Noctilucent Clouds Over Edmonton . ... Credit Copyright: Greg Scratchley ( RASC Edmonton ) Explanation: Sometimes it's night on the ground but day in the air. As the Earth rotates to eclipse the Sun, sunset rises up from the ground. Therefore, at sunset on the ground, sunlight still shines on clouds above. Under usual circumstances, a pretty sunset might be visible, but unusual noctilucent clouds float so high up they can be seen well after dark. ... NASA Official: Jay Norris. ...