The sky above this Singapore hotel seems perfectly normal...but then something weird starts happening in the clouds. They suddenly change shapes, brighten and dim, and seem to pulsate for no apparent reason. This strange phenomenon has baffled scientists...until now.

Videos capturing these strange, rapid light changes in clouds have popped up a lot in recent years, and they defied immediate explanation. But after what NASA rather charmingly calls some "inspection and contemplation", we now have a rather nifty explanation for just what's going on here:

In sum, this hypothesis holds that a lightning discharge in a thundercloud can temporarily change the electric field above the cloud where charged ice crystals were reflecting sunlight. The new electric field quickly re-orients the geometric crystals to a new orientation that reflects sunlight differently. In other words, a lightning discharge can cause a sundog to jump. Soon, the old electric field may be restored, causing the ice crystals to return to their original orientation.

Via NASA. Video by abrigatti. Check out forgetomori for more.