How the quantum vacuum perturbs atoms, could shrink black holes and may have helped form galaxies

The word "vacuum" may conjure the image of empty space. Maybe you think of a region far outside the solar system without planets, debris, gas clouds or light. According to quantum theory, however, a vacuum is never truly empty. Quantum mechanics extends the Heisenberg uncertainty principle—which states that we cannot measure the position and the velocity of an object exactly at the same time—to a vacuum. The result is that a vacuum can never be still.