"Shen Qi, please look at the question." Sun Erxiong pointed at the big screen.
A new question appeared on the screen. Whether they were ordinary or exceptional, all students at Yanda's Math Camp had to take a general knowledge test.
The screen displayed: "Which of the following four routes passes through the Papal Meridian: London–Mumbai, London–Hong Kong, London–New York, or London–Rio de Janeiro?"
"Shen Qi, please give us your answer," Sun Erxiong said.
"Hmm..." Shen Qi stared at the screen, lost in thought. The general knowledge question was only one short sentence, but it contained a huge amount of information.
I've been to London. Its longitude is 0 degrees East; the Greenwich Observatory is located there.
Mumbai is a port in India, and everyone knows where Hong Kong is. Ships sailing east from London would head to Mumbai and Hong Kong.
New York is in the United States, and Rio is in Brazil. Ships sailing west from London across the Atlantic to New York or Rio would head west.
So the key question is: where is the Papal Meridian?
A meridian is a longitude line. Today, the Prime Meridian passes through Greenwich in London, and Greenwich Mean Time is known as Standard Time.
The Papal Meridian must have been a Prime Meridian that existed at some point in history. With the Greenwich meridian as the reference line, what longitude was the Papal Meridian at?
This general knowledge question involved not only geography, but history as well.
"Shen Qi, have you thought it through?" Sun Erxiong asked.
"I... have." Shen Qi quickly worked it out in his head, using the process of elimination. He imagined a longitude line that could move east or west across the world map, and designated it the Papal Meridian. Starting from London, if it moved east