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“Nothing” can’t exist in any literal, physics-grade sense because space never becomes free of fields and quantum fluctuations. Even when engineers strip air out of a chamber, the best they can reach is an ultra-high vacuum—around 100 particles per cubic centimeter—far from the absolute emptiness implied by the word “vacuum.” The gap between “very empty” and “literally nothing” is where the real science lives.

In everyday terms, air is so dense that even a “not empty” glass is packed with molecules: one cubic centimeter of air contains nearly 30 quintillion molecules. Removing air can create a vacuum, but the practical challenge is removing every last gas molecule. Ultra-high vacuum systems get close by reducing the particle count dramatically, yet they still leave enough residual matter that the chamber isn’t truly empty. A vacuum cleaner illustrates the scale: at sea level, the vacuum inside the machine only reaches the thinness of air found in Denver, Colorado—meaning it barely changes the number of particles you’re breathing.

Altitude shows another limit: nature won’t wait for human comfort. Commercial aircraft keep cabin pressure so passengers experience conditions no higher than about 8,000 feet, even though the plane cruises around 30,000 feet. At extreme thinness, the body can’t get enough oxygen; within under a minute of breathing the outside air at very high altitude, hypoxia can set in. Push higher—past roughly 60,000 feet—and Armstrong’s Limit arrives: the boiling point of blood drops to about body temperature, so bubbles form inside the bloodstream. The body doesn’t explode because skin and organs are flexible, but the physiological risk becomes immediate.

Even in a lab, emptiness is undermined by outgassing. When air is pumped out, materials in the chamber begin releasing their own trapped gases. Outgassing happens in partial vacuums and is especially noticeable in confined spaces; it’s part of why a new car has “new car smell,” as adhesives and chemicals release volatile compounds that accumulate indoors.

Space does get emptier, but not to zero. Between planets, space contains roughly 10 particles per cubic centimeter; in interstellar space, it drops to about one particle per cubic centimeter; and in intergalactic regions outside the Milky Way, densities can fall to around one or two particles per cubic meter. Still, absolute nothingness remains out of reach.

Quantum mechanics supplies the final barrier. Gravitational and electromagnetic fields extend forever, and the particles responsible for those fields are effectively massless. On top of that, “virtual particles” are thought to constantly appear and vanish even in regions that look vacuum-like. Two observed phenomena motivate this picture: the universe’s continued expansion and the Casimir Force. In the Casimir effect, two very close metal plates in a vacuum attract each other, often explained by virtual particles interacting with the plates—long-wavelength fluctuations can’t fit between them, leaving an imbalance in pressure from outside versus inside. The upshot is simple but unsettling: whenever someone feels like nothing matters, physics insists there’s always something—fields, fluctuations, and residual particles—preventing true emptiness.