GRAVITY IN THE EXTREME
Bending Light
You know that gravity can pull objects toward each other, but did
you know that gravity can also affect light? Very extreme sources of
gravity cause the normally straight path of a light beam to bend.
Going in Circles
Although Earth is massive, the effects of its gravity on light are not
noticeable. However, scientists can model what a familiar scene
might look like with an extreme source of gravity nearby. The
image to the left shows how the light from the Seattle Space
Needle could be bent almost into circles if an extremely small yet
extremely massive object, such as a black hole, were in front of it.
Seeing Behind Galaxies
How do we know that gravity can
bend light? Astronomers, who study
space, have seen the phenomenon in
action. If a very bright but distant
object is behind a very massive one,
such as a large galaxy, the mass of the
galaxy bends the light coming from
the distant object. This effect, called
gravitational lensing, can produce
multiple images of the bright object
along a ring around the massive
galaxy. Astronomers have observed
gravitational lensing in their images.
Facts About
Bending Light
• Gravitational lensing
was predicted by
Albert Einstein in the
early 1900s, but the
first example was not
observed until 1979.
• The masses of distant
galaxies can be
found by observing
their effect on light.
Seeing Quadruple
This gravitational lens is
called the Einstein Cross.
The four bright objects that
ring the central galaxy are
all images of the same very
bright yet very distant
object that is located
20 times farther away
than the central galaxy.
EXPLORE
1. INFER Why are you unable to notice the gravitational
bending of light by an object such as a large rock?
2. CHALLENGE Look at the photographs in the Resource
Center. Find the multiple images of the distant objects and
the more massive object bending the light from them.
RESOURCE CENTER
CLASSZONE.COM
404
Find out more information
about gravitational lenses.