[attention to Workplace browsing] does the laser pointer kill people? How much do you have?

If you say it first, you can die. It's just.

We all know that you can't look at the laser pointer to the eye. Although the blink reflex is highly likely to protect the eyes, there is also the possibility of blindness. But if some bad person wants to use a laser pointer to create light, is it possible? So how many laser pointers do we need?

The laser pointer on the market is safe and can be used for daily use. Having said that, it is common sense that it is too dangerous to look at the light. So, how powerful is the laser pointer?

Speaking of which, the laser is

Let's confirm the basics before we get to the point. What on earth is a laser?

The word "laser" narrows down "Light Amplification by Stimulated Emission of Radiation" (the amplification of light by the inductive emission of radiation). In other words, a laser is a beam of light in which many photons move in the same direction (usually light moves in all directions). A powerful laser injects a large amount of energy into the focus to generate heat, which in extreme cases can cause severe burns. For example, the United States Navy has a powerful laser cannon that can shoot down drones.

The power of the laser and its danger depend on the amount of output power (usually in mW). In the United States, the Food and Drug Administration (FDA) stipulates that all products should be less than 5 mW. As a result, most complete laser pointers are only less than 1 mW. Having said that, search Google with "cheap laser pointer" and you can find 5 mW of things under 2 dollars (about 240 yen). Many of the laser pointers are products outside the United States, so there are often no reminder stickers as stipulated by FDA. In addition, the usual laser pointer has a protective shield to prevent dangerous infrared rays from coming out, but there are things that even it doesn't have.

The danger of infrared rays is not enough to kill people at the level of leakage from the laser pointer. It's just that infrared is dangerous because you can't see it without blinking reflexes until the retina starts to burn. Even so, you will only be deprived of your eyesight (which is too much) to die. In order to produce light, a laser that is more powerful than 5 mW is needed.

And then we got to the point.

The scary thing about lasers is that multiple low-power laser beams can be collected to make powerful beams. But it's not easy. The energy of many laser pointers must be fully focused on the direction of the target using the lens.

If you want to use a laser, it is easiest to shoot it into the eye. Because the laser will cut open the retina and burn the brain tissue. But to do that, we need to continue to focus the laser on one point. So the target must be tied up, or unable to act in some way.

So, as is common in animation, putting the laser cannons together is over. James Kakalios, a professor of physics at the University of Minnesota and author of The Physics of Superheroes, says it is very difficult to make light with a laser pointer.

【職場閲覧注意】レーザーポインターで人は死ぬ? いくつあれば?

"to punch a hole in something with a laser, you need to inject more energy in a faster and shorter time," Kakalios explained. " "if you can do this, you can overwhelm what connects the target material, and the atoms fly away. However, if the extra energy of the laser comes out as heat, then it only needs to heat the material. "

But what happens if you heat up the brain tissue? The brain melted. Having said that, it still takes time to burn someone's brain with a piece of laser pointer.

Irradiating a laser in the brain may seem absurd, but it is a surge in neuroscience. The use of a proper laser beam can cause brain activity and eliminate pain. Tim Spellman, a doctoral researcher in neuroscience at Columbia University, irradiates the brains of mice with lasers every day for medical research. However, he is keenly aware that the continued use of powerful lasers can cause considerable damage to the brain.

"[to melt the brain] you need to heat up enough tissue to burn fat. Because most of the brain is fat. That's 300 to 500 degrees Fahrenheit, "Spellman said. "but in the actual human brain, how long it is possible is not known until it is actually tried. But in my opinion, it may take dozens of seconds or minutes. "

So, how many do you need?

Therefore, we find that we can use the lens to gather multiple laser pointers in one place to form a powerful beam. I also found that if you spend enough time shining a powerful laser on your eyes, you can melt your brain. So, how big will the laser pointer group be?

Rebecca Thompson of the National Physics Society, who holds a PhD in physics from the University of Texas, says the answer is "quite large". How to use the laser pointer to make the light? She made some calculations and answered the question. Here is its answer.

Killing people with a laser requires enough heat to boil or bake the tissue. In a normal time, that is, a short period of time when the target will not escape, it takes about 1kW's laser to boil the brain through the eyes. The cat toy laser pointer is about 5 mW. In other words, to make a laser that is powerful enough to kill, 200000 laser pointers must be focused on one point with the lens.

The width of each laser pointer is 5 mm (assuming the tip of the laser pointer is smaller than a cat's toy). If you arrange 200000 into a grid, that's 7 feet square. To focus it in one place, you need a semicircle with a radius of 5.5 feet. In other words, if you use a laser pointer to make a laser pointer, you need to buy 200000 laser pointers and paste them on a sphere with a radius of 5.5ft so that they point at the target through the lens and will never move to the target.

How accurate is the aim?

Focusing on the brain through the eyes is the easiest, but to make a person die, you need to pierce it quite accurately. The brain stem is right there, but it needs to be accurate.

So, with 200000 laser pointers and spheres about the size of the car, the brain stem of a motionless person shoots correctly, and if a certain amount of time is given, that person is dead.

Because it is very dangerous, please never try it at home.

Image by Jim Cooke/Photo via U.S.Navy/ Wikipedia

Adam Clark Estes-Gizmodo US [original]

(Miho)