Evening star., 1932-07-26
SPEED OF LIGHT
| AGAIN IN QUESTION
Discrepancies Found in Re.
suits Obtained in Measure
ments on Pacific Coast.
BY THOMAS r.. HENRY.

The speed of light once again is in
question.
Because of paradoxical and mex
plicable variations found in the most
precise measurements, the Coast and
Geodetic Survey has been requested by
the Mount Wilson Observatory of the
Carnegie Institution Of Washington to
remeasure a distance of mile which
has already been measured with almost
unbelievable accuracy.
The speed of light is the fundamental
time constant, from which all others
must be derived. Three years ago the
late Prof. Albert A. Nicholson of the
most physicists of all time, undertook
to settle finally the question of how
fast light travelled. 1t was to be the
crowning achievement of his life.
Measurement Is Checked.
BY extraordinarily delicate physical
devices he measured the speed at which
light travelled between two mountain
peaks in Southern California. The
distance between the two mountain tops
Mount Wilson and San Antonio
Geodetic Survey at DR.. MichelSon'S re-
quest. He informed the Government
agency that he would be satisfied If
this distance could be measured as
precisely as one part in 100000. He
was informed that modern surveying
refinements probably would make it
possible to measure the distance with
o possible error of only one part in
million.
In determining this distance the
Coast and Geodetic Survey used the
most refined methods known to science.
The measurement was checked and re-
checked. The error, Coast and Geo.
detic Survey officials say, can hardly
be much greater than one part in
million. In, fact, according to Maj.
william Bowie, chief of the division
of geodesy, the probable error is only
about one part in 100000. No two
other mountains have had their dis
tances apart determined with such pre-
cision
With such assurance. DR.. Nicholson
began his measurements. These were
checked over and over again. Every
possible precaution was taken and
everything that might affect the re-
suits was allowed for. As a result, he
announced the velocity of light at 299,-
797 kilometers a second-slightly great
er than the previously accepted figure.
Results Are Different.
This was believed to represent the
closest measurement possible to human
ingenuity at present, figure which
would stand without much possibility
of challenge for many years. But light
should have the same speed, regardless
of the place where the measurements
were taken DR.. Nicholson, as further
check, had mile-long vacuum pipe
installed along the surface of the earth
at Santa Anna, Calf. This mile also
was measured and remeasured by the
Coast and Geodetic Survey until the
probable error was reduced to almost
zero. The same precise methods were
used in measuring the speed of light
through this pipe as through the longer
one-but the results did not come out
anywhere near the same. DR.. Michel
son could not explain the difference.
He died last Winter with this uncer-
tainty on the elimination of his life
work.
The Coast and Geodetic Survey was
requested to remeasure the mile. It
did SO. This time the extremely minute
difference of 5.3 millimeters was found.
1t represented a difference OF only about
one part In 100000. This was far from
enough TO account for the observed diff
ference in the speed of light. The ac-
tual difference between the two speeds
has not been announced, but it has
been described as considerable, so that
it cannot be explained by any survey
ing error which is conceivable with the
present refined methods.
The request to remeasure the mile has
been made to remove any lingering
doubt, although 1t Is considered almost
absolutely certain that the difference
cannot be due to surveying error. The
Temeasurement will be made some time
this Fall, Maj. Bowie said, and if prac-
ticable, by the same man.
Scientists Puzzled.
It is possible, Maj Bowie said, that
some slight difference might be found,
due to the change in the surface of
the earth between wet and dry seasons
But even when the utmost allowance
Is made for this, 1t Is far from sufficient
to account for the observed difference
in the speed of light
There Is O bare possibility, it was
pointed out, that some slight error may
have crept in when the positions fur
nished by the Coast and Geodetic Sur
vey engineers were transferred to the
pipe line. Such extreme precautions
were used that this is extremely un-
likely.
A second possibility Is that there may
have been some error in the manipula-
tion Of the extremely delicate apparatus
used in measuring the light speed it
self. But the measurements were re-
peated again and again. The results
seem to remain consistent within them
selves.
A third most remote possibility, it
was pointed out, is that the discrepancy
may be due to an actual difference in
the speed of light over the two bases
and that such a paradox, If it can be
resolved, may lead to the discovery of
hitherto unsuspected physical laws
which may lead to revolutionary
changes In present conceptions Of the
mechanics Of the universe.