Why are heat and light not matter? – Crystallography Zone

Question: Why are heat and light not matter?
- Keywords:
  heat,
  light,
  matter
Asked by rhooper821 to Ben, Dave, Ed, Sam, Susana on 18 Jun 2013.
- Benjamin Hall answered on 18 Jun 2013:
  
  To be considered ‘matter’, something must have what is called resting mass and volume. This is simply a measure of how heavy a thing is and how much space it fills. Heat and light are forms of energy which does not have resting mass or volume, so are not considered to be matter.
  
  However, mass and energy are very much related. You’ve heard of Albert Einstein’s famous E = MC squared equation, right? That’s the relationship between mass and energy.
  
  E stands for energy, M stands for matter and C squared is the speed of light squared. What it means is that if you times the mass of an object by the speed of light squared, you can find out how much energy that object has!
- Ed Lowe answered on 18 Jun 2013:
  
  Removed a misleading comment about waves and particles.
- David Briggs answered on 18 Jun 2013:
  
  Great question.
  
  Heat is energy.
  Light is made of photons – which are sub-atomic particles – so they could be considered as matter. But light also behaves like energy. It is pretty confusing!
  
  However, as Ben says, energy and matter can be converted from one thing to another! Even more confusing!
- Susana Teixeira answered on 20 Jun 2013:
  
  I think Ben has already explained: neither light nor heat have an invariant mass and volume so they are not considered “matter”.

Question: Why are heat and light not matter?

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