Why do some particles have mass while others have none?

Question: Why do some particles have mass while others have none?
- Keywords:
  physics,
  properties,
  subatomic
Asked by to James, Jennifer, Kim, Liam, Ricardo on 23 Jun 2014. This question was also asked by .
- Jennifer Stephens answered on 23 Jun 2014:
  
  Hi analazic
  
  Particle physics isn’t my strong point. 😮
  I know photons have zero mass. And if a particle has zero mass, it can still get its energy from momentum (like photons).
  Einstein’s full equation may explain this better.

Question: Why do some particles have mass while others have none?