I would like to know why there is no constant in this equation. If a second is slightly longer, a meter slightly shorter, or mass slightly different, then would it would be E=mc^2*CONSTANT. The distance,mass,time, and energy units where created arbitrarily before this equation was created. It seems a incredible coincidence that they all match up. So why no constant.
Oh sorry... Just worked it out. E is defined by mass distance and time. E=mc^2 in both metric and imperial systems. Silly me..Please Register or Log in to view the hidden image!
Just to expand a little: In the MKS system of units, energy is measured in Joules, mass in kilograms and the speed of light in metres per second. The rest mass energy in Joules of a given number of kilograms of matter is found by multiplying the mass in kilograms by the square of the number 299792458, which is the constant speed of light. The number 299792458 is an artifact of this particular choice of units system. We can equally use other units. For example, in so-called natural units, the numerical value of the speed of light is 1, so the equation reduces to E=m. Is is important to recognise that energy and mass still have different dimensions when we use natural units, even if they have the same numerical value.
