Oxford Democrat. [volume] (Paris, Me.) 1833-1933, 1907-11-12
OF THE DAYS|
Difference Between the Star Day
and the Sun Day.
IT IS GREATEST IN WINTER.

Why the Difference Occurs and How
II May 30 observsd-oddly Enough
the Shortest Day In the Year 10
Really the Longest Day In Time.
How long, after all, is a day? The
Biographies say that 1t is the TIM re-
quired for the earth to turn once on
its axis, that it measures twenty-four
hours by the clock and that fraction
more than 1865 of them are to be found
in year.
1t is a good plan when one reads
anything in a book to test 1t when he
can for himself. We want to see just
how long it takes the earth to turn
over once. Let us take any one Of
the fixed stars that chances to be In
line with some convenient point and,
watch in hand, notice the precise mo-
ment ut which the star touches, let US
say, a particular tree, branch or stee-
pie on the horizon line. II on the next
evening we stand at precisely the same
spot and sight the same star again In
line with the same point as before,
then we shall know that the earth has
turned on its axis just once.
Curiously enough, however, we shall
discover, If this Is done carefully, that,
in spite of what the books say, it does
not require twenty-four hours for the
earth to turn over once About four
minutes before the day is up, by the
clock, the earth has revolved once and
brought the star back to its old posi-
ton in the sky. Really, then, the earth
turns on It's axis once in twenty three
hours, ffty-six minutes and four Sec
onds and, as one can easily reckon,
makes something more than 1863 revo-
lutions In year.
But human beings are not so much
Interested In the stars as in the sun.
We really don't care much how long 1t
takes the enrth to turn over and bring
Il star back again to the same point In
the sky or how many times In year
.. star seems to go by. We set. our
clocks and reckon our year by the
turning of the earth under the sun,
and because the earth not only turns
under the sun, but also goes round 1t,
it takes about four minutes longer to
bring the sun up to its old place In
the sky than to bring back star. This
comes about simply enough. Suppose
one Is In Il room looking out the win
dow at a tree. If he turns round once
exactly lie will find himself looking
straight Mt the tree again, but II he
tried the same thing when he was on
moving train he would find that
while he was making the turn the tree
had fallen behind. He would then, &C
cording to the way be twirled, have to
turn Il little more or little less TO
bring the tree straight before his nose.
Therefore it is not quite true that
day l.; the time required for the earth
10 turn once on It's axis. 1t really Is
this time plus the four minutes. or so
required for it to turn and look back
ut the sun The time required for this
extra turn Is not the same Mt all times
in the year One can easily see In the
case Of the moving train that the fast-
or the cars were moving or the nearer
the track the tree stood the more the
latter would seem to shift It's position.
Since the earth is some 100000 miles
nearer the sun IN winter than in sum
mcr. and since also the nearer the sun
1t is the faster it travels, the difference
| Letween star day and sun day Is
greatest In winter.
Oddly enough. it happens that Dec.
90. which has the least daylight or
any day in the year and Is therefore
commonly said to be the shortest OF
all days. is really the longest. 1t does.
| us natter Of fact. run almost half
minute over twentyfour hours. while
the true shortest day. which comes on
Sept. II. falls short by about the same
time.
So we really have three different
! days" There is the star day, which
Is the time during which the earth
turns over once. This, because the
earth spins steadily, is always the
same length. twenty-three hours, fifty
six minutes. four and nine-hundredths
seconds. and there are 3GG Of them in
year. Then there Is the ordinary le-
gal day. which is the time required for
Il proper clock to get round twice.
This is Just twentyfour hours. Be-
sides these. there is the sun day, its
time told by the sundial, which. TAX
ing short with long, averages twenty
four hours, but Is never found to be
exactly the same length for two days
in succession.
There Is string Of long days in the
winter, followed by series Of short
ones in the spring. In the summer the
sun days get long again, though not
quite so long as in the winter. In the
autumn come the shortest days Of all.
Only occasionally are clock day and
sun day of the same length. Only
four times year do clock noon by
the clock hands and sun noon by the
sundial occur ut the same moment.
while, because the long and short sun
days are found in sets, they oftentmes
may be more than fifteen minutes
apart.
The vast majority Of the people
reckon their time by the sun. But
time for civilized men Is time by the
clock. The days are all twenty-four
hours long, and no matter where the
sun Is 1t is noon for us when the clock
strikes r. Nevertheless, astronomers
often 20 by star time, get In an extra
day In each year and have their noon
fall at all times Of the day or night
L. 7. brewster In Chicago Record-Her-
| all