German and American scientists jointly created a laser with a spectral width of only 10 milli-Hz (1 Hz at 0.001 Hz), setting a new world record in laser monochromaticity. According to a press release issued by the German Federal Institute of Physics and Technology, this is the closest laser to monochromatic monochrome so far. Using it to measure atomic frequencies can make photonic clocks more accurate and contribute to spectroscopy and radio astronomy research. Frequency and wavelength determine the color of light, the sun is composed of many different frequencies of light, after decomposition can form a rainbow. The more single light, the better the monochromaticity, and the narrower the area occupied by the spectrum. The ideal laser has only one frequency and wavelength, the line is a line without width, but in reality can not be achieved. Ordinary laser linewidth is usually a few thousand hertz to several million hertz, not suitable for high precision experiments. The German Federal Institute of Physics and Technology and the American Institute of Experimental Astrophysics co-operate to create two lasers with a wavelength of about 1.5 microns. The comparison shows that the linewidth is 10 milli-Hz. The paper was published in the American Journal of Physics Review on. The two lasers are very stable and all the light waves that make up the laser are very similar, with a consistent height of oscillation steps that can be synchronized for at least 11 seconds at 194 trillion oscillations per second. During this time, the laser can spread 3.3 million kilometers, which is equivalent to nearly 10 times the distance from the earth to the moon.