QUESTION:
Why is our planet called Earth?

ANSWER from Dave Hollenbach on May 20:
"Earth" is a word which means the ground, the dirt, the rocks, the
things we humans walk on.  Long ago, it was not known that the other
planets were like the "Earth".  They also have rocks and solid ground
and mountains.  But people didn't know that then.  They looked like
stars, except they moved in their positions in the sky if you looked
at them night after night.  So they were named after the gods.  The
word "planet" comes from an old word which meant "wanderer", because
the planets wander through the constellations of stars.
Of course, the planets are much closer than the stars, but if you        
see Jupiter some night, you might see it in the direction of the
star constellation Leo, while a month later it might be in the direction
of the star constellation Scorpio.