The Washington times. [volume] (Washington [D.C.]) 1902-1939, 1924-12-15
DAY GRADUALLY
LENGTHEN|NG,
IT IS PROVED
Fact It Will be Tenth Of SEQ
ond Longer In 10000 Years
Of Interest to Science
By PROF. ERNEST w. BROWN
Department Of Astronomy, Yale
University.

The study of ancient eclipses
gave the first evidence that the
day Is gradually getting longer.
The change that is taking place is
not sufficiently great to cause any
trouble--in fact, 1t is so small that
1t can only be detected by the most
careful study. But 1t is Of great
scientific interest because 1t is
bound up with the evolution of the
earth and moon bth in the past
and the future.
In 1898, the English Astronomer
HALEY, a friend and helper Of Isaac
Newton and q man Of great ability,
found that he could not reconcile
the motion of the moon as 1t was
then known with its motion many
centuries earlier, and he suggested
that something must have occurred
to change 1t
A century later the great French
mathematician and astronomer La.
place proved that the very small
attraction OF the planets produced
such a change and the matter seam
ed settled for the time being. Then
half a century later, Adams, the
discoverer with Leverrier of the
planet Neptune, stirred everything
up again by showing that in his
calculations Laplace had made
omissions which changed the
amount seriously, so that the ancient
eclipses could not be fully explained
in this way. Many astronomers
followed him and finally justified
his criticisms.
Effect of Tides,
Then an era of speculation start
ed to explain the difference. The
German philosopher Emmanuel
Kant thought that the friction of
the tides, as they continually trav.
eled around the globe, would act
as a brake and tend to slow down
the earth. Since the earth Is the
Clock which we use to measure our
time, this meant that 1t was the
clock which was losing and not
the moon which was hurrying.
Astronomers gradually came round
20 this view because 1t was Ger.
.ainly true that the friction caused
oy the tides must slow down the
tarth as we'll as quicken the mo.
ton of the moon.
But after all, it was still only
guess because 1t did not seem pos
sible to calculate whether the fric.
ton was sufficient. to explain the
observations. Many workers, in
Guiding Simon Newcomb, who was
for many years head of the Maui
teal Almanac Office in Washing.
ton, examined the records of the
ancient echpses to see whether
HALEY had been right and found
other eclipses to use, more than
two thousand years back, but they
did not seriously change his re-
suits.
Friction Caused By Seas.
The last phase of the story
occurred since the war. Professor
8. l. Taylor, working in Cambridge,
England, started out to find how
much friction the shallow Irish Sea
could produce. He had no political
object to serve. In face he found
that 1t was quite small, only about
one-fiftieth of the amount required.
A colleague Of his, Doctor Harold
Jeffries, went to work and calcu-
| lated the amounts produced by
other shallow seas and found that
there was sufficient friction to
produce what HALEY had observed.
Curiously enough, two-thirds of it
is caused by the Behring sea,
which lies between Alaska and
Siberia, all the other seas together
accounting for the rest.
The whole amount is so small
that the day will only be about
one.tenth Of a second longer ten
thousand years hence than it is
now. But its discovery and investi-
cation is one of the big triumphs of