Space is a really freakin’ scary place. Besides the fact there’s no air, no water, it’s infinitely cold, and filled with deadly radiation, there’s this whole otherworldliness that has made space the center of horror films for decades. Space is dark, and desolate, and terrifying.

But it’s explainable. We know what space is: mostly a vast emptiness. Sure, there’s a few stray particles here and there, and depending on which theoretical physicist you talk to they’ll also say that space is actually time (and vice versa), but a lot of the terror we find in space has disappeared as we continue to send men out into the great beyond inside rocket ships.

That is unless you keep talking to those physicists. Then they might tell you about even more terrifying things you could find in space, like supernovas, gamma-ray bursts, and most dreaded of all: the black hole.

Black holes are the things that keep astronomers up at night. Much like how space used to be scary because it was unexplained, black holes are terrifying because so much about them can’t be explained. We have theories about where they come from, and we know what kind of effects they have on surrounding space, but what happens inside a black hole we can’t know by definition. The rule with black holes is: whatever goes in can never come out.

Or can it? Let’s take a look at a few theories that try to explain black holes.

15. Portal To An Alternate Dimension

To start, let’s get a few things stated for the record. We know that black holes are (usually) super massive stellar objects that have become so large the gravity they exhibit sucks in light itself, preventing anything from escaping once beyond the event horizon (that’s the black disk you see around a black hole – not the black hole itself).

The event horizon is the scary bit since nothing can escape once inside. Even if you were traveling at the speed of light, the fastest thing in the known universe, you couldn’t escape a black hole’s immense gravity.

But once inside, where do you go? Some theories posit that black holes aren’t just zones of crushing gravity, but actual portals to other dimensions. Whether you survive the journey to said dimension is up for debate, but as with most things about space, people usually don’t survive being inside it.

14. Time Travel

We still don’t have all that great of an understanding about what time actually is, but we do know that gravity has a profound effect on its passage. As you get closer to a gravity well (like a planet, or a black hole), time actually slows down. The greater the gravity, the greater the slowing effect on time. This has actually been proven by sending an atomic clock into space, and when it came back down the clock was a few nanoseconds faster than the one which remained on Earth.

Since the gravity of a black hole is so much greater than found on any planet the theory states that as you head into a black hole you’ll actually travel forward in time since you have slowed down relative to the rest of the universe. Thus, black holes are actually time machines with the only problem being you can never escape from them. Maybe.

13. Wormholes

One of the more exciting theories about black holes is that of wormholes. A wormhole is a theoretical construct that occurs due to Einstein’s field equations that would link two places in spacetime. Thus, if you could go inside a wormhole and travel to the other end you’d find yourself in a completely different part of the universe. The implications for any potential space travel are huge.

Some theorize that some black holes could actually be wormholes, and that if you go inside one you’ll just wind up in another part of the universe. Or another time in the universe. The problem with spacetime mechanics is that the two are practically interchangeable, so you can’t really count on a wormhole getting you to a specific place at a specific time.

12. Black Holes Are Actually Other Universes

We know that matter gets sucked into a black hole and that it never comes out, and that the matter is theoretically compressed down to a single point due to its immense gravity. But there’s still matter there, and since it’s all compressed into a singularity all known physics breaks down. The truth is, we have no idea what’s happening to all that stuff.

One theory postulates that stuff actually becomes another universe, and that all black holes are actually tiny universes within ours. Our own universe could itself even be a black hole that exists within an even larger universe, and that universe may be a black hole that exists in an even larger universe after that. It’s universes all the way down and up!

11. You Will Die Horribly

While all these theories about black holes are great, and while some are more optimistic than others, we’re pretty sure that coming anywhere near a black hole would just be a death sentence.

The forces that a black hole is known to put out are immense – many, many times the force of gravity found on Earth. Coming even close to the event horizon of a black hole would exert so much force on a spaceship – as well as the human bodies within – that you’d basically die of your blood not being able to circulate to your brain. If you managed to survive that, then that same gravity would start tearing apart the ship as the front half was pulled that much harder than the back half, stretching everything out in a process astrophysicists have creatively coined “spaghettification”.

You might not even live long enough to get close. Black holes emit enormous amounts of radiation that would burn anything to a crisp from light years away.

10. There Are Actually No Black Holes

While we’re pretty sure black holes exist, they have a lot of problems. One of those problems is the whole event horizon thing – the point at which nothing can escape. According to known quantum mechanics, such an object shouldn’t be able to exist, and instead there should be an intensely energetic area as particles break down on their way to the singularity.

Renowned theoretical physicist Stephen Hawking has posited a theory that states there is actually no event horizon, and thus no black holes at all. Rather, these massive celestial objects have an “apparent” horizon with no singularity at the center. Matter is instead temporarily suspended behind the apparent horizon as it gets closer to the center before eventually dissipating.

I doubt this’ll get astronomers to change the name from “black holes” though.

9. They Don’t Last Forever

Hawking has an even earlier theory (which so far seems accurate with actual findings) that state black holes don’t last forever and that the mass it ingests doesn’t stay locked away forever. The effect is called “black hole evaporation” and the cause is due to Hawking Radiation.

For the longest time, black holes were thought to be celestial prisons for which there was no escape, but astronomer’s observed known black holes emitting radiation – and lots of it. Hawking them came along and postulated that black holes were not these ever-growing gravity wells that would eventually consume all before it, but rather they’d give back the matter they swallowed in the form of highly energized particles. Once the energy and mass ejected equaled the energy and mass the black hole initially had, it would evaporate. The bigger the hole, the longer it would take to disappear.

8. There Are Tiny Black Holes Everywhere

The Big Bang theory states that at one point our entire universe was like the center of a black hole. Mass was condensed into such a small area that the laws of known physics break down. Then the whole thing exploded and the universe was born.

But in the first few moments (and by moments I mean seconds) that the universe existed the laws of physics may be there, but the constants were all different. For example, we know that a black hole forms once it reaches a certain mass, but that required mass was much smaller at the beginning of the universe. One theory states there could be tons of super tiny black holes left over from the beginning of time zipping all over the universe as we speak.

7. There’s One BIG Black Hole At The Center Of The Milky Way

Black holes are already huge, so it’s common to refer to them as supermassive objects, but black holes can get really big. We’re talkin’ billions of times the size of our sun. And there’s a truly colossal one right in the center of our own galaxy, the Milky Way.

The curious thing about these supermassive black holes is that despite their size, they’re not nearly as scary as the regular black holes. The supermassive black hole at the center of the Milky Way is huge, but the forces it exerts is comparable to what you’d find on Earth if you were close to the event horizon.

And the weirdest part is we really don’t know why because we’re still not clear on how supermassive black holes form in the first place. Some theories say they’re the combination of a bunch of smaller black holes, but that doesn’t explain why the force it exerts is comparatively less than a regular black hole on its own.

6. A Supermassive Black Hole Will Consume The Universe

On the other hand, since we don’t really know how they work we could be totally wrong, and a supermassive black hole will eventually consume the galaxy, other galaxies, and the rest of the known universe in something scientists call The Big Crunch.

And it plays out exactly how it sounds. The giant black hole at the center of the galaxy grows to consume nearby stars, and then grows beyond that to consume nearby galaxies, and eventually consumes everything like a celestial hungry hungry hippo. Afterward the universe may start again in another Big Bang, and the whole thing starts over again.

What we know so far says that this doesn’t appear all that likely. We believe that black holes eventually dissipate and that the mass they contained is given back, but we don’t have a lot of information on a long enough timescale to say for sure.

5. Supermassive Black Holes Are Actually Previous Universes

One of the theories being floated around on how supermassive black holes are created is that they’re actually leftover black holes from a previous universe. After a Big Crunch like scenario in which the universe resets itself for another Big Bang, there could be leftover black holes from the previous universe that don’t quite get as crunched as everything else is. This could be because they’re already crunched down to begin with, but nobody knows so it’s pointless to speculate (although fun).

In any case, those black holes might survive the Big Crunch and appear in the brand new universe, in which case they have gone through some massive changes that make them less “sucky” than they were in the previous universe, but a whole lot bigger. They then go on to form the center of brand new galaxies.

4. Dark Matter Could Be Black Holes

One of the greatest mysteries in modern astronomy is the fact that according to the math there should be a lot more mass in the universe than we can see. That mass has been given the name “dark matter” by physicists simply because we can’t see it and don’t know what it is, but it ought to be out there.

One theory suggests that dark matter is actually made up of black holes – small ones, so they can’t be seen on telescopes, but their combined effect would explain observational data of how galaxies move throughout the universe.

Most physicists say this idea is a bit nutty, but then again, they also say most theories surrounding dark matter are a bit nutty.

3. White Holes

One of the more interesting theories that came from the discovery of black holes is the existence of “white holes”. Basically, they’re the opposite of black holes – stuff can come spewing out of it, but nothing can go inside.

The entire concept of a white hole is born from the math describing general relativity but has never been observed in the universe. We’re also not sure how a white hole could ever form since, while we’re pretty certain a black hole can form when a star collapses after running out of hydrogen, there’s nothing that would explain a region in space that’s just constantly spewing matter and energy for no reason.

It could be that white holes are the other end of a wormhole, in which case the answer of whether or not you’d come tumbling out the end of a black hole is answered. Although you’d still probably not survive the journey.

2. Rogue Black Holes

Most black holes are thought to be fairly stationary, either at the center of a galaxy or wherever a star has died. But some black holes don’t play by the rules, and much like a maverick cop with nothing to lose, they go rogue.

In this case, rogue black holes detach from the center of their parent galaxy and start wandering around space. The terrifying thing here is the potential for such a rogue black hole to wander into another galaxy and start eating solar systems. Theoretically, such a black hole could one day wander into our own galaxy and eventually eat our very own solar system.

Rogue black holes are thought to be created when two galaxies collide and the massive gravitational forces of the two supermassive black holes just cause one of them to fly off the handle. Just like a maverick cop would.

1. Anything Could Become A Black Hole

One of the scariest theories about black holes states that in theory, literally anything could become a black hole. Take any bit of matter and squeeze it down hard enough and you’d eventually cause its very atoms to collapse in on themselves and form a black hole.

The amount of force you’d have to exert is way more than the force required to turn your mom’s ashes into a diamond, so I wouldn’t be too concerned, but it is possible in some of Earth’s particle colliders. Like, say, the Large Hadron Collider found in France.

The Large Hadron Collider is capable of accelerating elementary particles to a fraction of the speed of light in search of ever more elementary particles. Those particles usually just have glancing blows, but if two were to strike head on it could hit with enough force to collapse into a mini-black hole. However, such a black hole wouldn’t exist for longer than a few nanoseconds and would emit all its mass as Hawking radiation and evaporate relatively quickly.

Just keep in mind the next time you get up to nearly the speed of light that you too could become a black hole if you’re not careful.