|
BLACK HOLES
|
|
Space
has always puzzled men. It is so huge that we can’t know all that happens in
the universe. Still, scientists have been interested in some strange events. One
of these is called Black Holes. It is a kind of celestial body from nothing can
escape even light. But this is not a new concept.
Actually,
the idea of a mass concentration so dense that even light would be trapped goes
all the way back to Pierre Simon de Laplace in the eighteenth century. They
wonder what would happened if the escape velocity of a star would be higher than
the light velocity. Then, they supposed that such stars might exist. They have
felt this studying the universal gravitational theory of Isaac Newton.
Then,
we had to wait for the 20th century to see black holes theory
evolved.
Almost immediately after Einstein developed general relativity (E = mc²), Karl Schwartzchild, in 1916, found one solution to Einstein's equations
(the curvature
due to a massive non rotating spherical object. That is, using Einstein's
equation, Schwartzchild had determined how spacetime is curved due to the
presence of a non-rotating spherical mass. In practical terms, the Schwartzchild
spacetime describes the gravitational field of the Sun, or of the Earth. (The
Sun and the Earth do rotate, but this rotation is negligible in these cases.).)
Some stars should attract all that is around them, deforming spacetime. The
name of “black hole” was first given by John Wheeler in 1960. He has done a
great deal to increase the understanding of black holes while utilizing the
concepts of relativity. His “Equation of State for Cold, Dead Matter” helps
determining what is occurring inside a dying star. This was useful to pave the
way for the theory that when the more massive stars die they become black holes. In
1979, Peter Young and Wallace Sergent thought have located a black hole in the
middle of the galaxy M87. They estimated that this hole was 3, 000, 000,000
times the mass of the Sun. This is the most important black hole ever localized.
Nowadays,
in 1996, Reinhard Genzel has discovered a black hole in the center of our Milky
Way. It is 2.5*106 the mass of the sun.
Could
this black hole threaten the Earth?
|