Science in Prehistory

1. Science in Prehistory Mankind has had a long fascination with the ‘heavens’: the motion of stars, Sun, Moon, planets, comets, meteorites, aurora, even observation of supernovae. Stonehenge (Salisbury Plain, UK) ~2500BC

2. STONEHENGE (Salisbury Plain, UK) built over ~17 centuries from~2800BC to 1100 BC. With the biggest stones being laid about 2450BC.Stone configuration correlated to winter and summer solstices.

3. Newgrange(County Meath Ireland)~3000BC

4. Newgrange: Passage Tomb Central Chamber Illuminated Around the Winter Solstice.

5. Stonehenge and Newgrange: Conclusions An Awareness of the repeatable motions of the Sun and Moon Despite popularised controversies, Stonehenge is not regarded as the birthplace of predictive astronomy. In comparison to their contemporary Egyptian culture, we know very little of the Neolithic and early Bronze Age peoples of Northern Europe.

6. Egyptian’s Observation of the Sun and Moon Motions. Monitoring seasonal variation for agriculture Nile Flooded when sun rose near the star Sirius (the “Dog star”, in the Canis Major constellation; brightest star in the sky). Link lunar and solar ‘birth’ and ‘death’ to religious festivals and an elaborate mythology.

7. Babylonian Era • Monitored the movement of the Sun, Moon and Venus. • Note special events: eclipses and comets • Prediction requires mathematics and record keeping! (necessitates a long-lived, stable culture)

8. Numbers and Early Calendars Early Egyptians and Babylonians had 360 days in a solar year. Origin of 360 in a circle. Egyptians divided the day into 24 hours. Babylonians developed a base 60 number system. Origin of 60 seconds and 60 minutes Egyptians introduced Leap years. Formalised by Julius Caesar (46 BC)

9. Gregorian Calendar (1582 AD) • Introduced by Pope Gregory XIII • The precession of the equinoxes (due to earth’s wobble on its axis) results in seasons drifting over ~26,000 year cycle. • Gregorian Calendar maintains the seasons in the ‘proper’ months of the year.

10. Gregorian Calendar • 1 extra day in every 4 years (leap year) is too much! • Leap year at the close of the century omitted, unless year a multiple of 400! i.e : 1600, 2000 leap years 1700, 1800, 1900 not leap years

11. Aristotle (384-332 BC) and Ptolemy (~150AD) • In Greek period, there were a variety of views on the nature of ‘reality’: Earth, Fire, Air, Water • Aristotle’s view spherical, stationary Earth dominated. • Developed to its full by Ptolemy in the “Almagest” (Arabic for ‘the greatest’).

12. “7 Wanderers” = 7 Day Week • “Wanderer” is the Greek meaning of “planets” • Wanderers in the Zodiac: Sun, Moon, Mercury, Venus, Mars, Saturn and Jupiter (Latinised names)

13. Greek, Islamic and Chinese Cultures Monitored the Heavens • Greek Philosophers formalised Geocentric solar system • Islamic Astronomers developed new tools, e.g. Astrolabe • Chinese observed the supernova of 1054 AD

14. Native Americans also Observed the Motion of Key Stars Big Horn Medicine Wheel, Wyoming. Spokes are aligned to the rising and setting of the Sun and certain stars.