Yes, yes,--and I can now see why the Great Bear seems to go away from
us, as we get up the hill toward the equator. That constellation is
opposite to a part of the earth a good way to the north of us. As
we rise higher from that place, we must appear to rise higher than
the stars over it. How I do long to stand under that bright Belt of
Orion, and under Sirius! And how I should like to see the pretty Cross
stretched over the mast-head!
Wait a bit, my lad, and you may see all these wonders in time.
How delighted I am to make out that all those funny motions among the
stars are simply owing to the world being round.”
SIZE OF THE WORLD
It was while half tired of ship life already, and longing for the
excitements of shore in a new country, that the boy turned round to his
father, and said, with a sort of yawn--
“What a long while we shall be getting to Australia, father.
It is a great distance to go, James.
Well, I think the earth must be a good big ball to roll about among the
stars.
You ought to know its size.
I have been told that it is 25,000 miles round; but who has measured it.
Why as to that, you and I might measure it some evening by the stars.
You know that the great space between the Belt and Polar Star is
one-quarter of the great circle of the heavens.
Of course.
Every circle is reckoned to be divided into spaces called degrees, of
which 360 go to form the circumference; so that one-fourth will be
ninety degrees. You can imagine that space divided into ninety of these
portions, called degrees.
What rare compasses that would take!
Those two bright stars overhead, which are about twice the same
distance apart as the apparent diameter of the Sun, would be nearly
equal to one of these ninety portions. Now, you know that if you were
at the pole, you would have the Polar Star above you; and, if at the
equator, Orion’s Belt would be over your head.
I understand all that, father.
You know, then, that you might be in a place where one of those two
bright stars would be overhead, and you might journey on to another
place further south, where the other one would be at the zenith or
overhead.
This is all clear to me.
Then if you measured the ground you had gone over, it would be equal to
one-ninetieth part of the space between the pole and the equator, or
about seventy miles. Can you tell how many miles it would be from the
pole to the equator?
That would be seventy times ninety--which is 6300.
But that is only one-quarter of the way round--is it not?
Yes; the whole distance round would be four times 6300, or about 25,000
miles.
Well done--we have measured the circumference of the world.”
THE EARTH NOT QUITE ROUND.
“Father,” exclaimed James one day, “the captain has been giving me
a riddle which I cannot guess. He asks where a pound of shot is not a
pound. Is he joking with me?
Not at all, lad. A bag of shot weighing a pound in London, or even in
Melbourne, will not weigh a pound on the equator.
Public-domain text, read in full here on John Shaqi.
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