Under Pressure

August 3, 2009 5:29 PM

How would you get through a black hole?

I've been thinking about this one for a while, I've found some info about the possibility but not anything that gets into the mechanics.

Say we did find one of these "milder" singularities - presumably the gravity would still be almost neutron star crushing levels, what kind of ship/situation would we need to get through this? I was thinking maybe some kind of oxygenated liquid to inhale and fill the ship?

I have no idea. My physics knowledge is effectively nil. Help me, Mefites, you're my only hope!

posted by smoke to science & nature (28 comments total)

I don't have much of a back ground in either physics or astronomy but Phil Plait aka the Bad Astronomer does. Seriously, I doubt there is really any chance of surviving even getting near a black hole because of Spaghettification.
posted by hector horace at 5:42 PM on August 3

I was thinking maybe some kind of oxygenated liquid to inhale and fill the ship?

What, like in The Abyss?

IANAPhysicist, but reading the linked article suggests basically that sometimes there are approaches to certain black holes that don't totally destroy things the traverse them -- what the article refers to as "finite tidal distortions." My suspicion is that it's exactly how finite the distortions are that's at issue here; if they're sufficiently small then the object passing through won't be destroyed in the process.
posted by axiom at 5:44 PM on August 3

There isn't any "through" to get. You go into a black hole, and once you're inside the event horizon you're not coming out again.
posted by Chocolate Pickle at 5:48 PM on August 3

Get through to what? Black holes are the ultimate dead end streets.
posted by wfrgms at 5:50 PM on August 3

Fine, nitpickers, not through, into, without squished. Work with me here, sheesh!
posted by smoke at 5:56 PM on August 3

Get through to what? Black holes are the ultimate dead end streets.

This is not a given, and in fact some prominent physicists such as Lee Smolin think otherwise. Mind you, their theories are often way out there (Smolin thinks black holes led to new galaxies, and has a curious natural selection theory re: multiple universes).
posted by hiteleven at 6:03 PM on August 3

Yup, spaghettification. No way around it.
posted by phrontist at 6:16 PM on August 3

Really phrontist? The article I linked to seems to imply otherwise. Any further information you have will be gratefully received. :)
posted by smoke at 6:19 PM on August 3

You can enter the event horizon of a Supermassive black hole without much problem, but you're certainly not getting out.
posted by 0xFCAF at 6:38 PM on August 3 [1 favorite has favorites]

IANAPhysicist, but apparently, there is the Morris-Thorne wormhole which is held open by exotic matter so that the wormhole will not collapse, presumable allowing something to go through (if advanced alien civilizations are involved).

Also, Burko's article that sparked the press release.

But, why not pick up a copy of A Brief History of Time? I know not everyone likes it, but it's fun and easy to read. And you'll get a better sense of why spaghettification is so much more likely than the above example.
posted by Mouse Army at 7:05 PM on August 3

Space-time folding back upon itself infinitely to a point of absolute density? You ain't getting through.

Perhaps a mush of radiation that was you might get through, but there would be no re-building you because the data need to recompose you would be destroyed (or maybe just scrambled).

Perhaps the black-hole, like all the deepest ideas, should be best understood as a metaphor for the ultimate unobtainable.
posted by 0bvious at 7:08 PM on August 3

I am not a physicist.

The article you link to describes a proof that under some circumstances, tidal effects in/near a black hole can be finite.

A billion trillion gees is a finite tidal effect.

To be survivable, you would need a proof that under some circumstances, the tidal effects in/near a black hole are within survivable limits. Call it 100g for convenience.

The underlying article might do that, but the article you link to doesn't.

presumably the gravity would still be almost neutron star crushing levels, what kind of ship/situation would we need to get through this? I was thinking maybe some kind of oxygenated liquid to inhale and fill the ship?

It won't matter. The problem is tidal forces.

These arise when one part of an object feels noticeably stronger gravity than another part of the object. You don't feel a tidal force on Earth, but there presumably is one -- your feet are being pulled toward the center of the Earth very very slightly more than your head is.

The problem for a traveler is that near a singularity (or other very sharp, deep gravity well), it's easily possible for your feet to feel a gravitational pull that's 1g or 3g or 500g stronger than your head feels, and this difference tears your body to tiny bits.

AFAIK, it won't matter a whit what kind of ship you surround yourself with, or what you're immersed in. The only thing that would conceivably help would be to be restrained in such a way that your length along the radii extending from the singularity is minimized. But even then, I expect that the tidal forces (even if they remain finite) can get strong enough to tear you apart.
posted by ROU_Xenophobe at 7:16 PM on August 3

The gravity becomes so strong that the difference in strength on even an atom from the small distance between the side close to the hole and the opposite site is so great that the atoms themselves are ripped apart into their subatomic components.

You. You would be ripped apart long before that happened.
posted by 6550 at 7:25 PM on August 3

ok, so it's impossible.

But what would you need to make it possible?
posted by titanium_geek at 7:44 PM on August 3 [3 favorites has favorites]

You'd need to change the universal electrical constant. That's the only way to make materials strong enough to cope with that kind of force. But as far as we know that can't be done.

Or you'd need to wrap yourself inside a space-distortion bubble, effectively turning your ship into a self-contained universe which wasn't affected by outside gravity. But there's no theoretical basis for that, either.

In other words, yeah it's impossible. You can't negotiate with the laws of physics.
posted by Chocolate Pickle at 8:00 PM on August 3

[bunch of comments removed - non-lulzy comments that have some science in them, okay, other comments, less okay]
posted by jessamyn at 9:27 PM on August 3

imagine you did devise a ship that could travel through a black hole, and could survive the 'spaghetti forces' everyone is talking about. there are several things about black holes that DO NOT allow 'passage' through them (look up schwarzschild, kruskal, and eddington-finkelstein solutions on wikipedia).

1) in the frame of reference of a spaceship going into a black hole, the time it takes to reach the event horizon goes to infinity. what this means is that if you were to begin outside of a black hole and travel inwards, you would never make it.

2) let's pretend you could get into the black hole. once you are inside the event horizon, (called 'region II' in most texts with kruskal coordinates) there is (in the coordinate system) instantaneously a very narrow tunnel through which people hope to pass. however, this tunnel is highly unstable due to the added energy to the black hole (once you are in the black hole, you are the black hole), and also is rigged by nature to automatically snap closed after almost no time. the tunnel is like the shutter of a camera, maybe. it is unreasonable to think that something not travelling the speed of light (i.e. something with mass) can cross through it, due to it's short lifespan.

3) let's pretend you could get through the black hole. you would come out of a 'white hole' which spits everything out, rather than sucks you in. the existence of white holes is not entirely certain. we've never seen one. there is not all that much empirical evidence that suggests that they exist in our corner of the universe. they are probably just a mathematical construct, byproducts of a clever coordinate system which is useful for calculating physical problems, but not entirely real.

basically, the idea of traveling through a black hole is total bullshit.
posted by chicago2penn at 9:29 PM on August 3

So, to expound a bit on the tidal forces:

The pull of gravity decreases with the square of the distance. Right up against a black hole the size of an apple (which would have about as much mass as Jupiter), one part of your body might be 40x as far from the center of mass as another - which means it's getting 1600x the gravity!

So, the smaller the black hole, the larger this effect will be, near the event horizon. I think crossing the event horizon is the only part that seems to make sense to talk about. Getting "through" a dimensionless point while retaining your three dimensional features doesn't really even make sense.

That's why 0xFCAF's mention of the supermassive blackhole makes sense. The big ones are about as big as our Solar System. Pluto doesn't experience very significant tidal effects at all.
posted by aubilenon at 10:16 PM on August 3

1) in the frame of reference of a spaceship going into a black hole, the time it takes to reach the event horizon goes to infinity. what this means is that if you were to begin outside of a black hole and travel inwards, you would never make it.

No, that's not the case. From the frame of reference of someone falling into the black hole, the event horizon is a finite distance away, and you will pass through it without noticing anything, other than perhaps being torn apart by tidal forces. But you certainly hit it in finite time.

It's from the frame of reference of someone watching you that you never hit it. As you fall towards it, the light you emit being redshifted to a greater and greater degree means that someone outside will never see you hit the horizon. But you certainly do. In finite time.
posted by vernondalhart at 2:05 AM on August 4

Hmm... just tossing something out there, but would having no mass do the trick? (can electrons get in and out?)
posted by paultopia at 2:54 AM on August 4

Taking this in the spirit in which this was intended ...

You either want to use the black hole as a gate to somewhere else, or you would like to thread the needle, so to speak. How to thread the needle:

First off, you need a supermassive black hole. The larger the black hole, the smaller the tidal effects. That gets you through the event horizon and whatnot, but you've still got the singularity proper to deal with.

Of course, you'd want your supermassive black hole to obey a Kerr geometry, which is to say that it ought to be rotating. This is perhaps the easiest, as supermassive black holes have consumed big chunks in the center of a galaxy and probably have rotation just as galaxies do themselves, though they'd always be radiating away some of that rotational energy in the form of gravity waves. Why do we want this? Because in a Kerr (or Kerr-Newman — rotating and charged) black hole, the central singularity* is smeared out into a ring.

Yeah, you could therefore say you've been through the center of a black hole, but you haven't hit the singularity, which would kill you. You've threaded the needle.

Now, your ship would have to be made of some fairly ridiculous materials — some kind of exotic matter, superdense, with negative energy density. No, not antimatter; weirder than that. Negative energy density, something we've never seen. Generally speaking, once you have one impossible thing, many others follow. In any case, this highly unlikely state of matter has been one of those wildly hypothesized things capable of "pushing back" on some stressed portion of spacetime. If done correctly, it means that the tidal forces wouldn't reduce your body to some kind of energetic smear of leptons. Good luck with that!

On the other hand, perhaps you want to journey to far away places and never see your friends again. In that case, what you want is a wormhole. More importantly, it must be "traversable." It's possible to construct "simple" solutions for wormholes which are so unstable that they collapse as soon as you attempt to send through a single photon.

These usually involve some pre-conditions I would call unlikely — such as some matching black hole which had to have existed at t = 0 (aka "dawn of time") and whatnot. And some of them have to be held open with ... you guessed it, negative energy density matter again. Some folks have managed it with negative mass cosmic strings.

The guy whose work you want to look up is Matt Visser. He writes a lot about this sort of thing. I've met him and he's a very amiable guy, unless you're at a symposium and he's firing pointed barbs at your ideas and puncturing them neatly.

Mind you, you'd need a civilization whose industrial capabilities made humanity's appear like that of a slime mold in comparison, along with some extremely forgiving physics and some unlikely circumstances to pull any of this off, but you asked.

* it is expected that if we ever get a quantum theory of gravity (don't hold your breath), singularities will vanish, to be replaced by fuzzy areas where things are just Very Very Bad, rather than Simply Impossible.
posted by adipocere at 3:05 AM on August 4 [2 favorites has favorites]

paultopia: Hmm... just tossing something out there, but would having no mass do the trick? (can electrons get in and out?)

Well, electrons do have mass. It's very small, but it's there. Photons, which might have been what you meant, do not have mass. However, there's a reason that they're called black holes: Not even photons can escape.
posted by vernondalhart at 4:04 AM on August 4

Thanks very much everyone, this is exactly the kind of discussion I was looking for, especially you Adipocere! Keep em coming. :)
posted by smoke at 4:46 AM on August 4

It's worth stating that, since general relativity predicts nothing can leave the event horizon, any speculation about the interiors of black holes can never be tested by any experiment. Ordinarily phenomena that can never be tested get kind of a gruff dismissal from the scientific community. I don't quite know why black hole interiors get special treatment; maybe it's because there's so much interesting physics in the environment around a black hole, or maybe because it took so many decades to prove that an event horizon really is a one-way surface.

It's pretty easy to show that crossing the event horizon takes a finite amount of proper time, and is even (for a supermassive black hole, with small tides) uneventful. To an external observer, the last moments before your spacecraft crossed the event horizon would stretch ("dilate") to an infinite amount of time. You would stick to the event horizon, returning less and less light and heat; any message they sent to you would also stick to the event horizon, never quite reaching you; eventually your external observer would get bored and go home.

There is no "through"; to everyone outside, there is no interior.
posted by fantabulous timewaster at 5:58 AM on August 4

You should listen to this NPR story, which has a very abridged version of this book, which you might want to pick up - I hear it's very accessible and can teach you some of the science of black holes through fiction.
posted by exhilaration at 8:05 AM on August 4

"For ordinary black holes of a few solar masses, there are actually large tidal forces well outside the event horizon, so I probably wouldn't even make it into the hole alive and unstretched. For a black hole of 8 solar masses, for instance, the value of r at which tides become fatal is about 400 km, and the Schwarzschild radius is just 24 km. But tidal stresses are proportional to M/r³. Therefore the fatal r goes as the cube root of the mass, whereas the Schwarzschild radius of the black hole is proportional to the mass. So for black holes larger than about 1000 solar masses I could probably fall in alive, and for still larger ones I might not even notice the tidal forces until I'm through the horizon and doomed."
posted by DevilsAdvocate at 9:44 AM on August 4

I rather like Stephen Hawking's recent hypothesis. I'll try to drop it in a very simple way, and also try to get it right. :) (Please correct me if I'm totally off.)

Light, and other radiant energy, can't escape a black hole. It curves back around, and goes to the center. However, there are both some forms of radiation that *do* escape, as well as an unexpected stream of subatomic particles that are emanated from it. We don't know why, this is what the big radio telescopes tell us.

Hawking recently changed his working hypothesis to say that the energy and matter are neither destroyed nor entirely captured by the black hole - some of it escapes, because the forces pulling them in are stronger than their ability to escape, but not stronger then their resistance to being squeezed into a single point and staying there. So, essentially, some of it "squirts" out. (That's me trying to make the effect relate to something we can imagine.) The fascinating "revelations" of this model are:

1. Not all matter is captured forever - matter and energy do eventually escape,
2. All matter and energy pass through the singularity, even if they don't stick around,
3. All *information* that came with the captured mass/energy is lost. You can pass through the black hole, but you will be somehow destroyed and remade, probably in multiple parts, and there's no way to tell what your original form was, since everything had to get squeezed through the one point.

This is not definitive - there's always loads of discussion among theoretical physicists about this. But, it this is the state of the art. Maybe there will be a better model tomorrow?
posted by Citrus at 12:20 PM on August 4

… We don't know why, this is what the big radio telescopes tell us.

You're mixing two things here.

Hawking is famous for having argued that a black hole has an entropy, and computing how the entropy depends on the energy, which defines a temperature. The mechanism for blackbody radiation leaving the horizon involves pair creation in the vacuum near the horizon, but I think (not sure, please correct) that the spectrum viewed far from the hole is the same as any other blackbody at the same temperature. A black hole is very cold: the Hawking temperature is 60 nanokelvin for a solar-mass black hole, and a million times closer to absolute zero for a million-solar-mass hole like the ones at the cores of galaxies. The cosmic microwave background is nearly a billion times hotter, at about 3 K.

There is no observational evidence for Hawking radiation. There was talk that Hawking radiation would be observed if the LHC made black holes, but it doesn't have enough energy.

The radio telescope evidence generally suggests accretion disks, which form around compact objects but aren't limited to black holes. The dynamics for an accretion disk happen pretty far away from the event horizon. (The Schwartzchild radius for a million-solar-mass black hole is only about four times the radius of the actual sun.)
posted by fantabulous timewaster at 2:59 PM on August 4