# Is the total mass of the universe constant in time? [duplicate]

Is the total mass of the universe constant in time?

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What doubt do you have? –  udiboy Sep 14 at 16:25
I don't know why this person gets 2 down votes. Actually his question is nice.His wordings may not be right as he may be poor in English. –  Rajath Krishna R Sep 14 at 16:50
@RajathKrishnaR I downvoted because of the "This questions does not show any research effort" reason. Good questions put forth some effort to answer themselves and explain where the OP doesn't understand something. This makes no such effort. –  tpg2114 Sep 14 at 20:18

## marked as duplicate by Ben Crowell, Qmechanic♦Sep 15 at 0:12

Mass is obviously not conserved, as $E=mc^2$ state. But if you want to consider the total mass of the Universe, the problem is that "total" mass (energy) in General Relativity is not well defined, see: Energy conservation in General Relativity