请将下面这段话翻译成英文：

计量，古称度量衡，是实现单位制统一，保证量值准确可靠的活动，是现代国家经济、科技、社会发展的重要基础。计量历史悠久，关系国计民生。公元前221年秦朝建立，秦始皇统一度量衡，成为中国古代统一计量制度的里程碑。1875年5月20日《米制公约》的签署，开辟了全球范围内推行国际单位制的近代计量新纪元。以量子物理为基础的现代计量科学技术的研究与应用，为人类文明发展提供了更加精准的现代计量技术保障。1999年第21届国际计量大会决定：自2000年起，每年5月20日为“世界计量日”。2015年世界计量日的中国宣传主题与国际主题一致，为“计量与光”。

参考译文：

Measurement, which is called metrology in ancient times, is the important foundation of social development of the modern countries' economy, science and technology. It has a long history and plays an important role in national welfare and the people's livelihood. Established in 221 BC, in the Qin dynasty, Qinshihuang unified weights and measures, and became a unified system for the measurement of milestone in ancient China. On May 20th, 1875, the signing of the convention on metric, opened up a worldwide to implement new era of modern international system of units of measurement. Based on quantum physics, research and application of modern measurement science and technology, provides more accurate modern metrology technical support for the development of human civilization. In 1999, the 21st international conference on measurement made a decision that since 2000, May 20 is for "World Metrology Day". China's propaganda theme of 2015 is in line with international theme for "measurement and light".

词汇详解：

1.Measurement  n. 测量法；度量制；测量；尺寸

2. metrology n. 度量衡学,度量衡

logy n. 技术，科技；技术应用

ide 世界范围的，遍及全球的；在世界各地；在全世界

5. propaganda n. 宣传；鼓吹

备考推荐：“碾压”六级指南