RENEE MONTAGNE, HOST:
Good morning, I'm Renee Montagne. For years, visitors have stood on the stainless steel Greenwich Meridian Line thinking they were standing on the exact middle point between east and west. But they were wrong. Scientists say that's because the astronomers who calculated the line didn't take into account distortions caused by gravity. When GPS arrived 30 years ago, the real prime meridian was revealed. It's 334 feet to the east, and it's currently marked by a trashcan. It's MORNING EDITION. Transcript provided by NPR, Copyright NPR.