Some people say there are no miracles, just phenomena for which the cause is unknown. 
To a large degree, I agree with them.  Miracles can be understood by science.  Where I disagree is in the belief that all things have a physical or material cause so eventually material science will discover it.  There are things that have a non-physical cause.  A spiritual cause that physical science will never understand because instruments and methods used to measure and understand the material world will reveal nothing about the spiritual world. 
    Like UFOs for example.  Most scientists don't believe they are alien visitors but don't know what they are.  The strange maneuvers of flying saucers seems impossible to physical science.  If you consider the possibility that UFOs are more spiritual than physical, they are understandable.  Since the limitations of physical objects don't apply to spiritual things, something that is more spirit than material can make the strange turns and rapid flights often reported in UFO sightings.