Geodesy and Celestial Mechanics

The centrifugal force is caused by Earth's rotation and depends on distance from the rotation axis. At the poles, you're on the axis itself (distance = 0), so there's no centrifugal force. At the equator, it's maximum.

About 1.3 million Earths could fit inside the Sun by volume, not 1 million. This demonstrates the Sun's enormous scale compared to Earth - the Sun's radius is roughly 109 times Earth's radius.

Cape Three Points in Ghana (approximately 4°44'N 2°05'W) is generally considered the nearest land point to 'Null Island' (0°N 0°E), where the equator meets the prime meridian in the Gulf of Guinea, about 500 kilometers away.

The Solar System formed approximately 4.6 billion years ago from the gravitational collapse of a giant molecular cloud. This age is determined by radiometric dating of the oldest meteorites, calcium-aluminum-rich inclusions (CAIs), and lunar samples. This is also consistent with the estimated age of the Sun.

The Sun is approximately 4.57 billion years old, based on helioseismology and models of stellar evolution. This age is consistent with the oldest meteorites (4.56-4.57 billion years) that date to the Solar System's formation. The Sun will continue fusing hydrogen for about another 5 billion years before becoming a red giant.

Earth is approximately 4.54 billion years old, determined through radiometric dating of the oldest terrestrial minerals and meteorites. The age is based on dating of lead isotopes in meteorites and Earth's crust. Earth formed shortly after the Sun's formation, through accretion of planetesimals in the protoplanetary disk.

The Moon is approximately 4.53 billion years old, formed shortly after Earth's formation from debris after a Mars-sized body impacted early Earth (the Giant Impact Hypothesis). Lunar samples brought back by Apollo missions have been radiometrically dated to confirm this age. The Moon formed within about 50 million years after the Solar System's formation.

Earth completes one rotation on its axis in approximately 24 hours, creating day and night. The 365-day figure refers to revolution around the sun.

Mercury completes one orbit around the Sun in approximately 88 Earth days, which is the shortest orbital period of any planet in our solar system. This is because Mercury is the closest planet to the Sun and experiences the strongest gravitational pull, causing it to orbit at the highest velocity among all planets.

Aryabhatta calculated the Earth's circumference as approximately 24,835 miles (or 4,967 yojanas in ancient Indian units), which is remarkably close to the modern value of 24,901 miles. This demonstrates the sophistication of ancient Indian astronomy and mathematics.

The Astronomical Unit (AU) is defined as the average distance between Earth and Sun, approximately 149.6 million kilometers (93 million miles). It is the standard unit for measuring distances within our solar system. A light-year is the distance light travels in one year (about 63,241 AU). 'Astronomy Unit' is not the correct term.

The Prime Meridian is a longitude line (0°) running from north to south pole, while the Equator, Tropic of Cancer, and Tropic of Capricorn are all latitude lines running east-west. The Prime Meridian is the only longitudinal reference line among the options.

Earth completes one rotation relative to the fixed stars in 23 hours, 56 minutes, and 4 seconds, called a sidereal day. This is slightly less than 24 hours due to Earth's orbital motion.