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FIG. 296.--Diagram repre-senting stellar aberration.

Summary: C
FIG. 296.-- Diagram repre-
senting stellar aberration.
From "Text Book of General Physics," by Joseph Sweetman Ames (1904) page 568
Method of Bradley.Another method by which the velocity of light could be
determined was discovered by Bradley, the great English astronomer, in 1727. He had observed
that if a fixed star was observed through a telescope, this instrument had to be pointed in slightly
different directions at different times of the year; so that, if the image of the star were kept on the
cross hairs of the telescope during the whole year, the
instrument had to be kept in continual motion in such a
manner that its end described a small curve. The
explanation given by Bradley was extremely simple.
Consider a long tube closed at its two ends by caps in
which there are two openings directly opposite each
other. A particle entering at one opening, with a motion
parallel to the axis of the tube, will escape through the
opening at the other end, if the tube is at rest. But, if the
tube is moving at right angles to its length, the opening in


Source: Henry, Richard C.- Department of Physics and Astronomy, Johns Hopkins University


Collections: Physics