Nullary Sources

A researcher at the Institute for Nuclear Research of the Russian Academy of Sciences in Moscow published a paper on arXiv on Monday studying orbits inside the event horizon of a black hole. We all know that black holes are supermassive objects in space with so much gravitational force that not even light can escape once it gets too close, right? Well, not being able to escape doesn’t mean that you have to be sucked into the singularity in the middle and destroyed:

A black hole is a region of space where gravity is so strong that nothing can escape, not even light. However, cosmologists have known for some time that there are regions inside charged, rotating black holes where objects such as photons can survive in stable periodic orbits.

[Vyacheslav] Dokuchaev’s contribution is to study these orbits in detail and to explore their dynamics. …

It’s well known that a traveller passing through a black hole’s event horizon arrives in a region in which the radial dimension becomes time-like, rather than space-like. Conventional orbits are clearly impossible here.

But travel further in and there is another horizon where the dimensions switch back again (at least, inside charged and rotating black holes). This is the inner Cauchy horizon and it’s beyond here that Dokuchaev says the interesting orbits for massive planets exist.

Since the orbit is inside the event horizon, it’s impossible to leave once you enter that orbit. Likewise, it’d be impossible to tell from the outside that there was something orbiting a black hole on the inside. But heck, if something can orbit a black hole, why not a whole civilization?

Of course, such a civilisation would have to cope with extraordinary conditions such as huge tidal forces and the huge energy density that builds up in these stable orbits as photons become trapped. There’s also the small problem of causality violations, which some cosmologists predict would plague this kind of tortured space-time.