AST101H5 Lecture Notes - Ptolemy, Nicolaus Copernicus, Ellipse

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purpleporcupine571

23 Nov 2011

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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.

Related Questions

Astronomy Parallax Lab

SCENARIO: Your lab group is planning an expedition to measure the distance to Mars by carefully measuring its position in the sky from two locations simultaneously when it is next at “opposition” (that is, when it is exactly opposite from the sun in the sky) on October 13, 2020. For the best, and most straightforward distance determination with the parallax method, Mars should be high in the sky (as near to your zenith as possible). This can be done by observing Mars: (a) from locations whose LATITUDES are similar to the DECLINATION of Mars at the date of measurement and (b) at the time of night when Mars is highest in the sky.

1a). Determine the Sky Coordinates of Mars on the date of opposition. The relevant coordinate is the Declination (RA/DE J2000 coordinates should be used) – this is the sky coordinate analogous to Latitude on the Earth’s surface. (Note, it is ok to determine these coordinates for Mars from anywhere on Earth for this initial measurement)

Mars DECLINATION on October 13, 2020: ___________________________

Your lab team needs to send observers to two cities that:

(a) have latitudes that are similar to the declination of Mars on that date (within 20 degrees); and

(b) have nearly the same longitude (that is, are nearly due North-South from each other (hint, you will need to go close to the equator!).

1b). Choose two of the cities below and use google maps, google earth or another online resource to record their names and Latitudes.

Melbourne, Australia	Kampala, Uganda	Tokyo, Japan
Omaha, NE, USA	Mumbai, Italy	Khartoum, Soudan

1c). At what time should you measure the sky coordinates (right ascension and declination) to get the most accurate possible parallax distance?

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AST101H5 Lecture Notes - Ptolemy, Nicolaus Copernicus, Ellipse

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