section_path: Other proposed states/Photonic matter
section_name: Photonic matter
paragraph_text: Photonic matter
  
  Photonic matter is a phenomenon where photons interacting with a gas develop apparent mass, and can interact with each other, even forming photonic "molecules". The source of mass is the gas, which is massive. This is in contrast to photons moving in empty space, which have no rest mass, and cannot interact.