re never able to show the sizes and distances
correctly. If they were to begin by making the sun one inch in diameter,
then the earth would have to be three yards off, and as small as a grain
of dust; some of the planets would have to be across the street, and
others away beyond the opposite houses. So when you look at these little
solar systems, as they are called, you must remember that the sizes and
distances are all wrong.

"Still, you can get from them some idea how the sun stands in the
middle, and the earth and other planets go round, and how the earth,
while going round the sun, keeps also turning itself around. You have
seen how a top, while spinning, sometimes runs round in a circle. That
is just the way our earth does. And if you imagine a candle in the
centre of the circle that the top makes, you will see why it is
sometimes day and sometimes night. When the side of the earth we are on
is turned toward the sun, we have day; and when we have spun past the
sun, night comes.

"The sun seems to go past us, and people used to think it really did.
But we know now that it is as if we were in a rail-car, and the trees
and houses seemed to be rushing along, when we ourselves are the ones
that are moving. The sun and all the stars seem to move through the sky
from east to west; but it is only our earth that is turning itself the
other way, and carrying us with it."

"What makes summer and winter?" asked Joe.

"I think that the top will help you to understand that too. You have
noticed that when it spins it does not always stand straight up, but
often leans over to one side. So sometimes the upper part of it would be
over toward the candle, and sometimes over away from it. The earth leans
over too in this same manner; and that is the reason why we have summer
and winter. When by this leaning our part of the earth is toward the
sun, we get more heat, and have a warm season; when we are leaning away
from the sun, and are more in the shadow, the cold weather comes, and
continues until we get into a good position to be warmed up again.

"A kind Providence brings this all around very regularly, and there is
no danger of our being kept so long in the cold that we would freeze to
death. Everything works like a clock that is never allowed to run down
or get out of order. In spinning, the earth carries us round twelve or
fifteen times as fast as the fastest railway train has ever yet been
made to run; and in making its cir