ble distance from us that it is
probable we shall never learn a great deal about them. Why, men have not
even yet been able to communicate with the planet Mars, at its nearest
only some thirty-five million miles from us, and this is a mere nothing
in measuring the space between us and the stars. To express the
distances of the stars in figures is really a waste of time, so
astronomers have invented another way. You know that light can go round
the world eight times in a second; that is a speed quite beyond our
comprehension, but we just accept it. Then think what a distance it
could travel in an hour, in a day; and what about a year? The distance
that light can travel in a year is taken as a convenient measure by
astronomers for sounding the depths of space. Measured in this way light
takes four years and four months to reach us from the nearest star we
know of, and there are others so much more distant that hundreds--nay,
thousands--of years would have to be used to convey it. Light which has
been travelling along with a velocity quite beyond thought, silently,
unresting, from the time when the Britons lived and ran half naked on
this island of ours, has only reached us now, and there is no limit to
the time we may go back in our imaginings. We see the stars, not as they
are, but as they were. If some gigantic conflagration had happened a
hundred years ago in one of them situated a hundred light-years away
from us, only now would that messenger, swifter than any messenger we
know, have brought the news of it to us. To put the matter in figures,
we are sure that no star can lie nearer to us than twenty-five billions
of miles. A billion is a million millions, and is represented by a
figure with twelve noughts behind it, so--1,000,000,000,000; and
twenty-five such billions is the least distance within which any star
can lie. How much farther away stars may be we know not, but it is
something to have found out even that. On the same scale as that we took
in our first example, we might express it thus: If the earth were a
greengage plum at a distance of about three hundred of your steps from
the sun, and Neptune were, on the same scale, about three miles away,
the nearest fixed star could not be nearer than the distance measured
round the whole earth at the Equator!

All this must provoke the question, How can anyone find out these
things? Well, for a long time the problem of the distances of the stars
was thought to be too