THE RIDDLE OF BLACK HOLES

The most mysterious objects in the universe must certainly be the invisible and inconceivably dense objects known as black holes.Nothing can escape its grip.But how can we be certain of their existence if we cannot see them??

To imagine a black hole, think of an abyss- small in size yet unimaginably dense- swallowing everything that comes within its reach. Einstein's theory of general relativity, developed in 1916, explains BLACK HOLE as when large enough amount of mass is present within a small enough volume, all paths through space arewarped inwards towards the center of the volume. When an object is compressed enough for this to occur, collapse is unavoidable . When an object passes within the event horizon at the boundary of the black hole, it is lost forever .

INDICATIONS FOR EXISTENCE : INDIRECT TRACES

According to astrophysicists' calculations , the mass of all the matter in space is not sufficient to hold the distant stars. This has given rise to the idea that there is some invisible mass of matter that is capable of exerting sufficient force on all existing stars. It is possible that this force could be exerted by one or two gigantic black holes at the centre of the universe.

SIZES OF BLACK HOLES

Black holes can be of almost any mass. Super massive black holes containing millions to billions of times the mass of the sun, Intermediate-mass black holes, whose size is measured in thousands ofsolar masses,Stellar-mass black holes have masses ranging from about 1.5-3.0 solar masses to 15 solar masses , or Micro black holes, which have masses much less than that of stars.

WHY IS BLACK HOLE INESCAPABLE ???

General relativity describes mass as changing the shape of space time, and the shape of space time as describing how matter moves through space. For objects much less dense than black holes,this results in something similar to Newton's laws of gravity: objects with mass attract each other, but it's possible to define an escape velocity which allows a test object to leave the gravitationalfield of any large object. For objects as dense as black holes, this stops being the case. The effort required to leave the hole becomes infinite, with no escape velocity defined.

BLACK HOLES AND EARTH

Black holes are possibly the most serious potential threats to Earth and humanity,as a naturally-produced black hole could pass through our Solar System , and a large particle accelerator mightproduce a micro black hole, and if this escaped it could gradually eat the whole of the Earth.