Geodesy and Celestial Mechanics

About 50% of the world population is concentrated between latitudes of 20°N and 40°N because most populous countries and areas like Asia, USA, Europe and India lie within these latitudes.

The average distance from the Earth to the Moon is approximately 238,855 miles or 384,400 kilometers.

Apogee is defined as the point in the Moon's orbit where it is at its maximum distance from the Earth.

Perigee is the point in the Moon's orbit where it is closest to the Earth.

Pluto's diameter is approximately 1,473 miles, which is slightly less than the width of Australia at its widest point (about 2,500 miles, but often cited in trivia as comparable to the width of Australia).

Earth completes one full rotation on its axis every 24 hours, which creates the cycle of day and night. A year is the time it takes to orbit the Sun.

The average distance from the Earth to the sun is approximately 93 million miles, a distance often referred to as one astronomical unit.

During the Northern Hemisphere's winter, the Earth's tilt causes the Northern Hemisphere to lean away from the sun, meaning the sun's direct rays hit below the equator.

The Earth's orbit around the sun is not a perfect circle but an ellipse, which is an elongated or flattened circle.

• Sun rays falling vertically move between 23 and 1/2 degrees north and 23 and 1/2 degrees south latitudes throughout the year. On 22nd december, the sun rays fall vertically at the 23 1/2 degrees south.

The axis of the Earth is tilted at an angle of 23 1/2° from a perpendicular to the orbital plane.  This tilting of the axis is called the inclination of the Earth's axis. Due to this inclination, the axis of the Earth makes an angle of 66 1/2° with the plane of the Earth's orbit.