- Gaia Hypothesis
- named for the Greek Earth goddess Gaea, holds
that the Earth as a whole should be regarded as a
living organism and that biological processes
stabilize the environment. First advanced by
British biologist James Lovelock in 1969.
- Galle, Johann Gottfried
1812-1910
- German astronomer who, with Heinrich Louis d'Arrest, made the first
observation of Neptune based on calculations by Le Verrier. Though
Galle was the first to observe Neptune, its
discovery is usually credited to Adams (who made an earlier
calculation) and Le Verrier.
- Galilean Moons
- Jupiter's
four largest moons: Io, Europa, Ganymede and
Callisto; discovered independently by Galileo and Marius. (Galileo proposed
that they be named the Medicean stars, in
honor of his patron Cosimo II de Medici; the
present names are due to Marius)
- Galileo Galilei
1564-1642
- Italian astronomer and physicist. The first to
use a telescope to study the stars. Discoverer of
the first moons of an extraterrestrial body (see
above). Galileo was an outspoken supporter of Copernicus's heliocentric
theory. In reaction to Galileo, the Church
declared it heresy to teach that the Earth moved
and imprisoned him. The Church clung to this
position for 350 years; Galileo was formally
exonerated in 1992.
- gegenschein
- a round or elongated spot of light in the sky at
a point 180 degrees from the Sun. Also called
counterglow.
- George III 1738-1820
- King of Great Britain and Ireland (1760-1820).
His government's policies fed American colonial
discontent, leading to revolution in 1776.
- geosynchronous orbit
- a direct, circular,
low inclination
orbit in which the satellite's orbital velocity
is matched to the rotational velocity of the
planet; a spacecraft appears to hang motionless
above one position of the planet's surface.
- granulation
- a pattern of small cells seen on the surface of
the Sun caused by the convective motions of the
hot solar gas.
- greenhouse effect
- increase in temperature caused when incoming
solar radiation is passed but outgoing thermal
radiation is blocked by the atmosphere (carbon
dioxide and water vapor are the major factors).
Very important on Venus
and Earth but
very weak on Mars.
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