Black holes have come up a couple of times this week, and I've always wondered something. When you fall into a black hole, all sorts of strange things happen.
The most well-known one is that nothing -- not even light -- can ever escape once it falls in. Well, my question is, if you fell in to a black hole, as you crossed the event horizon in your sturdy, well-lit spaceship, would the lights stay on or would they go out as you crossed into the black hole? (Ignoring the tidal forces that would rip you and the spaceship apart.)
In other words, you've read the first 1497 pages of the Count of Monte Cristo as you cross the event horizon; will you be able to finish your book with your last remaining moments?
What do you think? Feel free to discuss below; I'll post the answer with an explanation on Monday!
Physical Science
Comments
I would have guessed that the answer would have to be: we don't know. Because we don't really know that the laws of physics are still the same within the event horizon of a black hole. Am I wrong?
Posted by: Brian | November 20, 2009 8:04 PM
Of course they'd stay on. We're in free fall, so we'll be unable to detect any deviation of the laws of physics (ignoring, of course, tidal forces).
Now the annoying astronomers, who've been reading Monte Christo over our shoulders, though, will be forced to go get their own book if they want to know the ending.
In short, nothing can leave a black hole, but that says nothing about what can happen on the other side of the even horizon.
Posted by: Sili | November 20, 2009 8:04 PM
Depends on the mass. Sili is right that you wouldn't notice anything unusual as long as the event horizon was large enough. On the other hand, Brian is right that we have (as it stands) zero information on what happens past the event horizon. It could be a recreation of the Mad Hatter's tea party by hyperintelligent squids for all we know, and the no-hair theorems tell us we don't need to care. At least for classical holes.
Posted by: John Armstrong | November 20, 2009 8:49 PM
When you fall into a black hole, nobody can hear you scream.
Posted by: _Arthur | November 20, 2009 9:48 PM
I don't think you could see the light because of gravity. The light wont be able to travel to your eyes.
Maybe you could see it you were between the light and the gravity well...briefly.
Posted by: Clint | November 20, 2009 10:25 PM
I would guess yes? Assuming the laws of physics inside the Event Horizon are the same, it would kind of be like a miniature (closed) universe, wouldn't it?
I guess if the black hole were old enough, inside the event horizon would be so much captured light that it would be too bright to read?
I'm just guessing.
Posted by: Andrew | November 20, 2009 10:33 PM
Actually... once you've fallen in, there's no chance you can escape, and since you're probably not a photon, you probably won't be able to stop yourself from falling in even further... so wouldn't you quickly be pulled into the singularity, or the core made up of whatever-is-denser-then-neutron-stars, and be crushed?
Maybe if you're a fast reader and have some wicked awesome sunshades.
Posted by: Andrew | November 20, 2009 10:37 PM
Light can not escape the black hole horizon because the curvature of space-time is so severe that it can not get out. It curves back.
The light is still traveling at the speed of light. Special relativity will not be violated.
Posted by: NewEnglandBob
| November 20, 2009 10:45 PM
The event horizon is about the global properties of spacetime, in that the causal future is entirely inside the horizon. The local properties of spacetime are the same everywhere (except possibly at singularities), namely that if you take a small enough bit of it, it looks flat, and special relativity holds (local Lorentz symmetry). Nothing weird happens as you cross the horizon.
Posted by: Derek | November 20, 2009 10:55 PM
As they say, I don't think special relativity is violated inside the Horizon. Why should it be?
Posted by: Daneel | November 20, 2009 11:23 PM
The only thing that happens at the event horizon is that you lose your ability to communicate to the outside universe. (They can still send information to you, but you can't reply.) The lights stay on until either tidal forces destroy your spaceship or radiation (it can't escape, but it can still slosh around) fries the electrical systems.
Posted by: Eric Lund | November 20, 2009 11:29 PM
I'm not sure this is how I want to spend my final moments: I never finished The Count of Monte Cristo all those years ago back on Earth, so finishing it under these conditions is going to be a challenge...
The lights would stay on, but - well, I started to think about how tidal forces might eventually affect the light itself, but then I realized I don't know if the ship is falling straight in, or going round like driftwood in a whirlpool, and then does that depend on if the black hole is rotating and in order to maintain air-speed velocity, a swallow needs to beat its wings forty-three times every second, right? So it could be carried by an African swallow but not a European. That's my point.
Posted by: DaveH | November 21, 2009 12:12 AM
I THINK, according to relativity, yes, light would stay on.
Posted by: Sophos | November 21, 2009 12:57 AM
Let me not take your bait.
Instead let me ask a question. I think that I am correct in saying that a black hole is like an elementary particle in that it has only elementary properties like mass and spin and thus there are no surface distinquishing features like hair, astronauts, meteors and such stuck on the surface of an event horizon of a black hole. (i.e if a black hole has no hair, I can't see how it could have a red dim astronaut, comet or meteor that it gobbled.)
OK my question. It seems to me that in the standard theory, when I look at a black hole I should see nothing. That is, I should see the stars behind the black hole as if there was nothing in between the stars and me even though their is a massive black hole. So when we look at the chart that you showed at the center of the Milky Way galaxy, do we see both the stars in front of the black hole and the stars behind the black hole. I assume we'd see the stars behind the black hole because some of the light from them will be curved around the black hole. OK that's a serious question and assumption about current black hole theory. feedback please. Thanks.
Posted by: Thomas Neil Neubert | November 21, 2009 2:47 AM
Nice vid, showing how the Earth and our sky look if we had rings like Saturn's:
http://www.youtube.com/watch?v=UT2sQ7KIQ-E
Posted by: AutoFocus | November 21, 2009 3:24 AM
As others have commented, we're assuming it's a very large black hole so the ship could at least make it through the even horizon before being destroyed by tidal forces. And we're assuming there is no other nearby matter falling in, otherwise the ship would be toasted, which is what would happen to the ship in the picture, because there's an accretion disk. Then, as others have said, any lights near the observer would be in her local inertial frame and would appear normal to her. But, say the ship went in bow first-- a lantern on the bow would disappear when it crossed the horizon. (I'm guessing here-- IANAP) (that means "I am not a physicist").
BTW, I love the space "ship" in the picture! It's funny how in all the sci fi movies space ships always have an up and down.
Posted by: Riesz Fischer | November 21, 2009 8:10 AM
"meteors and such stuck on the surface of an event horizon of a black hole. (i.e if a black hole has no hair, I can't see how it could have a red dim astronaut, comet or meteor that it gobbled.)"
The rapidly dimming image of astronauts stuck almost on the event horizon is just an 'optical effect'. I.e. the astronaut has crossed the event horizon loooong time ago, but the light they've emitted takes a long time to reach observer at infinity.
Posted by: Alex Besogonov | November 21, 2009 8:20 AM
It would seem that some form of death would happen. Brain death, heart not beating or no breath of life. Does the Christian soul get sucked up or down?
Posted by: ralph137 | November 21, 2009 8:23 AM
@Thomas:
On its "surface" (which doesn't really exist - the event horizon is not really a "surface" in the usual sense), or rather surrounding its surface, black holes can have many features, even a "red dim astronaut". The stuff on the surface, or surrounding it, is not part of the black hole, hence the "no hair theorem" does not apply to that.
The resolution in Ethan's picture of the center of the Milky Way isn't good enough to judge if the Black Hole blocks light from stars or lets it through - in that resolution, the Black Hole is much too small to see!
Back-of-the-envelope calculations: The Black Hole has between 2 and 4 million solar masses; let's use 3 million solar masses for an estimate. The Schwarzschild radius for our sun is about 3 km; that gives a Schwarzschild radius of about 9 million km for the Black Hole in the Center of the Milky Way - only about 30 light seconds!
In contrast, in the first picture which Ethan provided, a length scale of 1 light *year* is given; in the second, the scale given is 0.1 arc seconds. At a distance of about 27 000 light years to the galactic center, that translates to a length scale of about 0.013 light years; that's still about 400 000 light seconds!
Posted by: Bjoern | November 21, 2009 8:29 AM
C = C and that's good enough for me.
Posted by: Damon B. | November 21, 2009 10:14 AM
I posted "other" above. My thinking is: past the event horizon, all particles proceed directly to the singularity (do not pass GO), including photons. Definitely photons can't move away from the singularity, so you won't be able to see any lights or parts of your ship that are closer to the singularity than you are (regardless of how massive the black hole is, and thus how low the tidal forces are). But I suspect you would still be able to see the lights in some parts of the ship farther from the singularity, if they're not too far to one side. These lights will go out, though, as the electrons will be unable to complete their circuits--if they could, some would be moving across the event horizon outwards (and others inwards) as the ship crosses the horizon. So, I change my opinion--the ship will go dark immediately.
In conclusion, better finish the book ahead of time. But really, who would keep their nose in their book while they're plunging through an event horizon?
Posted by: Craig Heinke | November 21, 2009 11:33 AM
Lights would "stay on" in a sense, but man would things look weird. In fact, they'd probably look pretty odd as you're getting close to the black hole anyway, and I'm not sure that you'd notice you've crossed the event horizon; that is, that there is a measurable abrupt change in the way things look.
Posted by: Lex | November 21, 2009 12:00 PM
Ha! trick question. Where the event horizon is depends on the reference frame. In the reference frame of something freely falling into a black hole, there is no event horizon. There is no singularity at the center because space has expanded and diluted the mass density to zero. You fall for forever (in your own reference frame) and space around you expands infinitely too; sort of what we are observing right now. What is “outside” becomes infinitely red shifted and gradually disappears as it gets red shifted into oblivion.
Posted by: daedalus2u | November 21, 2009 12:28 PM
Light can´t get out. But it can get in. I wonder how other stars would look when their light gets sucked into a black hole to an unsquasable observer.
Posted by: Beasjt | November 21, 2009 12:29 PM
You write a lot about black holes lately. Does this have anything to do with the LHC's restart?
Posted by: Andy | November 21, 2009 1:28 PM
'if you want to know what happens inside a black hole, look around!' Darn i dont remember who said that. was it Suskind?
Posted by: vaibhav | November 21, 2009 2:53 PM
Not a very interesting question. There would be nothing locally that would allow you to know when you crossed the event horizon.
Better question, if you shine polarized light on a black hole would it cause it to spin? If not then what happened to the angular momentum?.
Posted by: ppnl | November 21, 2009 3:16 PM
Has the LHC destroyed the world yet?
Posted by: NewEnglandBob
| November 21, 2009 4:43 PM
Well you would only be able to see where light would be coming from, so you wouldn't be able to see in front of you only what's behind you.
Posted by: erik | November 21, 2009 5:37 PM
As I understand relativity, an outside observer would see the ship approach the event horizon asymptotically, and the ship's crew would see the universe (highly red shifted) evolve all the way to its end. I suspect that one would have time to finish the book before demise.
Posted by: complex field | November 21, 2009 6:04 PM
Since you're falling as fast as the book, unless you're at such a high speed that the light is shifted out of the visible, I guess you won't see anything unusual happen.
What type of matter can exist in a black hole? Would, for example, neutrons still exist or will they fall apart? What happens to photons which go in - can they interact with what's in there?
Posted by: MadScientist | November 21, 2009 6:41 PM
Would the lights stay on? Assuming you mean "would whatever's emitting light on your ship continue doing so", I'd answer yes, until the black hole separates the atoms too much to interact with each other in a way which causes them to emit a large number of visible-wavelength photons. As for "would you still be able to see", it depends on how long your eyes/optic nerve/total neural processing center remains intact enough for you to process images. Also, it depends on your tolerance for 1500ish-page novels; I'd probably choose NOT to by then.
As for the physics, my understanding of GR and its weirdo consequences is limited but: it seems as you approach the singularity, the "extra pull" of gravity (greater spacetime curvature, right?) would draw light that would normally be able to reflect off the book, into your eyes past you towards the singularity, but light that would otherwise have bounced off of atoms behind you might potentially reach your quickly-atomizing corneas. Perhaps it would be hard to read with a laser, but a diffuse source in your frame within the black hole must be, uh, "visible". Certainly photons aren't destroyed just from being within the event horizon (i.e. I agree with Craig H and am being obnoxious - simultaneous in all frames).
Posted by: Kevin | November 22, 2009 4:36 AM
http://www.smbc-comics.com/index.php?db=comics&id=1452#comic
Posted by: Jim Bob Cooter | November 22, 2009 9:46 PM
I voted 'lights go off' using the following reasoning:
If a light bulb is straddling an event horizon, it can't exactly make a current--on one side of the current, electrons would have to move out of the black hole to complete the circuit.
What do you think?
Posted by: Max | November 23, 2009 12:54 AM
There is no event horizon; it is just an illusion created by gravitational lensing, ie self magnification of the small ball of collapsing matter.
From the outside it would look like the matter is forever falling towards the event horizon, but really it is all just collapsing to the center, but magnified.
I think they call them incipient black holes
Posted by: Mudbox | November 23, 2009 5:53 AM
Could it depend on which direction you're looking?
If facing away from the center of the black hole, would the light become blue-shifted and brighter instead of red-shifted and darker?
Posted by: Mr T | November 23, 2009 10:13 AM
At first I thought it doesn't matter since you won't have time to turn a page until you smack into whatever is at the center. But according to Wikipedia, there are supermassive black holes with 10 AU event horizon. Wouldn't it suck to surprisingly survive going through the EH and then see a little dot about 100 min flying time ahead?
I'd skip to the last page to find out who'd done it right away.
Posted by: Mu | November 23, 2009 11:27 AM
It's all relative!
Posted by: Doug Little | November 23, 2009 1:39 PM
Thank you Alex and Bjoern. Your answers make sense.
Posted by: Thomas Neil Neubert | November 23, 2009 2:21 PM
Where the event horizon is depends on the reference frame. In the reference frame of something freely falling into a black hole, there is no event horizon. There is no singularity at the center because space has expanded and diluted the mass density to zero. ~ solved it.
Posted by: Medical Spa MD | November 29, 2009 9:03 PM
1st of all, a black hole isn't really a hole
It's a condensed dead star, the reason it appears to be a black hole is because it's mass is squeezed into a tiny fragment that it has massive gravity pull that it even pulls light from all and any direction. It's still a solid piece.
Posted by: YESMAN | January 21, 2010 6:37 PM