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Name: George
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This question is essentially about the nature of "vacuum energy." If virtual particles pop in and out of existence based on the rules of quantum uncertainty, why is not the energy of the vacuum being progressively depleted given that space is expanding and the conservation laws say that energy cannot be created? I would like to add that I understand virtual particles mutually annihilate so the net energy balance remains zero, in the vicinity of a black hole, one such particle can be absorbed and another set loose outside the event horizon, therefore, creation ex-nihilo?

Hi George,

I sense a little confusion in the question you're asking, so maybe restating your question might help. If I understand you, it sounds like you are asking "if the universe is expanding and the total energy in the universe is constant, then is the average energy density of the universe declining?" --- which when stated that way, the answer would be yes for macroscopic systems. When you consider very small systems (where quantum effects dominate), it is a little harder to define boundaries, but the law of conservation of energy still applies. I am oversimplifying a bit here, so let me know if you are asking about a specific detail regarding quantum/relativistic details.

Hope this helps,

Burr Zimmerman

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