Once the size of the universe is doubled, both matter energy and gravitationenergy double correspondingly.
当宇宙的尺度加倍，物质和引力能都加倍——这样，零的两倍仍为零。
2
Although today's universe is still expanding, Professor Hawking holds that the plus matter energy balances the minus gravitationenergy, thus the total energy is zero.
The universal gravitation field is described by imaginary number in the paper. It's energy density is negative real number. And it accord with conservation of energy.