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/sci/ - Science & Math

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3331690 No.3331690 [Reply] [Original]

So black holes are black holes because their escape velocity exceeds the speed of light, right? That means we can't directly observe what is going on behind the event horizon. But hypothetically speaking, would it be possible to sample space from behind the event horizon if we were to send a probe in attached to a very strong rope and pull it out? I realize this is almost absurd in the practical sense, but that's why I said hypothetically speaking.

>> No.3331695

You would have to pull that rope out faster than the speed of light, chum.

>> No.3331705

>>3331695
wai

if you're stood on the moon trying to lift a rock off the earth with a rope, you don't have to lift it at escape velocity. you just have to constantly apply a force greater than its weight.

escape velocity is for objects with no subsequent force applied to them (except by the field)

>> No.3331707

>>3331695
I don't think you would. The escape velocity only exceeds the speed of light if you assume the probe would need to break the gravitational force on its own. Isn't that the whole point of space elevators? That you wouldn't have to reach a certain speed but can simply use mechanical force to overcome gravity?

>> No.3331713

This will only ever be a thought experiment... So it would help if you said that is what it is.

>> No.3331716

>>3331695
Let's say you have a vacuum cleaner sucking through the hose at, I dunno, 50mph.

Then you tie a pebble to a strong string and let the vac suck the pebble into the hose.

You do not have to exceed 50mph of pulling speed to retrieve the pebble. The string just has to be strong enough to hold the pebble.

You can pull the probe out slower than the speed of light but you'd have to have some awesome rope. That is all.

>> No.3331718

>>3331707
escape velocity is one of the most misunderstood concepts by dumbfags

they somehow think a rocket needs to get up to 7000km/h or whatever it is to break out of orbit

>> No.3331720

>>3331713
Are you trolling / joking or just stupid? I guess if I even have to ask the question that means you must be trolling.

>> No.3331724

>>3331716
That's all I needed to know. Thanks!

>> No.3331736

Hypothetically, sure that's possible. It just probably won't ever happen though.

>> No.3331742
File: 97 KB, 360x360, Gasp_Far.jpg [View same] [iqdb] [saucenao] [google]
3331742

>if we were to send a probe in attached to a very strong rope
this is actually possible with large black holes where the tidal forces arnt that big.

>and pull it out
no, you wont be able to pull it out, no matter how hard you pull or how strong the rope is.

>> No.3331745

are there any qualifiedfags who can answer this? it doesn't seem right.

basically we're saying that, if there's a particle within the event horizon, you can apply a force to it and have it exit the event horizon.

>> No.3331746

>>3331724
There's one more thing, though.

It is impossible for any material to have the tensile strength necessary to oppose the tidal forces.

>> No.3331751

>>3331742
Your statements are contradictory, it seems. If there is ANY tensile strength left over after keeping the rope in one piece, you can use it to pull the object out.

It's not possible, because those tensile strengths are not possible.

>> No.3331753

>>3331742
>no, you wont be able to pull it out, no matter how hard you pull or how strong the rope is.
Why though?
>>3331746
How come? Can you calculate the maximal tensile strength of any material possible based on chemical bonding or something?

>> No.3331754

>>3331746
you can make the tidal force arbitrarily small by making the black ole arbitrarily big, counterintuative i know.

>> No.3331763

>>3331753
>Why though?
for one, time stops at an event horizon. I should have said that it is possible if you are the one who is lowered into the black hole, but to someone who is anchoring the line, you will just get closer and closer to the event horizon and never cross it, it would require an infinite amount of time to cross it.

>> No.3331769

>>3331763
Fuck, I should have remembered that. Fucking relativity.

Thanks.

>> No.3331771

the rope would have to be spun from the pure essence of a mother's love - the strongest bond known to mankind.

>> No.3331772

>>3331754
Well, yes, the problem scales that way, but how do you interpret the fact that you can't retrieve the object from beyond the event horizon? I still think your line of thought contains a contradiction.

>> No.3331778

>>3331771
lol'd

>> No.3331781

>>3331751
>If there is ANY tensile strength left over after keeping the rope in one piece, you can use it to pull the object out.
you can ably a force to keep the rope from falling in further, but if you apply a grater force than that the rope will not move or will snap

>> No.3331784

i checked wiki and it's impossible.

as you get closer to the event horizon, the force required to keep an object stationary increases without bound

>> No.3331790

Don't forget that, in accordance with relativity, within the event horizon, SPACE ITSELF turns inwards and ONLY inwards.

Within the event horizon, "out" is not a direction.

>> No.3331793

>>3331781
So your rope has a tensile strength that is EXACTLY equal to what is necessary to keep an infinitesimal mass an infinitesimal distance beyond the event horizon? As opposed to, say, the required tensile strength for immobility being infinite as soon as ANY mass is within the event horizon?

Something is wrong here.

>> No.3331800

>>3331793
i thinks its a matter of perspective, from outside the event horizon, the rope feels all of the force it will ever feel over infinity concentrated at a single moment, at the horizon, the rope feels the force normally.

>> No.3331809

>>3331793
>>3331800
I like you both.

>> No.3331818

>>3331809
Reciprocated.

>>3331800
I'm starting to think that time dilation effects might be the culprit, which includes the observer-dependency you brought up.

>> No.3331821

The electromagnetic force holds all materials we can fashion together. The electromagnetic force is carried by photons. Photons cannot escape the event horizon. Event horizon cuts all rope. This is just one of many reasons (some already enumerated here) you cannot get information to cross from the inside of an event horizon to the outside.

>> No.3331826

"Never can return" is a common misconception about the event horizon. Escape velocity = c just means an object in freefall will eventually fall back past the event horizon. There's nothing that says a freefall object can't pop above the horizon if its launched up. And an object tied to a rope is NOT IN FREEFALL. As other have said, it depends on the rope, the strength of the black hole's gravity and it's tidal forces.

>> No.3331827

>pulling rope faster than the speed of light

You dumb fucking cunts don't seem to realize that the attraction of the black hole is strong enough to overcome the nuclear forces and break the rope apart at the particle level. You wouldn't even have a rope left to pull back.

>> No.3331828

>>3331818
>dilation effects might be the culprit
yes, its all because time stands still at the horizon from an outside perspective.

>> No.3331846

>>3331827
that only occurs due to tidal forces and they can be made arbitrarily small with a large enough black hole.

>> No.3331849

>>3331827
>You dumb fucking cunts
There's no need for that. Lets pretend we're actually normal people in a normal discussion for once.

>> No.3331852

>>3331705
>>3331707
>>3331716
You're applying classical mechanics to a far more complicated problem.
Speed doesn't add up like that when it's close to speed of light. To achieve speed of light, you need to have 0 rest mass. Otherwise it's not possible.
All the forces from "rope" and whatnot would add like "relativistic speed".

>> No.3331856

>>3331846
No. If a photon CANNOT cross the event horizon, neither can the electromagnetic force. There goes all the tensile strength of the rope.

>> No.3331864

>>3331856
correct, however the rope will still physically exist the same. i mean that without tidal forces it won't be ripped apart into particle constituants until it gets right by the singularity

>> No.3331886

>>3331856
Photons are in freefall. Atoms in ropes are not.

>> No.3331903

>>3331886
Nothing has a higher momentum/mass ratio than photons. If photons are in irretrievable freefall towards the singularity, the atoms sure as hell aren't doing any better.

>> No.3331917
File: 34 KB, 462x477, facepalm.jpg [View same] [iqdb] [saucenao] [google]
3331917

>>3331903
> momentum/mass ratio

>> No.3331927

>>3331903
You can't tie a rope to a photon.

>> No.3331929

>>3331917
You're not half as clever as you think you are. It's OK though.

>> No.3331931

>>3331903
OP here, isn't momentum just a function of mass and speed, even in relativity? How can something have a high momentum / mass ratio? Just trying to understand here, I don't know that much about physics.

>> No.3331938

>>3331927
>>3331917
>>3331929
I can't tell who's trolling who.

But yeah, atoms are even more fucked than photons are when it comes to black holes.

>> No.3331950

>>3331938
No. Photons are always in freefall, atoms are not.

>> No.3331958

>>3331690
The force/bond force holding the molecules/atoms together would not be strong enough to hold the force of the individual atoms together. They would be pulled off.

>> No.3331964

>>3331950
I'm not sure what you think that means in the context of black holes.

>> No.3331998

>>3331958
So no one else willing to answer this?

>> No.3332000

How does gravity in fact interact with photons? How could the pull of any gravity well exceed the speed of a photon? Intuitively it does not seem weird, but the physics of it I don't get.

Crap, how do we experience light as moving if it's stuck in the same instant?

>> No.3332008

>>3332000

Relativity, dear.

Photons travel straight, but gravity curves space itself. So a straight line in a gravitic well is, naturally, a curve.

Also photons move at c at all frames of reference.

>> No.3332024

Not sure, but, wouldn't the probe melt down into singular matter anyway? Sounds to me like we're fishing in a frozen lake.

>> No.3332025

>>3332008
>Also photons move at c at all frames of reference.
except the photon's frame of reference, right?

>> No.3332045

>>3331950
Escape velocity only applies to objects in freefall. An object on a rope is not in freefall.

>> No.3332069

>>3332045
I think we've established that already.

>> No.3332102

>>3331690
>even light can't escape
>expects to be able to pull a *rope* back out
..and now that I've put it in perspective, do you really still need someone to answer this question for you?

>> No.3332122

>>3332008
>photons move at c in all reference frams

i don't understand how this can be so, please elaborate?

>> No.3332148

>>3332102
Go away.

>> No.3332161

What if we "flood" a small black hole with more mass than it can quickly crush?

Like slapping some engines on a few empty world and toss them in.

Would they all just get crushed slower, or would the black hole explode or disappear, or is there no answer for the question?

>> No.3332165

>>3332161
fullretard.jpg

>> No.3332174

>>3332165
No need to sage. That wasn't me (OP).

>> No.3332184

>>3332148
>go away
No. I specifically *WON'T* "go away", not now. Fucking MAKE me, asshole. Oh, that's right, you CAN'T. :p

>> No.3332187

>>3332165
>someone asks a question
>oh look they know nothing about the subject!
>better not enlighten them at all, let's call them a retard instead
>that way I feel better about my own inadequacies by shifting the focus onto his

>> No.3332214

>>3332187
OP here. It'll turn into a quasar. Hope that answers your question.

>> No.3332219

>>3332214
Thank you.

Now I need to wiki Quasar.

>> No.3332227

>>3332219
>wiki quasar
>energy output of an entire galaxy
>mygod.jpg

Boy, a Dyson Sphere around one of those would solve all our problems forever.

>> No.3332230

time doesn't stop, that's bullshit

spacetime is bent though so every path an object inside the horizon can take goes towards the black hole.

>> No.3332236
File: 109 KB, 492x600, tumblr_lep2v7QLKK1qcjnc1[1].jpg [View same] [iqdb] [saucenao] [google]
3332236

>>3332184
Someone's sure buttmad.

>> No.3332244

>>3332230

Time does not stop indeed.

However, time SEEMS to stop, because the information of "x item entering the event horizon" cannot be transmitted. Therefore, only the information of "x item at the event horizon" can be transmitted, for all eternity.

>> No.3332251

>>3332230
Time does not stop for the observer going into the black hole, but it does for the outside observer. Considerer a probe sending pulses every second. As it gets closer to the event horizon the pulses will be received by the outside observer at exponentially increasing intervals, because time slows. The last pulses being sent will not be received by the observer. From the frame of reference from the probe it still sends out pulses every second as it nears the event horizon.

>> No.3332252

>>3332244
no, the object seems to freeze at the event horizon because the photons corresponding to the object falling further never reach you. Then the picture is quickly redshifted into nothingness. Time doesn't stop, not for the object nor the observer
spacetime is bent all the way though. Nothing can get out of an event horizon because there is no line that leads outside of it.

>> No.3332262

>>3332244
>"x item at the event horizon"
no, it never reaches the event horizon, just hovers above it getting red shifted.

>> No.3332273

>>3332236
-> >>3331849

>> No.3332275

>>3332262
the image, not the object

>> No.3332284

>>3332252
>>3332251
>>3332244

<div class="math"> c^2 {d \tau}^{2} =\left(1 - \frac{r_s}{r} \right) c^2 dt^2 - \left(1-\frac{r_s}{r}\right)^{-1} dr^2 - r^2 \left(d\theta^2 + \sin^2\theta \, d\varphi^2\right) </div>

put in <span class="math"> r_s = r [/spoiler] and you get


<div class="math"> c^2 {d \tau}^{2} =0 dt^2 - \left(0\right)^{-1} dr^2 - r^2 \left(d\theta^2 + \sin^2\theta \, d\varphi^2\right) </div>

meaning no time passes.

>> No.3332291

>>3332275

you are talking like time is absolute, its not.

>> No.3332297

>>3332284
it still takes a finite amount of time for an object to traverse the event horizon and reach the singularity so time does pass

>> No.3332302

>>3332297
From the probes reference...

>> No.3332307

>>3332291
I am not?
spacetime gets bent, all paths and timelines lead towards the singularity after passing the horizon. What I meant with that post is that an outside observer would see the image frozen at the horizon. Ofc the object itself would reach the singularity in a finite amount of time...

>> No.3332308

>>3332297
why do you think they call it gravitational <span class="math">time[/spoiler] dilation?

>> No.3332309

>>3332214
But the mass would be even bigger than before, How can a black hole get bigger but then suddenly not be a black hole anymore. Wouldn't it just be a bigger black hole instead of a quasar like you think?

>> No.3332310

>>3332302
>>3332308
we were talking about the probe's pov right?

>> No.3332318

>>3332309
A quasar is still a black hole, it just shoots out jets mass heated due to friction. This mass has never crossed the event horizon, and below the layer of heated mass there is still a black hole.

>> No.3332319

>>3332309
the energy given out by the black hole (accretion disk, heat etc etc) MAY counteract gravity. This is what happens in stars too, the energy given out by the core counteracts collapse

>> No.3332320

escape velocity in a 4d plane is greater than light. to "go behind" you essentially have to go through a higher dimension.

>> No.3332323

>>3332310
No, we were talking about the outside observer's point of view. For the probe time doesn't stop or slow.

>> No.3332326

>>3332307
>>3332307
yes you are,
>an outside observer would see the image frozen at the horizon
no, he would see the object just before the horizon, time runs differently for the probe and the observer

>the object itself would reach the singularity in a finite amount of time
yes, from its perspective, it would also see all the radiation the black hole will receive from outside at once, because time will run infinitely fast outside the black hole from its perspective.

>> No.3332330

>>3332323
oh right, I was talking about the probe's pov in all my posts
that explains a lot

>> No.3332341

>>3332309
a quasar is a black hole, with a layer of matter around it.

>> No.3332343

>>3332326
I see.

>> No.3332346

>>3332330
Well then, it seems we all agree.

>> No.3332355

>>3332346
wow we agree with theories that would, if not true, go against quantum mechanics and general/special relativity

>> No.3332367

>>3332355
something which is not very common on /sci/

>> No.3332607

What if you entangle 2 particles, then drop one into a black hole? Wouldn't the particle on the outside reflect the state of the particle on the inside?

I'm guessing no, since you probably couldn't keep the two particles coherent as one passes the event horizon. Thoughts?

>> No.3332630

i dunno, give er a shot there copernicus.

>> No.3332634
File: 79 KB, 360x360, Impressive_Up.jpg [View same] [iqdb] [saucenao] [google]
3332634

>>3332607
if you entangle the spin of the 2 particles, then the black holes spin will get entangled with the particle on the outside.

>> No.3332696

>>3332634

You are the best tripfriend I have ever seen. Ponies and all.

>> No.3332779

hm... interesting thread... what if instead of a rope, we just took a giant magnet? electrons have a certain charge to them, and if a powerful enough magnet was constructed, could it not counteract the gravitational force? (assuming electromagnetism COULD permeate the event horizon, which I'm not sure of)

Second question... When something approaches the black the hole, it "stops" at the event horizon relative to the outside observer, aye? Well then what happens to that object when the black hole's event horizon shrinks to 0 due to stephen hawking radiation?

>> No.3332781

>>3332779
No, see the discussion of photons and the electromagnetic force ITT.

>> No.3332789

>>3332779
As for the second question, the object only stops from the point of view of an outside observer. The hawking radiation question is interesting though. Does the apparent rate of evaporation increase from your perspective as you approach and pass the event horizon?

>> No.3332817

What if you made a rope made of Black holes? That way the rope negates the gravity of the original black hole and you can pull it out

>> No.3332828

>>3332817

I like the way you think.

>> No.3332845
File: 94 KB, 360x360, Think_Back.jpg [View same] [iqdb] [saucenao] [google]
3332845

>>3332779
magnets dont attract electrons, they move perpendicular to the magnetic field, but if you use something that is, it will work like the rope.

im not sure about hawking radiation but I have read that a possible explanation of it is that the radiation is particles that have fallen into the black hole and is stuck just outside the horizon which gets re-emitted when the horizon fluctuates, so the object will get re-emitted before the black hole reaches size 0 in the reverse order that it fell in, only the re-emition is random so the object doest get re-emitted in one piece.

>> No.3333075

>>3332845

Nope, Stephen Hawking radiation is when a particle-antipaticle pair (which are naturally created in a vacuum) is created, with one getting sucked into the event horizon, the other escaping. The one that falls in has negative energy (dont understand that one either. Sounds like tachyons), and detracts from the total mass of the black hole.