Black Holes

Black Holes

Every day we look out upon the night sky, wondering and dreaming of what

lies beyond our planet. The universe that we live in is so diverse and unique,

and it interests us to learn about all the variance that lies beyond our grasp.

Within this marvel of wonders, our universe holds a mystery that is very

difficult to understand because of the complications that arise when trying to

examine and explore the principles of space. That mystery happens to be that of

the ever elusive, black hole.

This essay will hopefully give you the knowledge and understanding of

the concepts, properties, and processes involved with the space phenomenon of

the black hole. It will describe how a black hole is generally formed, how it

functions, and the effects it has on the universe.

By definition, a black hole is a region where matter collapses to

infinite density, and where, as a result, the curvature of space-time is extreme.

Moreover, the intense gravitational field of the black hole prevents any light

or other electromagnetic radiation from escaping. But where lies the “point of

no return” at which any matter or energy is doomed to disappear from the visible

universe?

The black hole's surface is known as the event horizon. Behind this

horizon, the inward pull of gravity is overwhelming and no information about the

black hole's interior can escape to the outer universe. Applying the Einstein

Field Equations to collapsing stars, Kurt Schwarzschild discovered the critical

radius for a given mass at which matter would collapse into an infinitely dense

state known as a singularity.

At the center of the black hole lies the singularity, where matter is

crushed to infinite density, the pull of gravity is infinitely strong, and

space-time has infinite curvature. Here it is no longer meaningful to speak of

space and time, much less space-time. Jumbled up at the singularity, space and

time as we know them cease to exist. At the singularity, the laws of physics

break down, including Einstein's Theory of General Relativity. This is known as

Quantum Gravity. In this realm, space and time are broken apart and cause and

effect cannot be unraveled. Even today, there is no satisfactory theory for

what happens at and beyond the rim of the singularity.

A rotating black hole has an interesting feature, called a Cauchy

horizon, contained in its interior. The Cauchy horizon is a light-like surface

which is the boundary of the domain of validity of the Cauchy problem. What

this means is that it is impossible to use the laws of physics to predict the

structure of the region after the Cauchy horizon. This breakdown of

predictability has led physicists to hypothesize that a singularity should form

at the Cauchy horizon, forcing the evolution of the interior to stop at the

Cauchy horizon, rendering the idea of a region after it meaningless.

Recently this hypothesis was tested in a simple black hole model. A

spherically symmetric black hole with a point electric charge has the same

essential features as a rotating black hole. It was shown in the spherical

model that the Cauchy horizon does develop a scalar curvature singularity. It

was also found that the mass of the black hole measured near the Cauchy horizon

diverges exponentially as the Cauchy horizon is approached. This led to this

phenomena being dubbed “mass inflation.”

In order to understand what exactly a black hole is, we must first take

a look at the basis for the cause of a black hole. All black holes are formed

from the gravitational collapse of a star, usually having a great, massive, core.

A star is created when huge, gigantic, gas clouds bind together due to

attractive forces and form a hot core, combined from all the energy of the two

gas clouds. This energy produced is so great when it first collides, that a

nuclear reaction occurs and the gases within the star start to burn continuously.

The hydrogen gas is usually the first type of gas consumed in a star and then

other gas elements such as carbon, oxygen, and helium are consumed.

This chain reaction fuels the star for millions or billions of years

depending upon the amount of gases there are. The star manages to avoid

collapsing at this point because of the equilibrium achieved by itself. The

gravitational pull from the core of the star is equal to the gravitational pull

of the gases forming a type of orbit, however when this equality is broken the

star can go into several different stages.