Rock Island daily Argus. (Rock Island, Ill.) 1886-1893, 1891-04-10
THE VELOCITY OF LIGHT.
Speed That Is Too Great for the Average
Mind to Fully Comprehend.


Mind TO Fully Comprehend.
II you could take all the people in the
world and set them out In space mile
apart, like mile posts along railroad, and
then at the farther end use all the dogs and
cats to extend the line Of mile posts, you
would run far short of material to mark
the distance out 10 the earth's brother
planet, Neptune Again, if YOU could use
all this material of men, women, children.
dogs and cats. and put them out so that
they would be as far from one another as
Boston is from San Francisco. your line
wouldn't be half long enough TO reach to
the nearest star.
On a clear night the average eye will
readily see stars as low as the sixth magni-
tude. Such a shining beauty as Sirius
winks at you so archly that it seems al
most impossible that years are consumed
in the passage of its rays to the earth,
when we remember that light travels more
than Isl, 600 miles in second. Yes, if the
nearest of the beautiful twinklers should
be blotted out at this moment we should
still see it without the slightest change in
appearance two or three years after Chi
cago cleans up the debris of the Worlds
fair.
But even star SO far away as that seems
nearly within touching distance when we
find that otSer stars, visible with the tele-
scope, are so far away that, for all we
know, they may have been blotted out be-
fore Cain and Abel were born. That is to
say, if one of those far distant CRIBS had
been utterly annihilated, as you would
snuff out candle. when Adam and Eve
were enjoying themselves ia the Garden of
Eden, the rays then starting toward the
earth, notwithstanding the awful speed of
light. could not get here in time 10 meet
the closing of the Nineteenth century.
How DO we know that light travels at
such wonderful speed Up TO about two
hundred and twenty-five years ago il was
supposed that rays of light from ali the
celestial orbs passed instantly to the OBJ
servers eye. The old astronomers. in fact.
never took thought of the matter at all.
They simply saw the sun and the stars,
but they never dreamed that the rays from
them had to journey millions. billions and
trillions of miles in getting to mundane
eyes. Ii was the great fortune of Danish
astronomer TO make the discovery that
light, as well as sound or a railway train,
requires given time to travel given dis
lance
Roemer, the famous Dane alluded to,
WAS led to his discovery by observations of
the eclipses of Jupiter's moons. He found
that there was a difference OF several min
utes in these eelipses, that they occurred
earlier when the earth was on the side of
the sun nearest to Jupiter and later when
farthest away. With this data as a start
ing point he soon found that the differ
| ence of apparent time resulted from the
| time required for light to travel across the
diameter Of the earth's orbit, about one
hundred and eighty-two million miles.
This time proved 10 be about sixteen min
| utes. and as half that would be the time
| from the earth to the sun the mystery was
solved
The accuracyof this calculation has since
been verified by other methods, and all
| authorities now agree that the velocity of
| light is not far from Isl. 600 miles a second.
Ii Is difficult for the mind to grasp and
| comprehend such speed The swiftest ami
mated thing Is undoubtedly the pigeon,
| which has been known to travel hundreds
| of miles at the rate of fifty miles an hour
| y little arithmetical exercise Will show
that it would take pigeon more than zoo
years to cover the distance TO the sun at
| fifty miles an hour without a stop, and TO
go as far as Neptune it would take the
bird nearly thousand years.
When we want an illustration of speed
we often use the expression swift as a
cannon ball" But if you could fire a can
| non ball to the sun when you are a college
freshman your hair would be sprinkled
with gray when the ball stopped. for you
| would be seventeen years older than when
you fired the shot.-Philadelphia Times