What If A Black Hole Appeared On Earth? | Unveiled

What if a Black Hole Appeared on Earth?

Black holes are among the most mysterious objects in the universe, ready and willing to devour anything that gets too close to them. Luckily, the closest black hole to us is more than a thousand lightyears away… But what would happen if one showed up actually on this planet?

This is Unveiled, and today we’re answering the extraordinary question; what if a black hole appeared on Earth?

Because black holes generally form when a star dies and collapses, they themselves are extremely massive. For an ordinary black hole, you first need a star with a mass at least eight times greater than that of our sun – which is why the sun will never become a black hole itself. Supermassive black holes naturally demand even more mass, while ultramassive black holes have a mass more than ten billion times that of the sun. The largest discovered so far was found in 2019, at an incredible size of forty billion solar masses.

If a black hole this size (or anything remotely close to this size) came close to Earth, the entire population of the planet would quickly die – and not in a pleasant way. When you fall into a black hole, the force of gravity acting on your feet is so much stronger than the force of gravity acting on your head that you get stretched out. Infinitely stretched out. Until your entire body is reduced to one long, single string of atoms, which ultimately gets crushed down into the singularity like literally everything else. This process is called “spaghettification” and, were a black hole to appear here, it would happen to all of us all at once. All of us together, plus everything we’ve ever known, being ruthlessly, inescapably pulled apart at the atomic level… it’s not exactly a happy thought, is it.

Aside from the destruction, though, black holes are also widely known for distorting the time and space around them. In reality, if we ever shared a planet with a regular, stellar black hole or bigger, we’d be dead far too quickly to notice any kind of strange time dilation or gravitational warping that might happen. Time dilation, in particular, is only really noticeable if you had an observer both inside and outside of the black hole – an impossible feat. Say a black hole really did appear here, pulled us all past its event horizon, and we were all alive and aware enough to know what was going on (which definitely wouldn’t be the case)… all we’d really see is everyone else experiencing time and space, life and death in the exact same way as ourselves. To us, the time warp wouldn’t exist.

But what about for an extremely tiny black hole – does such a thing even occur? So-called micro black holes are still hypothetical, but this doesn’t mean they’re not real (and that they’re not a real concern). For years, now, people have worried that particle accelerators – specifically the Large Hadron Collider in Europe - might be able to create black holes. And, of course, if they ever did, then this really would constitute a black hole appearing on Earth. Experiments started at the LHC in 2010, so they’re more an ongoing study nowadays, a background story for life on Earth rather than regular, headline-making news. Still, if anything ever did go wrong, we’d all know about it.

It’s thought that, were a micro black hole to appear on this planet, whether as a result of particle accelerator experiments or not, then it would instantly dissipate because of its small size. Which sounds like a good, non-life-threatening situation… but, unfortunately, it’s also believed that the energy released just from that happening would easily dwarf that released from a nuclear bomb. While this wouldn’t necessarily be world-destroying, it would certainly kill everybody in the immediate area - potentially millions of people. If we had a particle accelerator at the bottom of the sea, rather than beneath the France/Switzerland border as per the LHC, maybe micro black hole creation wouldn’t be quite as deadly to humans – though it would still devastate marine life and trigger untold tsunamis.

A slightly larger black hole (but one that’s still smaller than a stellar black hole) would bring its own set of problems, too. Say one with close to the mass of Earth opened up tomorrow (a wholly hypothetical prospect, because science doesn’t yet know of a way that a black hole like this could even happen)… Well, it would also wreak havoc. A black hole of this size would still look very small to the human eye, but it would be strong enough to slowly consume our entire planet piece by piece. We might be afforded a little bit of time - time enough, perhaps, to escape to the moon or Mars in a far-future world - but before long, with the planet itself devoured, such a black hole could even take Earth’s place in the solar system. The moon would now orbit around it, potentially without any other major changes. Theoretically, though, the opposite could also be possible. You can fit all of the other solar system planets end-to-end between the Earth and the moon, so our closest satellite is still a long way away. If a black hole, then, with the same mass as the moon, took up the same spot as the moon, could it also orbit around us? For at least a short time, maybe it could… even if it would appear tiny compared to the moon, and far too tiny to see from the ground.

Thanks to modern science and astronomy, we know today that many exoplanets and stars orbit black holes perfectly safely out in the universe. We also know that black holes can orbit each other, and that our galaxy has a supermassive black hole at its centre (or, according to some theories, two supermassive black holes at its centre). What’s especially crucial to this thought experiment, though, is that scientists have also discovered before that a black hole can orbit a star - the star just has to be more massive. Ultimately, black holes are objects in space like everything else, and they behave according to the mass of what’s around them. Place a hypothetically moon-sized black hole (in terms of mass) precisely where the moon is now, then, and the night sky would look totally different! And scientists would have the ultimate opportunity to study these cosmic enigmas at close quarters. Today, we have just a single, blurry image of an extremely distant black hole… but now, we’d have the universe’s ultimate destroyers within touching distance.

The downside? Well, having a black hole that close to us could well prove unsettling. Every time we looked into (or thought about) the sky, there’d be a reminder of how close we are to a quick demise via the dreaded spaghettification. But it’s perhaps worth noting that Earth is already affected by distant and dangerous celestial objects – not least the sun. While sunlight is needed for life on Earth, the sun would be just as dangerous as a black hole if it were ever to move closer to us. In terms of potential for danger, falling into a star isn’t any more or less fatal than falling into a black hole… both will quickly kill you. Yet, we’re obviously used to the sun… it’s been there for all of our lifetimes, and throughout Earth’s existence, so we rarely imagine that it will be the end of us. Perhaps, in an alternate world where a tiny black hole hung in the sky as well, we’d grow to feel the same way about it.

On the planet’s surface, even a micro black hole could have devastating consequences, potentially killing millions or even the Earth’s entire population. If the right-sized black hole appeared just in the vicinity of Earth, though, we might, maybe, stand a chance. And that’s what would happen if a black hole appeared on Earth.