were estab- the time when the Sun passes directly overhead. e lished, and detailed observations of the Sun, Moon, latitudes of most of their cities being below the Tropic and planets were undertaken. of Cancer, these zenithal passages would occur twice a year equidistant from the solstice. To represent this Instruments used by the Islamic astronomy were: ce- position of the Sun overhead, the Maya had a god lestial globes and armillary spheres, astrolabes, sundi- named Diving God. als and quadrants. 23 incorporated 5 sacrificial, or Nemontemi, days. Like almost all ancient peoples, the Aztecs grouped into associations the apparent bright stars (constella- tions): Mamalhuaztli (Orion’s Belt), Tianquiztli (the Pleiades), Citlaltlachtli (Gemini), Citlalcolotl (Scor- pio) and Xonecuilli (e Little Dipper, or Southern Cross for others, etc.). Comets were called “the stars that smoke”. e great periods of time in the Aztec cosmology are Fig. 2: Chichén Itzá(Mexico) is an important archae- defined by the eras of different suns, each of whose end ological remains of the Maya astronomy. was determined by major disasters such as destruction by jaguars, hurricanes, fire, flood or earthquakes. Venus was the most important astronomical object to the Maya, even more important to them than the Sun. Inca Astronomy e Mayan calendar is a system of calendars and alma- Inca civilization is a civilization pre-Columbian An- nacs used in the Mayan civilization of pre-Columbian dean Group. It starts at the beginning of the 13th cen- Mesoamerica, and in some modern Maya communi- tury in the basin of Cuzco in Peru and the current then ties in highland Guatemala and Oaxaca, Mexico. grows along the Pacific Ocean and the Andes, cover- ing the western part of South America. At its peak, it Although the Mesoamerican calendar did not origi- extends from Colombia to Argentina and Chile, across nate with the Mayan, their subsequent extensions and Ecuador, Peru and Bolivia. refinements of it were the most sophisticated. Along with those of the Aztecs, the Mayan calendars are the e Incas considered their King, the Sapa Inca, to be best documented and most completely understood. the “child of the Sun”. Its members identified various dark areas or dark nebulae in the Milky Way as ani- Aztec Astronomy mals, and associated their appearance with the season- ey were certain ethnic groups of central Mexico, al rains.