ttention upon a single vibration of light, C, while
we on the other hand give to the projectile, B, a speed equal to that
of light, then we can conclude that B and C in their continued motion
can always remain next to each other. Now if we watch all this, not
from the movable compartment, but from a place on the earth, then we
shall note the usual falling movement of object A, which shows us that
we have to deal with a sphere of gravitation. The projectile B will,
in a bent path, vary more and more from a horizontal straight line,
and the light will do the same, because if we observe the movements
from another standpoint this can have no effect upon the remaining
next to each other of B and C.

DEFLECTION OF LIGHT

The bending of a ray of light thus described is much too light on the
surface of the earth to be observed. But the attraction of gravitation
exercised by the sun on its surface is, because of its great mass, more
than twenty-seven times stronger, and a ray of light that goes close by
the superficies of the sun must surely be noticeably bent. The rays of
a star that are seen at a short distance from the edge of the sun will,
going along the sun, deviate so much from the original direction that
they strike the eye of an observer as if they came in a straight line
from a point somewhat further removed than the real position of the
star from the sun. It is at that point that we think we see the star;
so here is a seeming displacement from the sun, which increases in the
measure in which the star is observed closer to the sun. The Einstein
theory teaches that the displacement is in inverse proportion to the
apparent distance of the star from the centre of the sun, and that for
a star just on its edge it will amount to 1'.75 (1.75 seconds). This is
approximately the thousandth part of the apparent diameter of the sun.

Naturally, the phenomenon can only be observed when there is a total
eclipse of the sun; then one can take photographs of neighboring stars
and through comparing the plate with a picture of the same part of
the heavens taken at a time when the sun was far removed from that
point the sought-for movement to one side may become apparent.

Thus to put the Einstein theory to the test was the principal aim of
the English expeditions sent out to observe the eclipse of May 29,
one to Prince's Island, off the coast of Guinea, and the other to
Sobral, Brazil. The first-named expedition's observers were