The idea that red means stopping and green means going has influenced our lives in more ways than just traffic signals(信号). We have been taught from a young age that the colour red means danger and green means it's okay to move forward. But why were those colours chosen for traffic lights in the first place? For something we have to look at every day, why couldn't they be prettier colours?
Well, it's important to know that before traffic lights for cars, there were traffic signals for trains. At first, railway companies used red to mean stopping, white to mean going, and green to mean warning. As you could imagine, trains ran into a few problems with white meaning going. For example, one train mistook a bright star for a white light and something unexpected happened. Because of that, railway companies finally used green to mean going and used yellow to mean warning. And it's been that way ever since.
Red has always been a colour that meant danger. This most likely started because it's the colour with the longest wavelength(波长). It can be seen somewhere farther than other colours.
But, believe it or not, yellow was once used to mean stopping. Back in the 1900s, some stop signs were yellow because it was too hard to see a red sign in a poorly lit(昏暗的) area. Finally, highly reflective materials(高反射材料) were developed and red stop signs were born. Since yellow can be seen well at all times of the day, school zones, some traffic signs, and school buses continue to be painted yellow.
So next time you're impatiently waiting at traffic lights, don't get so mad at them. They've certainly come a long way.
Have you ever looked up at the night sky and seen a blue moon? A blue moon doesn't happen at a fixed time and it is not a common sight. And most of the time, it isn't actually 1 . A blue moon takes place when there 2 two full moons in one month. Most months have 30 3 31 days, so sometimes a month will have two full moons.
In fact, the moon doesn't change the color to make 4 appear orange, red or blue. Instead, particles(微粒)in the Earth's atmosphere(大气层)lead to the 5 . For example, the moon suddenly appeared blue in Indonesia in 1883. That year, the volcano Krakatoa erupted(爆发). The ash(灰) 6 into the air, which stayed in the atmosphere for quite a while. It had the effect of making the moon appear blue.
In 2020, skywatchers were in for a treat when a blue moon lighted up the night sky 7 October 31, the first time that had happened in nearly 20 years.
The blue moon also has another 8 . Have you ever heard the phrase " once in a blue moon " ? When people say that, they mean 9 something uncommon happens—like a blue moon.
What other colors have you seen the moon 10 ? Carry on watching the night sky and you are sure to see a beautiful moon at some point.
In Chinese culture, the color red stands for many good things, for example, happiness. But writing names and letters with red pens is usually 1 . Why?
In ancient times, red was the symbol of power. Not everyone could write with red pens—only 2 . They would reply to officials' memorials(奏折)with red pens. The red ink was made of cinnabar(朱砂), so their replies were known as zhupi. Writing with red pens also had something to do with 3 . In ancient China, 4 some criminals were supposed to die, the records of their names were all written in red words. 5 on the tombstones(墓碑)were red as well. Therefore, the person was thought to be 6 if his or her name was written with red pens. Since red words carry bad meanings, people don't write 7 with red pens. If you write to friends or family members with red pens, it means you want to 8 with them. Nowadays, red pens are used to read and correct a piece of written or printed work. Teachers 9 students' homework with red pens. So do editors who need to correct mistakes in newspapers and magazines. But writing names or letters with red pens is 10 a bad idea to many people.