Chapter 1 Flashcards
What is the celestial sphere
The celestial sphere is a 3D model that surrounds the earth and lets us place and observe celestial objects
Does the celestial sphere match physical reality?
No, it does not necessarily match physical reality.
What are constellations
Constellations are an arrangement of stars that connect to represent an animal, object, or mythological figure.
Are the stars in a constellation physically related?
No, they are not physically related. They can be light years apart and differentiate in size as well.
Do constellations change?
Stars move very slowly, constellations stay the same for thousands of years.
What were constellations used for
Their origin is unknown, but they seem to have been used for navigation and tracking the seasons
Is the sky different day to day? Month to month? Year to year?
The sky is not different day to day, it is different month to month, and it is not different year to year.
What is diurnal motion
Diurnal motion or “daily motion” is the movement of the sun, moon, and stars. They rise from the east and set in the west, this is due to earth’s rotation.
What is annual motion?
Annual motion or “yearly motion” is the movement of the earth due to its revolution around the sun.
What is the explanation of daily motion?
Daily motion is the rotation of the celestial sphere upon the celestial poles
What are the celestial poles
The celestial poles are imaginary poles extending from the north and South Pole
What is the celestial equator
The celestial equator is an imaginary equator line directly above the earths equator
What is the ecliptic
The ecliptic is the path the sun takes around the earth and through the celestial sphere.
What causes the seasons?
The seasons are caused by whether the earths axis is pointing towards or away from the sun. It is not caused by earths proximity to the sun.
What is the earths axial tilt?
23.5 degrees
