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E/m = c squared

  1. Aug 15, 2013 #1
    There is a closed thread c squared = e/m. I am piggy-backing off of that discussion. c is a constant, and thus so is c squared (no matter is unit). My question is then: what are the implications of the conclusion that E/m is a constant. How do we interpret that?
  2. jcsd
  3. Aug 15, 2013 #2
    It's called the law of conservation of mass/energy. Matter/energy cannot be created or destroyed, but only transformed into different states. The total matter/energy in a closed system must stay constant. That is what the equation means. The c is just to make the units work. In naturalized units, the equation reads E = m or E/m = 1. Note that most physicists consider energy to be fundamental, and mass just to be a certain manifestation of energy. So they call it the law of conservation of energy, and imply that this includes mass as well.

    Note that E = m c^2 is not the most general form. That equation only applies to objects at rest. The full equation is E^2 = m^2 c^4 + p^2 c^2 where p is the momentum. What this tells us is that kinetic energy can be transformed into other forms of energy, including mass. This is what they do in particle accelerators. Particles are smashed together at high velocity in order to create hundreds of new particles with mass.
  4. Aug 15, 2013 #3
    E = mc^2 simple relates the rest mass of matter with its rest energy. The fact that E/m is constant just means that rest mass and rest energy are proportional.
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