Pituusasteviivoja

Pituusasteviivoja, also known as meridians, are imaginary lines on Earth's surface that run from the North Pole to the South Pole. They are used to measure longitude, which is the angular distance, in degrees, east or west of the Prime Meridian. The Prime Meridian is the line of 0 degrees longitude, which passes through Greenwich, London, England. All other meridians are numbered east or west of this line, up to 180 degrees.

Meridians are semicircles, and they converge at the poles. The distance between meridians decreases as they approach the poles. This is because the Earth is a sphere, and the lines of longitude converge at the poles. The distance between meridians is greatest at the equator, where it is approximately 111 kilometers (69 miles) per degree of longitude.

Meridians are essential for navigation and cartography. They are used to determine a location's exact position on Earth, along with lines of latitude. Together, meridians and parallels of latitude form a grid system that allows for precise mapping and location tracking. Without meridians, it would be impossible to accurately chart courses or pinpoint specific locations on maps. Historically, determining longitude was a significant challenge for sailors. The development of accurate chronometers in the 18th century finally allowed for reliable longitude calculations at sea, revolutionizing maritime navigation.