Earth's Habitability Factors

• Earth's habitability is influenced by several factors, including its distance from the sun, size, orbit, rotation, and tilt.

Habitable Zone

• The habitable zone is the range of distances from a star where liquid water can exist on a planet's surface.

Habitable Size

• If Earth were smaller, its gravitational pull would be weaker, resulting in a thinner atmosphere.

• A thinner atmosphere would trap less heat, leading to a colder planet and less protection from the sun's harmful rays.

• If Earth were larger, it would have a thicker atmosphere, trapping more heat and increasing surface temperatures.

Earth's Orbit (Revolution)

• Orbital period refers to the time it takes for an astronomical object to complete one orbit around another object.
• Earth's orbital period around the sun is approximately 365.25 days.
• Earth's orbit is elliptical, not perfectly circular.
• Perihelion is the point in Earth's orbit when it is closest to the sun, occurring in the first week of January.
• Aphelion is the point in Earth's orbit when it is farthest from the sun, occurring in the first week of July.

Earth's Rotation and Tilt

• Earth rotates on its axis once every 24 hours, causing the apparent rising and setting of celestial bodies.
• Earth's axis is tilted at 23.5 degrees.
• The direction of the tilt remains constant throughout the year as Earth orbits the sun.
• Earth's tilt is the main reason for the occurrence of seasons.
• When a hemisphere is tilted toward the sun, it receives more direct sunlight and experiences warmer temperatures.
• When a hemisphere is tilted away from the sun, it receives indirect sunlight and experiences cooler temperatures.
• The seasons are opposite in the northern and southern hemispheres.
• The June 21 solstice marks the day when the northern hemisphere is most tilted toward the sun, resulting in the most daylight hours and the sun's highest path in the sky.
• The December 21 solstice marks the day when the southern hemisphere is most tilted toward the sun, resulting in the fewest daylight hours and the sun's lowest path in the sky for the northern hemisphere.
• The March 20 and September 22 equinoxes are the days when neither hemisphere is tilted toward the sun.
• The Tropic of Cancer and Tropic of Capricorn are located 23.5 degrees north and south of the equator, respectively.
• On the Northern Hemisphere's summer solstice, the sun is directly overhead at noon at the Tropic of Cancer.
• On the Southern Hemisphere's summer solstice, the sun is directly overhead at noon at the Tropic of Capricorn.
• The change in seasons in the tropics is characterized by wet and dry periods rather than hot and cold.
• The Arctic Circle and the Antarctic Circle are located 23.5 degrees south of the north pole and 23.5 degrees north of the south pole, respectively.
• Between these circles and the poles, there are times of the year when the sun can be up or down for more than 24 hours.
• The sun's rays are indirect at the polar regions, resulting in minimal warming.