Green laser pointer that can point to the moon
The power of an ordinary red laser pointer is 5 milliwatts. If the quality is good enough, the laser can hit the moon all the way. Of course, the beam of light will be scattered a lot when it reaches the moon. The earth’s atmosphere also affects the beam of light, but most light can reach the moon. The beams of light will probably be as large as the circles in the picture. Why didn't it work? Because the sun's radiation on the moon can reach more than 1,000 watts per square meter. Because the cross-section of the moon is about 10^13 square meters, it can receive 10^16 watts of sunlight. If it reaches 5 billion people on average, each person is 2 million watts per person, which is much stronger than a 5 milliwatt laser pointer. NS. Although there are many factors that affect efficiency in our system, these can't change the huge difference in orders of magnitude.
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The Green laser pointer we use can irradiate a beam of light with a width of 5 arc minutes and a brightness of 150 lumens, which is already brighter than most flashlights. These lights increase the lunar surface illumination by half a lux, and solar energy provides 130,000 lux. Even if all 5 billion people aim at one location, we can only increase the illuminance of about 6 lux on 10% of the lunar surface. To let everyone take a laser pointer to the moon, the prerequisite is that we can see the moon. Almost everyone knows that all people on the earth cannot see the moon at the same time. Because the relationship between the earth and the moon determines that only half of the earth is night and half day.
2021-09-10 10:32:36
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