Chapter 4: Earth, Moon, and Sky Vocabulary Flashcards

Vocabulary practice flashcards covering key terms and concepts from Chapter 4, including astronomical coordinates, timekeeping, calendar systems, seasonal mechanisms, Moon phases, and eclipses.

Latitude

The coordinate on Earth measured in degrees north or south relative to the Earth's Equator, which serves as its physically meaningful zero point.

Longitude

The coordinate on Earth measured in degrees (or time) east or west relative to an arbitrary starting point called the Prime Meridian in Greenwich, England.

Declination (Dec)

The coordinate on the celestial sphere measuring position in degrees north or south relative to the Celestial Equator.

Right Ascension (R.A.)

The coordinate on the celestial sphere measuring position in hours relative to an arbitrary starting point called the Vernal Equinox.

Solar Day

The time interval of $24\text{ hr}$ required for Earth to complete one rotation relative to the Sun (from facing the Sun to facing it again).

Sidereal Day

The time interval of $23\text{ hr } 56\text{ min}$ required for Earth to complete one rotation with respect to distant stars.

Solar Month (Synodic Period)

The time interval of $29.5306\text{ days}$ required for the Moon to complete a full cycle of phases from New Moon to New Moon.

Sidereal Month

The time interval of $27.3\text{ days}$ required for the Moon to complete one full orbit around Earth relative to distant stars.

Summer Solstice

daylight hours are at their annual maximum.

Winter Solstice

daylight hours are at their annual minimum.

Equinox

The position in Earth's orbit (occurring around March 21 and September 21) when every location on Earth receives exactly $12\text{ hours}$ of daylight.

Tidal Locking

The gravitational interaction that causes the Moon to rotate on its axis exactly once per orbit around Earth, resulting in the same side always facing Earth.

Waxing Phase

The stage of the lunar cycle in which the illuminated portion of the Moon visible from Earth is progressively increasing.

Waning Phase

The stage of the lunar cycle in which the illuminated portion of the Moon visible from Earth is progressively decreasing.

Full Moon

The lunar phase where the entire Earth-facing hemisphere of the Moon is lit by the Sun, rising at sunset, reaching its highest point at midnight, and setting at sunrise.

Third Quarter Moon

The lunar phase occurring three-quarters through the lunar cycle, rising at midnight, reaching its highest point at sunrise, and setting at noon.

Two reasons it is hot in the summer & cold in winter

1. sunlight is more direct in summer at a higher angle

2. there are more hours of daylight in the summer & less in winter

   1. more hours of daylight =

Direct light

• DIRECT: there is a higher angle between the sun rays & the earth, therefore more rays are concentrated in a small area

Indirect Light

• INDIRECT: the sun rays strike the Earth at a lower angle, spreading the energy over a larger area, resulting in less concentrated heat.

Nodes (Orbital)

The two intersection points where the Moon's tilted orbital path crosses the plane of Earth's orbit (the ecliptic).

Eclipse Season

The specific period when the Moon is located near an orbital node, making solar and lunar eclipses possible.

Umbra

The dark central region of a shadow cast by an illuminated body where the light source is completely blocked.

Penumbra

The outer region of a shadow cast by an illuminated body where the light source is only partially obscured.

Total Solar Eclipse

An eclipse occurring at New Moon when the Moon passes directly between the Sun and Earth at an orbital node, fully covering the Sun and revealing its corona.

Annular Solar Eclipse

A solar eclipse occurring when the Moon is at an orbital node near its farthest distance from Earth (apogee), leaving an outer ring of the Sun visible around the Moon.

Lunar Eclipse

An eclipse occurring at Full Moon when the Moon enters Earth's shadow, visible to any observer on the night side of Earth.