Sometimes it's night on the ground but day in the air. As the Earth rotates to eclipse the Sun, sunset [ http://antwrp.gsfc.…] rises up from the ground. Therefore, at sunset on the ground, sunlight still shines on clouds [ http://ww2010.atmos. uiuc.edu/(Gh)/guides /mtr/cld/home.rxml ] above. Under usual circumstances, a pretty sunset [ http://antwrp.gsfc.…] might be visible, but unusual noctilucent clouds [ http://lasp.colorad…] float so high up they can be seen well after dark. Pictured above [ http://www.clearski…] last month, a network of noctilucent clouds [ http://science.nasa…] cast a colorful but eerie glow after dusk near Vallentuna [ http://en.wikipedia…], Sweden [ http://en.wikipedia…]. Although noctilucent clouds [ http://en.wikipedia…] are thought to be composed of small ice-coated particles, much remains unknown [ http://www.nlcnet.c…] about them. Recent evidence [ http://www.nrl.navy…] indicates that at least some noctilucent clouds [ http://www.gsfc.nas…] result from freezing water exhaust from Space Shuttle [ http://antwrp.gsfc.…]s.
Credit and Copyright:
P-M Hedén [ mailto: clearskies at bostream dot nu ]
