Why are post boxes on UK streets red?

Why are the post boxes on the streets of Britain red?

From the color of post boxes in countries around the world the UK's post boxes are dominated by red, which is said to symbolize the 100,000th emergency to show the efficient law of the British postal service. Germany, France, Switzerland, Spain, Luxembourg and other Western European countries, most of the mailboxes are mainly in yellow, while the Eastern European countries, the mailboxes to the light blue for the majority of Japan's mailboxes were first black, in 1901, when the British wind to follow a portion of the mailboxes painted red, in 1908, the full unification of the red along with the present. Singapore until 1971 to their own style of mailboxes to replace the colonial period of the round British-style mailboxes, but also in 1992 to change the four sides of the country's name printed on the white mailboxes, a unique style. The United States with blue, express mail letter mailboxes with the colors of the national flag, that is, blue, white and red. China is in 49 years after the founding of the country, in the first national postal conference, because the green symbolizes peace, youth, lushness and prosperity finally decided to use green as a postal special logo. Third, from the material side of the elephant domestic mailboxes are mostly made of cast iron, iron plate or cement and other materials, foreign mailboxes and wooden, plastic and non-ferrous metal.

Why is the British post box red

and the principle of traffic lights is the same

red is easier to find

Why is the Chinese post box is green and Japan's post box is red

green for China's postal symbols, symbolizing peace, youth, lush and prosperous,

China's post offices, post boxes, postman's clothes and postal packages, postal vehicles are all in green.

Japan was the first country to learn about the French postal service after the Meiji Restoration.

Post boxes were black. （

But before the Anglo-Japanese alliance was concluded, Japan followed the British lead.

Why is the flag red.

The reasons why the Chinese flag is red are as follows:

The red color of the Chinese flag symbolizes the revolution, which was dyed with the blood of countless revolutionary martyrs;

Chinese red, is a symbol of light and power.

The red color of the flag symbolizes the revolution, remember before the Anti-Japanese War, the army under the leadership of *** was called the Red Army, which means the same thing

Why are flowers red?

Flowers are not all red, the most colorful kinds of flowers are white, yellow and red. There is a selective relationship between insects and flowers. For example, bees don't like yellow very much and prefer red and blue. The reason flowers have a variety of beautiful bright colors is due to the presence of pigments in the cellular fluid of the petals. There are some flowers that are red, blue or purple in color, and these flowers contain anthocyanins. Anthocyanin turns red when it encounters acid and blue when it encounters alkali. There are also flowers that are yellow, orange-yellow, or orange-red in color because they contain carotenoids in their petals. And since there are more than sixty kinds of carotenoids, the flowers that contain carotenoids are colorful. A white flower has no pigment whatsoever. It appears white and that is because the petals are filled with small air bubbles. Various flowers contain different concentrations of pigments, acids, and bases, and as conditions such as nutrients, water, and temperature change, the color of the flower can be darker or lighter, thicker or lighter, and even change color. There are many flowers that change color. Such as the red trumpet flower, it is red when it first opened, when it failed to become purple; apricot buds when it is red, after opening gradually become purple, and finally almost white. The Colorful Hibiscus is white when it first opens, then turns light red the next day, then dark red, and then purple when it fades. Primrose flowers are red at normal temperatures and turn white in a dark room at 30 degrees Celsius. In addition, the color change of some flowers is also related to the acidity or alkalinity of the soil, its own stage of growth, and so on. For example, the Patagonian flower has blue flowers in some soils and pink flowers in others. The sea cave flower, initially yellow, becomes white after fertilization.

Why is the flower so red? First of all, there is its material basis. Whether it is a red flower or a red leaf, their cellular fluid contains anthocyanin that is turned from glucose. When it is acidic, red, the more acidic, the more red. When it is alkaline, it appears blue, and the more alkaline it is, the bluish-black color it becomes, such as ink chrysanthemum and black peony are. And when it is neutral, it is purple. Ten thousand purples, red and blue, are all anthocyanins in different acid-base reaction shows.

Why are flowers so red? It also needs to be explained by the principles of physics. Sunlight through a prism or water droplet refraction, will be divided into red, orange, yellow, green, green, blue, blue, purple seven colors. These seven colors of light waves of different lengths, red wavelength, violet wave short. Acidic anthocyanins will reflect the long red light waves and send them to our eyes, which we then perceive as bright red flowers. Similarly, neutral anthocyanins reflect violet light waves, alkaline anthocyanins reflect blue light waves, and carotenoids, which have different components, reflect yellow or orange light waves. White flowers do not contain pigments, but the tissue contains air, which reflects all the light waves. Some petals, the surface of the more subtle and neatly arranged glass ball-like protrusions, looks like velvet, can be as strong as diamond to reflect the light, the color is more bright, such as some moon flowers is.

Why is the flower so red? There is also its physiological needs. Light waves of different lengths, containing different heat: red, orange, yellow light wavelengths, containing more heat; blue, violet light wave short, containing less heat. Flower tissues, especially petals, are generally more tender. In the wild, red, orange and yellow flowers are grown in places with strong sunlight, reflecting long light waves containing more heat, not causing burns, and have a protective effect. Blue flowers are grown under the trees, between the grass, reflecting short light waves, absorbing weak long light waves containing more heat, favorable to its physiological role. White flowers are also mostly shady plants, some open at night, reflecting all the light waves, another adaptive measure. There are few black flowers in nature, and only a few have occasional black spots, because black absorbs all the light waves, too much heat, and is easily damaged.

Why are flowers so red? Examined from an evolutionary point of view, it has a process of development. The flowers of gymnosperms are primitive forms, all with a greenish color, while the anthers and pollen are yellow. Inside the spectrum, neighboring the green, there are yellows, oranges and reds at the long-wave end, and greens, blues and purples at the short-wave end. We can say that the flower colors start with green and progress toward the long-wave end of the spectrum, from yellow to orange and finally red; toward the short-wave end of the spectrum, blue and violet. Red should be the latest flower color to appear, in the evolutionary journey to the peak, the most vivid, the most dazzling.

Why is rain red?

Fishy rain?

Why is fire red

It is not always red, it depends on the composition of the burning substance.

When different substances burn, the flames have different colors.

The color of a fire is determined by the substance that is burning:

yellow if it contains sodium;

blue if it contains copper;

red if it contains soot (such as wax).

Fire is actually a type of radiation. It's similar to light. Light is a photon, and fire is a "plasma". Photons have no mass, and fire has no mass. The frequency of this radiation to a certain range will be super-generated heat sensation, in another range you will see it. And in this visual range, different frequencies produce different colors (colors are artificial sensations, the universe does not have the property of "color", only different frequencies of radiation. It is a subjective sense that humans have evolved to adapt to their survival). Since the combustion of different elements produces different radiation frequencies, naturally there will be a different flame color response. By the way, to see the flame color reaction can not be seen directly with the naked eye, to be separated from the purple nickel-cobalt mirror to eliminate the effect of the flame of the ignition material.

In fact, the fire has a color and different fire color is different. This is because the amount of carbon particles called "soot" mixed in the flame causes the color to vary. The flame of a candle is red because there is a lot of soot mixed in, and it looks flickering when heated at high temperatures. Gas fires, like gas stoves, contain almost no soot, and burn well when a lot of air enters, so they look blue. In terms of temperature, the flame of a candle is about 1,000 degrees, while the temperature of a gas stove is as high as about 1,700 degrees. The temperature of a blue-white flame, which you can't see clearly, is often much higher than the red flame of a bonfire, etc., so please keep this in mind.