Because mass is a property of things, not a thing. That's like saying energy turns into blue, instead of saying it turns into something that is blue.

Big Bang Theory didn't create any new mass but spread it all around from a point.

 

do you mean to say that mass was converted to energy [ i have heard that energy exists all over the universe and when it is denser ,it is called matter]

spreading with the speed of light..........e=mc2?

do you mean to say that mass was converted to energy [ i have heard that energy exists all over the universe and when it is denser ,it is called matter]

spreading with the speed of light..........e=mc2?

For a more complete (and more accurate) description of the Big Bang than math-helper provided you may want to read the Wikipedia article on it here:

http://en.wikipedia.org/wiki/Big_Bang

 

Chris