The Sky

Question 1

Celestial Sphere

Answer 1

Sky appears to our eyes as a large dome with Earth at the center. It is not static, but has many apparent motions, all of which seem centered on Earth
Earth has a tilt of 23.5 degrees

Question 2

Use and significance of constellations

Answer 2

The suns annual path is ECLIPTIC, passing through 13 Zodiacal Constellations. Had a symbolic significance to ancient cultures but have no physical significance. Helps navigation and calendars.

Question 3

Apparent motions of the sky

Answer 3

• Diurnal motion: apparent daily motion of all celestial objects from EAST TO WEST. Causes rising and setting.
• Annual Motion: apparent motion of the SUN wrt the “fixed” stars over the course of a year. Causes seasonal constellations.

Question 4

“True” motions of the sky

Answer 4

Diurnal Motion: Caused by Earth rotating West to East.
Annual Motion: Caused by Earth revolving around Sun.

Question 5

Seasons and their relation to apparent and real motions

Answer 5

Seasons occur because the Earth’s rotational axis is tilted. When the axis points towards the sun (diagram from notebook)

Question 6

Precession

Answer 6

Slow and continuous change in the orientation of the Earth’s Rotational axis in space. The tilt remains 23.5 degrees but changes direction with respect to the “fixed” stars; takes a period of about 25,800 years