Random Rambling: Physics (Pet Black Holes)

We have... let's say an eclectic mix of interests, and we feel our patrons do too.  With that thought in mind, we present a feature we call "Random Rambling."  It isn't quite random, but it's close:  we made a little spinner with some of our favorite subjects.  Every Friday, we give the thing a spin, and then you, lucky people that you are, get to learn a fact related to the subject the spinner landed on.

This week's topic is:

Physics!

Last time we landed on Physics, we talked about how we wouldn't be finding dinosaurs inside of a Hollow Earth, no matter how cool that might be.  This time around, we'll kind of talk about the opposite.  Instead of a planet with too little mass, we'll talk about a point with too much mass.

By that we mean black holes.  More importantly, whether or not you could safely keep one in a jar, as a pet.

Define "Jar"

Obviously, no ordinary jar would do.  No matter how small the black hole in question would be, if it comes in contact with the sides of the jar, Very Bad Things™ will happen.

Thankfully, we already have the technology to make jars theoretically capable of holding black holes in place.  The folks at CERN have connected a whole bunch of them together to make a particle accelerator, for example.  Coincidentally, they were at one point accused of creating conditions in which microscopic black holes would proliferate, eventually devouring the world.  Depending on when you're reading this, the world hasn't been devoured yet, so that last part was just some silly naysaying.

Anyway, a typical section of the Large Hadron Collider at CERN is about 50 meters long.  It consists of a cryostat (think of a straw-shaped thermos so big that you could, and did, shove a refrigerator in there), surrounding a series of superconducting magnets, which in turn surround a comparatively smaller straw containing the stream of particles that the CERN fellows would like to accelerate.  With a couple of minor adjustments, this setup could be used to instead decelerate* particles and particle-sized objects.  Objects like, say, a wee baby black hole.

*There is no such thing as deceleration in physics; acceleration is a change in velocity, which is in turn a combination of speed and direction.  When you "decelerate," you're just accelerating in the direction opposite to the direction of motion.

Size Matters

With CERN-sized superconducting magnets, we could hold black holes below a certain size in place.  How big is that "certain size"?  Funny thing about that:  black holes are weird about descriptions like size.  For example, you can easily determine the mass of a black hole, but trying to calculate the density will get you error symbols.  That's because, based on our understanding of physics, we're trying to divide by zero; a black hole has a mass, but no height, width, or depth.  It is, by certain definitions, a hole in spacetime, and by any definition, it does not follow the rules for three-dimensional objects.  And yet, black holes do have certain dimensions that describe them, such as a Schwarzschild radius.  That's the distance from the black hole that light has to be to have a chance of escaping the black hole.  Mass, which ordinarily does not move at the speed of light, will need to be farther away still.

Given how wide the safe area of our 1 meter-radius, 50 meter-length "jar" is, the maximum radius of the black hole's "maw" (the distance past which mass is invariably pulled in) is about 25 mm, or 1 inch.  It doesn't sound like much, but that distance matters.  Given how much force the magnets are designed to withstand, that means that the maximum safe mass of the black hole will be either the amount of mass the magnets could hold in place or the amount of mass before the black hole "eats" the magnets holding it in place, whichever is smaller.  Given that the first is, doing some really rough estimations, about 200,000 kg, and the second is about 1 billion kilograms, we'll go with the first.

Painting a Picture

Thankfully, we don't have the technology to make pet black holes yet, but say we did, and that, more importantly, we also had some stringent pet safety laws in place.  Using some safe, handwaved means, we condensed 200,000 kg of mass until it occupied a grand total of less than one atom's worth of space, collapsed on itself, and became a black hole.  We then sealed it up inside our giant jar, turned on the cameras, and took a look at our new pet.  What would it look like?

Not much, honestly.

The Schwarzschild radius of our pet black hole- the "black" part of the black hole- wouldn't be visible to human eyes.  The little black sphere that seemingly sucks all light into it would measure 6x10^-22 meters from side to side.  That's several orders of magnitude smaller than a proton, and probably just a little bigger than the light particles that we would be trying to shoot at it to see it in the first place.

This is, of course, leaving aside the very real problem of seeing a black hole to begin with.  Normally, we see things by bouncing light off them; what we see is the light that is reflected off the object.  That doesn't work with black holes, though.  By their nature, literally nothing reflects off of them.  They aren't black, they're a void, a point in space that no light will ever bounce off of.

Even bouncing light in the area around a black hole doesn't give us a better picture of the black hole itself, due to gravitational lensing.  Remember, the Schwarzschild radius is the radius that light can't escape, no matter what.  There's a slightly larger radius around the black hole where light can escape, but only by a combination of luck and taking a really wonky path.  The way light gets deflected around a black hole is called gravitational lensing, which means that, for example, no light at all will bounce off the area of the black hole, but a bright ring will appear around it of light that managed to escape, but got twisted in the process.

Or it would, normally, if our black hole weren't so darn small.  The ring radius we're talking about is roughly the size of the light particles in question.

So, at a visible level, our black hole would look like nothing was there at all.  The tiny little void would be smaller than a pinprick and impossible to see without an electron microscope that doubled as a telescope and a laser.  Kinda boring.

Feeding Time

Where our black hole gets interesting again is when we give it something to consume.  Light is too small.  We could potentially lightly bend lasers around the black hole, but only with some super-precise aiming.

Let's say we gave the black hole something bigger to play with: we'll throw an apple directly at it and see what happens.

The fun thing is, we're not really sure.

At an atomic level, we've got some ideas:  with as many atoms as there are in an apple, if we threw it directly at the black hole, at least some of those atoms are going to pass within the black hole's maw and get devoured.  More importantly, they'll first get pulled within orbit of the black hole, and those atoms will accelerate to a significant portion of light speed before being devoured, all within an insignificant fraction of a second.  As they accelerate, they'll become "spaghettified" (and yes, that's the actual scientific term) as the gravitational forces on one side of the atom are exponentially stronger than on the other.  The ordeal releases flashes of light, and the light itself may or may not get devoured by the black hole as well, but if it isn't, the light is going to shoot into the apple, potentially hitting other atoms and imparting energy.

How much energy?  It'll depend on how many atoms get devoured by the black hole, and at its size, the number of atoms is almost certainly nonzero but impossible to accurately gauge.  The likely number is somewhere between 1 and 10,000,000,000,000,000,000,000,000.

What will that look like?  At the lower end, not much.  You might not even be able to visibly spot the small hole carved out of the apple by the black hole.  At moderately higher levels, there might be visible flashes in the apple itself.  The reaction grows exponentially; if the black hole "eats" enough atoms to leave a visible hole in the apple, you still wouldn't be able to spot the borehole, because the energy released in the process would cause the apple to explode with a force similar to that of a hand grenade.  If we put the apple on a stick and then waved it in the area that the black hole occupied?

Let's just say that feeding time would be over in a hurry.

Conclusion

In theory, it might be possible to keep a black hole as a pet in a jar.  Some pretty hefty caveats would have to be applied, however.  For starters, the jar would take up space that you could have filled an Olympic swimming pool with.  For seconds, your electric bill is going to be hideous, because those magnets will have to be on constantly.  You'll also need to post a sign on the jar, in big, prominent letters, that says "Do NOT feed the singularity."  Last but not least, you're going to have to accept that your black hole will die eventually.  Smaller black holes effectively "evaporate" over time, and yours will be no different.

Still, we hope you enjoy the (doing one last bit of rough calculating) less than 5 seconds of your pet black hole's life.