Is it dangerous for people to touch the lightning rod ground wire in a thunderstorm?

Lightning is a strong discharge phenomenon between clouds, between clouds and the ground, or between different parts of a cloud (generally occurring in cumulonimbus clouds).

Cumulonimbus clouds usually generate charges, with negative charges at the bottom and positive charges at the top, and also generate positive charges on the ground, which follow the clouds. Positive and negative charges attract each other, but air is not a good conductor. Positive charges rush to the top of trees, hills, tall buildings and even human bodies in an attempt to meet clouds with negative charges; The negatively charged dendritic antenna extends downward, and the more it extends downward, the closer it gets to the ground. Finally, the positive and negative charges finally overcome the air barrier and connect. A huge current rushes from the ground to the clouds along a conductive airway, producing a bright flash. The length of a lightning bolt may be only a few hundred meters (the shortest is 1 meters), but the longest is several kilometers. The temperature of lightning varies from 17, degrees Celsius to 28, degrees Celsius, which is 3~5 times the surface temperature of the sun. The extreme heat of lightning caused the air along the way to expand violently. Air moves quickly, so it forms waves and makes sounds. When lightning is close, what you hear is a sharp crack; If the distance is far, what you hear is rumbling. You can start the stopwatch after you see the lightning, press it to stop when you hear the thunder, and then divide the number of seconds by 3 to get a rough idea of how many kilometers the lightning is from you.

[ Edit this paragraph] The process of lightning

If we put a high voltage between two electrodes and bring them closer slowly. When two electrodes are close to a certain distance, an electric spark will appear between them, which is called "arc discharge".

Lightning generated by thunderstorm clouds is very similar to the arc discharge mentioned above, except that lightning is fleeting, but sparks 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 the local area can reach as high as 1 thousand volts/cm. 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.

The process of a lightning bolt seen by naked eyes is very complicated. When the thunderstorm cloud moves somewhere, the middle and lower part of the cloud is a strong negative charge center, and the underlying surface opposite the cloud bottom becomes a positive charge center, forming a strong electric field between the cloud bottom and the ground. In the case of more and more charges and stronger electric field, a section of air column with strong ionization of the atmosphere 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 pilot of each step is a dim light beam with a diameter of about 5 meters, a length of 5 meters and a current of about 1 amps. It extends to the ground step by step at an average high speed of about 15, meters/second. When it is about 5-5 meters away from the ground, the ground suddenly strikes back. The channel for striking back is an ionization channel opened from the ground to the bottom of the cloud along the above-mentioned step pilot. The return stroke galloped from the ground to the bottom of the cloud at a higher speed of 5, km/s, emitting an extremely bright light beam, which lasted for 4 microseconds, and the current passed through exceeded 1, amps, which was the first lightning stroke. 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, which was called the straight-channeling pilot. When it was about 5-5 meters away from the ground, the ground hit back again and formed a bright light beam, which was the second lightning strike. Then, like the second time, the third and fourth lightning strikes were produced. Usually, 3-4 lightning strokes constitute a lightning process. A lightning process lasts about .25 seconds. In this short time, a huge amount of electric energy will be released on the narrow lightning channel, thus forming a strong explosion, generating shock waves, and then forming sound waves to spread around. This is thunder or "thunder".

[ Edit this paragraph] Chemical reaction during lightning

When lightning strikes, the chemical bonding of oxygen in the atmosphere can be changed to generate ozone; At the same time, oxygen and nitrogen can be combined to produce nitric oxide, which is an important form of natural nitrogen fixation.

The temperature of lightning varies from 17, degrees Celsius to 28, degrees Celsius, which is 3-5 times the surface temperature of the sun. The extreme heat of lightning caused the air along the way to expand violently. Air moves quickly, so it forms waves and makes sounds.

[ Edit this paragraph] The structure of lightning

It is the linear lightning that has been studied in detail, so we will take it as an example to tell the structure of lightning. Lightning is a pulsed discharge phenomenon in the atmosphere. A lightning bolt consists of multiple discharge pulses, and the interval between these pulses is very short, only a few hundredths of a second. One pulse after another, the following pulse travels along the path of the first pulse. Now it has been clearly studied that each discharge pulse consists of a "pilot" and a "counterattack". Before the first discharge pulse bursts, there is a preparation stage-"step-leading" discharge process: under the impetus of strong electric field, the free charge in the cloud quickly moves to the ground. During the movement, electrons collide with air molecules, causing the air to ionize slightly and emit light. The leader of the first discharge pulse propagates downward step by step, like a glowing tongue. At first, the smooth tongue was only a dozen meters long. After a few thousandths of a second or even shorter, the smooth tongue disappeared. Then, on the same passage, a longer light tongue (about 3 meters long) appeared, and it disappeared in a blink of an eye; Then a longer smooth tongue appeared ... The smooth tongue approached the ground step by step in a "nibbling" way. After many times of discharge-disappearance, the smooth tongue finally reached the ground. Because the leader of this first discharge pulse propagates from the cloud to the ground step by step, it is called "step leader". On the passage of the light tongue, the air has been strongly ionized, and its conductivity has been greatly increased. The process of continuous ionization of air only takes place in a very narrow channel, so the current intensity is very high.

when the first pilot, the ladder pilot, reaches the ground, a large amount of charge flows from the ground to the cloud through the highly ionized air channel immediately. This current is so strong that the air passage is blazing, and a winding and slender light column appears. This stage is called "counterattack" stage, also called "main discharge" stage. The ladder pilot plus the first counterattack constitutes the whole process of the first pulse discharge, which lasts only one hundredth of a second.

after the first pulse discharge process, the second pulse discharge process occurs only after a very short time (4 seconds). The second pulse also starts from the pilot and ends at the return stroke. However, after the first pulse discharge, "the ice has been broken and the route has been opened", so the pilot of the second pulse will not go down step by step, but directly reach the ground from the cloud. This kind of pilot is called "direct channeling pilot". After the direct-channeling pilot reaches the ground, it takes about a few thousandths of a second to strike back and end the second pulse discharge process. Then the third and fourth ... Straight lead and return stroke, complete multiple pulse discharge process. Because each pulse discharge consumes a large amount of accumulated charge in the thunderstorm cloud, the main discharge process in the future becomes weaker and weaker, and the pulse discharge can not be stopped until the charge reserve in the thunderstorm cloud is exhausted, thus ending a lightning process.

[ Edit this paragraph] Lightning frequency

As you read this article, there are about 1,8 lightning exchanges going on around the world. They emit about 6 flashes of lightning every second, 1 of which hit the earth.

lightning can change a part of nitrogen in the air into nitrogen compounds, which can be washed down to the ground by rain. In a year, every hectare of land on the earth can get a few kilograms of this free fertilizer from high altitude.

Kampala, the capital of Uganda, and Java, Indonesia, are the most vulnerable places to lightning. According to statistics, there were 3 days of lightning in Java one year. The most violent lightning in history was the one that struck a small house near Umtari in rural Zimbabwe in 1975, when 21 people were killed.

[ Edit this paragraph] Type

The most common lightning is linear lightning, which is some very bright white, pink or light blue lines. It looks like a river with many branches on the map, and it looks like a winding tree hanging in the sky. The "temper" of linear lightning has long been understood by scientists. The whole process of linear lightning can be completely recorded with a continuous high-speed camera, and the simulation experiment can be successfully carried out in the laboratory.

besides linear lightning, there are also spherical lightning and chain lightning, both of which are relatively rare.

most spherical lightning will appear in the bad weather of strong thunderstorm. After the linear lightning, a fireball suddenly appeared in the sky. The fireball floated in the sky along the winding path, and sometimes it may stop and hang in the air. This kind of fireball likes to drill holes, and sometimes it rushes into the house through chimneys, windows and cracks in the door, and then slips out of the house.

compared with spherical lightning, the trace of chain lightning is more difficult to find. At present, people only know that it also appears after linear lightning, and it appears on the same path as linear lightning. It hangs in the sky like a row of glowing hammer balls, and slowly slides on the cloud curtain like a dotted line against the cloud.

lightning has a great influence on human activities, especially buildings and power transmission lines, which may cause serious losses. The most practical way to protect buildings from lightning attack is to install lightning arrester (lightning rod) to lead the electricity in lightning to the pre-selected safety area on the ground.

linear lightning, ribbon lightning, flake lightning, rocket lightning, ball lightning and beaded lightning can all do harm to human beings, so you can't go out.

what we often see is linear lightning, which is like a branch with many branches and twists and turns. Banded lightning is similar to linear lightning, but the bright channel is wider, which looks like a bright band. Spherical lightning usually occurs after linear lightning. It is a fireball with a diameter of about 2 cm, emitting red or orange light and occasionally emitting beautiful green, which usually lasts for a few seconds. Fireballs drift in the air with the wind, like to slide along the edge of objects, and can enter the room through gaps. When they are about to disappear, there will be a deafening explosion.

Among all kinds of lightning, the most rare is the beaded lightning, which has never been seen by most people in the world. This kind of lightning is shaped like a string of glowing pearls extending from the cloud to the ground (on May 8, 1916, a lightning bolt with beads occurred over a bell tower in Dresden, Germany, and was recorded. People first saw a linear lightning coming down from the cloud; Later, people saw that the channel of linear lightning widened and the color changed from white to yellow. Soon the lightning channel gradually darkened, but the whole channel did not darken evenly at the same time, so the bright channel became a string of pearl-like bright spots hanging from the clouds, which was beautiful and moving. It was estimated that there were 32 bright beads, each with a diameter of 5 meters. After that, the bright beads gradually shrink and become round in shape; Finally, the brightness gets darker and darker, and then it goes out completely. ) Because there are very few chances for the lightning to appear and last for a very short time, people have little research on the causes of this lightning, and the reasons for its formation are still unclear.

[ Edit this paragraph] Types of lightning

Linear lightning

The difference between linear lightning and other lightning is that it has a particularly large current intensity, which can reach tens of thousands of amperes on average and 2, amperes in a few cases. Such a large current intensity can destroy and shake trees and sometimes hurt people. When it touches buildings, it often causes "lightning strikes" and fires. Linear lightning is mostly the discharge of clouds to the ground.

Flake lightning

Flake lightning is also a common lightning shape. It looks as if there is a flash of light on the cloud. This kind of lightning may be the back light of the invisible spark discharge behind the cloud, or the diffused light caused by the lightning in the cloud being blocked by the cloud droplets, or it may be a clustered or flickering independent discharge phenomenon appearing in the upper part of the cloud.

ball lightning

although ball lightning is a very rare lightning shape, it is the most eye-catching. It's like a fireball, and sometimes it's like a glowing "hydrangea" chrysanthemum. It is about the size of a human head, and occasionally it has a diameter of several meters or even dozens of meters. Spherical lightning sometimes swims slowly in the air, and sometimes it hangs in the air completely motionless. Sometimes it emits white light, and sometimes it emits pink light like a meteor. Ball lightning "likes" to drill holes. Sometimes, it can get into the house through chimneys, windows and cracks, turn around the house and then slip away. Spherical lightning sometimes makes a hissing sound, and then disappears with a muffled sound; Sometimes it only makes a faint crack and disappears unconsciously. After the ball lightning disappears, some smelly gas smoke may be left in the air, which is a bit like ozone. The life history of ball lightning is not long, about a few seconds to a few minutes.

banded lightning

banded lightning is composed of several consecutive discharges, and between each lightning, the lightning path moves due to the influence of the wind, which makes each individual lightning close to each other to form a banded lightning. The width of the belt is about 1 meters. If this kind of lightning hits a house, it can immediately cause a large area to burn.

beaded lightning

beaded lightning looks like a connecting line of luminous points sliding on the cloud curtain or passing through the clouds and throwing it to the ground, and it also looks like a shining pearl necklace. Some people think that bead lightning seems to be a transitional form from linear lightning to spherical lightning. Beaded lightning often follows linear lightning with almost no time interval.

rocket lightning

rocket lightning is much slower than other kinds of lightning, and it takes L ~ 1.5 seconds to discharge completely. Its activities can be easily tracked and observed with the naked eye.

black lightning

Generally, lightning is mostly blue, red or white, but sometimes there are black lightning. Due to the action of sunlight, cloud electric field and some physical and chemical factors in the atmosphere, a kind of particles with very active chemical properties will be produced in the sky. Under the action of electromagnetic field, these particles gather together to form many spheres. This ball will not emit energy, but it can exist for a long time. It has no light and is opaque, so it can only be observed during the day.

[ Edit this paragraph] Super lightning

Super lightning refers to those rare lightning whose power is more than 1 times that of ordinary lightning. The electricity generated by ordinary lightning is about 1 billion watts, while the electricity generated by super lightning is at least 1 billion watts, and may even reach trillions to 1 trillion watts.

Clock Island in Newfoundland was obviously hit by a super lightning in 1978, and even houses 13 kilometers away were rattled, and blue flames were sprayed from the doors and windows of the whole village.

[ edit this paragraph] submarine lightning

There are also lightning on the seabed, which was discovered by scientists from the former Soviet Union in Japan. Sensitive electric field instruments show that the frequency of submarine discharge is the same as that of lightning in the atmosphere, which puzzles scientists. Because according to the laws of hydrogeology, deep seawater has good conductivity, so it should be out of reach with Lei Gong Dian Mu.

after repeated experiments, scientists finally believe that the charge source actually comes from the air near the coast on land, and then passes through rocks and goes deep into the seabed. However, with the increase of conduction distance, the amount of electricity is gradually