Stonehenge in southern England is believed to be part of an astronomical device which was completed in 2000 B.C.
A section of its structure called the “avenue” points towards the location at which the Sun rises in the Summer solstice, and other sight lines created by the structure point towards the most northern and southerly risings of the Moon.
It was not used to track the Moons rising and setting points
Other Examples All Over the World Big Horn Medicine Wheel (Wyoming)
The passage tomb was constructed in such a way that on the Winter solstice light from the rising Sun penetrates the main passage shining into the inner chamber for just 17 minutes in the year.
Researchers have also discovered evidence that Newgrange may have been designed in order to allow light from the Moon to enter the inner chamber approximately every nine years when the Moon’s path crosses the position that the Winter solstice Sun would occupy.
Around 1200-1000 B.C., the Babylonians studied astrology – indeed they invented the 12 signs of the Zodiac that are still used today. Around the same time, the Greeks named most of the stars and constellations in the northern hemisphere (e.g. Hercules, Perseus, Cassiopea, Cygnus). They also named the "the wandering stars", which we now know to be planets. The Greeks named these after their gods, Mercury, Venus, Mars and Jupiter.
Mesopotamia/Babylon Modern political boundaries Ancient Babylon
Ancient Greek Astronomers A. Eudoxus (409 – 356 B.C.): Model of 27 nested spheres B. Aristotle (384 – 322 B.C.), major authority of philosophy until the late middle ages: Universe can be divided in 2 parts: 1. Imperfect, changeable Earth ,
Ptolemy calculated what he believed to be the size of the cosmos : 20,000 earth radii or 134,000,000 kilometers (radius) .
Ptolemy wrote the first astronomy textbook, the Almagest (the “Majestic Book”).
http://www.er.uqam.ca/nobel/r14310/Ptolemy/Images/Regiomontanus/1496.g.jpg The Almagest
IV. Rome The Romans most important contribution to the field of astronomy is the enforcement of a systematic calendar that would account for fact that the year is about ¼ of a day more 365 days. The astronomers of Julius Caesar convinced him to create the Julian Calendar which adds one day to the calendar every 4 years to account for the time we had skipped. This is known as a “leap year”.
History of Astronomy The sphere of the sky surrounds the Earth and is called the “celestial sphere.” Back
History of Astronomy The two constellations Leo, (A), and Cygnus, (B), with figures sketched in to help you visualize the animals they represent. (Photo (A) from Roger Ressmeyer, digitally enhanced by Jon Alpert. Photo (B) courtesy Eugene Lauria.) Back
History of Astronomy The Sun hides from our view stars that lie beyond it. As we move around the Sun, those stars become visible, and the ones previously seen are hidden. Thus the constellations change with the seasons. Back
History of Astronomy The Earth's rotation axis is tilted by 23.5° with respect to its orbit. The direction of the tilt remains the same as the Earth moves around the Sun. Thus for part of the year the Sun lies north of the celestial equator, whereas for another part it lies south of the celestial equator. Back
History of Astronomy These five diagrams show the Sun's position as the sky changes with the seasons. Although the Earth moves around the Sun, it looks to us on the Earth as if the Sun moves around us. Notice that because the Earth's spin axis is tilted, the Sun is north of the celestial equator half of the year (late March to late September) and south of the celestial equator for the other half of the year (late September to late March). Back
History of Astronomy The direction of the rising and setting Sun changes throughout the year. At the equinoxes the rising and setting points are due east and west. The sunrise direction shifts slowly northeast from March to the summer solstice, whereupon it shifts back, reaching due east at the autumn equinox. The sunrise direction continues moving southeast until the winter solstice. The sunset point similarly shifts north and south. Sunrise on the summer solstice at Stonehenge. (Courtesy English Heritage.) Back
History of Astronomy (A) The cycle of the phases of the Moon from new to full and back again. (B) The Moon's phases are caused by our seeing different amounts of its illuminated surface. The pictures in the dark squares show how the Moon looks to us on Earth. Back
History of Astronomy A solar eclipse occurs when the Moon passes between the Sun and the Earth so that the Moon's shadow strikes the Earth. The photo inset shows what the eclipse looks like from Earth. (Photo courtesy of Dennis di Cicco.) Back
History of Astronomy A lunar eclipse occurs when the Earth passes between the Sun and Moon, causing the Earth's shadow to fall on the Moon. Some sunlight leaks through the Earth's atmosphere casting a deep reddish light on the Moon. The photo inset shows what the eclipse looks like from Earth. (Photo courtesy of Dennis di Cicco.) Back
History of Astronomy (A) During a lunar eclipse, we see that the Earth's shadow on the Moon is curved. Thus the Earth must be round. (B) As a traveler moves from north to south on the Earth, the stars that are visible change. Some disappear below the northern horizon, whereas others, previously hidden, become visible above the southern horizon. This variation would not occur on a flat Earth. Back
History of Astronomy Eratosthenes's calculation of the circumference of the Earth. The Sun is directly overhead on the summer solstice at Syene, in southern Egypt. On that same day, Eratosthenes found the Sun to be 7° from the vertical in Alexandria, in northern Egypt. Eratosthenes deduced that the angle between two verticals placed in northern and southern Egypt must be 7°. Back
History of Astronomy Aristarchus used the size of the Earth's shadow on the Moon during a lunar eclipse to estimate the relative size of the Earth and Moon. Back
History of Astronomy How to determine linear size from angular size. Back
History of Astronomy Aristarchus estimated the relative distance of the Sun and Moon by observing the angle A between the Sun and the Moon when the the Moon is exactly half lit. Angle B must be 90° for the Moon to be half lit. Knowing the Angle A, he could then set the scale of the triangle and thus the relative lengths of the sides. Back
History of Astronomy Motion of the Earth around the Sun causes stellar parallax. Because the stars are so remote, this is too small to be seen by the naked eye. Thus the ancient Greeks incorrectly deduced that the Sun could not be the center of the Solar System. Back
History of Astronomy Cutaway view of the geocentric model of the Solar System according to Eudoxus. (Some spheres omitted for clarity.) Back