Hi all, Firstly, I do apologize if this is in the wrong forum or sub-forum, and if the title is a tad misleading, I wasn't quite sure how do phrase it. Onto the post, however, I am sure most if not all of you have seen the energy mass equivalence, [itex]e=mc^2[/itex] And there is also Einstein's original equation [itex]E^2 = p^2c^2 + m^2c^4[/itex] (I do hope this is the right one, I have a lot of equations lying around, and not to mention I have seen a lot of his "original equation" which are different from this one. Please let me know if this is the wrong one.) Now my question is, how do you get from [itex]E^2 = p^2c^2 + m^2c^4[/itex] to [itex]e=mc^2[/itex]? If somebody could explain it for me that would be great, thank you.