2. The Sky Around Us

Joshua Barnes -- Fall 1999

Just as Hawaii is a body of land surrounded on all sides by water, so the Earth is an object surrounded on all sides by space. It's convenient to pretend that the Earth is inside an enormous sphere, and plot the locations of stars and planets on this sphere. The daily rotation of this sphere and the annual progression of the Sun along the zodiac are both due to motions of the Earth.

Topics:

• Constellations
• The celestial sphere
• Daily rotation
• Solar motion
• Lunar motion

Web Resources:

• Earth and Moon [source]

  A view of the Earth and Moon together in space.

• Your Sky

  An interactive planetarium. You can view the sky from any location at any time, zoom in on selected areas, and more. Created by John Walker.

• Rotation (2.0 Mbyte gif animation)

  Shows how the sky over Hawaii changes during one day, from midnight on 8/30/99 to midnight on 8/31/99.

• Revolution (2.6 Mbyte gif animation)

  Shows how the sky over Hawaii changes over one year, from noon on 8/30/99 to noon on 8/31/00.

• Pole-to-pole trip (0.1 Mbyte gif animation)

  Shows how the sky changes as you travel from the south pole to the north pole.

Homework 2: Observing Mars, due 9/08. See also:

• Photographs of Scorpius and Mars
• Motion of Mars from 8/30/99 to 9/14/99 (40 kbyte gif animation)

Quiz 2: What Do You See?