Rotation

Earth's rotation refers to the planet's spinning motion on its axis. This rotation alternates day and night and creates the Earth's 24-hour day. The axis around which the Earth rotates is an imaginary line that extends from the North Pole to the South Pole, passing through its center, and is tilted at an angle of about 23.5 degrees relative to its orbit around the Sun. This axial tilt gives rise to the changing seasons as different parts of the Earth receive varying amounts of sunlight throughout the year.

The Earth rotates from west to east or counterclockwise when viewed above the North Pole. This rotation causes different parts of the Earth's surface to experience daylight and darkness as it revolves around the Sun. The speed of Earth's rotation is not constant across its surface due to its slightly oblate shape – it's slightly flattened at the poles and bulging at the equator. Therefore, Earth rotates faster at the equator than at the poles. At the equator, it rotates 1,600 kilometers (1,000 miles) per hour. At 60 degrees north, it rotates at 832.9 kilometers (518.7 miles) per hour. However, the earth rotates sluggishly near the poles, 0.00008 kilometers (0.00005 miles) per hour. This means a person who lives near the equator spins faster than one near the Arctic Circle.

The rotation of the Earth also plays a significant role in various natural phenomena, such as the formation of trade winds and the rotation of cyclones and anticyclones in the atmosphere. Additionally, the rotation affects the behavior of objects on the surface due to centrifugal force, which causes objects at the equator to experience a slightly weaker gravitational pull compared to those at higher latitudes.

Image: Earth’s Rotation

Attribution: Przemyslaw "Blueshade" Idzkiewicz, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0                          

Revolution

Earth's revolution refers to its orbital motion around the Sun. The Earth follows an elliptical path known as an orbit, completing one course in approximately 365.25 days, resulting in a calendar year. This orbital motion determines the length of a year and affects the distribution of sunlight on Earth, resulting in the changing seasons. There are four seasons: spring, summer, autumn (fall), and winter:

Spring: Spring marks the season when the hemisphere tilts towards the sun. It brings longer daylight hours, milder temperatures, and the awakening of nature. Flowers bloom, trees regain their leaves, and animals emerge from hibernation. It is a time of growth and renewal. This is the time of the equinoxes.

The vernal (Spring) equinox for the Northern Hemisphere falls about March 20 or 21. The spring equinox occurs when the tilt of the Earth's axis is neither towards nor away from the sun but perpendicular to the sun, resulting in equal day and night lengths. It marks the beginning of spring in the Northern Hemisphere and autumn in the Southern Hemisphere.

Summer: During summer, the hemisphere tilted towards the sun receives the most direct sunlight. It brings longer days, warmer temperatures, and abundant sunshine. It is a season of outdoor activities, beach trips, and vibrant life. Crops grow, fruits ripen, and the natural world flourishes.

For the Northern Hemisphere, the summer solstice falls around June 21. The summer solstice is the day with the most extended period of daylight and the shortest night of the year. It occurs when the Earth's tilt is at its maximum towards the sun, resulting in the sun reaching its highest point in the sky. It marks the beginning of summer in the Northern Hemisphere and winter in the Southern Hemisphere.

Autumn (Fall): Autumn occurs when the hemisphere begins to tilt away from the sun. It brings shorter days, cooler temperatures, and the changing colors of leaves. It is the harvest season, with agricultural abundance and the preparation for winter. The air becomes crisp, and nature becomes a beautiful tapestry of warm hues. The autumnal(fall) equinox in the Northern Hemisphere falls about September 22 or 23.

Winter: Winter arrives when the hemisphere is tilted away from the sun. It brings shorter days, colder temperatures, and often snowfall. Trees shed their leaves, and the landscape takes on a serene appearance. It is a season for indoor coziness, winter sports, and holiday celebrations.

The winter solstice is the day with the shortest period of daylight and the longest night of the year. It occurs when the Earth's tilt is at its maximum, away from the sun, resulting in the sun reaching its lowest point in the sky. December 21 or 22 marks the beginning of winter in the Northern Hemisphere and summer in the Southern Hemisphere.

Image: Earth`s Revolution

Perihelion and aphelion

Perihelion is the point in an object's orbit around the Sun where it is closest to the Sun. This occurs when the object is at its shortest distance from the Sun in its elliptical orbit. The term "perihelion" is derived from the Greek words "peri," meaning near or close, and "Helios," meaning Sun. During perihelion, the object experiences the highest gravitational pull from the Sun, and its orbital speed tends to be faster than other points in its orbit.

On the other hand, aphelion is the point in an object's orbit around the Sun where it is farthest from the Sun. It is the opposite of perihelion. The term "aphelion" is also derived from Greek, with "apo" meaning away or far, and "Helios" referring to the Sun. During aphelion, the object is at its furthest distance from the Sun. Due to the weaker gravitational pull from the Sun, the object's orbital speed tends to be slower than other points in its orbit.

For example, for Earth, perihelion occurs in early January when Earth is approximately 147 million kilometers (91 million miles) away from the Sun, and aphelion occurs in early July when it is approximately 152 million kilometers (94.5 million miles) away from the Sun. Fortunately, in the northern hemisphere, summer occurs when the earth is at aphelion and winter at perihelion. The seasons could have been worse otherwise.