A picture on the US military’s DoD Live website recently highlighted a fascinating, if often misconstrued, photo of flight:

The caption:

An F/A-18C Hornet…breaks the sound barrier over the USS Carl Vinson during an air power demonstration. (US Navy photo by Mass Communication Specialist 2nd Class James R. Evans)

While the Hornet may have been supersonic, the caption and image of the vapor cloud imply the “moment” of breaking the sound barrier was captured — a common, if incorrect, internet theme.

The vapor cloud is caused by aerodynamics (sometimes called the Prandtl-Glauert effect) when the environmental conditions are right, and it is likely more evident on aircraft approaching the Mach, but it is not exclusive to supersonic flight.  In fact, subsonic aircraft may have similar effects on their airframes under the right conditions.  (Even if the effect was caused by a shockwave, the shock would propagate on the aircraft before the plane itself was supersonic.)  Thus, seeing the vapor cloud does not equate to “breaking the sound barrier.”

Still, it’s a really cool picture.