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The Epic Interactive Encyclopedia 1998
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Epic Interactive Encyclopedia, The - 1998 Edition (1998)(Epic Marketing).iso
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INFOTEXT
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1992-09-02
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In astronomy, the apparent shape of the Moon
or a planet when all or part of its
illuminated hemisphere is facing Earth. The
Moon undergoes a full cycle of phases from
new (when between Earth and the Sun) through
first quarter (when at 90 degrees eastern
elongation from the Sun), full (when opposite
the Sun), and last quarter (when at 90
degrees western elongation from the Sun). The
inferior planets can also undergo a full
cycle of phases, as can an asteroid passing
inside the Earth's orbit. The Moon is gibbous
(more than half but less than fully
illuminated) when between first quarter and
full or full and last quarter. Mars can
appear gibbous at quadrature (when it is at
right angles to the Sun in the sky). The
gibbous appearance of Jupiter is barely
noticeable.
2.
In physics, a stage in an oscillatory motion,
such as a wave motion: two waves are in phase
when their peaks and their troughs coincide.
Otherwise, there is a phase difference, which
has consequences in interference phenomena
and alternating current electricity.
3.
In chemistry, a physical state of matter: for
example, ice and liquid water are different
phases of water; a mixture of the two is
termed a two-phase system.