
The strange fate of a person falling into a black hole - fhinson
http://www.bbc.com/earth/story/20150525-a-black-hole-would-clone-you
======
JonnieCache
I once saw a susskind lecture about the firewall problem where he explained
that to check if someone falling into a black hole was incinerated, you'd have
to fire so much energy at them, you'd end up incinerating them. Physics is
weird. And, apparently, kinda passive aggressive.

BONUS EDIT: here's a Greg Egan short story about transhumans diving into a
black hole and trying to do physics on the way down:
[http://gregegan.customer.netspace.net.au/PLANCK/Complete/Pla...](http://gregegan.customer.netspace.net.au/PLANCK/Complete/Planck.html)

also here's his page explaining the physics in the story:
[http://gregegan.customer.netspace.net.au/PLANCK/Planck.html#...](http://gregegan.customer.netspace.net.au/PLANCK/Planck.html#CONTENTS)

~~~
AceJohnny2
Is that the story in which there's a discussion about whether space-time is
continous or discreet, the former case allowing infinite computation as you
dive into, the latter not?

~~~
JonnieCache
I think I remember that coming up, amongst many other things.

------
amluto
I don't think this article is representative of current serious thought about
black holes. I'm a bit out of date on this stuff, and I was never any sort of
expert, but let's see:

1\. This reality splitting thing sounds wrong. I've never heard of it.
Ignoring quantum effects, if you fall into a black hole and survive crossing
the horizon, Anne will see you get closer and closer to the horizon, but she
won't see you get there. She won't see you burnt up and she certainly won't
collect your ashes. The only fundamental difference between what you see and
what Anne sees is that by the time she gets bored of watching, you will only
have perceived a tiny amount of time passing.

2\. Free fall doesn't protect you from burnination. If the horizon is
surrounded by enough fire and brimstone and you free fall through it, you're
still going to burn to a crisp.

3\. If I remember my old problem set correctly, a black hole big enough for
you to live your life in would be truly huge. IIRC the supermassive black hole
at the center of the Milky Way would give you about 0.1 ms before you hit the
singularity.

~~~
derekp7
Based on your point 1, if time (on the outside) seems to speed up infinitely
for the person falling into the black hole, and if the black hole will
eventually evaporate due to hawking radiation, then wouldn't the black hole
appear to completely evaporate prior to crossing the event horizon?

~~~
amluto
Indeed. I never really understood how things ever actually make it through the
horizon in the first place (as seen by far-away observers) in order to make
the black hole grow.

I /think/ what's going on is that, from the outside, you never really see a
big black hole. Instead, you see what is, for all practical purposes, a big
black hole, but really it's an exceedingly dense band of stuff, red-shifted to
the point of invisibility, around the horizon. Of course, once you go close
enough to inspect it for real, you get caught up in the time dilation enough
that it looks more and more like a real black hole. If you go through the
horizon, everything that ought to have preceeded you through the horizon
already has, and it all makes sense.

The math for this is quite hairy [1] and I suspect that we're mostly limited
to numerical simulations. The closed-form steady-state black hole metrics are
gnarly enough as is.

[1] Terrible pun -- look up the "no-hair theorem"

------
monocasa
So I've had a question about stellar mass black holes that I can't seem to be
able to get answered (the question was deleted for /r/askscience).

How does a stellar mass black hole actually form a singularity given the fact
that there's gravitational time dilation? Wouldn't the heart of a black hole
slow down relative to an outside observer as mass is added to it so that you
never actually reach infinite density? It seems like you're fighting the
upwards curve of a parabola to make that happen, and meanwhile you're
releasing pressure from above via hawking radiation.

~~~
ars
I reached the same conclusion years ago, and the answer is very simple (and
controversial): Black holes do not exist.

If they existed they could exist, but it's impossible for them to form.

I've asked many many physicists this very same question, and none could answer
me (or I've gotten hand-wavy non answers). It's like no one wants to be the
first to declare this well accepted thing as non-existing.

The black holes observed by astronomers are not actually black holes, but
rather super massive neutron starts. It's not possible to distinguish between
these two objects, astronomers assume a black holes based on size, not based
on observed phenomena.

~~~
4ad
Not true: [http://motls.blogspot.co.at/2008/11/why-can-anything-ever-
fa...](http://motls.blogspot.co.at/2008/11/why-can-anything-ever-fall-into-
black.html)

~~~
ars
That explained nothing whatsoever.

I'll even quote:

"At some moment, the radius of the star drops below the Schwarzschild radius -
that's where the yellow and orange lines intersect. At this moment, the star
is pretty much doomed. Right now I am not sure whether one can generally prove
that the event horizon becomes inevitable at this point but I am sure that it
is going to be there in a moment according to the picture above which is
surely realistic."

He simply skips right past the impossible point: "the radius of the star drops
below the Schwarzschild radius". It will take that Sun an infinite amount of
time to do that. Any conclusions you draw after that point are unscientific.

He draws all sort of conclusions from the diagram, without ever showing that
his diagram is actually true.

There was some talk of how to be a stationary observer near the black hole you
must keep accelerating, but a: I fail to see how that explains the infinite
time, and b: who said I have to be near the black hole to look at it?

~~~
4ad
> It will take that Sun an infinite amount of time to do that (drops below the
> Schwarzschild radius). Any conclusions you draw after that point are
> unscientific.

Not true. You incorrectly assume that when the star collapses there is already
an event horizon, somewhere. But it isn't. The event horizon will only form at
some particular proper time, and at that time most (but not all) of the
stellar mass will be trapped by the horizon and will form a singularity
(interestingly all the trapped matter will reach the singularity at the same
proper time).

This is all very clearly explained here:
[http://www.aei.mpg.de/~rezzolla/lnotes/mondragone/collapse.p...](http://www.aei.mpg.de/~rezzolla/lnotes/mondragone/collapse.pdf)

Related physics stack-exchange answer:
[http://physics.stackexchange.com/a/28837](http://physics.stackexchange.com/a/28837)

I don't want to sound rude, but you really need to understand GR. The seminal
work on the subject is "The Mathematical Theory of Black Holes" by
Subrahmanyan Chandrasekhar, you need to know GR very well to be able to
understand it, but the pdf I linked is comparatively much simpler on the GR
and the mathematics required.

~~~
ars
> You incorrectly assume that when the star collapses there is already an
> event horizon

I made no such assumption. You don't need an event horizon to dilate time,
just a massive gravitational field, and something resisting it.

When the sun collapses either the outer layers experience a repulsive force of
some kind from below (a bounce perhaps, which is already theorized for
supernovas, or maybe neutron degeneracy), or the outer layers accelerate to
nearly the speed of light, either way they dilate time, and from the POV of an
outside observer take an infinite amount of time to collapse.

Because of this dilation the rate of light output (as seen from outside) will
drop and the sun will "turn off" \- i.e. it will look [almost] identical to a
black hole, except without the physics breaking singularity or event horizon.

One visible effect will be extreme red-shift of the light, which will look (to
us) like a very distant object hubble-red-shifted by distance/time.

~~~
4ad
> just a massive gravitational field

There is no massive gravitational field inside a star.

~~~
ars
In the exact center, no. But there certainly is everywhere else in the star.

After all, if there was no massive gravitational field, what's causing it to
collapse? You can't have it both ways.

~~~
yexponential
Thank you both for this interesting discussion, helped me grasp a few things.

------
repsilat
>there is no paradox, because no one person ever sees your clone. Anne only
sees one copy of you. You only see one copy of you. You and Anne can never
compare notes.

Can't you? Why can't Anne "gather up your ashes" and send them into the black
hole, where you can inspect them? Shouldn't that go against the "no cloning
theorem"?

~~~
kagamine
Given the initial split in realities, Anne would create a new parallel
universe when she placed your ashes in the black hole, one in which they exist
outside the black hole and in a parallel universe where they exist inside the
black hole, but this is not the same parallel universe you are experiencing,
but a parallel parallel universe. Essentially, 2 instances of the black hole.

~~~
repsilat
The theory very explicitly does not posit a "split in realities" or "parallel
universes" or anything of the sort. It says there is quantum information both
inside the black hole and outside it, and this is ok because they're
supposedly causally disconnected from one another.

~~~
kagamine
> The instant you entered the black hole, reality would split in two.

From the 3rd paragraph. However, yes the alternate universe comes into
existence when you reach the singularity.

Still, if you can exist both inside and outside, then your ashes can exist in
both places alongside living you without causing a paradox because you simply
will not exist in the same space as you ashes that will arrive very much later
anyway as time slows at the edge of the black hole. You are more likely,
having read the article, to have a post-life crises knowing that outside the
black hole you are dead.

~~~
logfromblammo
Reality only splits in two in the sense that the observer-dependent reality of
the person falling into the black hole and the observer-dependent reality of
the person remaining outside of it can no longer exchange information anywhere
except inside of the black hole's event horizon.

The half of your light cone that extends into the future remains entirely
within that event horizon. The outside observer's cone can remain outside of
it only as long as she avoids crossing the event horizon.

Even if the outside observer decide to jump in just seconds after you, it is
possible that the physics inside the event horizon would prevent her from ever
catching up with you to compare notes, or even sending you a message. You
could send a message with modulated x-rays, and she might pick them up with a
VLF antenna. She might reply with a deep infrared laser and accidentally cook
your brains with cosmic rays. Assuming a steep spacetime gradient as you
approach the singularity, everything sent inward would be severely
blueshifted, and everything sent outward severely redshifted.

There might even be a sort of Zeno's Paradox inside, where once you cross the
event horizon, there's another event horizon beyond that, such that anything
that much closer to the singularity than you are can never communicate with
you, in the same way that you can never communicate with the universe outside
the first event horizon.

~~~
dragonwriter
> There might even be a sort of Zeno's Paradox inside, where once you cross
> the event horizon, there's another event horizon beyond that, such that
> anything that much closer to the singularity than you are can never
> communicate with you, in the same way that you can never communicate with
> the universe outside the first event horizon.

Isn't every step in from the event horizon effectively an event horizon? If
all the mass of a black hole is effectively at the singularity in the center,
and escape velocity is the speed of light at the event horizon, won't there be
no point within the event horizon where escape velocity is less than the speed
of light, such that at any point within the event horizon, no point farther
from the event horizon is within the future light cone of that point.

~~~
repsilat
I don't think that's quite what they meant by that.

In silly "outside universe coordinates", inside the black hole you can define
a "minimum inwards speed" as a function of distance from the singularity. This
is how fast a photon will go towards the singularity if fired directly away
from it. It's zero at the event horizon, and it increases as you go in.

Now, what (I think) logfromblammo was saying was, "If I'm at the event
horizon, can there be someone close enough to the singularity that I can never
catch up?"

Communication isn't much of a problem for two people falling into a black hole
one after another if they're close enough. The messages from the person lower
down don't "go up", they just go down more slowly than the person higher up.
If they're too far apart, though, this might not work.

~~~
logfromblammo
The distance between fallers determines the energy requirements for
communication. The lower person will also experience slower time than the
higher.

The analogy is as follows:

Two BASE jumpers leap from the top of an infinitely tall radio mast in a
vacuum, one after the other. They are in free-fall, so do not directly
experience the effects of gravity, but the increase in the gravitational field
as the distance to the singularity decreases will be detectable as a
pseudoforce in that reference frame.

The first jumper writes a note on a baseball and throws it at the second. The
second also writes a note on a baseball and throws it at the first.

The concern for the first jumper is not whether the baseball can be thrown
back to the top of the radio mast, but whether it can be thrown hard enough
and accurately enough for the second to ever reach it. The concern for the
second is whether the first can catch his ball without exploding like a paper
sack full of wet spaghetti.

The other thing to consider is that both fallers will "see" multiple images of
the other, and of themselves, because there is a direct light path, the light
path that twists around once, the light path that twists around twice, and so
on. Images further away will be lower, slower, and older. If you aimed
correctly, you could send messages to your older self, but I'm not entirely
certain if your older self could reply.

~~~
repsilat
> _The concern for the first jumper is ... whether it can be thrown hard
> enough and accurately enough for the second to ever reach it. The concern
> for the second is whether the first can catch his ball without exploding
> like a paper sack full of wet spaghetti._

This is just a practical difficulty. There might actually be stronger
constraints in play -- the two jumpers might be causally disconnected from one
another entirely (that is, their forward light cones might intersect only at
the singularity.) I have no idea whether that's possible, though.

> _If you aimed correctly, you could send messages to your older self, but I
> 'm not entirely certain if your older self could reply._

Any message has to be received "lower" than where it was sent, so all messages
go from younger selves to older selves.

~~~
logfromblammo
Which would also imply that you cannot communicate with a person who jumped in
right after you did. I think your model does not account for the jumper having
mass and his communication photons being massless.

The reason the photons cannot escape is not because they are affected by the
gravity, but because the space they must traverse is stretched and twisted to
such an extent that to an observer inside the event horizon, the entire
outside universe presents an infinitesimally small target that is receding
rapidly. Anything you might manage to shoot out would be indistinguishable
from the Hawking radiation coming from the event horizon.

On a closer scale, you could probably communicate uphill, but the conversation
would be like an ent talking to a chipmunk. At some point, you simply can't
target your uphill counterparty accurately enough, or with enough bandwidth to
hold their interest.

~~~
repsilat
> _Which would also imply that you cannot communicate with a person who jumped
> in right after you did_

That doesn't follow at all. It's conceivable we could drop three things into a
black hole one after another, and at some point the first two could send a
message to each other, and so could the last two, but the first and last could
not (in a situation similar to the cosmological horizon.)

> _the entire outside universe presents an infinitesimally small target_

No. There is literally no direction you could fire a photon that could take it
out of the black hole. You can talk to someone falling behind you only because
they can "fall onto" your transmissions. Light cannot go uphill at all.

~~~
logfromblammo
If you can communicate with someone who jumped in one second after you, you
could communicate with your younger self via a gravity-warped path that has
the same distance as the direct distance between you and the second jumper.

There are no one-way trapdoors with massless particles. If a photon can get
in, an anti-photon (aka a photon) following the reverse trajectory (including
moving backward through time) can get out. It seems almost tautological, but
the photon doesn't really care which way the time arrow points, and can't tell
whether it is coming or going.

The warping of spacetime is such that no photon crossing the event horizon
from the outside can return to the outside. All straight light paths between
any arbitrary point on the event horizon and any arbitrary point inside it do
not intersect any other point on the event horizon. If your point of origin is
inside the event horizon, you can fire a photon out of it. But you literally
need a perfectly accurate and perfectly predictive model of all mass in and
around the black hole to make the shot. A single neutron unaccounted for could
bend the spacetime that the photon traverses in such a way that it misses the
event horizon. So for all practical purposes, you cannot ever be certain if
your photon made it out or not, especially after your first second beyond the
event horizon.

There's also the little matter that your photon, if it does make it out, may
have done so billions of years later, and possibly with a wavelength longer
than the diameter of the event horizon, which might make it appear as though
it were radiating from the event horizon itself, rather than somewhere inside.
It would convey no information across. It would probably look exactly like the
Hawking radiation.

~~~
repsilat
> But you literally need a perfectly accurate and perfectly predictive model
> of all mass in and around the black hole to make the shot

I think where you're going wrong is assuming that gravity acts by "distorting
angles". Like, near a massive object, maybe more than 180 degrees point
downwards, and less than 180 point upwards. In a black hole, then, maybe 360
degrees (minus epsilon) point downwards, and there's a peephole pointing back
up. You might litter breadcumbs along that trail, or unspool some twine to
find your way back.

Alas, that's not the picture we have. It's closer to the truth to say that
gravity gives space a "base velocity" (downwards) equal to the escape velocity
at that point. Inside the Schwartzchild radius that velocity is higher than
the speed of light, and because you can't go faster than light you can't get
out.

------
gus_massa
I really don't understand this sentence:

> _So Anne takes her bit, A, and puts it through her handy entanglement-
> decoding machine, which spits out an answer: either B or C._

(Note: I have a Ph.D. in Math and half a major in Physics that include a few
quantum mechanics curses (for example, with the Sakurai book))

What is a entanglement-decoding machine? You cant use entanglement to send
information. Just repeat after me: You cant use entanglement to send
information. This is one of the most common misunderstandings about
entanglement.

When you make the measurement and get the collapse, you only get a random
value (with a weighted probability). It's not possible to use that to get
information about B or C.

~~~
golgappi
The article doesn't say that information from B or C is useful. All it
explains is only 2 particles can be entangled with each other. So either A is
entangles with B or it is entangled with C, not both. Which means that either
Anne's reality is correct, or yours. The whole thing about the decoding
machine is just described to oversimplify it for the benefit of the masses.

~~~
gus_massa
Near the bottom of the article:

> _One clue might lie in Anne 's decoding machine. Figuring out which other
> bit of information A is entangled with is an extraordinarily complicated
> problem. [...] In 2013 they calculated that, even given the fastest computer
> that the laws of physics would allow, it would take Anne an extraordinarily
> long time to decode the entanglement. By the time she had an answer, the
> black hole would have long evaporated, disappearing from the universe and
> taking with it the threat of a deadly firewall._

The "machine" is an oversimplification, but I don't understand the equivalent
experiment that can distinguish between B and C.

Also, there are more complicated situations. You can entangle 3, 4, ... or
more particles
[http://en.wikipedia.org/wiki/Multipartite_entanglement](http://en.wikipedia.org/wiki/Multipartite_entanglement)

Usually the discussions are only about entanglement of 2particles, because
that is weird enough, but the math for more particles is just a little more
complicated.

------
dvdkhlng
Somewhat related: there is a short story by Greg Egan, "The Planck Dive",
describing a voyage (without return) into a black hole, in a scientifically
not too absurd way. You can read it online:

[http://gregegan.customer.netspace.net.au/PLANCK/Complete/Pla...](http://gregegan.customer.netspace.net.au/PLANCK/Complete/Planck.html)

~~~
jamesdelaneyie
Have yet to read this but huh – manually responsive web design!

~~~
aesthetics1
That's actually really interesting. Imagine having a feature like this built
into browsers for dealing with long articles and text. Yes, we have 'zoom' but
that typically breaks things at a certain point. Easily swapping the
background and even the left/right bias of the text is a pretty neat tool to
include, even though it isn't that intuitive on the site.

------
BenderV
"That's the thing about black holes. They're not just annoying obstacles for
space travellers. They're also theoretical laboratories that take the subtlest
quirks in the laws of physics, then amplify them to such proportions that they
can't be ignored."

I also use this strategy to think about philosophy and science. People often
think that because they are extremes, they are not relevant. However, they are
as relevant! And they force us to think outside our natural instinct.

------
Frompo
This was very confusing, and a prime example of the horrors of popularisation.

Watch this talk about the firewall paradox instead, more technical but at
least it makes sense!

[https://www.youtube.com/watch?v=tEtt4A7WsDg](https://www.youtube.com/watch?v=tEtt4A7WsDg)

------
Varkiil
"In a big enough black hole, you could live out the rest of your life pretty
normally"

Free falling in your ship and suit waiting for you to be crushed to death...
pretty normally

~~~
antimagic
It depends on what you mean by "inside" a black hole. If this means "inside
the event horizon", well, if the black hole is big enough, you can put
yourself in orbit around it relatively easily, you'll just never be able to
achieve escape velocity. If you take the Earth for example, a geosync orbit
has a velocity of 3.07km/s, whereas escape velocity is 11km/s

~~~
dvdkhlng
There aren't any stable orbits within the event horizon of a black hole (due
to General Relativity):

[https://en.wikipedia.org/wiki/Schwarzschild_metric#Orbital_m...](https://en.wikipedia.org/wiki/Schwarzschild_metric#Orbital_motion)

~~~
antimagic
Not so, only one of the two solutions is unstable:
[https://en.wikipedia.org/wiki/Schwarzschild_geodesics#Circul...](https://en.wikipedia.org/wiki/Schwarzschild_geodesics#Circular_orbits_and_their_stability)

Also, this applies only to circular orbits, and does not indicate that a
powered ship could not maintain orbit.

~~~
repsilat
Those orbits are all outside the event horizon. Inside it, all you can hope to
do is fall inward as slowly as possible.

------
PuffinBlue
I always assumed the differing 'views' of what would happen crossing into a
black hole was a product of the interplay of the equivalence principle and
'relativity of simultaneity' that Special/General relativity already accounts
for.

I had thought that upon reaching the event horizon the outside observer sees
time 'stand still' because no light from your continued motion the other side
of the event horizon can reach them, effectively freezing the observers view.
Or thought of another way, the curvature of spacetime at the event horizon
reaches the equivalent velocity of c due to the extreme warping of spacetime,
so light can't escape and 'time' stops for the observers view of the
freefaller because light can't get to them, the freefallers then image freezes
and slowly fades.

Special relativity says the relativity of simultaneity is pronounced at high %
of c, would it not be pronounced in an extreme gravitation field? A
gravitational field is equivalent to acceleration so...

If the curvature of spacetime at the event horizon has an equivalent velocity
inwards of c, thereby preventing light escaping, would this not lead the
outside observer to see one thing and the freefallers to experience another
which special relativity's relativity of simultaneity explains?

I say this becaue the light cone escaping the black hole must experience high
gravitational fields (i.e equivalence principle) and the free faller continues
on their geodesic experienceing 'no' force (save for tidal forces which in the
case of a large black hole won't spegetify them just yet).

So the _outside_ observer is seeing the effect of the freefaller and the
freefallers observable light cone experiencing the equivalence principle which
necessarily would cause relativity of simultaneity to become more pronounced.
At the event horizon, with an equivalent spacetime curtavure of velocity c,
surely this would mean that the outside observer would see no more regardless
of what the freefaller observs and all that would be accounted for by
relativity of simultaneity.

I guess I thought of it as applying relativity of simultaneity to a
gravitational field (by way of the equivalence principle) and not just
velocity as the train thought experiment did.

Is this line of reasoning incorrect - I'm assuming it is - why?

~~~
Thrymr
> Is this line of reasoning incorrect - I'm assuming it is - why?

You're trying to reason about black holes with special relativity, rather than
general relativity. Special relativity explicitly ignores acceleration (and
equivalently, gravitation). You mention the equivalence principle, which is
relevant, but "spacetime curtavure of velocity c" makes no sense, because the
curvature leads to acceleration, not velocity directly.

~~~
PuffinBlue
Well that was sort of the point really, I was seeing how special relativity's
relativity of simultaneity would work in an accelerated reference frame from
the point of view of both observers.

Intuitively (dangerous I know) it seemed that just because you're
accelerating, that doesn't mean relativity of simultaneity wouldn't apply.

I assumed the equivalence principle would be relevant because thinking about
simulaneity of relativity in an accelerated reference frame (like an
accelerating train at high c) would mean any outcome of the thought experiment
would likely be transferable to relativity of simultaneity in a gravitational
field, seeing as path through curved spacetime and acceleration is
'equivalent' (with caveats).

Spacetime curtavure of velocity c - this is clumsy language but c behaves
differently right? It's a constant, so unlike a helicopter hovering above the
earth, spacetime's curvature must 'equal' c at the event horizon i.e. cause it
to travel on a curved path back towards the singularity, or at least cause it
to orbit on the event horizon.

In this sense I was thinking about spacetime itself as the thing that was
accelerating and the light was stationary at the event horizon, which is just
a mental analogue really and likely unhelpful.

------
joelrunyon
Articles like these are great reminders to question everything you think you
know.

~~~
guard-of-terra
I find this "new age" mentality annoying.

Yes there are things we don't know, but we should try to come up with precise
questions, not to ponder about the meaning of black holes in philosophical
way.

Start small, figure things out.

~~~
joelrunyon
It's not really a new age mentality at all (I wouldn't classify myself as that
at all). If anything, it's a strictly scientific mindset.

It's more of a reminder to think that even when we start to understand some
incredible things, there's still a TON out there we DON'T know.

I think that's where the cool revelations come in, when you start to
understand how much out there you don't know much about. That's where the
wonder starts (which tends to bring up some of those specific questions).

------
alkonaut
What do we know about the nature of entanglement? Does it make sense to talk
about entanglement between regions inside and outside of an event horizon?
Couldn't it be the case that entanglement too breaks down somehow at the event
horizon?

------
nilkn
It's hard to say exactly why as I'm not a scientist, but I find the
credibility of this piece extremely suspect. It seems to be making a number of
sensational claims (splitting of reality?) and I don't get the feeling that
the author understands this material on anything other than a completely
amateur level. Also, this seems to commit the famous mistake of thinking that
you will be ripped to shreds by tidal forces the second you cross the event
horizon. This is well-known to be false. For sufficiently large black holes
you can peacefully pass beyond the horizon (unless there's something else
going on, like a firewall).

~~~
yellowapple
> For sufficiently large black holes you can peacefully pass beyond the
> horizon (unless there's something else going on, like a firewall).

The article addresses this by pointing out that the "tidal forces" in question
are only noticeable for smaller black holes (at which point
"spaghettification" \- which is, by the way, the formal technical term for
this phenomenon - occurs); for larger ones, spaghettification forces are too
small to even be felt.

The Wikipedia article on spaghettification [0] has more details. The mechanics
are similar to those of a body's Roche limit (the point where the tidal forces
of one body will disintegrate a satellite body held together only by its own
gravity; i.e. the reason why the gas giants tend to have rings).

Granted, my own understanding of astrophysics isn't a whole lot better than an
amateur level, either, but the article doesn't seem all that inconsistent with
how people who _do_ have expertise in astrophysics have described these sorts
of things.

[0]:
[https://en.wikipedia.org/wiki/Spaghettification](https://en.wikipedia.org/wiki/Spaghettification)

~~~
nilkn
You're right, I glossed over that the article does address that point. So I
retract that criticism.

I'm honestly at this point just exceedingly skeptical of mostly everything I
read about theoretical physics unless it's coming directly from an expert.

~~~
yellowapple
To be fair, I'm pretty skeptical of stuff about black holes even when they
_do_ come from experts, since there's so much contradiction between general
relativity and quantum mechanics in this particular context, and experts more
well-versed in one field over the other will try to use that field's
explanations over the other's.

Black holes are fuckin' _weird_.

------
MrBuddyCasino
Interesting read, but I must say I was a bit disappointed by the ending.
Resolving the paradoxon relies on the computational complexity of finding out
with which other particle it is entangled with? Somehow that doesn't feel
right.

------
joshdance
Thought it was weird in Interstellar that Cooper survived getting pulled into
the black hole. Interesting that surviving is one of the 2 possibilities.

~~~
yellowapple
Dude, spoilers! :)

But yeah, what I'd love to know is how he got _out_. Did it leave him behind
when it evaporated (due to Hawking radiation)? Is Cooper a "particle" in that
context that was _emitted_ as Hawking radiation?

Crazy stuff.

------
amongthe
So, what if you built a shell around the black hole so that no new radiation
whatsoever could reach the black hole, and then dumped enough matter into the
black hole to absorb all the Hawking radiation orbiting it, and then jumped
in. What would Anne see since you are no longer incinerated (she's inside the
shell too)?

Also, the article says that for the laws of quantum physics to be preserved,
no information can be lost, which is why one clone['s ash] must remain outside
the event horizion. But why doesn't the ash fall in the black hole after the
one clone gets incinerated, thereby being permanently lost?

------
peter303
There are minimal tidal forces for very large black hole. You would not be
torn apart approaching or crossing the event horizon then. You would be unable
to leave or signal out of the hole.

~~~
peter303
Note the observable universe has an event horizon 13.8B years in time or 92GLY
wide in space which we cannot communicate across. Some speculate the
observable universe may also have the mass-energy of a black hole with an
event horizon of that size. But the observable universe is not a singularity
with all the mass-energy concentrated at a infinitely small "center". So in
conclusion the observable universe SOME of the characteristics of being inside
a black hole, but not all of them.

------
helyka
I guess I've always misunderstood blackholes. I was under the impression that
they were simply a vacuum created as a by product of the every expanding
"space". Sure they are sucking things up and growing, but space is always
expanding.

------
selimthegrim
Didn't Patrick Hayden write a paper about this stating it was essentially an
unphysical situation in the lifetime of the universe? I seem to remember this
from the fundamental physics prize lectures....

------
sfdrozdov
What would happen if Anne was holding a rope attached to you?

Maybe a better question is what happens when something/someone is straddling
the edge of the event horizon?

~~~
entelechy0
From her perspective, you and the rope would burn up against the fire wall

------
tjake
sounds cool, except before you even got close close to the black hole you
would be ripped apart by the tidal forces.

~~~
ceejayoz
[http://en.wikipedia.org/wiki/Spaghettification](http://en.wikipedia.org/wiki/Spaghettification)

> The point at which tidal forces destroy an object or kill a person will
> depend on the black hole's size. For a supermassive black hole, such as
> those found at a galaxy's center, this point lies within the event horizon,
> so an astronaut may cross the event horizon without noticing any squashing
> and pulling, although it remains only a matter of time, as once inside an
> event horizon, falling towards the center is inevitable. For small black
> holes whose Schwarzschild radius is much closer to the singularity, the
> tidal forces would kill even before the astronaut reaches the event horizon.

~~~
jessaustin
That is the best word for a scientific phenomenon, ever.

------
ankurdhama
Most of theoretical science and science fiction is complete bullshit. They use
some analogy and run with their wild imagination to create anything utterly
non nonsensical. The space time fabric etc is just an analogy to avoid people
from the real mathematical equations of relatively and what people did with it
created whole shit load of theoretical science around that analogy.

~~~
rnhmjoj
Relevant xkcd: [https://xkcd.com/895/](https://xkcd.com/895/)

------
mksndz
This article reeks of phlogiston

------
jayman
I think we are in a black hole already. We just don't know it yet. :D

~~~
gpvos
There is actually a recent theory that says this is the case (in a way):
[http://scitechdaily.com/universe-may-emerged-black-hole-
high...](http://scitechdaily.com/universe-may-emerged-black-hole-higher-
dimensional-universe/) .

------
jkot
Falling into a black hole is booooring.

I want technical details about ship which can deliver human near the event
horizon.

------
racheldav
LOL, Is it great news on hackernews ?

------
NoMoreNicksLeft
And if you ever start to think Doctor Who is a wishy-washy-weeny, someone once
pissed him off and he did this to them. Moral of the story: don't fuck with
time lords.

------
guard-of-terra
You can only get inside black hole after time ends. That's because universe-
time stops at the horizon.

The moment you fall in, Anne is dead eternally long ago.

Also, you are incinerated by a billion years of starlight per your second,
including energetic particles I guess.

You will observe the end of universe and death of everything in it before
diving.

~~~
tvmalsv
If that were the case, wouldn't that mean that the moment a black hole is
formed, it would never become any larger? How have super-massive black holes
formed in less than 14 billion years?

~~~
ars
The answer is both simple and controversial: They have not. Black holes do not
exist because they take an infinite amount of time to form. See the thread
elsewhere on this page.

~~~
oldmanjay
You're making some awfully assertive statements for not having proved your
case. Dismissal of all answers as "hand-wavy" does not actually make your non-
argument more compelling.

~~~
jdmichal
The concept is known as "eternally collapsing objects", and has survived peer
review just as much as any other concept discussed here.

[http://en.wikipedia.org/wiki/Magnetospheric_eternally_collap...](http://en.wikipedia.org/wiki/Magnetospheric_eternally_collapsing_object)

This is actually something that is verifiable, given time, since traditional
black holes may not sustain their own magnetic field, but MECOs can.

------
lottin
How can something that doesn't really exist such as space and time possibly be
warped? Physicists need to get a grip and understand that their model of the
universe is completely wrong. There is no space or time and the universe has
no shape.

~~~
drdeca
Do you have a line of reasoning for that?

Models which take spacetime to be able to be warped, /to my understanding/,
make what are currently the predictions which are most matched by experiment.

I don't know why one would suppose that space and time do not exist, other
than as some philosophical idea, but even if one does suppose that, it still
appears to work well to model the universe as if they do exist.

One would not expect a Berkeleyan Idealist to complain on every article about
nuclear fusion because they do not believe that atoms exist.

If space and time "do not exist", it seems like speaking of them as if they do
would be a useful shorthand, in any case (Provided that they yield a useful
model, which they seem to.).

~~~
lottin
The reasoning is very simple - If space does indeed exist, it must be
somewhere, because everything that exists is somewhere, but space can't be
anywhere, because if it's somewhere it must be contained in space. How can
something be contained within itself? It can't.

~~~
stromgo
"Matter contained in space contained in space" might be a problem, but "matter
contained in space and space existing directly" should be ok, especially if
your alternative is "matter existing directly".

------
jetskindo
What a coincidence that I finish watching interstellar and the minute I check
my phone this is the number one post. Maybe I made that happen.

~~~
strictnein
Surprisingly, they only snuck in one Interstellar reference, and it was pretty
vague:

> "Alright, a l r i g h t, a l r i…"

[https://www.youtube.com/watch?v=FiTaK3Fyj0k](https://www.youtube.com/watch?v=FiTaK3Fyj0k)

~~~
juliangregorian
Ha, and here I thought maybe it was a reference to "Hey Ya"

------
PaulHoule
Talk about the moral decay of theoretical physics...

This is just like one of those miller lite ads where somebody smacks a beer
bottle on the table and on the TV they see a mix of dog racing and bikini mud
wrestling.

The trouble is that it is so hard to get established that the field is
dominated by old fogies; as a kid in the 80s I was aware of this contradiction
but it was censored from the physics literature. Instead the greybeards were
worried about the information paradox which turned out to be no paradox at
all.

~~~
guard-of-terra
Nobody prevents you from postulating your own theory, but those almost always
turn out "tinfoil hats".

------
DigitalSea
I recently saw the movie Interstellar starring Matthew McConaughey. It answers
the question of what happens if you fall into a blackhole and it involves a
bookcase, I don't want to spoil it for those who haven't seen it.

 __Edit: Seems the people downvoting me are a bit sensitive and don 't have a
sense of humour. Sorry to anyone who was somehow offended. __

~~~
Avalaxy
Very interesting if you want some more background is the book 'the science of
Interstellar'.

~~~
ekianjo
interstellar was more a pile of nonsense than Science.

~~~
jessaustin
This is not an insightful response. Of the people I know who watched the
movie, those who objected _the most_ to the science were those with little
scientific training. (Similar to a relative of mine who is certain that we
will "never" have self-driving cars...) If you are knowledgeable, and have
specific objections, those might be more insightful.

~~~
DannoHung
Nah. Someone should've realized Miller's world was a bad idea before they went
down there and made the whole thing a screw up.

Oh, or what about the fact that they "solve" Gravity and decide to leave
Earth. HELLO, YOU NOW HAVE INFINITE ENERGY! YOU CAN FIX ANY PROBLEM WITH BRUTE
FORCE!

~~~
jessaustin
Well considering they were looting really old Indian Air Force drones for
parts at the beginning, and they have giant self-sustaining luxury habitats at
arbitrary points in the Solar system at the end, I'd say energy utilization
has increased _a bit_.

