ASTB03H3 Lecture : Lecture 2

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skyelk398

17 Feb 2012

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Tried to prove that earth was stationary was not in motion. Evidence: objects would be left behind by rotating or revolving earth. Moving earth would produce parallaz shift in stars" positions. Relative measurements: comparing 2 things in nature (for example, the moon and the sun) How far the sun and moon are from the earth in relative form. Based on observations of timing of moon"s phases. Found that sun is 19x further away than the moon was. Found that sun is 7x diameter of earth. Sun is actually 109x the diameter of earth. Sun is never directly overhead in toronto. In a particular place in egypt (syene), sun was actually directly overhead. Position of sun was also observed from alexandria. They found the angle between alexandria & syene = 70 degrees. Distance all around the earth was 250 000 stade (40 000 km) Introduced two ways of describing the motion of things.

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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ASTB03H3 Lecture : Lecture 2

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