Artificial cloud created at the edge of space

 作者:都谩     |      日期:2019-03-08 09:13:03
CLOUD watching is hardly an extreme sport, but NASA took the pursuit to a whole new level this week by creating an artificial cloud on the edge of space. So-called noctilucent clouds float at high altitudes and glow when the sun illuminates them from below the horizon. They are formed when ice clumps onto charged particles high in the atmosphere, sometimes in rocket trails (see photo). NASA wanted to know whether radar measurements currently used to study the birth of these clouds are being accurately interpreted. To do this,