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70 CHAPTER TWO
Light Beam Bends

Room Near a Star

Acceleration or Gravitational Pull
FIGURE 2-33 Light not only bends in the presence of gravity; it actually
falls.

Gravity is this bending light. But if we maintain that light must travel in a straight
line at a constant speed, then we must conclude that gravity bends space itself. The very
existence of matter, which engenders gravitational force, bends our fabric of space.
Seems simple enough, right? Lest you worry about your warped existence, please be
assured that the bending of space is quite small and can be ignored in most of our every-
day existence.
Around the First World War, some astronomers decided to put Einstein’s General
Theory of Relativity to a test. They observed some known stars during a solar eclipse.
Sure enough, stars emerged from behind the sun and moon earlier than they were sup-
posed to. The stars’light was coming from behind the sun (where the astronomers should
not have been able to see it), bending around the sun’s gravity and appearing before they
were supposed to. Further, the amount of the observed bending closely matched
Einstein’s theoretical calculations. This was a revelation in the sciences and confirmed
Einstein’s major discovery. It was a beautiful piece of work (see Figure 2-34).
A few years after that, scientists found three stars in a row, with the outer two appear-
ing identical. It turns out that the light from one star was being bent around an inter-
vening star, so both images appeared to us on Earth. This was another manifestation of
gravity bending light and has been called a gravitational lens. Since starlight can bend