A hang-glider was filming the take-off of another glider near Sutter Buttes, California when he accidentally caught a small, dark, round object whizzes by so close it nearly hits him.
The object which has no wings or visible propulsion has an incredible speed and can only be seen in a split second. Only after slowing down and pause the footage it reveals an object with four pinched-off corners that rests on what looks like a round disk.
Some speculate it might have been a balloon, but the object simply has too much speed to be a balloon.