While I was resting from yard work under the fruit trees, something passed overhead so close to the tree tops, it cast a very tidy shadow on the grass. It was shaped like a hang glider or a boomerang but proportionately shorter winged. While the shadow was still visible passing over the yard, we looked up and saw nothing. It continued overhead and we checked again. Still nothing visible. We are accustomed to watching birds and airplanes and can always spot them. This was close, with no sound, no visible object, but it cast a definite dark, crisp shape on the ground. The shadow was about 5-7 feet across tip to tip. Speed seemed about 10-20 mph.It went East to West and we lost sight of the shadow.