Movements of the Earth: Rotation and Its Effects

Vocabulary flashcards created from lecture material detailing the rotation of the Earth, its speeds, scientific proofs, and environmental effects.

Rotation of the Earth

The spinning of the Earth on its imaginary axis ($66\frac{1}{2}^\circ$ inclined to its orbital plane) from west to east once in every $24\,\text{hour}$ (actually $23\,\text{hour}\,56\,\text{minute}\,4\,\text{second}$).

Diurnal Motion

The rotation of the Earth on its axis, also known as 'the daily movement of the earth', which causes the formation of day and night.

Rotation (A.N. Strahler)

According to A.N. Strahler, "The spinning of the earth in its polar axis is termed rotation".

Direction of Earth's Rotation

The spinning of the Earth from west to east or in an anticlockwise direction when looking down upon the Earth from outside.

Earth's Rotation and Revolution Movement Diagram

A diagram showing the Earth rotating on its axis while revolving around the Sun at a distance of $14\,\text{crores}\,90\,\text{lakh}\,\text{km}$, alongside the Moon.

Rotational Speed at the Equator ($0^\circ$)

The speed of the Earth's rotation at the equator, which measures $1670\,\text{km/hour}$.

Rotational Speed at Kolkata ($22^\circ34'\,\text{N}$)

The speed of the Earth's rotation at Kolkata, which is $1536\,\text{km/hour}$.

Rotational Speed at London ($51\frac{1}{2}^\circ\,\text{N}$)

The speed of the Earth's rotation at London, which is $1050\,\text{km/hour}$.

Rotational Speed at the Poles ($90^\circ\text{ N \& S}$)

The speed of the Earth's rotation at the North and South Poles, which is approximately $0\,\text{km/hour}$.

Equatorial Bulge

The shape effect of Earth's rotation resulting in a flattening at the two poles and bulging at the equator, making the equatorial diameter $43\,\text{km}$ longer than the polar diameter.

Rotational Deflection of Air and Ocean Currents

The effect of Earth's rotation that deflects moving air, ocean water, cyclones, and anti-cyclones to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.

Drop of Stone from High Tower Proof

A proof of Earth's rotation where a stone dropped from a high tower in still air falls slightly to the east of vertical due to the Earth's west-to-east rotational speed.

Foucault's Pendulum Experiment

An experiment where Foucault suspended a cannon ball to swing in a north-south direction, demonstrating that the Earth slowly turns beneath it from west to east as the path traced by the pendulum gradually shifts.

Photograph of the Pole Star Proof

A proof of rotation where a long-exposure photograph focused on the Pole Star captures light trails as curved lines instead of points due to the camera turning with the Earth.

Circle of Illumination

The imaginary line (also called the Shadow Circle) that separates the lit-up half of the Earth from the darkened half.

Formation of Day and Night Diagram

A diagram depicting how the Earth's rotation relative to the Sun creates day ($0^\circ\,\text{Noon}$), night ($0^\circ\,\text{Midnight}$), dawn ($0^\circ\,\text{Dawn}$), and evening ($180^\circ\,\text{Evening}$).

Buys Ballot's Law

The rule governing the relation of wind to pressure in the Northern Hemisphere, where air flow at high altitudes generally parallels the isobars.

Inclination of the Earth's Axis

The tilt of the Earth's axis, which makes an angle of $23\frac{1}{2}^\circ$ with the vertical or $66\frac{1}{2}^\circ$ with the plane of the Earth's orbit.

Formation of Dawn and Twilight Diagram

A diagram illustrating the inclination of the Earth's axis ($23\frac{1}{2}^\circ$ to the vertical, $66\frac{1}{2}^\circ$ to the axis plane), the equatorial circle, and alignment relative to the Pole Star.

Hours of Daylight at the Equator

The equator experiences $12\,\text{hours}$ of daylight and $12\,\text{hours}$ of night throughout the year because the circle of illumination always bisects the equator into two equal halves.

Transition Period

The gradual and continuous process of changing between sun-lit day and night darkness, encompassing stages such as dawn, sunrise, noon, evening, twilight (dusk), and midnight.