The letters which substitute the query marks are

AE

Reasoning

The letters given are, within the appropriate order, the initials of the individuals on this {photograph}

The absent initials belong to Albert Einstein

More Explanation

This is a photograph from the fifth Solvay convention in 1927 (discover how the primary image has the Roman numerals for “1”, “9”, “2” and “7” across the outdoors) which handled electrons and photons (the smaller issues in life) and the event of quantum idea (see the equations on the blackboard from the primary image).

Title

As identified by parz within the feedback, “Sun ~Road” have to be an approximation to “Sol vie” or “Solvay”