# THEORY OF RELATIVITY

#### 11 Aug, 2019

The theory of relativity usually encompasses two interrelated theories by Albert Einstein: special relativity and general relativity. Special relativity applies to all physical phenomena in the absence of gravity. General relativity explains the law of gravitation and its relation to other forces of nature and its relation to other forces of nature. It applies to the cosmological and astrophysical realm, including astronomy. With relativity, cosmology and astrophysics predicted extraordinary astronomical phenomena such as neutron stars, black holes, and gravitational waves.

Special relativity: Special relativity is a theory of the structure of spacetime. Special relativity is based on two postulates which are contradictory in classical mechanics:

1. The laws of physics are the same for all observers in uniform motion relative to one another (principle of relativity).
2. The speed of light in a vacuum is the same for all observers, regardless of their relative motion or of the motion of the light source.

Moreover, the theory has many surprising and counterintuitive consequences. Some of these are:

• Relativity of simultaneity: Two events, simultaneous for one observer, may not be simultaneous for another observer if the observers are in relative motion.
• Time dilation: Moving clocks are measured to tick more slowly than an observer’s “stationary” clock.
• Length contraction: Objects are measured to be shortened in the direction that they are moving with respect to the observer.
• Mass-energy equivalence: E=mc2, energy and mass are equivalent and transmutable.
• General relativity: It is a theory of gravitation developed by Einstein in the years 1907-1915. The development of general relativity began with the equivalence principle, under which the states of accelerated motion and being at rest in a gravitational field are physically identical. The upshot of this free fall is inertial motion: an object in free fall is falling because that is how objects move when there no force being exerted on them, instead of this being due to the force of gravity as is the case in classical mechanics. Some of consequences of general relativity are:
• Gravitational time dilation: Clocks run slower in deeper gravitational wells.
• Light deflection: Rays of light bend in the presence of a gravitational field.
• Metric expansion of space: The universe is expanding, and the far parts of it are moving away from us faster than the speed of light.
• Frame-dragging: Rotating masses “drag along” the spacetime around them.

The principle of relativity: In physics, the principle of relativity is the requirement that the equations describing the law of physics have the same form in all admissible frames of reference.

For example, in the framework of special relativity the Maxwell equations have the same form in all intertial frames of reference. In the framework of general relativity the Maxwell equations or the Einstein field equations have the same form in arbitrary frames of reference. Certain principles of relativity have been widely assumed in most scientific disciplines. One of the most widespread is the belief that any law if nature should be the same at all times;and scientific investigations generally assume that laws of nature are the same regardless of the person measuring them.

Einstein inspires creative thinking:

You might not discover the theory for relativity but you can learn from Einstein’s creative techniques and apply them to your creative problem solving challenges.

“Curiosity has its own reason for existing.”

Curious people learn more,discover more and change things. If you want to be more creative-be more curious.

“In the middle of difficulty lies opportunity.”

Real opportunity is the result of great diificulty. The ooportunity will require you to wade through the doubts and challenges that dissuade the weaker minds.