Chapter 3 - from observing to understanding (sept. 19) Look for trends - hours of daylight increase and decrease with seasons. Look for exceptions - eclipses do not occur every month. Greek astronomers (2000+ years ago) were not great observers. They applied logic to understand their observations. Model = idea/concept, how we imagine or picture an object in our mind. They let us get close to our subject. Merchants traveling from greece down into africa saw different stars. The observational evidence cannot be understood if the earth is at. Therefore d earth = distance x 360 degrees / (pi) x angle. We observe the sun, moon, planets moving around us = earth each day. Conclusion: astronomers pictured earth as stationary with everything orbiting around. Geocentric model = earth at the centre. Wrong, but believed for about 1500 years. Models also contain our assumptions based on our beliefs, not facts, without realization.