By the beginning of the twentieth century, the meridian passing though the Royal Observatory at Greenwich had become a near-universal reference for place and time. It was the zero of longitude. But our current standard of zero longitude is about 100 metres away from the original. That mobility needs historical context: Greenwich began to move in the years after the First World War, when wireless techniques for the astronomical determination of longitude and the standardisation of time were developed, and has carried on moving ever since. In this article, I describe how twentieth-century techniques for the determination of longitude not only brought improved precision but also led to fundamental changes in our long-standing conventions of longitude. And I show how – despite its mobility – our current standard of zero longitude continues to respect the original.

中文翻译：

---

二十世纪经度：格林威治搬家时

到 20 世纪初，穿过格林威治皇家天文台的子午线已成为几乎普遍的地点和时间参考。它是经度的零。但是我们现在的零经度标准，离原点大概有100米左右。这种移动需要历史背景：格林威治在第一次世界大战后的几年里开始移动，当时开发了用于天文测定经度和时间标准化的无线技术，并且从那时起一直在移动。在本文中，我将描述 20 世纪确定经度的技术如何不仅提高了精度，而且还导致我们长期存在的经度惯例发生根本变化。