- Empty set (Wikipedia)
In mathematics, the empty set is the unique set having no elements; its size or cardinality (count of elements in a set) is zero. Some axiomatic set theories ensure that the empty set exists by including an axiom of empty set, while in other theories, its existence can be deduced. Many possible properties of sets are vacuously true for the empty set.
- Max Headroom signal hijacking (Wikipedia)
On the night of November 22, 1987, the television signals of two stations in Chicago, Illinois, were hijacked, briefly sending a pirate broadcast of an unidentified person wearing a Max Headroom mask and costume to thousands of home viewers.