78 (number) - Definition and Overview

78 (seventy-eight) is the natural number following 77 and followed by 79.

In mathematics

78 is a triangular number, and its factorization makes it a sphenic number.

Karl A. Dahlke proved in 1989 that 78 heptominos of this shape ( ), at a minimum, are required to fill a rectangle.

In science

• The atomic number of platinum

In astronomy,

Messier object M78, a magnitude 8.0 diffuse nebula in the constellation Orion

The New General Catalogue object (http://www.ngcic.org/) NGC 78, a magnitude 12.8 barred spiral galaxy in the constellation Pisces

The Saros number (http://sunearth.gsfc.nasa.gov/eclipse/SEsaros/SEsaros1-175.html) of the solar eclipse series which began on -463 June 9 and ended on 817 July 18. The duration of Saros series 78 was 1280.1 years, and it contained 72 solar eclipses.

The Saros number (http://sunearth.gsfc.nasa.gov/eclipse/LEsaros/LEsaros1-175.html) of the lunar eclipse series which began on -125 April 10 and ended on 1155 May 18. The duration of Saros series 78 was 1280.1 years, and it contained 72 lunar eclipses.

In other fields

78 is also:

• The designation of Interstate 78, a freeway that runs from Pennsylvania to New York.
• In reference to gramophone records, 78 refers those meant to be spun at 78 revolutions per minute. Compare: LP, 33 and 45.
• A standard Tarot deck containing the 22 cards of the major arcana (including the fool) and the 56 cards of the minor arcana make up 78 cards.
• The total number of gifts in the song The Twelve Days of Christmas (since 78 is the 12th triangular number).
• The year AD 78, 78 BC, or 1978.