Why is there lightning?

Question 1: Why is lightning a common phenomenon? In summer, whenever the sky is overcast, thunder rumbles, and lightning flashes and thunders. But if I ask you, "How is lightning formed?" It's hard to answer. Before18th century, in ancient China, people thought that thunder and lightning were made by Lei Gong and Dian Mu. Westerners believe that lightning is the result of God's anger, and whoever does something bad will be punished by God with lightning. Therefore, people are always afraid of lightning. Some people of insight who don't believe in God try to explain the cause of lightning. American scientist Franklin was the first person to explore the mystery of lightning. He used kite experiments to prove that the electricity in the sky is the same as that on the ground. "Lightning is an electric spark". But so far, scientists still don't fully understand how lightning is produced. Why do rolling clouds carry a lot of positive and negative charges? The answer to this question is much more difficult than flying a kite in a thunderstorm and bringing lightning to the ground. In order to solve the mystery of lightning, scientists put balloons into lightning clouds for detection; Send planes around the thunderstorm, even through the thunderstorm; Use rockets to trigger lightning, and so on. But through these activities, the understanding of lightning is still very little. Scientists have found that in most cases, lightning can only be generated when the thickness of lightning clouds exceeds 3 kilometers. Clouds are usually positively charged at the top and negatively charged at the bottom. When the electric field between positive and negative charges is strong enough, it will break through the air and produce lightning. Generally speaking, the thicker the clouds, the stronger the lightning. However, what drives the separation of positive and negative charges? Many scientists think that rainfall may be a reason. They explained that falling raindrops or ice balls carry negative charges, while positively charged particles such as small dust particles and ice crystals gather in the upper part of the cloud, resulting in the upper part of the cloud being positively charged and the lower part being negatively charged. An electric field sufficient to cause lightning is generated. But this explanation is inevitably far-fetched, because lightning often occurs before rainfall, not all after or during rainfall. In addition, it cannot explain why lightning occurs when a volcano erupts. Then, another point of view was put forward: Thundurus charges are generated outside the clouds, and excessive positive charges in the atmosphere are absorbed into the upper clouds, thus attracting negative charges in the atmosphere above the clouds, and these negative charges are attached to cloud particles trapped by airflow. The separation of positive and negative charges is the result of these violent air currents moving up and down. However, this assumption has not been confirmed. It seems that it is not so easy to explain this natural phenomenon clearly. It is necessary to further understand the internal process of Thundurus in order to satisfactorily explain the lightning phenomenon. But even if this problem is solved, there are other problems that need to be clarified. For example, why does lightning always zigzag? (Of course, there is also a kind of spherical lightning, which is also a "mystery".) Why does lightning happen more often on land than on water? Why does lightning always happen in summer, not in winter? Why does lightning usually destroy tall objects, but not always?

Question 2: Why does lightning in the sky have a cause?

The atmospheric electric field in thunderstorm is obviously different from that in sunny days. The reason for this difference is the accumulation of charges in thunderstorm clouds, which forms the polarity of thunderstorm clouds, produces lightning and causes great changes in atmospheric electric field. But how does thunderstorm cloud get electricity? That is to say, what are the physical processes in the thunderstorm cloud that cause it to be charged? Why can so many charges accumulate in thunderstorm clouds and form a regular distribution? This section will answer these questions. As we said before, the macroscopic process of thunderstorm cloud formation and the microphysical process in thunderstorm cloud are closely related to cloud electrification. Scientists have made a lot of observations and experiments on the charging mechanism of thunderstorm clouds and the regular distribution of charges, accumulated a lot of data and put forward various explanations, some of which are still controversial. To sum up, the power-on mechanism of the cloud mainly includes the following types:

A. the hypothesis of "ion flow" in the initial stage of convective clouds

There are always a lot of positive ions and negative ions in the atmosphere. On the water droplets in the cloud, the charge distribution is uneven: the outermost molecules are negatively charged, the inner layer is positively charged, and the potential difference between the inner layer and the outer layer is about 0.25 volts. In order to balance this potential difference, water droplets must "preferentially" absorb negative ions in the atmosphere, which makes water droplets gradually negatively charged. When the convection begins, the lighter positive ions are gradually carried to the upper part of the cloud by the updraft; However, the cloud droplets with negative charges remain in the lower part because they are relatively heavy, resulting in the separation of positive and negative charges.

B. Charge accumulation in cold clouds

When the convection reaches a certain stage and the cloud reaches a height above 0℃, there are supercooled water droplets, graupel particles and ice crystals in the cloud. This cloud, which is composed of water vapor condensate with different phases and the temperature is lower than 0℃, is called Leng Yun. Leng Yun's charge formation and accumulation process is as follows:

A. Friction and collision charging between ice crystals and graupel particles

Polonium particles are composed of frozen water droplets, which are white or milky white and have a brittle structure. Because supercooled water droplets often collide with it and release latent heat, its temperature is generally higher than that of ice crystals. Ice crystals contain a certain amount of free ions (OH- or OH+), and the number of ions increases with the increase of temperature. Because of the temperature difference between the contact part of graupel and the ice crystal, the free ions at the high temperature end must be more than those at the low temperature end, so the ions must migrate from the high temperature end to the low temperature end. In the process of ion migration, the lighter positively charged hydrogen ions are faster, while the heavier negatively charged hydroxide ions (OH-) are slower. Therefore, in a certain period of time, the phenomenon of excess H+ ions at the cold end appeared, which led to negative polarization at the high temperature and positive polarization at the low temperature. When ice crystals come into contact with graupel particles and separate, the graupel particles with higher temperature are negatively charged, while the ice crystals with lower temperature are positively charged. Under the action of gravity and updraft, the lighter positively charged ice crystals are concentrated in the upper part of the cloud, while the heavier negatively charged haze particles stay in the lower part of the cloud, resulting in the Leng Yun being positively charged in the upper part and negatively charged in the lower part.

B, supercooled water droplets collide with graupel particles to freeze and generate electricity.

There are many water droplets in the cloud that will not freeze when the temperature is below 0℃. This kind of water drop is called supercooled water drop. Supercooled water droplets are unstable. Just shake it a little and it will freeze into ice particles at once. When supercooled water droplets collide with graupel particles, they will freeze immediately, which is called collision freezing. When the collision occurs, the outside of the supercooled water droplets immediately freezes into an ice shell, but the inside of the supercooled water droplets temporarily remains liquid. Because the latent heat released by the external freezing is transferred to the inside, the temperature of the liquid supercooled water inside is higher than that of the external ice shell. The temperature difference makes the frozen supercooled water droplets positively charged outside and negatively charged inside. When the inside also freezes, the cloud drops expand and split, and the outer skin breaks into many small positively charged ice chips, which fly to the upper part of the cloud with the airflow. The core of the negatively charged frozen drops adheres to the heavier graupel particles, so that the graupel particles are negatively charged and stay in the middle and lower part of the cloud.

C. Water drops are charged because they contain thin salt.

In addition to the above two electrification mechanisms in Leng Yun, it has been suggested that the electrification mechanism is due to the thin salt contained in water droplets in the atmosphere. When the cloud drops freeze, the crystal lattice of ice can accommodate negative chloride ions (Cl-) but repel positive sodium ions (Na+). Therefore, the frozen part of water droplets is negatively charged, and the unfrozen outer surface is positively charged (water droplets are frozen from the inside out). In the process of falling, the graupel particles frozen by water drops fall off from the surface water before freezing, forming many small clouds with positive charges, while the frozen core is negatively charged. Due to the separation of gravity and airflow, positively charged water droplets are carried to the upper part of the cloud, while negatively charged polonium particles stay in the middle and lower part of the cloud.

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Question 3: Why is there lightning in the sky? Wind is the horizontal movement of air, which is produced by air pressure. Air pressure is determined by the temperature and height of each region! The temperature is determined by the difference between the solar radiation received in this area and the reflection back to the atmosphere! Rain is brought by water vapor in clouds, which is a mixture of atmospheric dust and water vapor. When water vapor exceeds saturation, precipitation will form! When the cloud starts to move under the action of wind formed by air pressure, it is easy to generate static electricity in friction, which is divided into two ends, one with positive charge and the other with negative charge. When there are enough electrons, it is easy to discharge. This is lightning! In the process of discharging, there will be a violent explosion, which is lightning! The relationship among the sun, the earth and the moon is interactive. In elementary school, I learned that "the sun is big and the earth is small, and the earth revolves around the sun;" The earth is big and the moon is small, and the moon goes around the earth. " Of course, the moon goes around the sun, too! It is generally believed that the gravity of the moon and the sun has produced tidal changes, in which the moon is the main force. It is said that earthquakes are also related to the moon! There are even a group of Americans who have the crazy idea of blowing the moon into the Pacific Ocean with a nuclear bomb!

Question 4: Why is there lightning? Why does it thunder? The cause of lightning formation

In thunderstorm clouds, due to the friction and decomposition of water molecules, the airflow will generate static electricity. There are two kinds of electricity. One is the positive charge of positively charged particles and the other is the negative charge of negatively charged particles. Positive and negative charges attract each other, just like magnets. The positive charge is at the top of the cloud, and the negative charge attracts the positive charge on the ground at the bottom of the cloud. The air between the cloud and the ground is an insulator. It will prevent the current with bipolar charge from passing through. When the charge in the thunderstorm cloud and the charge on the ground become strong enough, these two parts of charge will break through the air barrier and contact to form strong current, positive charge and negative charge contact. When these opposite charges meet, neutralization (discharge) will occur. Strong charge neutralization will release a lot of light and heat, and these released light will form lightning.

Most lightning strikes twice in a row. The first time it was called lead flash, it was an invisible air called lead that went down to the place near the ground. This charged air is like a wire, which establishes a guide for the second current. At the moment when the conductor is close to the ground, a tie-back current jumps up along this conduit, and the flash produced by this tie-back is the lightning we can usually see.

The cause of thunder

Now we know that when the charge is neutralized, it will release a lot of light and heat, and instantly release a lot of heat, heating the surrounding air to a high temperature of 30,000 degrees Celsius. When a powerful current passes through the air, the air along the way will suddenly expand, and at the same time, it will push the surrounding air and make the air vibrate violently. The sound produced at this time is [thunder]. Don't forget to tell the baby that lightning happens at the same time, because the speed of light is much faster than the speed of sound, so we always see lightning first.

If lightning comes near, we will hear deafening thunder. If lightning falls in the distance, we will hear an inaudible thunder. This is because sound waves are refracted by the atmosphere and reflected by ground objects.

Necessary conditions for lightning to occur

1. The air should be very humid;

2. The cloud must be big;

Lightning is generally not easy to occur in arid areas.

The process of lightning

If we apply a high voltage between two electrodes, they will be closer together. When two electrodes are close to a certain distance, there will be an electric spark between them, which is called "arc discharge".

The lightning generated by thunderstorm clouds is very similar to the arc discharge mentioned above, except that lightning is fleeting, but the spark between electrodes can exist for a long time. Because the high voltage between the two electrodes can be artificially maintained for a long time, it is difficult to replenish the charge in the thunderstorm cloud immediately after discharge. When the accumulated charge reaches a certain amount, a strong electric field is formed between different parts of the cloud or between the cloud and the ground. The average electric field intensity can reach several thousand volts/cm, and it can be as high as 10000 volts/cm in some areas. Such a strong electric field is enough to break through the atmosphere inside and outside the cloud, so dazzling flashes are excited between the cloud and the ground or between different parts of the cloud and between different clouds. This is what people often say about lightning.

Seeing lightning with the naked eye is very complicated. When the thunderstorm cloud moves somewhere, the middle and lower part of the cloud is the center of strong negative charge, and the underlying surface opposite the cloud bottom becomes the center of positive charge, forming a strong electric field between the cloud bottom and the ground. With more and more charges and stronger electric field, a section of air column with strong atmospheric ionization first appears at the bottom of the cloud, which is called cascade leader. This ionized gas column extends to the ground step by step. The leader of each step is a dim light beam with a diameter of about 5 meters, a length of 50 meters and a current of about 100 ampere. It extends to the ground step by step at an average high speed of about 150000 m/s. When it was about 5-50 meters from the ground, the ground suddenly counterattacked. The channel of counterattack is from the ground to the bottom of the cloud, along. The return stroke galloped from the ground to the bottom of the cloud at a higher speed of 50,000 km/s, emitting an extremely bright beam, which lasted for 40 microseconds, and the current passed through exceeded 10000 amps. This was the first lightning strike. A few seconds later, a dim light beam from the cloud, carrying huge current, flew to the ground along the path of the first lightning strike. This is called a direct psychic pilot. When it is about 5-50 meters away from the ground, the ground strikes back again and then forms a bright beam, which is the second lightning strike. Then, like the second time, there were the third and fourth lightning strikes. Usually 3-4 lightning strikes constitute a lightning process. A lightning process lasted about 0.25 seconds. & gt

Question 5: Why does lightning happen? Lightning is an electrical phenomenon that occurs in thunderstorm clouds, and only thunderstorm clouds can cause lightning. Therefore, the existence of thunderstorm clouds has become a prerequisite for lightning. In most cases, thunderstorm clouds are accompanied by precipitation and lightning. Thunderstorm clouds are called cumulonimbus clouds in meteorology. Only mature cumulonimbus clouds that stretch very high have lightning phenomenon. In mature cumulonimbus clouds, positive charges are concentrated in the upper part of the cloud, and negative charges are concentrated in the middle and lower part of the cloud, but at the bottom of the cloud, there is a small area with positive charges, where the updraft has a local maximum. The generation and distribution of charges in clouds are related to the objective process of thunderstorm cloud formation and the microphysical process in clouds. In different parts of the thunderstorm cloud, two kinds of charges with different polarities were collected. When the collected charge reaches a certain amount, a strong electric field is formed between different parts of the cloud or between the cloud and the ground. The average intensity of this electric field can reach several thousand volts/cm, and it can be as high as 1000 volts/cm in some areas. Such a strong electric field is enough to break through the atmosphere inside and outside the cloud, so between the cloud and the ground, or between different parts of the cloud, between different clouds, a dazzling flash is excited. This is lightning. People often see lightning in the form of linear lightning or dendritic lightning, which has dazzling light. The whole lightning is like a branch, which hangs horizontally or downwards, and it is like a river with many tributaries on the map. Linear lightning is mostly clouds discharging to the ground, which is the most harmful lightning to human beings.

Question 6: Why is there lightning? Lightning occurs when two clouds collide with charges of the same nature. That is, the same charges repel each other.

Question 7: Why is there lightning called thunderstorm in meteorology? Cumulonimbus clouds that form thunderstorms are tall and dense, and there are often a lot of ice crystals at the top of the clouds. The vertical thermal convection in the cloud develops vigorously, and the phenomenon of charged discharge (lightning) occurs constantly. This mechanism is very complicated. In the process of discharge, the air temperature on the lightning channel rises sharply, and the water droplets in the air vaporize and expand, and even ionize. In a short time, the air expands rapidly, producing shock waves, thus producing strong thunder (thunder). Because the charge in the cloud causes the induced charge on the ground, a "flash track" is formed between the bottom of the cloud and the ground. When charge accumulates and other conditions (such as prominent buildings, isolated chimneys and people on the open ground, etc.). ) available, lightning strikes the ground, that is, lightning strikes, causing lightning disasters.

Question 8: Why is there lightning? It is normal that lightning is caused by the impact of clouds.