 Project Blue Book would eventually label the unknown Washington radar blips as false images caused by temperature inversion, and the visual sightings as misidentified meteors, stars, and city lights.In later years two prominent UFO skeptics, Dr. Donald Menzel, an astronomer at Harvard University, and Philip Klass, a senior editor for "Aviation Week" magazine, would also argue in favor of the temperature inversion/mirage hypothesis.In 2002 Klass told a reporter that "radar technology in 1952 wasn't sophisticated enough to filter out many ordinary objects, such as flocks of birds, weather balloons, or temperature inversions."