Re: When is the next eclipse?

It depends mainly on where you are and what kind of eclipse you're talking
about.

Because an eclipse is basically the blocking of the either the sun and
moon, there are two types: lunar and solar.  A solar eclipse is when the
moon blocks the sun from earth -- it also can be defined as when the earth
enters the moon's shadow.  A lunar eclipse is when the earth blocks the sun
from the moon-- it also can be said defined as when the moon enters the
earth's shadow.

For an eclipse to happen it only takes an alignment of the earth, sun and
moon system. For an eclipse to be visible by someone on earth, however,
this alignment needs to take place in a particular way.

For a lunar eclipse, the sun, earth and moon are aligned in that order and
the observer needs to be on the rear side of the earth from the sun.  That
is, it needs to be nighttime.  Since the earth rotates before, during, and
after the lunar eclipse, an observer may not get to see an entire lunar 
eclipse because the moon may not even be visible from that observer's
location. Whether or not you see a total or partial lunar eclipse depends
mainly on how good the alignment is between the sun, earth and moon.  If
the moon doesn't completely pass through earth's shadow, then you get a
partial lunar eclipse.

For a solar eclipse, the sun, moon and earth are aligned in that order. The
neat part about a solar eclipse is that the angular diameter (the amount of
sky in degrees) for both the sun and the moon is about half of a degree! 
That means that every now and then, the moon completely blocks the sun
(total eclipse).  The hard part about seeing a total solar eclipse is that
the earth does not completely fit into the shadow of the moon made by the
sun!  This means that only some places on earth will even pass through the
shadow and actually see the eclipse.  Whether or not you see a total or
partial eclipse depends mainly on the your location on earth! The moon's
shadow on earth has two distinct regions, the umbra (the region completely
blocked from the sun) and the penumbra (the region partially blocked from
the sun). If the umbra of the shadow crosses over an observer, the observer
sees a total solar eclipse. The umbra is only about 167 miles in diameter
making it very unlikely for just any observation to "catch" a total solar
eclipse.  However, the penumbral shadow is relatively large, making a
partial solar eclipse far more likely. Yet another type of solar eclipse is
called an annular eclipse, which occurs when the moon is slightly farther
from the earth, making it smaller in the sky and not quite big enough to
completely cover the sun.  This makes the eclipse look like a ring in the
sky: an annulus.

But, independent of location on earth, here are the upcoming total solar
and lunar eclipses:

Next Total Solar Eclipse: June 21, 2001 and will be visible over Africa. A
map of the location of this eclipse can be seen at http://sunearth.gsfc.nasa.gov/eclipse/SEplot/SE2001Jun21T.gif

Next Total Lunar Eclipse: July 16, 2000 but will only really be visible
from Australia and southeast asia. A map of this eclipse and where it is
visible can be seen at: http://sunearth.gsfc.nasa.gov/eclipse/LEplot/LE2000Jul16T.gif



Some good websites for eclipse information:

Solar Eclipse Explanation: http://csep10.phys.utk.edu/astr161/lect/time/eclipses.html

People who chase solar eclipses: http://www.eclipse-chasers.com/

NASA's eclipse page (where I got the maps): http://sunearth.gsfc.nasa.gov/eclipse/