Can energy/mass be created?

[uros]

Can energy/mass be created? If doesn't, how has it come to exist? If does, how can it be achieved?

[fss]

http://en.wikipedia.org/wiki/Conservation_of_mass
http://en.wikipedia.org/wiki/Conservation_of_energy

[James Leighe]

Is invariant mass always conserved? I mean, if you have a particle and anti particle annihilate wont you be left with relativistic mass only now?

As far as I can tell, you can have a ton of photons with some energy in the same place then they can 'transform' into a particle-anti particle pair which in turn transforms their relativistic mass into the rest mass of the particles... Right?

Also, since light always travels at c does it not always have the same relativistic mass in every reference frame?

Sorry for random questions and not helping.