I learned about black hole, how are they possible? (just started). On the sunday morning, I started reading a paper about BBC Reith Lecture. It all started with Albert Einstein writing a paper in 1939 claiming that stars could not collaspe under gravity because matter could not be compressed beyond a certain point, many scientist thought the same but an American scientist John Wheeler, who in many ways is the hero of the black hole story. In his work in 1950s and 1960s, emphasized that many stars would eventually collapse and pointed out problems that possibility posed for theoretical physics. Durring most of the life of a normal star, over billons of years, it will support itself against its own gravity by thermal pressure caused by nuclear processes which convert hydrogen into helium.

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Eventually, however the star will exhaust its nuclear fuel. The star will now contract. In some cases it may be able to support itself a “white dwarf” star.

Singularity

Robert Oppenheimer after getting the fame of atomic bomb (i now become death the destroyer of worlds) investigated the problem of what would happen if a star whose mass is greater than a white dwarf or neutron star when they exhausted their nuclear fuel? he showed that such a star could not be supported by outward pressure; and that if you take pressure out of the calculation, a uniform spherically systematic symmetric star would contract to a single point of infinite density. such a point is called a singularity.

A singularity is what you end up with when a giant star is compressed to an unimaginably small point.

After this a lot of interesting discoveries occured (am not gonna tell) but a dramatic advance in our understanding of these mysterious phenomena came with a mathematical discovery in 1970. This was that the surface area of the event horizon aka the boundary around the black hole. It always increases when additional matter or radiation falls into the black hole. This property suggests that there is a resemblance between the area of the event horizon of a black hole and conventional newtonian physics, specifically the concept of entropy in thermodynamics. Entropy can be regarded as a measure of the disorder of a system, or equivalently as a lack of knowledge of its precise state. The famous Second Law of Thermodynamics says that entropy always increases with time. this discovery (in 1970) was the first hint of this crucial connection.

Entropy means the tendency for anything that has order to become more disordered as time passes - so, for example bricks neatly stacked to form a wall (low entropy) will eventually end up in a heap of dust (high entropy). And this process is described by the Second Law of Thermodynamics.