Thermodynamics of the black hole

Hi Friends, One of my fellow blogger asked me to answer regarding this topic, Thermodynamics of the black hole – Bekenstein-Hawking formula.

Asked By : Malavika K (Do Visit her Colorful, thought soothing poetry Blog),

So let us move on to Bekenstein-Hawking formula, this formula describes the thermodynamic entropy of a black hole with a given mass.

It is named after Jacob Bekenstein and Stephen Hawking, who found that the entropy of a black hole is proportional to the area of its event horizon.


Jacob Bekenstein
Stephen Hawking

First Let us know

1.What are Black Holes? Black Holes are regions of space in which gravitational fields are so strong that no particle or signal or information can escape the pull of gravity, even the light. (Even light ? We knew the speed of light, 3Lac Km/Sec but that’s nothing, LOL)


The boundary of this no-escape region is called the event horizon(I have Illustrated as a Event horizon), since distant observers outside the black hole cannot see events inside. Hence the name black hole. then How we able to detect the black hole it’s another topic, any how (To check the “first image of the black hole“, visit my other post)

2.How are they Formed? A black hole is usually formed from the collapse of a quantity of matter or radiation, both of which carry entropy isn’t’ it? For more: “Black hole formation

The event horizon is defined as the outer boundary of the region from which there cannot be escaped by any objects, even light.

3.Thermodynamics of the black hole, here we go it’s the main topic of interest.

Entropy : Entropy is described as a measure of disorder within a macroscopic system. But it can also be defined as the amount of information that you can pack into an object.

1.The formula is significant in understanding the thermodynamics of the black hole, Stephen hawking along with bekenstein came up with this equation.

2.The S in the equation relates to entropy that is the measurement of the amount of chaos and disorder in the black hole system.


‘h’ is the Plank constant

G’ Newton’s constant

The A refers to the area of the event horizon.

The “c” is the speed of light

‘k’ is Boltzmann’s constant. For the enthusiast with UG/PG level, I recommend to check out useful links below to understand the equation.

The Bekenstein-Hawking entropy it is the amount of entropy that must be assigned to a black hole in order for it to comply with the laws of thermodynamics as they are interpreted by observers external to that black hole.

The entropy of a black hole is proportional to its surface area, The surface of the black hole is its event horizon, beyond which, nothing can escape. Hawking himself extended this work to a more general and far-reaching interpretation.

The whole universe could be seen as having a “cosmological event horizon” suggesting that the universe as a whole has an entropy value and a specific temperature.

Use full links:




– Akshay Kumar Das

Copyright © 2018 by Akshay Kumar [Samal das akshay] All rights reserved. This Post or any portion thereafter may not be reproduced or used in any manner whatsoever without the express written permission of the publisher.

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