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What If All Black Holes Closed? | Unveiled

VOICE OVER: Noah Baum WRITTEN BY: Dylan Musselman
Black holes are one of the greatest mysteries in the universe. Massive structures that are both wildly destructive and crucial to how the universe works. But what would happen if they all disappeared? In this video, Unveiled finds out how whole galaxies would change if all the black holes suddenly closed.
Transcript

What If All the Black Holes Closed?


The universe has order thanks to gravity. It’s what keeps the earth in a stable orbit around the sun, and the sun in a stable orbit around the galactic centre of the milky way. And that mass in the galactic centre keeps every star and planet in the galaxy rotating in a spiral motion around it. But what if the major source of that mass suddenly disappeared?

This is Unveiled and today we’re answering the extraordinary question; What if all the black holes closed?

Even though they’re tremendously destructive forces of nature capable of devouring every type of matter, black holes are actually incredibly important structures in the universe. Their discovery and study has greatly increased our understanding of gravity, the most fundamental aspects of existence, and has led to the formation of theories on everything from wormholes to time travel.

Despite their popularity in academic and sci-fi circles and even after a century’s worth of research, however, black holes are still as mysterious as they are fascinating - there’s just so much we still don’t know. We do know it’s likely that every galaxy has a supermassive black hole at its centre, though, in some way governing the formation of that particular system. Black holes may not always be the single reason for why galaxies behave as they do, but their massive gravitational influence certainly plays a large part in holding all of the stars together.

If all the black holes suddenly closed, then, the first question is; where would all that energy go? The conservation of mass says that matter can’t be created or destroyed, while Einstein showed with his famous equation E=Mc2 that matter and energy are relative to each other and interchangeable. So, the black hole energy needs to go somewhere or to do something.

These structures are extremely massive, and therefore extremely energetic. If they suddenly closed all across the universe, we’d see some kind of spectacle to “balance the books” - a gigantic surge of energy released back out into the cosmos. Space-time, which was bent or depressed under the mass of the black hole, now rebounds back and effectively “flattens” out… but it wouldn’t likely be a quiet affair, with massive explosions and torrents of radiation to release an unimaginable amount of pressure. It’d be as destructive as a supernova event, and probably even more so.

As they are, it’s a seeming impossibility that a black hole would explode, but there’s actually a theory that black hole explosions do sometimes happen as a result of matter that’s unable to shrink into the infinite singularity. It’s a phenomenon known as a quantum bounce, which transforms black holes into white holes, which are essentially the exact opposite to a black hole; repulsive structures that pour tremendous amounts of energy out of themselves, but which are impossible to get in to. In fact, if you subscribe to the theory, it’s believed that some cosmic events previously thought of as plain supernova explosions could even have been black holes transforming in this way. In either case, should every black hole close as part of a hypothetical universal shake-up, then perhaps this is what we’d see happening across the sky… supermassive structures switching to gargantuan voids that now eject thousands or millions of planets and stars out of every galaxy, rather than drawing them in. The balance of the cosmos would be disrupted, even destroyed, beyond all recognition.

But wait. Hold up. The sudden, cataclysmic emergence of white holes is by no means a given, particularly because we’ve never actually identified a white hole before. The main concern should even a single black hole close would still be the simple displacement of energy, and the damage that that could cause.

So, what of humans? Would we be destined for a fiery grave were our closest black hole to disappear? Well, no, actually. Mostly because we wouldn’t even be aware of a change until thousands of years later. The supermassive black hole at our centre is twenty-six thousand light years away from us, meaning when we “see” it, we’re seeing twenty-six thousand years into the past. So, for all we know, our particular black hole anchor might’ve closed, say, twenty-four thousand years ago - and we’ll only truly realise it in around the year 4,000.

It applies even more so to every other black hole in the universe, as viewed by us. The closest galaxy to our own, the Andromeda galaxy, would appear the same for some 2.5 million years until the light reached us to show what had happened when it’s black hole closed up. In that sense, we only ever know that any black hole possibly existed at any given point in the dim and distant past… they may all have disappeared already, and we’re just waiting for that information to get back to us - monitoring the night sky, ready to notice when something changes.

But, back to the supermassive black hole at the centre of our galaxy. It isn’t solely responsible for the orbit of every star, but it does exert its pull to some degree on every bit of matter within its massive field. Should that tremendous source of gravity disappear, the celestial bodies that are closest to the galactic centre would be the first to be thrown out of order, before general order crumbles in a domino effect of chaos extending outwards. Over hundreds of thousands of years, every star (and every star system - including the solar system) in the Milky Way would be pushed, pulled and realigned as though at random. The galaxy at large would eventually stop resembling a spiral at all, and would now more closely mimic a massive and unpredictable swarm… with every other galaxy facing a similar fate. The black holes that had served as lynchpins for their stability would now have toppled them - leaving behind a universe of randomness.

But all hope needn’t be lost, because that same universe has ways of resetting itself. Stellar black holes form from massive stars collapsing in on themselves… so, given the unparalleled upheaval in this extreme scenario, we’d soon see black holes reappear all over the place as thousands of stars died. Scientists aren’t yet sure exactly how supermassive black holes form, but various popular theories say that they’re either stellar black holes accreting enough mass, or they’re a group of smaller black holes merging together. Either way, there is a route for supermassive black holes to also reappear even in the hypothetical scenario that they’d all close. It’d set off a sequence of events that could feasibly rebuild shattered galaxies… and while it would never reset exactly (or even close to) what it once was, the universe could resume some sort of order. And that’s what would happen if all the black holes closed.
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