The Egyptian Painting No One Can Explain

A man kneels before the Sphinx, his ear pressed to her lips, as if waiting for an ancient secret to be whispered. There are no temples, no hieroglyphs—only sand, silence, and a skull half-buried in the desert. The painting is called The Questioner of the Sphinx, and although it was created in 1863, no one has been able to fully understand it.

What is happening in this scene?
Why does the Sphinx remain silent?
And most importantly… what question is this man asking?