Earth As A Planet

Earth’s Shape: The Earth possesses a spherical shape, also known as a GEOID. Although our everyday experience may suggest a flat surface, the Earth is nearly spherical, exhibiting slight flattening at the poles. Numerous pieces of evidence support the Earth’s spherical nature.   Earth’s Size: Ranked as the fifth largest planet in our solar system, […]

Earth’s Shape:

The Earth possesses a spherical shape, also known as a GEOID. Although our everyday experience may suggest a flat surface, the Earth is nearly spherical, exhibiting slight flattening at the poles. Numerous pieces of evidence support the Earth’s spherical nature.

 

Earth’s Size:

Ranked as the fifth largest planet in our solar system, Earth spans an approximate surface area of 443 million square kilometers (197 million square miles). With a polar diameter of about 12,722km and an equatorial diameter of about 12,762km, Earth measures approximately 40,085km in circumference at the equator and 39,955km at the poles. Its mean density is estimated at 5.5 grams per cubic centimeter.

 

Proofs of Earth’s Sphericity:

  1. Circumnavigation: Ferdinand Magellan’s 1519-1522 voyage around the world, and subsequent similar journeys, confirms the Earth’s spherical shape. Such expeditions would encounter an abrupt edge if the Earth were flat.
  2. Sunrise and Sunset: Varied times of sunrise and sunset worldwide refute a flat Earth, supporting its spherical nature as it rotates from west to east.
  3. Aerial Photographs: High-altitude photographs from rockets provide contemporary evidence of the Earth’s spherical shape.
  4. Lunar Eclipse: During a lunar eclipse, the Earth casts a circular shadow on the moon, a phenomenon consistent with a spherical Earth.
  5. Ship’s Visibility: Observing ships approaching or departing ports reveals a gradual appearance or disappearance, which aligns with the Earth’s curvature.
  6. Shape of Other Planets/Planetary Bodies: The circular outlines of celestial bodies, including the sun, moon, and stars, further affirm the Earth’s spherical shape.
  7. Experimental Proof/Engineer Surveys/Driving Poles: In level ground, driving three poles of equal length at the same depth results in the center pole projecting slightly above the others due to the Earth’s curvature.

 

Earth’s Movement:

The Earth is in constant motion, revolving around the Sun and presenting different sides to the Sun at different times. This movement encompasses both the Rotation of the Earth and the Revolution of the Earth.

 

Rotation of the Earth:

The Earth’s rotation involves its movement on its axis, completing a full rotation of 360° every 24 hours, constituting a day. Notably, the Earth rotates through 15° in one hour or 1° in four minutes.

 

Effects of Earth Rotation:

  1. Day and Night: Rotation causes only one part of the Earth’s surface facing the Sun to experience daylight, while the opposite part in shadow experiences darkness (night).
  2. Time Differences: The Earth’s rotation creates local time differences between places, advancing by 1 hour for every 15° eastward and lagging by 1 hour for every 15° westward.
  3. Apparent Sunrise and Sunset: Earth’s rotation leads to the apparent phenomena of sunrise and sunset as different parts emerge or move away from the Sun’s rays.
  4. Deflection of Wind and Ocean Current: Rotation causes wind and ocean currents to deflect, clockwise in the northern hemisphere and anticlockwise in the southern hemisphere.
  5. Daily Rising and Falling of the Tide: Earth’s rotation contributes to the daily tidal cycles, manifesting as the rising and falling of water levels in seas and oceans twice each day.

 

Earth’s Revolution:

“Revolution” denotes the orbital movement of a celestial body around the sun. In our solar system, the moon orbits the Earth, and the Earth, in turn, revolves around the sun.

 

The moon completes one orbit around the Earth every month, while the Earth and moon jointly orbit the sun, completing a full revolution once a year. Eclipses occur when the sun, Earth, and moon align in a straight line. A solar eclipse happens when the moon comes between the Earth and the sun, while a lunar eclipse occurs when the Earth is positioned between the sun and the moon.

 

Revolution, specifically Earth’s orbit around the sun, takes approximately 365 1/4 days, defining one year. Leap years, with 366 days, occur every fourth year, while all other years consist of 365 days.

 

Effects of Earth Revolution:

  1. Determination of a Year: The time it takes for Earth to complete one revolution around the sun defines a year on our planet, lasting 365 1/4 days.
  2. Seasonal Changes: Revolution influences the seasons, with the tropical belt experiencing two main seasons—rain and dry—while the temperate belt has four distinct seasons: summer, autumn, winter, and spring.
  3. Changes in Altitude of the Mid-Day Sun: Equinoxes and solstices are observed as a result of Earth’s revolution.
  4. Varied Lengths of Day and Night: Depending on Earth’s position in relation to the sun, the length of day and night fluctuates throughout the year.
  5. Seasonal Temperature Changes: The arctic region experiences warm and bright summers and cold, dark winters due to Earth’s revolution.

 

Dawn and Twilight:

Dawn is the brief period between sunrise and full daylight, while twilight is the brief period between sunset and complete darkness.

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