80 days around the world day 18 place local color,condition and custom

Greenwich meridian is mentioned in this article. Let's get to know it. Where is Greenwich? Greenwich is the site of the former Royal Greenwich Observatory in the southern suburb of London, England. It is the demarcation point of the Earth's primary meridian and the starting point of the world's calculation of time and longitude. It is famous for its maritime history, as the standard point of the original meridian, and Greenwich Time. It has a dangerous terrain, beautiful scenery, historical and local flavor, and is also London's eastern gateway to the Thames River. Greenwich Time Not only do astronomers use Greenwich Time, but the term often appears in newspapers and magazines. We know that there are local times everywhere. It will be complicated and inconvenient to record an important international event in local time. It will be easy to make mistakes in the future. Therefore, astronomers have proposed an acceptable and convenient recording method, which is based on the local time of Greenwich. Average solar time starting at midnight of the original meridian. Also known as Greenwich Peacetime or Greenwich Time. The difference between a place and the world in peacetime is equal to its geographic longitude. Before 1960, it was widely used as a basic time measurement system. Since the Earth's rotation rate was once considered uniform, the world was considered a uniform time before 1960. Because of the influence of the change of the earth's rotation speed, it is not a homogeneous time system. It has no theoretical relationship with atomic time or mechanical time. Only through observation can we compare them. Later world time was replaced by calendar time and atomic time successively, but it is still necessary in daily life, astronomical navigation, geodesy and space flight. At the same time, world time reflects the change of the earth's rotation rate, which is one of the parameters of the earth's rotation, and is still the basic information of astronomy and geophysics. 文中提到了Greenwich meridian（格林威治子午线），我们来了解一下。 ● 格林威治是哪里 格林威治是英国伦敦南郊原皇家格林尼治天文台所在地，地球本初子午线的标界处，世界计算时间和经度的起点。以其海事历史、作为本初子午线的标准点、以及格林尼治时间以其命名而闻名于世。这里地势险要，风景秀丽，兼具历史和地方风情，也是伦敦在泰晤士河的东方门户。 ● 格林威治时间 不光是天文学家使用格林威治时间，就是在新闻报刊上也经常出现这个名词。我们知道各地都有各地的地方时间。如果对国际上某一重大事情，用地方时间来记录，就会感到复杂不便．而且将来日子一长容易搞错。因此，天文学家就提出一个大家都能接受且又方便的记录方法，那就是以格林威治的地方时间为标准。 以本初子午线的平子夜起算的平太阳时。又称格林威治平时或格林尼治时间。各地的地方平时与世界时之差等于该地的地理经度。1960年以前曾作为基本时间计量系统被广泛应用。由于地球自转速率曾被认为是均匀的,因此在1960年以前,世界时被认为是一种均匀时。由于地球自转速度变化的影响，它不是一种均匀的时间系统，它与原子时或力学时都没有任何理论上的关系,只有通过观测才能对它们进行比较。 后来世界时先后被历书时和原子时所取代，但在日常生活、天文导航、大地测量和宇宙飞行等方面仍属必需；同时，世界时反映地球自转速率的变化，是地球自转参数之一，仍为天文学和地球物理学的基本资料。