The term black holes was first coined by the Physicist and journalist Ann Ewing in her article “Black Holes” in space on January 1964 which reported in the meeting of the American Association for the Advancement Of Science (AAFAS). John Wheeler used the term “Black Holes” at a lecture in 1967 which was commonly used at that time and also in present time.
Note: In wormholes we have traverse wormholes which can have negative energy. Whereas in black holes one can define it with a powerful gravitational force in various regions of space and time so as to create a different kind of space-time region.
Black Holes which are responsible for their immense gravitational field and even light cannot escape from their strong gravitational field, also electromagnetic radiation. The boundary of that region where nothing escapes is called “Event Horizon”. Schwarzschild radius (rs) represents the ability of mass to cause curvature in space-time. The Schwarzschild radius is the radius of a sphere where all the mass of an object was compressed within that sphere, the escape velocity (minimum speed needed for an object to break free from the gravitational force of massive bodies) from that surface of the sphere is equal to the speed of light. An object which is the Schwarzschild radius is “Black Holes”. This Schwarzschild radius was given by the German Physicists “Karl Schwarzschild with the help of the General Relativity in 1916.
(NOTE): For large black holes, it continues to fall on itself and become “Stellar Black Holes”.
If someone wants to send a signal from the black holes, his signals may reach that place (say on earth) not according to his time as he send these signals.
Example TO UNDERSTAND: If a person A wants to send a signal or say message from black holes event horizon to the earth where a person B receives this message. When this person sends this message at 11:30pm to the person B, this person B receives message at 11:45pm as there is a difference in time due to strong gravitational field of black hole.
1) Into the black holes there is no possibility to send any message which is due to the region of invisible energy absorb by black hole. But this is in the case of inside the event horizon, not outside of the event horizon.
2) Super massive stars become black holes due to their immense gravitational field.
3) Stellar black holes are 20 times massive than that of sun.
4) CygnusX-1 a black hole is 10 times massive than that of sun.
5) One should remember that outside the Event Horizon, nothing can fell into the black hole.
Noting can escape from these black holes as according to the Classical Mechanics of Physics. Under the Quantum Mechanics, for every particle there exists an antiparticle which has the same mass but have a opposite electric charges. When they met that is particle and antiparticle they annihilate each other.
One is drawn into the black hole itself and the other is ejected. This reduces the event horizon of black holes and black holes decay, which was rejected under classical Mechanics.