Most people are no strangers to mosquitoes; If you meet them while traveling or sleeping, you just want to cry. According to estimates, mosquitoes kill about 700,000 to/kloc-0,000,000 people every year, which is the first in the animal killer world, greatly defeating the second-place human itself; But think about it with empathy for animals. In fact, mosquitoes are in a rather difficult situation. In addition to avoiding the pursuit of the most powerful species on earth-human beings, there are many natural enemies. In addition, the weather environment seems to be a potential threat: for example, the weight of raindrops can be as high as dozens of times that of mosquitoes (imagine that we are in heavy rain filled with hundreds of kilograms to several metric tons of raindrops), so when it rains, will mosquitoes be killed by heavy rain? How has it survived to this day?

Study on the Influence of Pexel Water Drops on Mosquitoes In order to solve the above problems, Lide Hu [1], a Taiwanese-American scientist from Geia Institute of Technology, and his team conducted a detailed study on 20 12. In fact, it is a very difficult task to beat mosquitoes with raindrops; Lide Hu said:

"The first thing we did was to drop water into a container full of mosquitoes from the third floor of our building-you can guess it's useless, just like playing the worst darts game you can imagine. 」

So they changed their practice: shooting water droplets at mosquitoes in the laboratory and recording the process with ultra-high-speed cameras.

They observed that mosquitoes did not deliberately dodge or fight raindrops. On the contrary, their wings or bodies will be affected by raindrops and move along them in a way similar to hitchhiking. The research team simply estimated the force exerted by water droplets on mosquitoes in this case, and found that when water droplets are much heavier than mosquitoes, the force exerted by mosquitoes is roughly proportional to their own mass.

Therefore, although in the experiment, the weight of water droplets is 20-50 times that of mosquitoes, but because mosquitoes did not catch the impact of water droplets hard, and the weight is extremely small, the force they bear is not high-the hard exoskeleton of mosquitoes can completely resist the impact.

Top left: mosquitoes are deflected by water droplets; The upper row on the right shows the relationship between deflection angle (vertical axis) and time (horizontal axis), and the pink * * * block shows the contact period between mosquitoes and water droplets. Lower left row: mosquitoes are driven downward by water droplets. The graph on the right of the next row shows the relationship between displacement distance (vertical axis) and time (horizontal axis), with black representing mosquitoes and blue representing water droplets. Reference 1 Even so, raindrops can still do harm to mosquitoes under certain conditions: if mosquitoes are hit when flying very close to the ground, they may be dragged into the ground by raindrops.

Raindrops can't hurt mosquitoes, can they hurt people? With the research results of mosquitoes, we can continue to think: when people are in the rain, they don't move in the direction of raindrops like mosquitoes, and they don't have hard exoskeleton protection like mosquitoes or insects; The kinetic energy and momentum of raindrops can be said to be ruthlessly used to attack our fragile flesh and blood. So, will raindrops do harm to human beings? Obviously, the answer is: no.

Then why? (/‵д')/~ ╧ ╧ (turning over the table) Why is it completely different from mosquitoes? The simple answer is that the quality and speed of raindrops are not big enough.

How big can the quality of raindrops be? Because the density of water is generally fixed and does not change much, the most important factor affecting the quality of raindrops is its size. In principle, water droplets can be as big as they want, but if you think about the raindrops we have seen since childhood, even the largest diameter is hard to exceed 5 mm.

In the microgravity environment of the International Space Station, the size of water droplets can be very large. Shadow//National Aeronautics and Space Administration Johnson In the past, scientists thought that raindrops would collide with other raindrops around them in the process of falling, and then merge or split, eventually forming the size of raindrops we saw on the ground.

However, in 2009, scientists from the University of Aix-Marseille published a paper confirming that the size of raindrops actually depends on their interaction with the air: once raindrops are formed and fall in the sky, they will not keep their shape because of air resistance, but will split into small raindrops.

Schematic diagram of the splitting of raindrops in the process of falling. When the diameter of raindrops is small, they are roughly spherical; The larger the diameter of raindrops, the greater the deformation under the action of air resistance, which eventually leads to division. Wikipedia is not only that, but the research team also estimated the upper limit of the size of raindrops, and concluded that the maximum diameter of raindrops in a stable and undivided state is about 6 mm, which is basically consistent with experimental observation and daily life experience. So the quality of raindrops can never be enough to harm human beings.

Is it feasible to accelerate raindrops? Even if the quality of raindrops can't be too big in reality, we still don't need to give up hope. As long as you know physics, physics will help you: if raindrops fall at a very high speed, they can still generate enough momentum to cause casualties; There was a story in the cartoon Nautical King, which said that the water droplets on the firing hand destroyed the rocks ―― but is this really possible?

In Neptune, water droplets from villains can penetrate rocks. As early as about 2,000 years ago, the Romans would store a large amount of water in high places, and search for veins by releasing it all at once and washing away the overburden on the bedrock. This technology is now called silent exploration. /kloc-in the middle of the 0/9th century, miners began to spray the deposit directly with high-pressure water column until it disintegrated, and then washed the ore, which is called hydraulic mining.

/kloc-photos of miners who used hydraulic mining in the 0 th and 9 th centuries. By Wikipedia 1930, human beings have been able to cut objects with very small high-pressure water column, which is called water jet cutting machine. With the evolution of the times, the water pressure we can produce is getting stronger and stronger, and the power of the water column is getting bigger and bigger; In other words, as long as the speed is fast enough, the destructive power of water can be great.

In that case, why don't raindrops hurt people quickly? The reason is still the air resistance mentioned above. When an object moves in a fluid, it will feel the reverse resistance given by the fluid; The faster the speed of an object, the greater the resistance. When an object falls from the air because of gravity, as long as the speed is fast enough, the air resistance will be large enough to offset the effect of gravity. At this time, the object will move at the same speed, which is called the final speed.

The final velocity of an object is related to its mass, cross-sectional area in the fluid and the properties of the fluid. As far as raindrops are concerned, the maximum terminal speed is almost 10 meter per second (36 kilometers per hour), which is not fast-so it is impossible to cause human injury.

The dream of weapons of mass destruction