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Page 5
Another method which would have a more limited application, would depend
on the velocity of light. It has been maintained that the velocity of
light in space is not the same for different colors. Certain stars,
called Algol stars, vary in light at regular intervals when partially
eclipsed by the interposition of a large dark satellite. Recent
observations of these eclipses, through glass of different colors, show
variations in the time of obscuration. Apparently, some of the rays
reach the earth sooner than others, although all leave the star at the
same time. As the entire time may amount to several centuries, an
excessively small difference in velocity would be recognizable. A more
delicate test would be to measure the intensity of different portions of
the spectrum at a time when the light is changing most rapidly. The
effect should be opposite according as the light is increasing or
diminishing. It should also show itself in the measures of all
spectroscopic binaries.
A third method of great promise depends on a remarkable investigation
carried on in the physical laboratory of the Case School of Applied
Science. According to the undulatory theory of light, all space is
filled with a medium called ether, like air, but as much more tenuous
than air as air is more tenuous than the densest metals. As the earth is
moving through space at the rate of several miles a second, we should
expect to feel a breeze as we rush through the ether, like that of the
air when in an automobile we are moving with but one thousandth part of
this velocity. The problem is one of the greatest delicacy, but a former
officer of the Case School, one of the most eminent of living
physicists, devised a method of solving it. The extraordinary result was
reached that no breeze was perceptible. This result appeared to be so
improbable that it has been tested again and again, but every time, the
more delicate the instrument employed, the more certainly is the law
established. If we could determine our motion with reference to the
ether, we should have a fixed line of reference to which all other
motions could be referred. This would give us a line of ever-increasing
length from which to measure stellar distances.
Still another method depends on the motion of the sun in space. There is
some evidence that this motion is not straight, but along a curved line.
We see the stars, not as they are now, but as they were when the light
left them. In the case of the distant stars this may have occurred
centuries ago. Accordingly, if we measure the motion of the sun from
them, and from near stars, a comparison with its actual motion will
give us a clue to their distances. Unfortunately, all the stars appear
to have large motions whose law we do not know, and therefore we have no
definite starting point unless we can refer all to the ether which may
be assumed to be at rest.
If the views expressed to you this morning are correct, we may expect
that the future of astronomy will take the following form: There will be
at least one very large observatory employing one or two hundred
assistants, and maintaining three stations. Two of these will be
observing stations, one in the western part of the United States, not
far from latitude +30�, the other similarly situated in the southern
hemisphere, probably in South Africa, in latitude -30�. The locations
will be selected wholly from their climatic conditions. They will be
moderately high, from five to ten thousand feet, and in desert regions.
The altitude will prevent extreme heat, and clouds or rain will be rare.
The range of temperature and unsteadiness of the air will be diminished
by placing them on hills a few hundred feet above the surrounding
country. The equipment and work of the two stations will be
substantially the same. Each will have telescopes and other instruments
of the largest size, which will be kept at work throughout the whole of
every clear night. The observers will do but little work in the daytime,
except perhaps on the sun, and will not undertake much of the
computation or reductions. This last work will be carried on at a third
station, which will be near a large city where the cost of living and of
intellectual labor is low. The photographs will be measured and stored
at this station, and all the results will be prepared for publication,
and printed there. The work of all three stations will be carefully
organized so as to obtain the greatest result for a given expenditure.
Every inducement will be offered to visiting astronomers who wish to do
serious work at either of the stations and also to students who intend
to make astronomy their profession. In the case of photographic
investigations it will be best to send the photographs so that
astronomers desiring them can work at home. The work of the young
astronomers throughout the world will be watched carefully and large
appropriations made to them if it appears that they can spend them to
advantage. Similar aid will be rendered to astronomers engaged in
teaching, and to any one, professional or amateur, capable of doing work
of the highest grade. As a fundamental condition for success, no
restrictions will be made that will interfere with the greatest
scientific efficiency, and no personal or local prejudices that will
restrict the work.
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