The rotation and revolution of Earth are two fundamental motions that shape the planet’s appearance and behavior.
Earth rotates on its axis, which causes day and night, while it revolves around the Sun, resulting in the changing of seasons.
Earth rotates eastward, meaning from west to east, eventually making the apparent rotation of this celestial body from east to west.
So, in this article, we will now discuss some amazing Earth Rotation and Revolution Facts.
Interesting Earth Rotation and Revolution Facts
Difference Between Earth’s Rotation and Revolution
Though often confused, there is a significant difference in both the concepts of the rotation and revolution of Earth. In fact, Earth revolves around the Sun while rotating on its axis.
Earth’s rotation results in the day and night cycle, whereas Earth’s revolution is the actual cause behind the changing seasons.
Rotation is mainly the circular movement of a certain object around a center as rotation. The Earth and some other planets rotate around a specific imaginary line called the rotation axis.
Earth’s Rotation Takes Nearly 24 Hours
Rotation is the motion of a specific object around its axis. Planet Earth rotates on its axis from westwards to eastwards, completing one rotation in almost 24 hours.
The axis of this rotation is an imaginary line that usually passes through the Earth’s North and South Poles and has an angle of 23 and a half degrees. Thus, planet Earth is said to rotate or spin upon itself.
Earth’s rotation has multiple effects, such as the day and night cycle, the flattening of the poles, and even the Coriolis effect.
Earth’s Original Rotation from Angular Momentum of The Cloud
The original rotation of Earth was a vestige of the cloud’s angular momentum. The cloud is made of rocks, dust, and even gas that coalesced to form our Solar System.
This primordial cloud was made of helium and hydrogen produced in the Big Bang, along with the heavier elements ejected by supernovas.
As this interstellar dust is not homogenous, any asymmetry during gravitational accretion may result in the eventual planet’s angular momentum.
Pole Flattening Due to Earth’s Rotation
Earth’s rotation forces the planet to bulge at the equator and flatten at the poles. This celestial phenomenon is known as the oblate spheroid shape of our planet Earth.
Earth’s equatorial diameter is around 43 kilometers larger than the part called the polar diameter.
This phenomenon of flattening of Earth’s poles is caused by the centrifugal force created by the rotation of Earth.
Day and Night Cycle: Effect of Earth’s Rotation
Another important effect of Earth’s rotation is its day-and-night cycle. As Earth rotates, different parts of the planet receive sunlight while some remain in darkness.
This cycle lasts about 24 hours, giving rise to the 24-hour day we experience. The actual length of this day does not remain constant throughout the year; hence, it varies depending on the season and the latitude.
Coriolis Effect in Northern and Southern Hemispheres
The Coriolis Effect is a force that can be seen in a rotating object. Gaspard Gustave de Coriolis first described this effect using mathematics in 1835.
They spin clockwise in our Earth’s northern atmosphere, while they spin anticlockwise in the southern hemisphere.
An example of this Coriolis Effect is that liquids, mainly water, flow down opposite drains in the southern and northern hemispheres.
However, the force of this effect is not powerful enough to realize this phenomenon in such a small amount of water.
Revolution Causes Day and Night Length Variation
The revolution of planet Earth around the Sun causes the difference in the length of both day and night.
As our home planet revolves, different parts of the planet receive different amounts of sunlight, changing the length of the day and night.
Thus, at any moment, half of our planet is in the nighttime while the other half is in the daytime.
On Earth, an average night is actually shorter than the daytime because the Sun’s apparent disk has an angular diameter of around 32 arcminutes.
Earth’s Elliptical Orbit Revolution
Revolution is the actual motion of an object around another object. Planet Earth revolves around the Sun in an elliptical orbit.
Thus, Earth completes its one revolution in about 365.25 days. This phenomenon, known as the revolution of Earth, has multiple effects, such as changes in seasons and variations in the night and day.
Equinoxes: Equal Day and Night
When the Earth’s axis is tilted or inclined neither away from nor towards the Sun, this results in “nearly” equal amounts of nighttime and sunlight at all latitudes.
These phenomena are known as equinoxes. Equinox originated from the Latin words “request” or equal and “nox.” There are two equinoxes on which the Sun remains exactly at the equator at noon.
Variation Between Equinoxes
These almost equal lengths of day and night are caused by the Sun’s rays being refracted or bent, making it look like the Sun is located above the horizon, whereas it actually is below the horizon.
Moreover, the days become a little longer as the sunset and sunrise happen longer at higher latitudes.
Thus, during the equinox and after a few days of this equinox, the length of the day usually varies slightly.
Solstices Due to Earth’s Inclination
The term solstice is derived from the Latin word solstitium. This Latin word comes from sl, “sun,” and sisters, “to stand stationary or still.” Hence, “solstitium” means “the standing stationery or still of the sun.”
Our planet Earth is inclined toward or away from the Sun. This happens maximum during the summer solstice; hence, the Sun comes at its maximum elevation on this specific day, known as the summer season’s solstice.
The noontime position of this planet remains constant for several days after and before the summer solstice.
The Summer Solstice Explained
The summer solstice occurs when the Sun appears over the Tropic of Cancer. This line spans Mexico, Saudi Arabia, the Bahamas, India, Egypt, and Southern China and is located at 23.5 degrees North latitude.
At that time, the Sun is at its maximum point in the sky for all locations north of the Tropic of Cancer, and it is also known as the longest day of the entire year.
The Winter Solstice Explained
In contrast, during the winter solstice, our Earth encounters its longest night and shortest day of the year.
It occurs in the Northern Hemisphere when the Sun is above the Tropic of Capricorn, which is 23.5 degrees south of the equator and extends through areas like Australia, Chile, northern South Africa, and southern Brazil.
Various famous festivals experience these solstices, such as the Christmas holiday, which occurs a few days after the December solstice.
Earth’s Rotation Is Slowing Down
An interesting fact about Earth’s rotation is that it gradually slows down. The gravitational forces of the Moon and the Sun affect the Earth’s rotation, dragging it down.
This drag eventually slows down the rotation of planet Earth by around 1.8 milliseconds per century. However, this effect is not noticeable in our daily lives.
Earth’s Elliptical Orbit Shape
Another amazing fact about Earth’s revolution is that it is not a perfect ellipse. The orbit of Earth is affected by the gravitational forces of some other planets present in the solar system, resulting in the orbit’s shape varying over time.
This variation in the shape of the Earth’s orbit affects the distance between the Sun and Earth, which may have crucial effects on our home planet’s climate and weather patterns.
Changes in Earth’s Axial Tilt Over Time
Earth’s axial tilt also changes over time, which may affect its climate. The tilt of Earth’s axis changes between 22.1 and 24.5 degrees over a cycle of about 41000 years.
This variation can affect the amount of sunlight that various parts of planet Earth receive, resulting in changes in the climate and the length of the seasons.
Famous Test Proving Earth’s Rotation
The Foucault pendulum is the most celebrated and famous test on planet Earth’s rotation. It was first built in 1851 by physicist Leon Foucault.
This test included a lead-filled brass sphere suspended about 67 m from the top of Paris’s Pantheon.
Due to Earth’s rotation under the swinging pendulum, the pendulum’s plane appears to rotate at a rate according to the latitude.
At Paris’s latitude, the observed shift was almost 11 degrees clockwise per hour. These pendulums Foucault now swing in museums around the globe.
So, Earth’s rotation and revolution are the two most basic features of our home planet, which shape its appearance.
Understanding these motions helps us comprehend the weather patterns and changes day and night on this planet.
Ready to explore the wonders of Earth’s movements with your kids? With just one simple click, you can download and print these educational resources.
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