What was the need to set up internationally accepted uniform longitude as prime meridian?
Answers
In the past, the prime meridian has been a bit of everything for different seafarers; Paris, Amsterdam, Rome and, the island of Hierro in the Canary, for Christopher Columbus.
Today, as you know, it is the Royal Observatory of Greenwich, near London.
But then, what about the time? Well, when the first railroad came to Britain, they had a big problem: The local clocks were set to solar time (noon, when the sun is highest in the sky). Hence the impossibility to make train time tables. They then decided that everybody should keep Greenwich time.
Today, we keep the time as relative to that prime meridian time, what was called GMT (Greenwich Mean Time) but that is now called UTC (Universal Time Convention).
When the only ship from Magellan’s expedition came back to Sevilla, in Spain, the captain got really scared; he had missed one day in his calendar! How was it possible? The question was asked to learned savants of the university of Salamanca and they came with an extraordinary answer: If we circumnavigate the earth westward, as Magellan did, you loose one day!
… but where? It was then necessary to define the … date line as the opposite side of the Greenwich time and … it was perfect because that longitude is covering nearly only the sea.