SIZES AND DISTANCES
IN THE SUN-EARTH-MOON SYSTEM:
An Introductory Astronomy Lab
Rung 1: The size of the Earth
You will now determine the zenith angle of the sun by measuring the
height of the obelisk and the length of its shadow on the following
image, which is of an actual obelisk in Alexandria. The sketch is
believed to have been made around local noon on the day of the summer
solstice, June 22.
Step 1: Calibration
First we need to estimate the scale of the picture. Notice that there
are two people standing next to the obelisk. Let's measure the height
of one of them:
- Pick one of them; click on his feet.
