With a “boom”, the thunder and lightning fell on the head, hitting the person who was sheltering from the rain under the tree, and then ignited the pile of fallen leaves, and the fire was raging… As a common weather phenomenon, thunder and lightning will bring us accidents from time to time. and loss, how to solve this problem? Now that human beings have mastered the methods of changing the weather such as artificial rainfall and artificial hail removal, can we control lightning?
The first appearance of artificial lightning
The way humans control lightning was inspired by an accidental discovery: in 1961, American meteorologist Brook discovered that the U.S. Navy conducted an underwater bomb explosion experiment in the Chesapeake Bay. (a cumulonimbus cloud with lightning) pulls the next lightning bolt. So, Brooke thought, could we imitate the plume of explosives and draw lightning down from the sky?
Brook made many experiments with conductive objects such as strings and steel wires. He tied multiple balloons to the top of several kilometers of wire, and then released the balloons under the thunderstorm cloud to see if lightning could be guided through the wire. down. However, no matter how Brooke changed the material of the wire, he still didn’t see lightning falling down the wire once, and only measured the current intensity of a few milliamps on the wire.
After comparing the differences between the explosive plume and the experimental conditions, Bruker guessed that under the action of a strong electric field, a large amount of electric charges accumulated instantaneously formed a shielding layer, preventing the flow of current. Subsequently, Bruker designed another experiment to penetrate a ground wire into a strong electric field environment at a speed of 20 m/s, and observed the phenomenon of current flowing through the wire. From this, Bruker concluded that as long as the wire moves fast enough to break through the charge shield, a discharge can form at the tip of the wire.
So, in practice, what is the fastest in the sky? People quickly thought of rockets. In August 1966, American scientists first implemented artificial mine triggering on a ship near the coast of Florida. They attached a very thin wire to the tail of a small rocket, and then launched the rocket into a thunderstorm cloud. In this experiment, the scientists tried 23 times, of which 17 were successful, and accumulated rich experience. Later, countries such as France, Japan, and China successfully implemented artificial mines. Now, each country conducts dozens of artificial lightning experiments every year.
The Essentials of Controlling Lightning
The method of artificially triggering mines seems to be very simple, but it is just “launching arrows” into the air, but in fact, it is not easy to successfully trigger mines.
First of all, it is necessary to meet the conditions of “the right time and the right place”: the time should be selected when a large amount of electric charge is accumulated in the air, that is, the eve of the lightning or the “intermission” of the thunderstorm, and the location should be selected in the lightning-prone area. Only when these two conditions are met can the lightning energy be successfully triggered. Therefore, scientists have to do a lot of monitoring and calculation work before triggering mines.
The second is the choice of rocket and wire. The cost of small rockets is not high, and multiple rockets can be launched in one experiment, and small rockets are also beneficial to control the speed of movement. The launch speed of the rocket is too fast, and it is easy to break the wire and lead to the failure of triggering the lightning; the rocket is too slow, which is not conducive to breaking through the shielding layer, and it is also difficult to trigger lightning.
In the actual lightning strike, the wire is generally made of thin steel wire or copper wire with a diameter of 0.2 mm. In order to increase the mechanical strength of the copper wire, a layer of high-strength Kevlar fiber is also coated on the copper wire. In order to prevent the wire from being pulled off by the high-speed rise of the rocket, a piece of elastic band is often connected between the wire and the rocket. Whether the wire is grounded is also important. If you want to simulate the formation process of natural lightning, the wire cannot be directly grounded, but is grounded again through a nylon rope of a certain length. The lightning formed in this way is very “natural”, which is beneficial for scientists to study the causes of lightning. When the wire is directly grounded, it is easier to trigger lightning successfully, and at the same time, a large amount of negative oxygen ions will be released into the air, which has the effect of sterilizing and purifying the air.
The artificial lightning test is very dangerous, therefore, strict safety measures must be taken during operation. In the selected lightning induction site, it is necessary to install a solid and reliable metal shelter with good shielding and grounding, that is, the “Faraday cage”. Even if the Faraday cage is struck by lightning, the test personnel inside will not be electrocuted. During the whole process of triggering the mine, all the test personnel must stay in the Faraday cage. Except here, no one is allowed to get close to humans or animals within a radius of 100 meters. The rocket launcher is mounted around the Faraday cage to ensure that the induced lightning strikes are nearby. At a distance of tens of meters from the Faraday cage, equipment that can automatically detect lightning electromagnetic data is also installed, so that researchers can obtain data more safely.
Laser: a new direction for artificial lightning
With the above conditions, artificial lightning can be successful, but whether it is successful or not depends on the will of God, because the existing technical means cannot directly detect the strength of the electric field in the air, and it may not really be able to trigger lightning after the rocket is launched. On the whole, the success rate of launching rockets to trigger mines in countries around the world is about 60%. And once the lightning strike fails, it is also a difficult problem to safely recover the potentially charged wires, so manual lightning strike is still a difficult and dangerous operation.
In order to improve the success rate and safety of triggering mines, scientists have come up with some new methods of triggering mines, such as water column mines, microwave mines, flame mines and laser mines. Laser detonation is the most practical new method at present.
In 1974, American scientist Paul first proposed the concept of laser triggering mines, but for a long time, scientists have not come up with a method to achieve this operation. It was not until 1994 that Chinese scientists Wang Daohong and others came up with a feasible method for laser lightning triggering – using a strong electric field near the tip of an iron tower to trigger laser lightning. In the thunderstorm cloud electric field environment, due to electrostatic induction, there is a strong electric field near the top of the tower. At this time, when the laser is focused on the top of the tower, the laser can “ignite” in this area, generating an upward current, which continuously gathers charges , which eventually triggers lightning.
Based on this theory, a research team from Osaka University in Japan built a 50-meter-high iron tower on a hill where thunderstorms often occur, and conducted field experiments of laser-induced lightning. The results show that the electric field strength required for the laser-triggered discharge does exist on the top of the tower during thunderstorms. However, when the thundercloud is over the top, due to the influence of snow and rain, the laser intensity is severely attenuated, so that “ignition” cannot be achieved. To successfully ignite, a larger laser generator is required to generate a stronger laser, and the cost and equipment scale again limit the development of laser-induced mines.
Fortunately, recently, scientists at the Australian National University have come up with a way to “ignite” a small laser, perhaps not far from the success of laser-induced mines. The team added some graphene particles between two energized metal plates, then fired a laser at the metal plates with a lab-specific laser to see if the laser beam could induce an electrical current. The laser intensity used in the experiment was only one-thousandth of the lowest laser intensity calculated to trigger lightning, but the results were surprising: such a low-intensity laser beam still caused “lightning”. If graphene particles can also reduce the intensity of the laser beam required for ignition in field practice, this new method will become the optimal solution for artificial lightning.
Having mastered the “super power” of artificially triggering lightning, we can not only change the location of lightning and eliminate the hazards of lightning as much as possible, but also use lightning to produce chemical fertilizers (ionize nitrogen and oxygen in the air into ions, which are combined into natural nitrogen fertilizers) ), artificial breeding (producing powerful electromagnetic radiation, inducing crop mutation) and fresh air (producing negative oxygen ions, purifying the air). In the future, thunder and lightning may become a controllable and environmentally friendly new energy source.
