Concept of momentum-less bodies and a suggestion for its experimental   verification using ultra-cold atoms
  General Principle of Relativity unequivocally supports the notion of momentum-less energy for bodies (energy-quanta) moving at the {\em same} or {\em constant} speed relative to all the reference systems. In this communication, we point out that whether energy-quantum is a momentum-less body or not is verifiable using ultra-cold atoms trapped in an optical lattice, perhaps with some minor modifications to the existing such experimental setups. 
Sanjay M. Wagh