Mysterious Face on a Famous Ceiling

Photo date: February 5, 2015. Photographer: Mark Mahin.

Below is a photo of the ceiling of Grand Central Station in New York. We see several unexplained orbs which are not part of the permanent art work on this ceiling.

Below is a closeup of the orb in the top left corner. We seem to see a smiling face.

Some will say: this cannot exist, because heads cannot float around without bodies. But we can have a credible hypothesis about such a thing if we imagine it to be not a permanent organism but simply a fleeting manifestation or representation produced by some unknown intelligence trying to attract our attention.  What better way to attract human attention than to show a floating face for an instant?  Of course, this is just a speculation, and I don't claim to understand the mystery behind this phenomenon.  I do know that this site and this site have many similar photos of faces in orbs.