are being created from quantum fluctuations in this "empty" space all the time. If these pairs do not mutually annihilate right away, they could be detected as real particles, for example if one falls into a black hole and its opposite is emitted as Hawking radiation. Alexander Vilenkin defines "nothing" as "a state with no classical space time." See also References Further reading Lucretius. (2007). The Nature of Things. Trans. A. E. Stallings. New York: Penguin Classics. External links Lucretius' De Rerum Natura, translated by William Ellery at the Internet Classics Archive Philosophical arguments Philosophy of physics Physical cosmology