量子力学表明，即使将一个盒子中的物质、气体乃至不可见成分全部移除，内部仍残留能量，即零点能或基态能量。这种能量存在于受限系统中，源于不确定性原理：位置与速度无法同时被精确确定。场与粒子在接近绝对零度时仍保留能量，因此看似“空无一物”的状态依然充满活动的统计痕迹。

零点能的概念由普朗克于1911年提出，随后爱因斯坦在20世纪初加以重视，用以解释分子和晶格在最低能态下的振动，以及液态氦在常压下即使接近绝对零度也不凝固的现象。1948年卡西米尔预测了真空零点能导致的吸引力，1958年首次观测，1997年被精确验证。2025年，欧洲X射线自由电子激光设施的实验显示，一个由11个原子组成的有机分子在接近绝对零度时仍存在相关振动，进一步证实零点运动的普遍性。

在量子场论中，每个场由无穷多个振子组成，意味着零点能在数学上趋于无穷。虽然能量差可通过重整化处理，但引力无法忽略真空能量。1946年，泡利指出如此巨大的真空能应产生足以摧毁宇宙的引力场，这一矛盾至今未解。真空因此并非真正的“无”，而是包含所有粒子与场的潜能，即“什么都没有，却可能成为任何东西”。

Quantum mechanics shows that even if all matter, gas and unseen components are removed from a box, energy remains inside as zero-point or ground-state energy. This energy arises in confined systems because the uncertainty principle forbids simultaneously fixing position and velocity. Fields and particles retain energy even arbitrarily close to absolute zero, so an apparently empty state still exhibits statistical traces of motion.

The concept of zero-point energy was introduced by Max Planck in 1911 and taken seriously by Albert Einstein in the early 20th century to explain molecular and lattice vibrations and why liquid helium fails to solidify at ordinary pressure near absolute zero. In 1948, Hendrik Casimir predicted an attractive force from vacuum energy, first observed in 1958 and precisely measured in 1997. In 2025, experiments at the European X-Ray Free-Electron Laser showed that an 11-atom molecule vibrated even near absolute zero, confirming pervasive zero-point motion.

In quantum field theory, each field consists of infinitely many oscillators, implying formally infinite zero-point energy. While energy differences can be renormalized, gravity cannot ignore vacuum energy. As early as 1946, Wolfgang Pauli noted such energy should generate gravity strong enough to destroy the universe, a paradox still unresolved. The vacuum is therefore not true nothingness but a state containing the potential of all particles and fields, known and unknown.