Home > Amateur Astronomy, Astronomy, Lunar Eclipses, Moon, Solar System > International Measure the Moon Night – Dec. 10, 2011

International Measure the Moon Night – Dec. 10, 2011


This week’s total lunar eclipse will offer a rare opportunity for students, teachers, and the general public to measure the Moon’s distance and size duplicating the same techniques — with a Digital Age twist — used by Greek astronomers thousands of years ago.

On the night of December 10, The Classroom Astronomer (TCA) magazine will coordinate worldwide observations of the Moon’s position in the sky and its passage through the Earth’s shadow. (See Note 1 for regions of eclipse visibility.) These are key techniques — both now and in antiquity — for measuring the Moon’s diameter and distance from the Earth. The actual measuring methods are called the Shadow Method and the Lunar Parallax Method. TCA has created the website MeasureTheMoon.Org as a place for teachers — classroom and informal — students, and interested members of the general public to get information on how to measure the distance of the Moon (see Resources below).

The Shadow Method uses the transit of the Moon through Earth’s central shadow, the umbra. The angular size of the cross section made visible by the shadow on the Moon’s face is directly related to a unique distance. This was first accomplished by astronomers thousands of years ago, though they assumed a cylindrical shadow instead of the conical one we know it is today.

The Lunar Parallax Method uses a technique familiar to the ancient Greeks, triangulation, but which could not be done then because they could not communicate with observers far from Greece. Two observers today, thousands of miles apart, communicating via the Internet or telephone, can snap photos of the Moon at the same instant. They would see the Moon in front of different star fields, an angular shift directly related to the Moon’s distance and the distance between the observers.

Full Story: http://astronews.us/2011-12-05-1211.html

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