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I've heard that some physicists think that the net energy of the universe is zero. For this to happen, I would assume that the negative gravitational energy of a body ought to cancel out its rest energy. A back-of-the envelope calculation for the Earth gives me a rest energy around $10^9$ greater than its gravitational energy. I would assume that for other ordinary matter we get a disparity on the same order of magnitude. This means that the rest-energy of ordinary matter far outweighs its gravitational energy. Even if ordinary matter only contributes 4% of the gravitational energy in the universe, a claim I've heard, the rest energy of ordinary matter still far outweighs the total gravitational energy in the universe. So how is it still a plausible hypothesis that the net energy of the universe is zero? Where does the rest of the negative energy come from?