沃森峰上空的彩虹, 巨人柱国家公园, 亚利桑那州, 美国 Rainbow over Wasson Peak, Saguaro National Park, Arizona (© Frank Staub/Getty Images)

沃森峰上空的彩虹, 巨人柱国家公园, 亚利桑那州, 美国 Rainbow over Wasson Peak, Saguaro National Park, Arizona, USA (© Frank Staub/Getty Images)

天空无极限 The sky is the limit

沃森峰上空的彩虹, 巨人柱国家公园

您是否曾偶然发现彩虹，并感受到一股幸福感？你是否曾想在雨后捕捉阳光下的七彩奇观？从北欧神话中的众神，到爱尔兰妖精的聚宝盆，彩虹一直被赋予神秘的意义。但除了传说，彩虹背后的科学同样引人入胜，德国物理学家狄奥多里克在1304年给出了第一个合理的解释。他发现，阳光进入雨滴后会发生折射，然后在雨滴内反射，再折射出雨滴。这个过程将光线分解成不同的颜色，形成我们看到的光谱。虽然我们知道 “ROYGBIV”（红、橙、黄、绿、蓝、靛、紫）是彩虹的基本颜色，但彩虹实际上包含了数百万种颜色的渐变混合物。

并非所有彩虹看起来都相同。当第二道较暗且颜色顺序相反的彩虹出现在主彩虹上方时，便形成了双彩虹。今日图片展示了美国亚利桑那州萨瓜罗国家公园瓦森峰上空的一道绚丽彩虹。在干旱少雨的沙漠景观中，仙人掌与岩石山坡构成的背景下，这道彩虹格外醒目，证明了即使在最干燥的土地上，大自然依然能带来惊喜。

National Find a Rainbow Day

Have you ever spotted a rainbow and felt a little lucky? National Find a Rainbow Day, celebrated today, is all about looking to the sky for that magical mix of sun and rain. Nature's color wheel has long been linked to myths and legends, from Norse gods to the Irish leprechaun's pot of gold. But beyond folklore, the science behind rainbows is just as compelling. The first real explanation came from Theodoric of Freiberg, a German physicist, in 1304. He discovered that rainbows form when sunlight enters a raindrop, bends, reflects inside, and then bends again as it exits. This process splits light into its colors, creating the spectrum we see. The classic 'ROYGBIV' (red, orange, yellow, green, blue, indigo, and violet) doesn't tell the whole story—rainbows contain millions of colors blended together.

Not all rainbows look the same. Double rainbows occur when a fainter, reversed arc appears above the main one. Moonbows happen at night when moonlight refracts through water droplets. The rare supernumerary rainbow features extra pastel bands inside the primary arc. Today's image features a rainbow over Wasson Peak in Saguaro National Park, Arizona. Against a backdrop of desert cacti and rocky slopes, the vibrant arc stands out in a place where rain is scarce, proving that even the driest landscapes can surprise you.