CHAPTER 3: Rotation and Revolution

A set of Q&A flashcards covering rotation, revolution, axial tilt, Coriolis effect, solstices/equinoxes, heat zones, twilight, and related concepts from the notes.

What are the two main motions of the Earth described in CHAPTER 3?

Rotation and Revolution—the spinning of the Earth on its axis and its orbit around the Sun.

What is Rotation?

The spinning of the Earth on its axis from west to east, taking about 24 hours.

In which direction does the Earth rotate?

From west to east.

What is Revolution?

The Earth's orbit around the Sun in an elliptical path.

How long is a day on Earth?

Approximately 24 hours.

What are the end points through which the Earth's axis passes?

The North Pole and the South Pole.

How is the Earth's axis tilted relative to vertical and the plane of its orbit?

Tilted about 23.5° to the vertical (about 66.5° to the plane of orbit).

What is the approximate speed of Earth's rotation at the Equator?

About 1670 km per hour.

What is the circumference of the Earth?

Approximately 40,075 km.

What is the Coriolis effect?

A deflection of moving air and water due to Earth's rotation; in the Northern Hemisphere deflection is to the right (clockwise), and in the Southern Hemisphere to the left (anticlockwise).

What causes day and night?

The rotation of the Earth on its axis.

What causes sunrise and sunset?

The rotation of the Earth from west to east causing different parts of the surface to face toward or away from the Sun.

What is centrifugal force in this context?

An apparent outward force due to rotation; contributes to the equatorial bulge and polar flattening.

How much time difference does longitude create per degree?

About 4 minutes per degree of longitude.

What is the apparent motion of the Sun, Moon, and stars, and why does it occur?

They appear to move from east to west because the Earth rotates from west to east.

What is an elliptical orbit?

The shape of the Earth's orbit around the Sun.

What is the average speed of Earth's revolution around the Sun?

About 29.8 km/s (roughly 100,000 km/h).

How long is a solar year and how are leap years determined?

365 days and about 6 hours; every 4 years an extra day is added to February (366 days) to form a leap year.

What is perihelion.

Closest point of the Earth to the Sun, around January 3, about 147.3 million km away.

What is aphelion?

Farthest point from the Sun, around July 4, about 152 million km away.

What are the three heat zones and where are they located?

Torrid Zone (between 23.5°N and 23.5°S), Temperate Zone (between 23.5° and 66.5° in both hemispheres), Frigid Zone (between 66.5° and the poles).

What are solstices and their dates?

Summer Solstice on June 21 (NH longest day); Winter Solstice on December 22 (NH shortest day).

What are equinoxes and their dates?

Spring (Vernal) Equinox on March 21 and Autumnal Equinox on September 23; days and nights are equal.

What is the circle of illumination?

The lighted part of the Earth separated from the dark side as the Sun moves.

What is twilight and when does it occur?

Diffused light before sunrise (dawn) and after sunset (dusk); more prolonged at higher latitudes.

How long can twilight last near the poles?

Up to about seven weeks in polar regions.

What is the Midnight Sun?

24 hours of daylight beyond the Arctic Circle during summer.

Why don’t we feel the Earth’s motion continuously?

Gravity keeps objects attached to the Earth; Newton’s First Law means motion is not felt as constant acceleration.

What happens to day length at the equator?

Day length is approximately 12 hours everywhere at the Equator.

What happens if the Earth’s axis were vertical?

There would be equal day and night everywhere and no seasons.

Why do seasons occur?

Because the Earth's axis is tilted relative to its orbit around the Sun, causing varying sun angles and day lengths throughout the year.