The Richmond palladium and sun-telegram. [volume] (Richmond, Ind.) 1907-1939, 1907-10-12
OF THE DAYS
Difference Between the Star Day
and the Sun Day.
1T is GREATEST IN WINTER.
Why the Difference Occurs and How
II May Be ohserved-Oddly Enough
the Shortest Day In the Year Is
Really the Longest Day In Time.

How long. after all, is a day? The
Biographies say that it Is the time re-
quired for the earth to turn once ON
its axis. that ii measures twenty-four
hours by the clock and that a fraction
more than 365 OF them are to be found
in a year
1t is a good plan when one reads
anything in a book to test it when he
can for himself. We want to see just
how long IL 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 at which the star touches. let us
say, particular tree. branch or stee-
pie on the horizon line. If 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.
Curlously enough, however. we shall
discover if this is done carefully, that,
in spite of what the books say. il 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 its axis once in twenty three
hours, fifty-six minutes and four sec
onds and. as one can easily reckon,
makes something more than 800 revo-
lutions In a 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 earth to turn over and bring
a 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,
1t 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 a room looking out the win
dow at tree If he turns round once
exactly he will find himself looking
straight at the tree again. but If 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, ac-
cording to the way he twirled, have to
bring the tree straight before his nose.
Therefore 1T is not quite true that a
day is the time required for the earth
to turn once on its axis. 1t really Is
this time plus the four minutes or so
required for it to turn and loo back
at the sun. The time required for this
extra turn Is not the same at all times
in the year. One can easily see in the
case Of the moving train that the fast
er the cars were moving or the nearer
the track the tree stood the more the
latter would seem to shift its position.
Since the earth is some 100000 miles
nearer the sun in winter than in sum-
mer, and since also the nearer the sun
it Is the faster it travels, the difference
between star day and sun day is
greatest in winter.
Oddly enough. it happens that Dec.
%, which has the least daylight of
any day in the year and is therefore
commonly said to be the shortest of
all days. is really the longest. 1t does,
az q matter of fact, run almost half a
minute over twenty-four hours, while
the true shortest day, which comes OH
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 366 Of them In
a year. Then there is the ordinary le-
gal day, which Is the time required for
proper clock to get round twice.
This is just twenty-four hours. Be
sides these, there is the sun day, its
tine 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.
mere Is SITluS OI louS Gays III IHe
winter, followed by a 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 COM the shortest Gays Of all.
| Only occasionally are clock day and
| sun day of the same length. Only
| four times a year do clock noon by
| the clock hands and sun noon by the
sundial occur at the same moment
| while because the long and short sun
| days are found in sets, they oftentimes
! may be more than fifteen minutes
| apart.
The vast majority of the people
reckon their time by the sun. Blu,
| time for civilized men is time by the
clock. The days are all twenty-four
hours long, and no matter where the
sun is it is noon for US when the clock
strikes u. Nevertheless. astronomers
often go by star time, get in an extra
day in each year and have their noon
fall at all times of the day or night
E. T. Brewster in Chicago Record Her
| Aid