Geodesy and Celestial Mechanics

Longitude lines run from the North Pole to the South Pole (meridians). Latitude lines run east-west parallel to the equator. 'Parallels' specifically refers to latitude lines, not longitude. Option D is incorrect because these are distinct systems.

The upper limit of Earth's atmosphere extends to approximately 10,000 km, which is about half the distance to the Moon. While the Kármán line (100 km) marks the boundary of space, atmospheric particles exist much farther out, gradually thinning until they merge with the solar wind.

Earth is not a perfect sphere but an oblate spheroid - slightly flattened at the poles and bulging at the equator due to Earth's rotation. The equatorial diameter is about 43 km larger than the polar diameter. This shape was confirmed by measurements and is consistent with physics of rotating bodies.

At the equator, day and night are approximately equal (12 hours each) throughout the year. This is because the equator always receives about 12 hours of daylight due to Earth's axial orientation relative to the sun. The duration varies more at higher latitudes with seasons.

The distance between two consecutive latitudes is approximately 111 km (69 miles). This is because lines of latitude are parallel circles and the distance between them is calculated based on Earth's circumference of about 40,075 km divided by 360 degrees.

The Prime Meridian is the 0° longitude line, which passes through Greenwich, London. It serves as the reference point from which all other longitudes are measured. Longitudes west of this line are labeled W and east are labeled E.

The Tropic of Capricorn is located at 23½° S (south) latitude. It marks the southernmost point where the sun appears directly overhead at noon during the December solstice. The 66½° latitudes refer to the Arctic and Antarctic Circles.

The Equator is the imaginary line of 0° latitude that divides the Earth into Northern and Southern Hemispheres. It is the reference point from which all other latitudes are measured north or south.

The troposphere is the lowest layer of Earth's atmosphere, extending from the surface up to about 6-20 kilometers altitude. It contains approximately 75% of the atmosphere's mass and virtually all weather phenomena. The stratosphere, mesosphere, and ionosphere are progressively higher layers farther from Earth's surface.

A light year is a unit of distance equal to the distance light travels in vacuum in one year, approximately 9.46 trillion kilometers. It is commonly used to measure astronomical distances between stars and galaxies.

2. Overhead as seen from the north pole

Mercury has a very slow rotation and a fast orbit, leading to a solar day (sunrise to sunrise) that lasts about 176 Earth days. This is significantly longer than its sidereal rotation period of approximately 59 Earth days.

A light year is the distance that light travels in a vacuum in one Julian year. Despite having the word 'year' in its name, it is a unit of astronomical distance, not time. It is approximately 9.46 trillion kilometers.

The Earth's rotational speed is highest at the equator because it has the largest circumference to cover in a 24-hour period. As you move toward the poles, the distance traveled in one rotation decreases, thus the speed decreases.

The earth rotates on its axis at a speed of approximately 1,670 km/h at the equator, or about 0.46 km/sec, which does not match any of the provided numerical options in kilometers per second. Therefore, none of these is correct.