Chapter 2

The tilt of Earth's spin axis to the direction perpendicular to the ecliptic plane (known as the ecliptic pole) is

23.5 degrees

In modern astronomy, the constellations are

88 regions of sky, covering the entire sky

The direction of Earth's rotation about its axis is the same as teh direction of its revolution about the sun. How does a solar day compare to a sidereal day on Earth?

A solar day is always longer

The lowest amount of solar energy per square meter is incident on the surface of Earth in the northern hemisphere on or about

December 21, the beginning of winter

A sundial isn't considered to be a good timekeeper because the

Earth's orbital speed around the ecliptic is variable

What is the primary cause of Earth's seasons?

Earth's rotation axis tilts with respect to the plane of its orbit around the sun

The celestial equator is defined as the

Line in the sky that is perpendicular to Earth's spin axis

The two angles used by astronomers to define the position of a star in the sky and define a coordinate system applicable anywhere on Earth are

Right ascension and declination

Diurnal motion of objects in the sky is caused by the

Rotation of Earth on its axis

Polaris, the "pole star", is at present

Within 1 degree of the north celestial pole

Precession is

a very slow conical motion of Earth's axis of rotation

By observing the sky closely night by night, you would note that a particular star rises

about 4 minutes minutes earlier every night

The arctic circle is defined as a line on Earth where the sun

can be seen for 24 hours on at least one day of the year

constellations are generally made up of stars which are

merely located along more or less the same line of sight as viewed from Earth

The phenomenon of precession of Earth's spin axis is caused by the

gravitational pull of Moon and Sun on Earth's equatorial bridge

The ecliptic is defined as the

line traced in our sky by the sun over one year against the background stars

For an observer at a fixed location on Earth, the angle between the north celestial pole and an observer's horizon depends on the

observer's latitude

If the daytime sky were not bright, in which direction would we see the sun move along the ecliptic over the course of a year, relative to the background stars?

toward the east

The ecliptic crosses the celestial equator at

two points, known as equinoxes

The zenith defines a direction

vertically above an observer