[1]   Phase Transition: The transition between frames of reference. It is the physical process of a transition between one state of a medium and another state. 

 

[2]  Gray Area: A region of velocity starting slightly before, and ending slightly after the speed of light. Similar to the transitional zone between subsonic and supersonic.

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[3]  Apparent Mass: The ability of matter to perform work. A good example being the ability of infrared radiation to heat versus X-rays passing through mater.

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[4]  C+ Transparency: Actual physical and optical properties of mater as it transitions beyond the speed of light.