Why do we need general relativity and how is it different from special relativity?

Answer 1

Special relativity describes how the measurements of two inertial observers relate to one another.

But what if the observers are not inertial? What if they are accelerating or in a gravitational field? Then you need a deeper theory--that's GR.

Answer 2

General relativity and Special Relativity are both the product of the Lorentz Transformation.
Special Relativity applies only to Inertial systems : whereas, General Relativity applies to non - Inertial systems.

General Relativity is really based on the idea of Invariance using the Pythagorean Theorem. It basically indicates that the Universe is a Finite Entity having a finite Volume.
It is a mathematical Model which describes the Energy per unit volume of Space in terms of the Curvature of a Manifold of Space and Time. It is another way of stating Newton's Universal Gravity Constant which is described as follows;

Guv x C^4 / (8pi Tuv ) = G

This is Einstein's Field Equation of General Relativity;
Where Guv is the Curvature of space Tensor in Units of per meter.
C is the speed of light,in unit of meters per seconds.
Tuv is the Energy stress Tensor in Units of force per meter.
And G is Newton Universal Gravitational Constant in Units of inverse mass density per seconds square.

Special Relativity attempts to describes relative oscilliatory inertial motion of Mass Structures, relative to an absolute speed of Light in a particular frame of reference. It indicates in general ,that when a mass is made to move at a steady state ,given its Inertial Power and velocity , it must first experience a mass change.

This is a simple way, per my opinion, to describe Einstein's Theory of Special and General Relativity. However; there are other theories which also attempt to describe the Phenomena of the Universe. Whether we need one Theory over the other is just a matter of belief system.

Answer 3

SR only applies to problems that don't involve gravity or acceleration. Can you name one real-world problem where SR can be applied? Take the so-called "twins paradox". That was Einstein's idea of a joke; the punch line is how do you make a round trip without gravity or acceleration?

Answer 4

(In a Nutshell) SR was Alberts 1st theory which explained relativity without
the influence of gravity and without delving into quantum physics too deep.
It was, in my opinion, his attempt to introduce the concept
of inertial frames.