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Loading contentThe lowest possible energy of a quantum system, which is never zero — even empty space seethes with quantum fluctuations. This vacuum energy is a real, measured effect (the Casimir force), and its possible connection to the accelerating expansion of the Universe is one of the deepest open problems in physics.
Facts on this topic will be cited from these primary and reference sources.
Mission data, planetary science, space telescopes, and public-domain imagery.
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