The sun and the moon [why the sun and the moon sometimes have rings and so on. ]

Why do the sun and the moon sometimes have halos? The sky above the earth is covered with faint clouds. When the sun or the moon appears from the clouds, it sometimes produces a circle or even several circles around them. Meteorology calls this halo halo halo. Solar halo is a light phenomenon formed by refraction when sunlight passes through ice crystals in clouds, which surrounds the sun in a ring shape and is colored. The halo around the sun is called solar halo, and the halo around the moon is called lunar halo. Solar halos are mostly colored, just like rainbows, but the order of seven colors is just the opposite of rainbows. From the inside out are red, orange, yellow, green, blue, indigo and purple. The color of the lunar halo is mostly white. The appearance of halo often indicates the coming of stormy weather, because halo is often produced when warm and humid air meets cold air. Hot air containing a lot of water vapor rose above the cold air and climbed to a height of more than 6000 meters. Because the temperature there dropped to about-20℃, rain formed.

Why are sunspots darker?

Wang Yulu

Sunspots are the most common phenomenon of solar surface activity. Through ordinary optical telescopes, we can see that there are many black spots on the surface of the sun. These are sunspots. Sunspots are produced by the huge vortex airflow on the surface of the sun, which is an important symbol of the activity of the photosphere on the surface of the sun. Sunspots are darker because their temperature is lower than that of the photosphere. Usually, the temperature of the photosphere is around 6000℃, and the temperature of the sunspot is lower than that of the photosphere 1000℃ ~ 2000℃, so the sunspot is dark.

What is a nebula?

Chang xingheng

Nebula is a cloud-like celestial body composed of gas and dust, and its main component is hydrogen. With a few exceptions, most nebulae can only be seen through telescopes. It is the most beautiful celestial body known to people, because its shape is irregular and there is no clear boundary. According to their shapes, nebulae can be divided into planetary nebulae, diffuse nebulae and supernova remnants. People sometimes refer to galaxies, various clusters and various types of dust and gas in space as nebulae. Compared with stars, nebulae have the characteristics of large mass, large volume and low density. The mass of an ordinary nebula is at least equivalent to thousands of suns.

Why are there more stars in summer than in winter?

zhenhua li

There are many stars in the whole galaxy, which are roughly elliptical in distribution. In summer, the earth moves between the center of the Milky Way and the sun. The widest, densest and brightest part of the Milky Way is the sky above us at night. In other seasons, the densest and brightest part of the star sometimes appears during the day, sometimes at dusk and sometimes in the morning, so it is not easy to see. Especially in winter, the earth runs between the edge of the Milky Way and the sun, and the central part of the Milky Way can only be seen during the day. But because of the strong sunshine during the day, people can't see the stars. At night, people see the thin edge of the Milky Way, where there are few stars. So people see more stars in summer nights than in winter nights.

Why is the lake salty?

spark

There are many large and small lakes on the earth. Most of these lakes are freshwater lakes, but some are saltwater lakes. The water in most lakes flows in from rivers. In the process of flowing, the river dissolved some salts in the soil and rocks passing through the area. River water flows into the lake, bringing salt into the lake, thus forming a salty lake. If the lake can continue to flow out from another exit, the salt will also flow out. For example, the Great Lakes in North America and Dongting Lake in China will eventually flow into the sea, so they are all freshwater lakes.

But some lakes have inconvenient drainage and dry climate. Evaporation consumes a lot of water, so the salt will accumulate more and more, and the lake will become more and more salty and become a salty lake. Some people think that in geological times, salt lakes were originally part of the sea. After the seawater receded, some seawater was left in low-lying areas to become lakes, so the lakes retained a lot of salt.

Why does pollen make people sick?

Tian Xiaolei

Some people get very strange diseases at a fixed time every spring, from the light ones with red pimples, tears and runny nose to the heavy ones who breathe. But after a while, it will be fine without taking medicine or injections. These "germs" that joke with humans are actually pollen.

There are pistils and stamens in the petals, and there are many tiny pollen at the top of the pistil. When the flowers bloom, insects such as bees and butterflies will fly to pollinate, and the wind will also help the flowers pollinate. But some pollen is blown to people's skin by the wind, which will affect people who are allergic to pollen. Through the joint research of botanists and medical scientists, it is found that some pollen contains a special kind of protein, and this kind of protein can cause allergic reactions in some people.