Baby Black Holes

Black holes are much smaller than you think. In the movies, they are always depicted as huge swirling masses of clouds and debris being sucked into a giant nothingness. The ones that we can see with Hubble are the big ones. The one in the picture to the left is 1.2 billion times the size of our sun.

The size and mass of a black hole are related. There is a direct relationship. A black hole forms when the light leaving the object cannot escape the gravity of the object. The point where light must fall back in to the black hole is called the Schwarzschild Radius after the physicist that did the calculation for the first time. The Schwarzschild Radius marks the Event Horizon.

The Schwarzschild Radius for an object the size of our sun would be about 3 Kilometers. The Earth, if collapsed into a black hole would be about 9 Millimeters – about the size of marble.

The math for calculating the Schwarzschild Radius is quite simple:

  Rsch is the Schwarzschild radius;
G is the gravitational constant, that is:
  6.67 x 10-11 N m2 / kg2;
M is the mass of the black hole;
and c2 is the speed of light squared, that is:
  (299,792,548 m/s)2 = 8.98755 x 1016 m2/s2.


Here is a cool little Schwarzschild Radius JavaScript Widget which will do the calculation for you.

Mass Radius

Currently, scientists think that black holes are created by large collapsing stars. If a dying star is big enough, it can collapse down to a small mass which is smaller than the Schwarzschild Radius. The star has to be big, a lot bigger than the sun, to collapse into a black hole. Although we can calculate the Schwarzschild Radius for small black holes, the mechanism for creation of tiny black holes is not known.

Although, in theory there could be tiny black holes, scientists have never seen one and don’t really have a good idea if they are ever created. It has been speculated that a small black hole would radiate energy faster than it would eat it and would soon wink out of existence.

Stephen Hawking, of course, came up with the idea that black holes are not as black as we thought. There are quantum effects at the event horizon that could allow a particle to escape the hole. Hawking even speculated that the particles might even have information about the state of the matter inside the event horizon.

How might baby black holes be created? I would speculate that the turbulence around a really large nasty black hole might give us what we need.

Large, active black holes, perhaps in the process of sucking in a very large star, produce a huge maelstrom of swirling dust, gas, and debris that is falling at really high speeds into the black hole. The way we detect most black holes is through the huge amount of X-rays that the swirling plasma gives off as it accelerates to near light speeds on its way into the hole.

I am not a physicist, but I would imagine that the whirlpool would not be “smooth”, but would have lumps, gaps, and swirls. The matter falling into the hole, doesn’t go straight in, but is twisted by the huge magnetic fields generated by the plasma until it is a roiling mass of dense matter. Might it be possible for some very dense, but small, lump to momentarily compress into a clump that is smaller than the Schwarzschild radius? I don’t know, but I can visualize the process. It would take a greater mind than my own to calculate the range of densities that would be found in a really turbulent black hole.

Let’s speculate for a moment that really small black holes are possible and that they have a long enough life span that we might be able to find one. What would they be like? Could man use them for something?

Even baby black holes are massive. If we have one in our possession, trapped in a magnetic bottle of some sort, it might mass a few hundred tons. Such a mass would have a large negative potential energy. An electron falling into a baby black hole would radiate as it gained speed and came closer and closer to the event horizon. The gravitational field itself would grow denser as relativistic effects become measurable close to the radius. The electron would radiate as it whirled around the black hole, faster and faster, until it slipped past the event horizon. And, if Hawking is right, it might just pop back up again and squirt off another bit of energy.

Black holes appear to have strong magnetic fields surrounding them, which directs the radiation out from the magnetic poles. This directional radiation might have its uses.

Think of a star drive that uses the nearly 100% efficiency of a plasma beam created by a baby black hole and bent by the black hole’s magnetic field to point backwards and drive the ship at near light speeds towards the distant stars.

A very dangerous weapon could be made from a beam of radiation from a directed baby black hole. The Earth could be turned to a cinder in a few seconds.

A baby black hole might radiate information from within it. If we can drop information back and there is anyone listening could we set up a dialog?

When the Mars Landers set out on their journeys, they used a “slingshot orbit” that used the mass of the moon to increase their speed and save on fuel. What if we could bring a pair of baby black holes along with us on our space explorations and use their gravitational fields as slingshots?

I have done a lot of supposition here on very little real knowledge. I have more college physics than the average Joe, and I was a math major, but I am still just pie-in-the-sky speculating about these things. Speculation, however, is what Science Fiction is all about. The next time you write a hard SF story, you may want to throw in a baby black hole. I’ve got a story started already, but it needs a good ending, and I am not going to have my hero fall in – that’s too easy!


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I started reading Science Fiction in the 1950s. I started Writing SF in the 1960s. Then, I had a life. Now I am retired, raising chickens and keeping bees. I am still an avid reader and I have sold about 70 stories in the last 20 years.
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