NASA captured the amazing photos shown here using the schlieren technique. Never heard of it? It's a way of photographing air density gradients, like shockwaves in the air, by using something like the sun or a speckled desert as a background. This technique has been use in air-to-air situations, but now NASA is experimenting with capturing similar photos from the ground. Scientists achieved these images by using the sun or moon as backgrounds while an aircraft flew by at supersonic speeds.