A light blue spiral appeared in the night sky on April 15 among the northern lights, fueling people’s interest in unidentified flying objects (UFOs). However, this time the science behind the event was simple.
4月15日，夜空的北极光中出现了浅蓝色螺旋形物体，这引起了人们对不明飞行物的好奇。其实，这一事件背后的科学原理很简单。
The cause of the spiral was the fuel released from the SpaceX rocket that had been launched from California, US, about three hours before the spiral appeared, reported The Guardian. It was just a cloud of frozen fuel in the sky. It’s also the third spiral, as similar shapes were observed in June 2022 and January this year, both after the launch of SpaceX rockets, according to the Space Weather website.
据《卫报》报道，在美国加利福尼亚州出现螺旋约三个小时前，SpaceX火箭发射升空，其释放的燃料导致螺旋的形成。人们看到的蓝色螺旋物体，其实只是天空中的一团由冰冻燃料形成的云。据“空间天气（Space Weather）”网站报道，2022年6月和今年1月，在SpaceX 火箭发射后，人们都观察到了类似的形状，这已经是第三次了。
On April 16, people in Shandong province observed a green object with a long golden tail flying across the sky. Qingdao Aishan Observatory confirmed later that it was a piece of meteor. “Even the aliens are coming for the local barbecue,” an internet user joked as barbecue in Zibo, Shandong, has recently become popular.
4月16日，我国山东省民众观测到一个带着一条长长金色尾巴的绿色物体飞过天空。青岛艾山天文台后来证实那是一颗流星。一位网友调侃说：“甚至外星人都来吃淄博烧烤了”。那时，山东淄博烧烤火爆全网。
Strange sights in the sky never cease to attract people’s interest. So what else could the “UFOs” we see in the sky be? People may believe that they have seen a UFO right before sunrise or after sunset. The “UFO” may be glowing and climbing, as if it’s getting out of Earth’s atmosphere. However, they may be just airplanes. At those times, the sky is dusky when observed from Earth, but high in the sky, there is still light that shines on the aircraft, which is why it’s glowing. Also, the shape of the airplane isn’t clear when it’s climbing, leading to confusion among observers.
天空中的奇怪景象总会引发人类的好奇。那么，我们在天空中看到的“不明飞行物”还可能是什么呢？在日出前或日落后，经常有人观测到所谓的“不明飞行物”。该物体可能一边发光一边缓缓升空，仿佛正在脱离地球大气层。然而，其实可能只是飞机。因为在这些时刻，从地球上看，天空是昏暗的，但在高空中，依然有光线照射在飞机上，所以它才会发光。此外，当飞机在上升时，其形状并不清晰，导致观测到的人产生误解。
Something else that can shine strangely in the sky is a noctilucent cloud, which can be mistaken as a UFO. Usually appearing after sunset, these clouds are formed when the temperature in the atmosphere is at its lowest. Due to the high altitude, water vapor can freeze into clouds of ice crystals, which then reflect the sunlight. The reflected sunlight can reach out toward the edge of space, according to the Space website.
在天空中还可能观测到另一种能够奇异发光的物体——夜光云，它有时候也被误认为是“不明飞行物”。夜光云通常在日落后出现，其在大气温度最低的时候形成。高海拔让水蒸气凝结成冰晶云，然后反射阳光。“太空（Space）”网站介绍，这些反射的阳光可以延伸至太空边缘。
Sometimes, when you take a picture of the night sky in the city, weird lighted objects may appear in the picture – but you can’t see them in the sky! The “objects” are actually reflections of other lighted things, such as a lamp or street lights. The camera on smartphones usually has several layers of glass – for example, the camera on iPhone 12 has seven layers. The light goes through these layers before reaching the sensor which controls when the picture is taken.
有时候，在城市里拍摄夜空，照片中可能会出现奇怪的发光物体，但肉眼却无法观测到！这些“物体”实际上是其他发光物体反射的光，比如街上的灯光。智能手机上的摄像头通常有几层玻璃，例如iPhone 12上的摄像头就有七层。光线在到达传感器之前会穿过这些玻璃层。
In the 1940s and 50s, reports of “flying saucers” became a cultural phenomenon in the US. Sightings of strange objects in the sky became material for Hollywood and UFOs were a frequent topic in movies. This is partly why people usually think a UFO is a disk-shaped object. However, modern sci-fi movies show different types of alien spaceships.
在20世纪40年代和50年代，关于“飞碟”的报道在美国成为了一种文化现象。天空中奇怪物体的目击成为了好莱坞素材，UFO在电影中也成为了一个频繁出现的话题。这也是人们通常认为UFO是圆盘状物体的部分原因。然而，现代科幻电影也展示了不同类型的外星飞船。
What is your impression of a UFO? If aliens were real, what would they visit Earth for?
你对UFO有什么印象？如果外星人是真实存在的，你觉得他们为什么会访问地球？
