Earth’s Rotation Day is an annual occurrence celebrated on January 8th of every year. All of us are very well aware that Earth rotates. The planet will take 24 hours to complete one full rotation, and due to the rotation, we tend to see the day and night alternatively.
Most of us probably know the Earth rotates on an almost-vertical axis every 24 hours, which gives us one Earth day. Being the only planet in which humans survive, Earth rotates about its own axis. Earth’s Rotation Day is observed as a day to celebrate the French Physicist, Leon Foucault who in 1851 had demonstrated that the Earth rotates on its axis.
Earth rotates around its own axis from west to east. When seen from the North Star Polaris {Alpha Ursae Minoris}, Earth turns counter-clockwise. Rotation of Earth results in days and nights. Earth’s rotation is mostly the result of angular momentum left over during the formation process of Earth.
There are three distinct motions, the most noticeable being Earth’s rotation. Earth rotates once every 23 hours, 56 minutes, causing our cycles of day and night. Earth also has precession (a wobble of the rotational axis) and nutation (a back-and-forth wiggle of Earth’s axis), caused primarily by the gravitational pull of the Moon as it orbits Earth. Precession and nutation, over long periods of time, cause Earth’s north and south poles to point toward different stars.
Global Glacial Rebound
The average position of water is always nearer the equator. During glaciations, water is taken from the oceans and deposited as ice over the higher latitudes closer to the poles. These poles are close to the polar axis or rotational axis of the Earth. When the moment of inertia of Earth-water-ice system gets reduced which is very much similar to a rotating figure skater bringing her arms closer to her body, the Earth should spin faster. This process leads to an increase in the rotation speed of the Earth and therefore, to a decrease of the length of day.
Sidereal Day
The spinning of the Earth on its polar axis takes 23 hours, 56 minutes and 4.09 seconds for rotation through the 360 degree. This is called sidereal day. During the time needed by the Earth to complete a rotation around its axis (a sidereal day), the Earth moves a short distance (approximately 1°) along its orbit around the sun. So, after a sidereal day, the Earth still needs to rotate a small additional angular distance before the sun reaches its highest point. A solar day is, therefore, nearly 4 minutes longer than a sidereal day.
Precession Movement of earth
The Precession movement of Earth is very slow and proceeds in the direction of the opposite of Earth’s Rotation. The one cycle completes in 28000 years. The reason of precession movement is gravitational attraction of Moon as well as Sun. The slightly irregular movement of earth’s axis due to precession is called Nutation.
HISTORY OF EARTH’S ROTATION DAY
The rotation of the Earth and its relationship to our daylight cycles has fascinated philosophers and scientists for thousands of years. As far back as 470 BCE, ancient Greeks speculated the Earth itself moves, rather than having the rest of the sky revolving around us. In the 10th century CE, Muslim astronomers started building astrolabes and other instruments to measure the movement of the Earth relative to the stars.
The first human depictions of the cosmos date back to 1,600 BCE. A bronze disk found in Northern Europe shows the sun, a crescent moon, and the Pleiades star cluster, and written records from the Babylonians record the position of celestial bodies. Arguably the earliest scientific observations, these records make astronomy the oldest known science.
Although humans have observed the stars for thousands of years — some early theories proposed that the Earth moved — the geocentric theory remained dominant in Europe until the work of Nicolaus Copernicus in the 1500s, proving the Earth does actually revolve around the sun. Following his work, others tried to prove the rotation of the Earth through various experiments. While the theory became accepted by the mid-1800s through observation of astronomical movements, it was Foucault’s pendulum that demonstrated, visibly and spectacularly, the rotation of the Earth.
Foucault first conducted his pendulum experiment in the Paris Observatory, then the Panthéon, where it remains an impressive centerpiece today. While they vary in size, pendulums work best with long lines, typically between 40 and 100 feet. A heavy, swinging lead bob is suspended at the end of a line. As the bob swings back and forth, it slowly moves in a clockwise direction as the Earth rotates under it.
Today, Foucault’s Pendulums are a fixture in science museums around the world. The simple but brilliant contraption uses a suspended lead ball to indicate the rotation of the Earth over the course of a day. The pendulum is surrounded by small pins arranged in a circle, which the pendulum knocks down one by one, eventually completing a full rotation.
How to celebrate Earth’s Rotation Day
The Earth rotates every day, but not every day is Earth’s Rotation Day, so you should celebrate it. If you want to see a Foucault Pendulum in real life, try visiting the nearest space and science museum as many of them have one. They’re actually quite interesting to look at in action.
At one time, it was a widely held belief that the Earth was the center of the universe and everything revolved around it – the planets, the sun, the moon, and the stars.
Then, the theory arose that the sun was actually the center of the universe before scientists realized that neither was actually the case. In other words, no, the Earth is not actually a fixed sphere at the center of the universe, simply pulling everything towards it. It rotates on its axis and Earth’s Rotation Day is in honor of that.
