Diameter of the Moon
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Teacher Page
Exploring the Moon -- A Teacher's Guide with Activities, NASA EG-1997-10-116-HQ
Purpose
To calculate the diameter of the Moon using
proportions.
Background
The diameter of the Moon is proportional to the diameter of a cardboard disk, given that
you know the distance to the Moon and the distance to the cardboard disk.
The relationship is:
d D
l L
so that:
D = L(d/l)
where D= diameter of Moon
d= diameter of cardboard disk
L= distance to Moon
l = distance to cardboard disk
In this activity, students will measure d and l. They will be given L.
They will calculate D.
The diameter of the Moon (D) is 3,476 km.
Preparation
Review and prepare materials listed on the student sheet.
Choose a day and location for this activity which is best for viewing a full Moon.
A cardboard disk of 2 cm diameter works well. Better accuracy may be achieved by
using a larger disk, thus a greater distance l. However, if obtaining or cutting cardboard
is difficult, then this activity can also be done with dimes. A dime held out at arm's
length will cover the Moon.
The distance from Earth to the Moon for a given date can be obtained by asking a local
planetarium staff, Or for this activity, students may use an average value of
382,500 km.
