Today we visited Greenwich, and the Royal Observatory Museum that sits atop the hill in Greenwich Park. It has an expansive view across the park, past the Old Royal Naval College and the River Thames, to the skyscrapers in the Canary Wharf financial district of London. This observatory is where the question of longitude was studied – and in particular, a decades-long challenge to find a reliable means for mariners to estimate their longitude while at sea. As a result, it was later selected as the zero point – the reference point for 0º0’0″ longitude, aka the Prime Meridian. Given the importance of measuring time for measuring longitude, Greenwich was also designated as the basis for universal time – hence Greenwich Mean Time (GMT), now known as Universal Time (UTC). We and the other tourists had fun standing on the meridian, one foot in the Western Hemisphere and one foot in the Eastern Hemisphere.
David Kotz 