Unit A Concepts - Motions of Earth & Moon

Axial Rotation direction

Prograde

Diurnal experience

The apparent motion of celestial objects across the sky over the course of a day/night

Axial Rotation

The day and night cycle is an effect of

Latitude

What stars appear to move across the sky in the diurnal experience depends on

Sidereal Time

A time system based around comparing the movement of earth (or another planet) with distant stars because they are often the most reliable

23 hours, 56 minutes

Sidereal Day (time it takes for earth to rotate once on its axis)

27.32 days

Sidereal month (The time it takes for the moon to make one rotation around earth)

365.256 days

Sidereal Year (time it takes for the Sun to return to the same position in the sky relative to the stars)

Axial Tilt

The angle between earth’s orbital axis and rotational axis, 23.4 degrees

Earth’s revolution

The movement of earth around the sun in an elliptical movement

Aphelion

When earth is farthest from the sun in July

Perihelion

When earth is closest to the sun in January

Ecliptic

The apparent path of the sun and planets across the celestial sphere

Equinoxes

When the sun crosses the celestial equator, making night and day equal in length

Solstices

When the sun reaches its maximum or minimum declination, making the day either the longest or the shortest of the year depending on whether it is winter or summer

Seasons

The tile of earth’s axis either towards or away from the sun causes

Winter

When it is summer in the northern hemisphere it is _________ in the southern hemisphere

Precession

The gradual shift of our axis over time

Anelemma

plot or graph in the shape of a figure eight that shows the position of the sun in the sky at a given time of day at one specific locale throughout the year.

Earth’s movement

Makes it appear as though all planets and constellations are moving along a similar and predictable path

Inverse

If the earth were to move clockwise instead of counterclockwise, all celestial motions would be

Mare

This is an example of a…

Impact Crater

This is an example of a…

Near side

This is the _____ of the moon

Far side

This is the _______ of the moon

Libration

The oscillation of the moon that causes around 60% of its surface to be visible to earth throughout its cycle

Synchronous Rotation

when an object's rotation period matches its orbital period, so it always shows the same face to the object it's orbiting (Ex: moon to earth)

Orientation

While the phases of the moon are consistent across earth, their ______ varies based on where you are

New Moon, Day 0

0/360 degrees

Waxing Crescent, Day 4

45 degrees

First Quarter, Day 7

90 degrees

Waxing Gibbous, Day 10

135 degrees

Full Moon, Day 14

180 degrees

Waning Gibbous, Day 18

225 degrees

Last Quarter, Day 21

270 degrees

Waning Crescent, Day 25

315 degrees

Synodic period

the average period of the Moon's orbit with respect to the Sun and Earth: around 29.5 (Earth) days

Sidereal period

The average period it takes for the moon to go 360 degrees around earth, as measured with respect to fixed stars: around 27.3 Earth days

Moving

The synodic period longer than the sidereal period because the moon is orbiting around earth, which is __________

1/2

How much of the moon is illuminated by the Sun at all times?

Spherical

The moon is _____ which prevents us from always viewing the illuminated half

Larger

Our moon is ______ compared to other moons in the solar system

Consistent

Our moon is a great time keeper because it’s changes are ________ on a repetitive cycle