Chuhukou
In the beautiful tropical ocean, a hungry predator is searching for prey everywhere. It's not bad luck, just in front of a delicious lunch. A few meters away from it, a group of flounders are gathering together and lying motionless on the bottom of the sea, as if they could easily eat them. Surprisingly, however, the predator didn't see the lunch in front of him and swam straight over. ?
Looks like the flounder managed to escape from the tiger's mouth again. For flounder, it is not difficult to escape successfully. Their magical color changes make predators stupid. Is this a coral reef or lunch? What's even more amazing is that the flounder can transform in a short time even if it suddenly meets a predator. Scientists have done experiments to dye the background of the aquarium in different colors, such as white, black, gray, brown, blue, green, pink and yellow. These flounders can quickly become the same color when they pass through different color backgrounds.
How do these amazing sea creatures with eyes on one side do it? It turns out that when the flounder sees the color change of the surrounding environment, the cells in its visual cortex signal will send signals to the brain cells, and the signals fed back by the brain will change the pigmentation or reflection characteristics of the skin cells, thus blending with the environment.
Revelation of flounder
The invisibility of flounder has inspired mankind's ambitious attempt. For example, South Korea is planning to build an "invisible" skyscraper with a height of 450 meters-the Infinite Tower. This skyscraper will use LED curtain wall and optical camera system to put a layer of "reflective skin" on the building. The tower is covered with cameras like flounder eyes to record the surrounding scenes. When people look at the tower, the LED screen will project the scenery blocked by the building, giving people an illusion and achieving the invisible effect.
Of course, the Japanese have achieved the invisible goal with flounder technology. On YouTube, a famous foreign video website, there is a video with more than 65,438+million views. In this video, a Japanese man wearing an "invisible" coat appeared. He stood on a busy street and made faces from time to time. However, pedestrians and vehicles passing by did not see him.
How did he do it? Similar to the skyscrapers in South Korea, the secret of this invisible man lies in his magical clothes, which are covered with reflective glass beads and equipped with several small cameras. When a Japanese man puts on clothes, the background image shot by the camera will be displayed in front of the clothes, and the foreground image will be displayed behind the clothes, so that the wearer can be integrated with the environment and achieve the invisible effect.
Although this technically uncomplicated invisible invention is far from our definition of "invisibility cloak", it still has its practical significance. For example, the current house looks very shabby after more than ten years, which affects the urban environment. If you use a rectangular glass bead carpet as a wall and reflect light through a mirror, you can make beautiful windows. For another example, we still have blind spots when driving, and the tragedies of reversing and hitting people frequently occur, which also provides the possibility for the elderly in China to "touch porcelain". If a car or truck wears this "invisibility cloak", the driver can have a 360-degree view without dead ends through mirror reflection and many cameras outside.
However, it is easier said than done. According to experts' prediction, to make a perfect invisibility cloak, six stereo cameras are needed, and the surface of the cloak should cover 1 1.6 million micro electronic display units. In addition, there should be a supercomputer to control stealth work and a small power supply that can continuously supply power. And if you stand in the wrong posture or position, this stealth trick will be revealed immediately. This is still a far cry from Harry Potter's magic suit.
Harry Potter's magic clothes
In The Sorcerer's Stone, Harry Potter received a special Christmas present, that is, an invisibility cloak. When Harry Potter and his friends were at school, they often walked around the castle in invisibility cloaks in the middle of the night, asking for all kinds of news and even shuttling under Voldemort's eyes.
Although invisibility cloaks only exist in science fiction, now some researchers will be able to invent real invisibility cloaks. We know that people can see objects because the light emitted by objects enters the human eye. Then, if the light around the object is diverted and the light automatically bypasses, will it achieve the purpose of making the object invisible?
In 2006, Smith, an electronic engineer at Duke University in the United States, invented the design of this kind of stealth equipment. A few months later, a prototype-stealth hood was developed, which successfully made microwave rays bypass the objects under the hood and make the objects invisible. Like running water in a stream. When it passes a stone, it will bypass the stone, then close the stone and move on as if it had never met a stone. ?
However, although Smith's invisibility cloak is a breakthrough, it is still not Harry Potter's cloak. Because the invisibility cloak is completely visible, it can only be invisible in the "microwave field". It changes microwaves instead of light waves.
In 20 15, researchers at the university of California, Berkeley drilled countless nano-sized holes in silicon materials, so that light waves can be completely reflected back, just like shining on a mirror. In this way, the object covered behind the stealth material will not scatter any light waves, just as it is completely invisible under the carpet. At present, researchers have successfully tested an ultra-thin invisibility cloak composed of tiny rectangular gold nuggets. These gold nuggets are attached to the surface of the object like skin, which can make the object undetected by visible light. If a fat man with a big belly wears this dress, his big belly will disappear. However, this invisibility cloak is still fragile and easily broken. If you move it, it will be full of flaws.
More application
Although it is impossible to make Harry Potter's magic costume with current technology, the idea of manipulating light waves has inspired people to think more about invisibility. Can we manipulate sound waves, water waves and seismic waves?
We know that although submarines can successfully avoid the pursuit of reconnaissance planes and reconnaissance satellites under the cover of seawater, they also have a fatal weakness, that is, they can't eliminate the sounds made by engines and propellers and are easily captured by sonar. So, how about an invisible acoustic cloak? Engineers from Duke University in the United States created a prototype of an acoustic cloak. This kind of cloak consists of a PVC low-noise plastic pipe with some holes of specific shape and filled with rubber-like polymer. If this cloak is covered on an object, sound waves can be bypassed and nothing in the cloak can be detected by sound waves.
Another invention is "non-inductive coating". Usually, if an elastic fabric, such as soft silk, covers a hard object, when you touch it with your hand, you will generally feel a hard pimple under your hand, and the fabric will be deformed by finger pressing. Recently, scientists have developed a "non-inductive jacket" that can repair the deformation caused by finger pressing. In this way, the "non-inductive coat" masks the existence of hard objects in our sense of touch. Is the result contrary to the mattress in The Fairy Tale of the Princess and the Pea?
What is even more amazing is that the huge metamaterial structure built around the building foundation can even redirect seismic waves and draw them away from the building. The University of Aix-Marseille in France cooperated with the French engineering company to develop the "earthquake cloak". They arranged in a grid on an alluvial basin and dug a series of vertical holes about 0.3 meters in diameter and about 5 meters in depth. Although the structure of this "earthquake cloak" is surprisingly simple, the effect is not bad. When French researchers use mechanical vibrators to vibrate the ground, the vibration degree of places with perforated grids is greatly reduced, and the reduction degree in some places is even more than four fifths compared with places without grids.
Magicians have long known
In fact, perhaps stage magicians know stealth technology earlier than we do. A long time ago, a stage magician could make everything disappear on the stage with some small magic in a limited time. They know that invisibility is not only an optical phenomenon, but also a spiritual phenomenon.
If you believe that you are invisible, just as you believe that magicians can really make things disappear, it will also affect the effect of invisibility. In a recent experiment, neuroscientists in karolinska institutet, Sweden conducted an invisible experiment involving 125 people. In the experiment, these participants were asked to wear virtual reality headphones. In this device, the experimenter can see the real-time video transmitted to him by the camera under the surface. In this video, they will see that their bodies are being made transparent by brushes, and they are becoming invisible people with smoke. At the same time, the experimenters are drawing on their real bodies with brushes.
This combination of illusion and real touch makes participants really think that they have an invisible body. This experiment further reveals the influence of stealth technology on human psychology. It can effectively relieve stage fright and calm down timid people.
This has not stopped ethicists from worrying. Once people really put on invisibility cloaks that come and go freely, will they become unrestrained and unscrupulous without the attention of others? Like stealing in an invisibility cloak, or poisoning your enemies in an invisibility cloak?
1897, the English novelist herbert george wells described this terrible scene in The Hollow Man. Griffin in the novel was originally high flyers of medical college, but when he became invisible after taking a self-developed invisible potion, Griffin began to lose his normal thinking, killing innocent people and planning to rule the world at will.
Now, researchers in karolinska institutet, Sweden are planning to use their virtual reality technology to put these participants who think they are "invisible" into trouble, and see if invisibility technology will disturb their moral compass. If so, we really have to think about whether invisibility is desirable.
(This article is from the 4th issue of the 20 16 encyclopedia of new theories of science and technology.)