Complex sentence: Human computers were also used in the Manhattan Project to calculate the complex formulae related to atomic fusion, prior to the widespread introduction of computers, and the term has also been applied to individuals with prodigious powers of mental arithmetic, also known as mental calculators.
Split into simpler sentences: Human computers were also used in the Manhattan Project to calculate the complex formulae related to atomic fusion, prior to the widespread introduction of computers. The term has also been applied to individuals with prodigious powers of mental arithmetic, also known as mental calculators.