The moon is up there
in the sky too; you just can't see it during the day of the eclipse because the
lit side is facing away from us (a phase called "New Moon")
and the blue sky washes everything out. As the moon just "touches"
the sun (actually coming between, us and the sun, not touching!)
you see the first bite taken out of the edge of the sun's disk.
This is called "first contact." This is where
the partial phases of the eclipse start.
For about the next
hour and a half the moon covers more and more of the sun's
disk. As the total phase of the eclipse approaches, the lighting around you
becomes very strange. It gets much darker, but unlike at sunset,
the color of the remaining light does not become orangish and
reddish. It just gets grayer. If there are animals around to observe,
the daytime animals become quiet and prepare for sleep, while
at the same time the nocturnal animals get ready to come out.
This must be a very confusing time for them because their internal
biological clocks must be telling them it's still daytime!
a sliver of the sun is left, with only a few minutes to go until
totality, you might notice long, straight bands of shadows moving
across the ground. These "shadow bands" form from refraction,
or bending of light in the earth's atmosphere similar to what you might see on the bottom of a pool of water.
This is the same
thing that causes stars to twinkle. With the sun only a long slit
of light, the distortions in the atmosphere become visible as
moving bands, parallel to the remaining slit of sunlight. They
are usually very low in contrast and it helps to spread a white
sheet on the ground to help viewing. They are VERY difficult to
photograph. We've never seen any pictures of shadow bands. Of course,
this could be because everyone has their cameras trained on the
main event about to happen which is, admittedly, much more spectacular.
Second contact occurs when
the moon completely covers the sun. Now the action really heats up! The edge of the moon
is not perfectly round. There are mountains and valleys that make
the edge less than smooth.