# Albert Einstein’s vs. Newton: General Theory of Relativity

**Topics:**General relativity, Special relativity, Spacetime

**Pages:**7 (2217 words)

**Published:**May 31, 2011

Albert Einstein, most famously known as a physicist, was a contributor to the scientific world with his many known researches and humanitarian work. As a Nobel Prize Winner in 1921, his chronicled and more important works include Special Theory of Relativity (1905), Relativity (English Translation, 1920 and 1950), General Theory of Relativity (1916), Investigations on Theory of Brownian Movement (1926), and The Evolution of Physics (1938). (Nobel Prize Foundation, 1921) In all his important works, Einstein’s Theory of Relativity has lead the way for how science currently views time, space, energy, and gravity.

Relativity, which all motion must be defined relative to a frame of reference and that space and time are relative, rather than absolute concepts, consists of two principal parts: The theory dealing with uniform motion, or the Special Theory of Relativity (1905) and the theory dealing with gravity, or the General Theory of Relativity (1916). (dictionary.com, pars. 2) Einstein’s Special Theory of Relativity is the physical theory of measurement in inertial frames of reference. Although Einstein’s Special Theory of Relativity was “special” because it dealt only with inertial reference frames; his General Theory of Relativity accounts not only for these, but also for bodies that accelerate and are based on the postulate that the local effects of a gravitational field and of acceleration of an inertial system are identical. (dictionary.com, pars.2)

An example of Einstein’s Special Relativity: One of the peculiar aspects of Einstein's theory of special relativity is that the length of objects moving at relativistic speeds undergo a contraction along the dimension of motion. An observer at rest (relative to the moving object) would observe the moving object to be shorter in length.

General relativity or the general theory of relativity (GR) in whole is the geometric theory of gravitation. It is what we currently define as gravity in modern physics. GR integrates with special relativity in relatively, but GR consists of Newton’s law of universal gravitation and describes gravity as a property of the geometry of space and time. Even though special relativity intertwines a lot with general relativity, these two viewpoints are really what GR is about and relate greatly to each other.

In the first viewpoint of GR, it is a theory of the behavior of space and time. Before the 20th century, all physics theorists assumed space and time to be absolutes, or separated from each

other. Now called spacetime, together space and time formed a background within which matter moved. (Felder, pars. 4-5) In Einstein’s theory of GR, this physical theory was to describe how different kinds of matter would interact with each other and predict their motions. The theories of space and time greatly changed after the development of the Special Relativity Theory and shortly later the General Relativity Theory by Einstein. This results that space and time came to be viewed as the important variables in physics, which are capable of being changed by the mater within them and in turn changing the way that matter behaves. (Felder, pars. 5)

Spacetime is an important factor in GR. In Newton’s world and before the 20th century, physics space and time again were viewed completely separately. In relativity theory, time is the fourth dimension our world has instead of the three one would think there is. It is hard to picture a 4D world, so to make things simpler let’s picture a 2D world. As shown in diagram 1, we can view spacetime as a 2D surface where the horizontal direction is space and the vertical direction is time. The diagram below shows the world line of an object in a one-dimensional space (Felder, pars. 7):

(Diagram 1)

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“Newton’s Laws.” The Physics Classroom. 1996-2009.

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