Black Holes Suck!

Sorry for the cheesy title. It's the best I could come up with.
Anyway, I've got a question that I'm hoping that someone can answer and explain for me.

In theory, a black hole has a gravitational pull so great that it draws in and breaks down all matter around it.

In theory, a black hole is encompassed by an event horizon.


Therefore, due to the very nature of a black hole, why is it not safe to assume the following:
Matter is drawn to a black hole, but never actually enters it.


Thanks in advance, Gear.

Once the matter entering a black hole has passed into the event horizon, it's in the black hole as far as outside observers are concerned. It adds to the mass of the black hole and no further information about it separate from the black hole as a whole is available.

Now, if you were a passenger on a space ship unwittingly headed towards a black hole, you could very well go into the event horizon without knowing it (especially in an extremely large black hole). Time would slow down for you as you approached the singularity and from your point of reference, you may never actually crash into it, time would just almost stop.

Hope that helps.

[edit on 1/26/2007 by djohnsto77]

Yup djohnsto77 is correct.
The event horizon is supposedly cause by light slipping into the small margin of being able to escape and not being able to escape and so pretty much orbits around the black whole.

So once inside the event horizon with the time dilation and all it wouldnt really matter.

on the bright side you would eventually be ejected as hawking radiation. Not that it would be any help.

Smile

phantom

this may be a little off subject but I have to speak my mind when it comes to black holes, and put out another sort of question to the topic. So black holes suck in light, and it cant escape, and everytime somthing enters it , it will grow. Well I recentlly heard of a thing called a dragon black hole ( may not actually be the real name of it) that doesnt stay in one place, but actually moves throughout the universe( and I guess theres a very large numer of these). If these "dragon" black holes move through the universe sucking up everything in their path, and growing in size while doing so, isnt it possible for them to suck up other black holes, and in theory suck up everything thing in the universe( continueslly growing in size) until it reaches the point that it will suck in upon itself bringing everything into a non-existance. ( sorry if anyone who reads this cant fallow me at all)

Sounds like a couple of crossed wires.
Black holes like any other body in the universe is effected by gravity, so yes it would move through the universe in its orbit around what ever galaxy it is in... so on so forth. they wouldnt as such roam the universe like some sort of sentient devouring machine.

When black holes collide they combine and generally become a larger black hole.

However its has been proved that black holes evaporate so things to escape...periodically. Something to do with quantum flactuations occasionally allows particles to exceed the speed of light for a short while and escape. This is less likely in large black holes due to the size of the event horizon. But in small primordial black holes the size of a proton with a mass of someting the size of a mountain would have a higher rate of evaporation thus dissappear quicker. This phenomena is called Hawking radiation.

As for the sucking up everything in the universe. Probably wont happen unless the universe begins to contract.

I advise getting a copy of Steven Hawkings "Universe in a nutshell" its speaks alot on the phenomena of black holes and is pretty easy to understand.

Smile

Phantom

Hi there.

Interesting subject.. Currently involved in a couple of projects revolving Black holes, hawking radiation, loop quantum gravity and dark matter.

Here are a couple of links to interesting white papers on the subject.

Hopefully should clear up some of the visualisation difficulties when dealing with black holes.

Matters of Gravity

Heavy calculus here, so if you need a simplified explanation, give me a shout.

Time Dilation in Gravity Wells

I'll gladly answer any questions you may have.

All the best,

NeoN HaZe


[edit on 26-1-2007 by Neon Haze]

thanks for that Neon. As always yields positive results.

and you are right the calculus in the second paper has just gone over my head: Dont suppose you can give a brief summary of the paper outline?

Cheers

Smile

Phantom

Ahh, Now I get it! Thanks.

My problem was that I thought time was delayed from the observers point of view, and was 'normal time' for the object travelling toward it, not vise versa.

Originally posted by bum_phantom
thanks for that Neon. As always yields positive results.
and you are right the calculus in the second paper has just gone over my head: Dont suppose you can give a brief summary of the paper outline?
Cheers
Smile

Phantom

No problem Phantom.

Nutshell...

The Time Dilation in a gravity well paper defines the calculations needed to work out several key components of the gravitational radius of various masses.

A Schwarzschild radius is the minimum spherical radius a mass has to be to become a singularity.

The most interesting calculations on this paper are the following.

The equations above are the calculations needed to give the exact amount of time dilation between two vectors.

The amount of time dilation beyond the event horizon of a black hole effects both time and space and this depends on the total mass of the black hole.

Though once an object falls beyond an event horizon of super massive black holes, such as Sagittarius A (the black hole at the centre of the milky way) the gravitational waves experienced are far less strong, as the longitude of the wave is also far higher.

So in the case of a super massive black hole the time dilation effects are will be felt far more slowly by any object falling in.

The best way to visualise this is image you are in a boat in the middle of the ocean. Now image very strong and fast small waves. The boat you are in is likely to capsize due to the frequency of the waves.
Now image you are in the same boat but this time, the waves carry far more energy but the waves are higher and slower. This time, your boat sales over the crest of the waves with very little ill effect.

matter falling into a black hole is effected in a very similar way, except instead of a ship floating across the surface your ship is travelling within the waves themselves.

The smaller the Schwarzschild radius is the tighter the gravitational waves become the more violently different the gravitational forces at any given vector.

This is where we get the term Spaghettification. Because as you fall into a black hole of a few solar masses the gravitation waves stretch you out into nothing more than a stream of atoms, visualised as a string of spaghetti

But with a Super massive black hole, spaghettification does not occur. You simple fall past the event horizon with no ill effects from the observer. However.... As you travel closer to your ultimate doom (a crunching singularity) you would see all the stars and the rest of the universe shrink to nothing more than a point of light over your head.

From an observer’s point of view looking in, it's a very different story. They would see you slowing down the closer you got to the event horizon to eventually dim out of existence.

In truth, the observer looking in wouldn't ever see you actually cross the event horizon, this is because of the effects gravity has on light, it’s a kind of optical illusion, caused by the apparent slowing down of light speed.

In all actuality, light speed is not slowing down, however around the event horizon, space speeds up to reach that of light speed, giving the impression to an observer that light stands still.

However, the light emitted by any object fallen towards the event horizon has a finite life. What the observer would see is the object getting ever dimmer, until eventually the object would just wink out.

Hope that all helps.

All the best,

NeoN HaZe.

Black holes make me uneasy. Not because they might eventually suck everything into oblivion, but because they just don't feel right to me. Compressing matter into a point of zero volume and infinite density sounds more like science fiction than science fact.

Yes, I know that a bunch of clever guys have worked out the physics and mathematics of how black holes supposedly work, but I'm still uneasy....

any one know any thing about stars being born from black holes sum breif stuff about these flashes in the sky. there was a race to find out this phenomenia apparently it was two polars of event horison collapsing or sum thing and then years or light years later. a combustion effect happens causing multable stars to form i remember nasa lost the race to explain and film it

any way my question is what happens to black holes after they colapse
what are these huge flashs in the sky
and if any one could contribute sum thing on this neon hase
cough cough

May be confused here but when 2 objects of similar size orbit each other, the highest point of gravity appears some place between the two. Is that correct? For example Pluto and it's moon, isn't the center of gravity somewhere between the 2? So if I were to fall towards Pluto, I would actually head towards that location and not Pluto its self?

I was wondering how this would effect 2 Black Holes Orbiting each other. Would this then create a point of gravity between the 2 higher than the gravity either 1 has, and thus everything would be sucked towards that point instead?

Would it then be possible for the 2 black holes to be pulled into that pooint and merge, or would it infact be possible for that 3rd point tobecome a blackhole it self?

Neon i had to vote you for a "way above" for that post.

That was almost as good as reading a Stephen Hawking book itself very good post

While there may not be any dumb questions, ats has yet to have me fire off a few, so that saying may need some revising.

Anyways registered just to ask a few questions I've been wondering about so here goes.

Soon there is a new superconducting supercollider opening. I've heard or read about the possibility it may create black holes while the search for ever smaller building blocks of nature are probed.

Now hawkings radiation would likely evaporate any that are created since they would be so tiny, however is it possible that one could become stable? Or that multiples could form and devour each other and thus become stable?

Also, what would be the minimum size a black hole would have to achieve before it stabilizes and begins to devour, well everything? Ok i know its not everything in a literal sense, but the solar system?

Now I'm all for scientific research, however is it possible someones ambition to be the first to discover a graviton (or in 20 years some yet to be thought of particle) could destroy us all? Or am I overreacting just a wee bit?

Hope someone can alleviate my concerns.

Neon -

You have voted Neon Haze for the Way Above Top Secret award. You have two more votes this month

You have me a headache looking at those calculations.

Great job with the information!