A black hole is the ultimate “dangerous object.” You get a regular
hole by digging stuff out of it. The more you dig, the bigger the
hole. Holes can be dangerous just because they are big. If you find
yourself trapped in a hole, the first thing you should do is stop
digging. There are holes, black holes, and the Black Hole of Calcutta.
That was a dangerous hole, but not nearly as dangerous as a
relativistic black hole. Some people actually got out of there alive,
and it even had a couple of small windows. With a relativistic black
hole, there’s no chance of either.
Let’s “Numinate” about these relativistic black holes—how they could
come about, and what they would be like. First of all, you shovel
stuff into them—you don’t get a black hole by digging stuff out of it.
As you pile more and more stuff together, gravity becomes greater and
greater. The gravity at the surface of an object depends on how much
mass the object has and how dense it is. An object with a given amount
of mass has a higher surface gravity the more its mass is concentrated
into a smaller volume—in other words, as its density is increased.
Theory has it that black holes can come in any size. They could be
microscopic or astronomic. They aren’t really measured by size so much
as by the mass they contain. A black hole can result from any amount
of mass—no matter how little— if it’s squeezed into a small enough
volume. Any concentration of matter produces gravity. Large, hot
concentrations are called stars. Our sun is a star. Smaller, cooler
concentrations of matter are called planets if they circle a star, or
moons if they circle a planet, or asteroids if they are small enough.
Each of these objects, due to the gravity at its surface, has a
particular escape velocity. That is, if you were standing on its
surface and threw a rock away from it fast enough, the rock would
escape and never fall back. The escape velocity of the earth is 25,000
miles per hour. This means you would have to fire a bullet from the
surface of the earth at about seven miles a second for it to escape
into outer space. If you fine-tuned the speed just right, the bullet
would orbit the earth once, come full circle, and hit you in your back.
At any speed less than escape velocity, whatever goes up, comes back
Imagine objects with higher and higher surface gravities. They would
have higher and higher escape velocities. When you talk about ever
higher velocities, of course, you eventually reach a limit—the speed of
light. A black hole is simply an object whose escape velocity is
greater than the speed of light. If you were standing on the surface
of an object whose escape velocity were exactly equal to the speed of
light, a beam of light from your flashlight would orbit once around it
and shine on your back. All light emitted from the object would fall
back onto it. No light would escape. No light could bounce off the
object either. The object would be absolutely black from a point of
view some distance away. Thus, the name “black hole.”
Large black holes could come about in the natural life span of a star
about three times the size of our sun. When this amount of matter
accretes into a star, a series of nuclear fusion reactions is
triggered. Each step in this series involves the fusion of heavier
atoms into still heavier ones. The series stops when the atoms are too
heavy to undergo another fusion cycle. We believe this point to be
reached when the matter is largely iron. Now, what happens? Up to
this point, the star is kept from gravitational collapse by the massive
conversion of matter into energy. This energy, in the form of heat,
holds the atoms apart. When no more energy is available, the star
begins to cool. Now, the star literally collapses under its own
weight. This is the story of the smallest of the large black holes.
It involves the “death” of stars three or more times the mass of our
Very large and very small black holes would come about in different
ways—very different from one another—and very different from the “death
of a star” scenario. This is because a small black hole relies on
matter compressed to fantastic densities to get it into a small enough
volume that its escape velocity exceeds the speed of light. Such
densities might be a by-product of the “death” scenario, or perhaps of
some bigger Bang scenario. As you increase the mass of a black hole,
the critical volume goes up and the critical density goes down. When a
very large mass is involved, the density doesn’t even have to be that
great. Inside a very large black hole there could easily be normal
stars and vast swirling vortices of dust and debris. Such a black hole
would be very like a universe unto itself.
Our conception of a black hole is based on the model we call the
general theory of relativity (again, we encounter Einstein). Various
extrapolations have been made from the simple logic that says: light
can’t escape from a region whose escape velocity exceeds that of the
speed of light. And, since nothing can travel faster than light,
nothing else can escape either. Two of the more common extrapolations
about black holes are that escape from them is impossible, and that
they contain a singularity inside them.
The fact is, these theories have never been tested. Other models are
possible. It’s hard to believe in a model proposing that all matter in
the universe erupted out of a single point in an event called the Big
Bang, and one that also says matter can disappear forever into a black
Let’s see if we can find a plausible way out of a black hole. When we
launch a rocket into outer space it needn’t reach the escape velocity
of seven miles a second. If a rocket has enough fuel, it can rise as
slowly as you like and still escape the gravity of the earth. The
point is that it doesn’t have to reach “escape velocity” to actually
escape. It’s kind of like climbing out of the Grand Canyon: you might
not go very fast, but at the end of the day you have escaped. A guy
who’s still at the bottom can’t hit you with a .22 from his rifle,
because the bullet doesn’t travel fast enough to reach the canyon rim.
Escape is a tradeoff between speed and persistence.
Perhaps escape is possible, but how do we avoid the singularity inside?
What is a singularity, anyway? Imagine crowding lots of atoms into a
very small space. At first, their atomic structure holds them apart.
The electrons around each atom repel those of the atom next to it. But
you are relentless, you keep adding more and more atoms, increasing the
force of gravity until the mutual repulsion of the electrons is
overcome. Now, the nucleus of one atom and that of the next are forced
ever closer together. You keep piling them on, increasing the force of
gravity until even the repulsion between one nucleus and the next is
overcome. At some point gravity exceeds all the forces that hold
matter apart, and then? Theory has it that matter, at that point, is
drawn together without limit. Everything caught in such a collapse
disappears into a point called a singularity. This happens at
densities well beyond the point at which matter vanishes into a black
hole. This happens at densities so extreme that the standard model of
what happens when you crush atoms might not extrapolate. Let’s look at
a scenario that might allow escape from a black hole long before a
singularity would occur.
The key to escaping a black hole would be a sustained outward force.
For example, if matter reached a sufficient density, it might begin to
annihilate itself. A fireball of energy would be produced that could
sustain an outward pressure for a period of time. Time enough that the
black hole’s strangle hold might be broken. This fireball would just
have to be persistent, it wouldn’t have to produce escape velocity.
How would such an annihilation occur? The only particles we know of,
that annihilate one another, are anti-particles. The primary example
is an electron and a positron. These particles are easy to get into
close proximity. They attract one another because they possess
opposite electrostatic charges. Ordinary matter consists of electrons,
neutrons, and protons. Neutrons and protons are located together in
the atomic nucleus. Electrons are located in “clouds” around the
nucleus. Each electron fiercely repels every other, just as each
atomic nucleus fiercely repels every other. The repulsion is fierce
because it is based on the electrostatic force that is vastly stronger
than the force of gravity (one followed by 42 zeros times as strong).
This force drives nucleus away from nucleus, and electron away from
On the other hand, the electron and the nucleus are attracted with an
equally strong force (this is the origin of the phrase opposites
attract). Electrons inhabit “probability clouds” around an atomic
nucleus. The chances of their being in some places are higher than the
chances of them being in other places. One place where they have
almost no chance of being is actually touching a nucleus. This is
based on the quantum model of the atom, not the simple fact that there
is an incredibly large force of attraction between them.
Particles that don’t touch, can’t annihilate each other. Particles
that do touch can have some or all of their mass converted into energy.
Long before they reached the point of a singularity, particles in a
gravitational collapse would be forced into contact with one another.
Total annihilation has to be considered as a possibility. If so, it
would generate quite a Bang. Certainly one big enough and persistent
enough that it might open up its black hole and allow escape.
Experiments that could bear this out, especially ones involving black
holes, tend to be inimical to our way of life. But, on a somewhat
safer and more limited scale, we have split atoms, we have fused them,
and we have both created and destroyed anti-matter. Experiments with
black holes are quite a way off for the present. And, until black
holes are the subjects of experimentation, they can only be the
subjects of speculation, fantasy, or Numination. And, of course,
awe—inspired by the extreme danger a black hole would pose to our life
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