Originally Posted by **ButchBegy** I need some sources to help me understand the relationships... matter to energy and energy to matter, what is the mechanism?
For example, in my search for information I have seen it stated that a photon of great enough frequency would "decay" into an electron? Is this true? What are some good sources for information.
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The relationship is actually between momentum and energy. You know the Einstein equation $\displaystyle E = mc^2$. This relates energy by its rest mass...the mass it has for 0 speed. The more general equation is $\displaystyle E^2 = (mc^2)^2 + (pc)^2$ where p is the momentum of the object in a given frame. (Set p = 0 to get $\displaystyle E = mc^2$.)

That being said there is no "mechanism" to energy-matter exchange. SR works best (IMHO) when dealing with 4-vectors. There is an energy-momentum 4-vector given by $\displaystyle \left ( \frac{E}{c}, p_x, p_y, p_z \right )$. This shows that the energy-momentum transfer really isn't a transfer at all...it merely means that some spatial momentum has transfered itself to the time component of the energy-momentum 4-vector (the E/c part), rather like a rotation of a 3-vector in Classical Physics.

A large energy photon will not create an electron out of the energy. We need to create

*two* particles so that spin can be conserved during the decay. So for this photon to decay we have to create an electron and it's anti-particle the positron for this to occur. The minimum energy that the photon needs to have is $\displaystyle m_e c^2 + m_p c^2 = 2 m_e c^2$. Where $\displaystyle m_e = m_p$ is the mass of the electron and positron (which has the same mass as the electron since they are anti-particles.)

-Dan