Our planet行星 ，the Earth, is the third planet from the sun.
It is a beautiful, rotating 旋转的sphere球，球体.
The side facing the Sun is in daylight在白天.
The side facing away from 远离the sun is in darkness黑暗.
For example, when it’s daytime 白天in the US, it’s nighttime 夜晚in China.
In fact, there’s a 12-hour time difference 时间差between Boston and Shanghai.
两个名词之间加一个-为形容词
When it’s midnight in Shanghai, it’s noon in Boston.
The earth rotates 旋转，围绕一个固定的点旋转from west to east.自西向东
from...to...从哪里到哪里
To know which direction is east or west, watch the Sun.
The Sun travels through 经过the sky from east to west.
The Sun comes up 升起in the east and goes down落下 in the west.
rise上升，in the west 在西方。
Again, this is because the Earth rotates.
It takes 24 hours for the earth to make a complete完整的 rotation旋转的名词.
It takes ...for...to花费多少时间做某事
And that is the length 长度of one day.
Because of the Earth’s rotation地球自转, the earth is divided into 被分成time zones时区.
Some countries, such as 例如the US, have several time zones.
When it’s 10 am in New York, it’s 7 am in San Francisco.
Europe and the US are separated by 被...分开several time zones.
When it’s 5:00 pm in Paris, it’s 11:00 am in Boston.
So there's a 6-hour difference 六小时时差between Paris and Boston.
One large country, China, has just one time zone for the whole 全部的，整个的country.
As a result, at the same time在同一时间, some parts of the country can be dark and other parts can be light.
As 随着，伴随，当...时you travel around 周游the earth, the time changes.
The time of day depends on 取决于your location地点，位置 on the planet.
When you travel east or west从...到..., you may cross several time zones.
For example, if you travel from Beijing to Los Angeles, you cross 8 time zones.
That means, when it’s noon on Sunday in China, it’s 8:00 pm on Saturday in Los Angeles.
For travelers, this means it can be very difficult to 很难做某事sleep after a long flight. 长途飞行
The clock may say说明，指示 8"00 pm, but for your body it’s noon.
This is called被叫做，被称为 jet lag时差.
It depends on how far east or west you travel.
Crossing several time zones causes jet lag.
网友评论