LIGO detect gravitational waves that form by two black holes that orbited each other and then merged to form a bigger black hole with having large energy. That black hole has a mass about 60 times greater than our Sun.

**Gravitational waves formed by black holes**

This event occurred around a billion of light years away from Earth. The merging of these black holes was extremely energetic (in a seconds the event released 50 times more energy in gravitational waves than all the stars in the entire Universe in light), but at that time the waves that reached on earth, they were so weak to detect and change in the length of LIGO’s arms was less than a 1000th of the diameter of the core of an atom.

**Astrophysics about gravitati****onal**

The astrophysics is branch of physics that tells us about binary black holes and many other heavy massive objects present in our universe.

It also tells us how they form, evolve and die during a shorter period than the age of the Universe. Lets we talk about black holes, we have never seen binary black holes before. We have never found huge black holes of this mass before.

It looks like these merging of black holes should be common enough that we will see more in future observations with LIGO. Then we can exactly understand what is out there and how these binaries are made.

**Concept about gravitational waves**

Firstly the concept of gravitational waves was given by Einstein in his general relativity theory is also known as the general theory of relativity, is the geometric theory of gravitation introduced by Albert Einstein in 1915 and the current description of gravitation in modern physics.

General relativity generalizes special relativity and define Newton’s law of universal gravitation, providing a unified description of gravity as a geometric property of space and time, or space-time curvature.

In particular, space-time is directly related to the energy and momentum of any matter and radiation are present. The relation is clarified by the Einstein field equations, by the system of partial differential equations.

Gravitational waves are generating ripples in space-time due to heavy massive. When objects move in space-time curvature, the curvature of space-time changes and these changes move outwards (like ripples on a pond) as gravitational waves. A gravitational wave is a contract and expands of space and so can be found by measuring the change in length between two objects.

**Theory of relativity about gravitational waves**

In general relativity, gravity can be thought of as the effect of the curvature of space-time. Massive objects bend space and time; the curvature in space-time changes how things move. Some predictions of general relativity is different significantly from the classical physics, especially concern about the passage of time, the geometry of space, the motion of bodies in free fall, and the propagation of light waves.

Such examples include gravitational time dilation, gravitational lasing, the gravitational red shift of light, and the gravitational time delay. The predictions of general relativity in relation with classical physics have been confirmed scientifically in all observations and experiments to date.

Although general relativity is not the only about relativistic theory of gravity, it is the simplest theory that is consistent on experimental data. However, unanswered questions remain, the most fundamental being how general relativity can be related with the laws of quantum physics to produce a complete and self-consistent theory of quantum gravity.

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