Can be spelt either way so take your pick
Gaea or , Gaia or or Ge or
n in Greek mythology, the goddess or personification of Earth, mother of Uranus and (by him) of Oceanus, Cronus and the Titans; (usu Gaia) Earth apprehended as a living entity within the solar system.
[Gr]
Gaea hypothesis or Gaia hypothesis n the hypothesis stating that natural life systems find their own balances.
\u00A9 Chambers Harrap Publishers Ltd: The Chambers Dictionary 2003; The Chambers Thesaurus 2004