A Ready Player One-like reality may not be just sci-fi. Recently, a research paper titled “Black holes as tools for quantum computing by advanced extraterrestrial civilizations” was cited by Andrew Côté on X, and it opens up new computational possibilities in our universe. The paper argues that black holes are the computationally most dense objects possible and are the ultimate computers. They can pack more information into a given size than anything else allowed by the laws of physics.
It is to be noted that the bigger a black hole, the less dense it is. A stellar-mass black hole is incredibly dense, whereas a supermassive black hole in the centre of our galaxy is less dense. Similarly, a black hole the size of our universe would be even less dense and pretty diluted. As per the calculations discussed alongside this idea, if you take all the mass-energy inside the observable universe and imagine packing it into a single black hole, the size of that black hole’s event horizon comes out almost exactly the same as the size of the observable universe itself. The event horizon is the invisible boundary around a black hole beyond which nothing, not even light, can ever escape.
That coincidence is what the post points to when it states that such a black hole would have roughly the same density as our universe’s critical density for a flat geometry. A flat geometry simply means that space is not curved on large scales, and it is the reason why a straight line always remains straight, and triangles always add up to 180 degrees. Critical density, on the other hand, means the average amount of matter and energy needed in the universe, or the exact density to keep space perfectly flat. That value also turns out to be the one set by the expansion rate of the universe (the Hubble constant). Observations thus indicate that the large-scale geometry of our observable universe is flat rather than curved.
To further double down, the X post states that “almost all the entropy in the universe is inside black holes, on the far side of an event horizon.” Entropy is simply a measure of disorder or the amount of hidden information. Black holes are exceptionally good at that since most of the information they contain is locked behind the event horizon, and no outsider could ever see inside it. Therefore, any sufficiently advanced civilization would use black holes as their ultimate supercomputers instead of making Dyson spheres or Dyson swarms. This point is also buttressed by the fact that black holes give off Hawking radiation and thus also act as heat engines. A black hole made by an alien civilization could very well serve a dual purpose of doing computations and being a mass-to-energy converter. Smaller black holes in this regard are even more interesting, as they give off heat faster than the bigger ones.
The post makes an interesting point that most of the stars in the universe have already been formed and the universe is already ahead of its nascent phase. There are very likely civilizations that are extremely old, and their engineering may be distinguishable from the actual physical structures of the universe. Our Milky Way is full of black holes, and it is possible that the same are supercomputers belonging to various alien civilizations. The post even speculates that many of these black holes might be giving birth to new universes, and we too might be living inside one of them.
I find this to be a fascinating idea. Black holes as supercomputers would solve at least one problem. They would make a Ready Player One kind of universe very much possible and fun to be in. Any virtual reality that is to be indistinguishable from and more flexible than the original reality will require crazy amounts of compute and energy. Black holes are the dream candidates here. Who knows, alien civilizations may have uploaded their digital selves inside the black holes and be busy playing crazy games or living in their dream simulations. Some of the black holes might even be prisons made by alien civilizations to keep harmful elements away from our universe. The possibilities are endless if black holes can actually be harnessed as computers and heat engines.
Both small and bigger black holes would serve different purposes, and it might be a matryoshka-doll kind of reality where there are black holes inside black holes. Who knows, the grand creator of all this might be hiding inside one of these black holes, and anybody who finds the grand creator might be awarded some even grander prize or might be given the keys to the entire universe or multiverse, just like in Ready Player One.