25.2. The Theory of General Relativity http://www.ck12.org
25.2 The Theory of General Relativity
The student will:
- state the conditions under which Einstein’s theory of gravity reduces to Newton’s theory of gravity.
- state two instances of experimental support for the general theory of relativity.
In a new study, scientists may have unexpectedly detected a merger of black holes about 160 million light-years
away in a galaxy dubbed NGC3393. Using NASA’s Chandra X-ray Observatory, investigators have detected two
black holes at its center, one about 30 million times the mass of the sun, and one at least 1 million times the mass of
the sun, separated by only about 490 light-years. They are the closest super-massive black holes to Earth ever seen,
according to a NASA statement. The scientists originally looked at this galaxy only to learn more about what they
thought was the sole black hole at its center.
The General Theory of Relativity
In 1905, Albert Einstein published the theory of special relativity, a theory about space and time. In the following
years, Einstein worked on the fact that acceleration produced the same effect as gravitation. For example, if you were
in an accelerating spaceship, or just an elevator, you could not tell if the force on you was from inertia or gravitation.
While Newton’s Law of Universal Gravitation works well for ordinary gravitational fields, it is inaccurate when the
gravitational intensity is high. Albert Einstein formulated thetheory of general relativityin 1914 as a new way to
explain gravity.
The classical explanation of gravity is that a force of attraction acts at a distance between two objects and the
magnitude of the force is directly proportional to each of the masses and inversely proportional to the square of the
distance between the objects. The objects move toward each other due to this force of attraction. Einstein’s new
concept of gravity states that matter (mass) causes the space around the matter to curve and also distorts time. A
straight line through this curved space would also be curved in order to be a straight line.