You might have seen beautiful rainbows in the sky before. They form when sunlight falls on water drops in the air. But in fact, moonlight can also create rainbows in the same way. They are called "moonbows". They are similar to rainbows, but they are created by moonlight instead of direct sunlight.
Moonbows are rarer than rainbows. Different weather and astronomical (天文学的) conditions have to be just right for moonbows to be created.
The moon has to be very low in the sky — only 42 degrees from the horizon (地平线). The moon period has to be a full moon or nearly full. The sky must be very dark for a moonbow to be watched clearly — any bright light can obscure it. Water drops must appear in the air in the opposite direction of the moon.
Moonbows appear on the opposite side of the moon and usually look white to the human eye. This is because their colors are not bright enough to be noticed by the human eye. It is possible, however, to view the colors in a moonbow using long exposure (长时间曝光) photography.
Moonbows more often appear in some locations around the world. Most of these locations usually have waterfalls, which create thin fog in the air. Some of these locations are the Yosemite National Park in California and Cumberland Falls State Resort Park in Kentucky, US; Victoria Falls on the border of Zambia and Zimbabwe; and Waimea in Hawaii, US.
Moonbows do really happen. So at a certain time and a certain place, when a moonbow happens to appear, you can't miss it if you're right there.
