I saw a video by a physics writer who said that the beginning of the universe was like digging a hole: the hole and the pile of dirt cancel each other out. This of course means that the ground, so to speak, before the digging was zero. But where is the "hole" once the universe began? I asked some people about this and they quoted Stephen Hawking's A Brief History of Time : "There are something like ten million million million million million million million million million million million million million million (1 with eighty zeroes after it) particles in the region of the universe that we can observe. Where did they all come from? The answer is that, in quantum theory, particles can be created out of energy in the form of particle/antiparticle pairs. But that just raises the question of where the energy came from. The answer is that the total energy of the universe is exactly zero. The matter in the universe is made out of positive energy. However, the matter is all attracting itself by gravity. Two pieces of matter that are close to each other have less energy than the same two pieces a long way apart, because you have to expend energy to separate them against the gravitational force that is pulling them together. Thus, in a sense, the gravitational field has negative energy. In the case of a universe that is approximately uniform in space, one can show that this negative gravitational energy exactly cancels the positive energy represented by the matter. So the total energy of the universe is zero."(adsbygoogle = window.adsbygoogle || []).push({});

When he says the matter of the universe of made of positive energy, is he referring to both the particles and anti-particles he mentioned? Are there two things cancelling the energy of matter: antiparticles AND gravity? How does this all fit together? THANKS!

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# The universe adds up to zero?

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