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 abelian
Joined: 1/12/2008
Msg: 160
Black holes...help!Page 4 of 9    (1, 2, 3, 4, 5, 6, 7, 8, 9)
If you think this is in error show the proof that it is wrong.


I've already done that. In addition, since the photon is massless, you can't apply an expression like, F = GMm/r^2. That expression is only suitable for a Galilean universe in which the only way to have a massless particle is for it to propagate at an infinite velocity. Your reasoning is based on hacking and patching parts of incompatible theories together. I gave you a reference to for this already. Photons propagate along null rays. Take the metric for the interior, consider rays with ds^2 = 0 and you'll discover that all future pointing null and timelike trajectories have decreasing r. That means that when you are inside the black hole, the horizon is in your past and the singularity is in your future. Unless you know how to turn around in time, your future awaits you at the singularity.
 abelian
Joined: 1/12/2008
Msg: 162
Black holes...help!
Posted: 2/18/2009 5:23:46 PM
No you did not. You have argued. But shown no proofs here or there.

Yes, I have. In fact, the post you inclded in your reply has all the information you need. Write down the schwarzschild metric and do a little arithmetic. If you're up to disputing general relativity, you ought to at least be able to understand it enough to know what the metric tells you.


A photon has a mass as per fh/c^2.

That is not a mass. That is a momentum and you cannot use it as a mass the way you are trying to use it.


A high energy photon (gamma ray) in passing through other matter can turn into a electron (which has a rest mass) and a positron (which has a rest mass) pair. Photons have mass - but not a rest mass.


If you do the calculation, you'll discover that a photon cannot turn into an e+e- pair. It requires 2 photons. I've built a gamma ray detector that performs such a conversion, so I'm very familiar with how it works. The second photon is the virtual photon from the field of a heavy nucleus, like Pb.

If you think you can get pair production from a single photon try calculating it and you'll discover you cannot conserve energy and momentum precisely because the photon is massless.
 Constitutionalist
Joined: 9/4/2008
Msg: 163
Black holes...help!
Posted: 2/18/2009 7:52:23 PM
Black holes are called in more modern terms dark stars.
A dark star is a collapsed collection of matter which has such gravitational pull that an event horizon forms. The event horizon, due to the phenomenon that gravity's strength increase exponentially based on the distance between two given objects, is the point in which the very small mass photon or light particles cannot travel past the escape velocity required to break the gravitational pull of the black hole. Hidden behind the event horizon is the singularity. As matter becomes more and more dense and warps the fabric of space and time the singularity is an estimated point of infinite curvature. Science has not yet merged the world of quantum mechanics, or the science of the nature of the universe on a sub atom scale, with the classical modern of physics. Since classical modern physics is accurate for objects with extremely large amounts of mass and quantum mechanics is very accurate for studying objects very small a merging of the two schools of physics is required in order to have a more complete understanding of what actually goes on behind the event horizon.

Black holes have been proven and detected by gamma ray bursts. This is the last sign of matter passing the event horizon. According to modern physics theories using quantum mechanics we can also detect the existence of black holes by detecting hawking radiation. Since "virtual particles" as predicted by quantum mechanics are created and annhiliate each other so quickly so as not to violate the laws of conservation of mass or conservation of energy are so common when a black hole pulls one of these "virtual particles" beyond the event horizon but the other anti particle can escape we can detect energy the anti particle's wave like function as it decays into electromagnetic radiation. Thus hawking radiation. It's quite a bit to understand and anyone that says they have an incredibly firm grasp on it is a fool.
 stargazer1000
Joined: 1/16/2008
Msg: 164
Black holes...help!
Posted: 2/18/2009 9:03:13 PM
You know, it's amazing the half-heard facts that people take to be the whole story and get repeated in these discussions. So here's a little black hole physics from an enthusiastic amateur astronomer.

First of all, they exist and their effect has been observed. They represent a stellar evolutionary end-point in that the mass of a star has contracted to virtually infinite density and the gravity well has become so steep as to be unscalable even by electromagnetic forces - photons.

Either that, or in the case of galactic black holes, have the mass of millions of stars, again contracted to infinite density.

Stellar-mass black holes have been observed and one of the most famous ones is Cygnus X-1, a source of X rays. A star was observed spectroscopically to be orbiting another stellar mass object but that second object couldn't be observed. Two stars orbiting one another can be discerned by their individual spectra so it had to be orbiting something invisible. It was also eating mass from the visible star and emitting xrays. The original term for it was "black star" but, after Einstein, black hole came to be preferred term.

And there's numerous instances of galactic black holes. Our own galaxy's center has been observed to have stars revolving around a central mass and speeds that should have them easily flying out of our galaxy. And we're talking a region of space no larger than a few times our own solar system. The speed of those stars tell of a mass millions of times that of our sun. That can only be one thing. A black hole.

Galaxy M87 at the centre of the Coma-Virgo cluster has something that is creating a massive jet. If a black hole is eating, it would create an disc of material that was being accreted into the black hole. Conservation of motion causes the material to revolve around the event horizon before falling in. This sets up tremendous friction which generate great heat and magnetic fields which twist, collimating a giant jet of material to be shot out of either poles of the system. Black hole environments are very dynamic places.

Then there's quasars - the active center of galaxies. The brightest one is 3c 273 in Virgo. It's dim but I have seen it in my telescope. Distance: about 2 billion light years.

Oh, by the way, someone mentioned gravity. No, you don't fall at the speed of light if you fall off a chair. However, gravity waves travel outward from objects in space rotating around one another at the speed of light. That's Relativity for you. Information is restricted to c. Darn that Einstein guy!
 Constitutionalist
Joined: 9/4/2008
Msg: 165
Black holes...help!
Posted: 2/19/2009 7:06:03 AM
Speed of mass containing particles is restricted to c however when we take advantage of particles' tendency to behave like waves and transmit them through denser mediums we increase the speed c is capable of.
 abelian
Joined: 1/12/2008
Msg: 171
Black holes...help!
Posted: 2/24/2009 5:25:47 AM

Your metric is called a Gauge Scalar.

A metric corresponds to a spin 2. A scalar is a spin 0.
 MtnBikeFun
Joined: 10/8/2009
Msg: 176
Black holes...help!
Posted: 12/10/2009 4:45:53 PM
Hi! I have not read the other posts on this topic so forgive if this question has already been answered. If you want to understand black holes there is a great book by Kip Thorne called Black Holes and Time Warps which covers the topic in depth and detail yet in an easy way for a layman to read.

As to the question. Remember that in relativity Space-time is a 4 dimensional continuum. Therefore a blackhole is a 4 dimensional singularity. This means:

1. Space-time is warped, actually time is stretched infinitely. The stretching of time implies that the wave length of light escaping a black hole is stretched infinitely. In other words light cannot escape.
2. The gravitational pull is equal in all 3 space dimensions.
3. The hole has a dimension defined by it's event horizon. This is 4 dimensional horizon, inside this horizon nothing can be observed.
4. Archibald Wheeler cointed the phrase "A black hole has no hair". In effect this means the physical processes along the event horizon are exactly the same from any point in space as an observer.

Now the interesting part. Black holes can actually emit radiation and ... explode! This is why one should not fear black holes being created in LHC, they will evaporate in nano seconds. Quantum processes govern the evaporation or explosion of black holes. It works something like this:

Quantum pairs of particles are spontaneously created in the quantum vacuum all the time. As long as the pairs are particle and anti particle and they move in opposite directions preserving momentum, charge, energy, spin etc. No laws of physics are violated. When this happens on an event horizon, one particle may be sucked into the hole, the other must escape. The rate at which this happens is proportional to the event horizon and increases gradually as the event horizon shrinks. So small holes evaporate quickly.

Well that was from memory from reading the above book, I may have a few details wrong but that's the gist of it AFAIK.
 AtomicGogol
Joined: 4/4/2008
Msg: 177
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History
Black holes...help!
Posted: 12/10/2009 8:33:02 PM
I believe you're spot on, mtnbike. I for one would like to know if naked singularities will ever be found. Black holes seem to me to be a flaw in general relativity because of their infinite nature. Further refinement of quantum gravity theory and any observation of a naked singularity would clear it up a lot, wouldn't it?
 scorpiomover
Joined: 4/19/2007
Msg: 179
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Black holes...help!
Posted: 12/17/2009 5:39:56 PM

thus it would be a black shpere not hole...?
It's a sphere. But any light that reaches the event horizon, never leaves. That makes it appear black against the blackness of space, only that because it also absorbs all the light behind it, you cannot see any stars there, even when there are some behind it. Even if a comet passes behind one, too far away from the event horizon to be trapped, you'll see it moving along, then suddenly it will disappear, and then a few minutes later, it will re-appear, as if it was travelling the same route all alone, and it passed through a giant "black hole". So all you see is a black hole in the sky, a place devoid of any stars, planets, comets, meteors, asteroids, whatever. It looks like a black hole to us. So that's what we call it, a black hole.
 AtomicGogol
Joined: 4/4/2008
Msg: 180
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History
Black holes...help!
Posted: 12/17/2009 9:19:11 PM
Surely a 1-dimensional point of infinite density is scientifically flawed. Does anyone here have a say on this?
 desertrhino
Joined: 11/30/2007
Msg: 181
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History
Black holes...help!
Posted: 12/17/2009 9:40:19 PM
I don't understand why you say a black hole is 1-dimensional and has infinity density. This would only be true of a zero mass black hole.

Otherwise: (math borrowed from: http://www.physicsforums.com/archive/index.php/t-143096.html)

The density required to create a black hole can be given by p = 3M/4piR^3
From Schwarzschild equation the radius of a black hole in relation to its mass is given by R = 2GM/c^2.
Substituting this into the previous equation, we obtain p = 3c^6/32piG^3M^2

Therefore - p is inversely proportional to the mass squared of the black-hole. The greater the mass, the less the required density.
 MtnBikeFun
Joined: 10/8/2009
Msg: 182
Black holes...help!
Posted: 12/18/2009 6:48:14 PM


I for one would like to know if naked singularities will ever be found. Black holes seem to me to be a flaw in general relativity because of their infinite nature. Further refinement of quantum gravity theory and any observation of a naked singularity would clear it up a lot, wouldn't it?


Supposedly observation of a naked singularity would violate relativity. If they are observed a new theory of gravity possibly based on quantum loop gravity would replace relativity for very specific observations.

I believe there are mathematical ways (tree/graph pruning algorithms) to map quantum loop gravity onto classical gravity. One of the problems is that quantum processes allow for states that are not allowed in classical theory. So you have to chose your trees/graphs very carefully.

Does it clear anything up? No, I think it makes everything more complicated.
 aremeself
Joined: 12/31/2008
Msg: 183
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History
Black holes...help!
Posted: 12/18/2009 7:20:39 PM
are black holes theorised to be necessary for the functioning of galaxies?

why? and how?
 stargazer1000
Joined: 1/16/2008
Msg: 185
Black holes...help!
Posted: 12/19/2009 6:57:17 PM
There does seem to be a mass ratio relationship between galactic center black holes and the mass of their central cores. It is thought central black holes were fundamental to the formation of galaxies.
 aremeself
Joined: 12/31/2008
Msg: 186
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History
Black holes...help!
Posted: 12/19/2009 8:50:05 PM
maybe its been recommended already, but an interesting little read is the end of everything.

It will probably turn out that black holes, or whatever they are, are necessary to keep the galaxies in some kind of balance or whatever.
something necessary to keep things in there proper orientation a few millennia longer from that supposed eventual end. [entropy?]
 reigny
Joined: 12/8/2009
Msg: 187
Black holes...help!
Posted: 12/30/2009 8:44:53 PM
NASSIM HARAMEIN won First Paper Award in Physics, in Belgium on his paper the atom as a mini black hole.

HERE he is being interviewed by Alan Steinfeld on NewRealities.com (Program entitled: Black Hole Physics to Power the World).

http://www.newrealities.com/index.php?option=com_content&task=view&id=470&Itemid=1081

His theory speaks to my experience. I absolutely agree when he says, "The Spiritual World is the physics we haven't understood yet."

YES!

He also confirms what I've come to Know ... Science and conceptualization and evidence comes after the KNOWING of something. So if you're waiting for science to explain things to you, you're behind the curve ball. Why hang out there when you can gain firsthand Knowledge by expanding your consciousness beyond the limited, closed loop of the 3D mind?

Enjoy the program!
 desertrhino
Joined: 11/30/2007
Msg: 188
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History
Black holes...help!
Posted: 12/30/2009 9:36:20 PM
Yep, ignorant ramblings of enlightened special knowledge are FAR easier than getting a real education and learning what the heck you're talking about.

Haramein is making money by preying on the ignorant and semi-educated, SOUNDING like he's saying something meaningful, when he is, in fact, just spouting pseudo-scientific gibberish. But that horse has been beaten to death already.
 Page 2u
Joined: 1/30/2008
Msg: 189
Black holes...help!
Posted: 1/2/2010 9:10:43 AM

Haramein is making money by preying on the ignorant and semi-educated, SOUNDING like he's saying something meaningful, when he is, in fact, just spouting pseudo-scientific gibberish. But that horse has been beaten to death already.


Yup the horse has been beaten to death—problem is the people beating the horse are donkeys, and who cares if you can’t make them drink—

If you’re interested in playing with Haramein theories and taking it a step further –ie. Into the black hole, check out Rodin coil—Now I’m no physicist nor am I particularly good at math, but I am an experienced mechanical designer. Unlike all the other theories this direction can be proven in practical / tactile experiments.

Possibly the black hole is a sphere – a toridial flow falling back onto itself..
124875—is the key, period doubling.
 Val101
Joined: 1/24/2010
Msg: 191
Black holes...help!
Posted: 1/27/2010 8:44:50 PM
Black holes are not necessary to the functioning of the universe.
They are dead superstar whose gravity was great enough to collapse space onto itself.
And string theory describes how given enough time it will evaporate.
 ArghStopItYouStupidDuck
Joined: 4/2/2011
Msg: 194
Black holes...help!
Posted: 5/14/2011 3:51:51 PM
So, let's say humanity finally tires of killing each other or plotting to kill each other, and decides to do Something Grand.

Demonstrating the brilliance of our species, we all work together, using every resource available to us on Earth, to build the first Starship capable of interstellar travel.

After years of careful testing, filtering, and competition we have jointly selected an elite crew of pioneers to represent all of us in their travels across the great abyss.


Then, in a typical example of the result of bureaucratic decision making, the first mission is determined. We'll send this pinnacle of human accomplishment straight into a black hole.


So, after the desperately failing arms of the proud pioneers are gently but firmly pushed back through the airlock and it's sealed shut to the cheers of the masses, the
engines light up and the ship soars off into the heavens to much joy and weeping (especially of the Pioneers), and the ship begins it's journey.




-Fast forward a long, long, long and really boring* time-

* - Except that time that the toilet overflowed, that was anything but boring


Our ship and enthusiastic protagonists are now approaching the black hole.

As they desperately say their prayers and curse The Department Of Interstellar Colonization And Human Expansion, the ship nears the radius of the whirlpool-like accretion disk...


This is where the question(s) lie:

If the ship approaches the black hole by traveling straight up the jet stream (and of course it's been carefully engineered and constructed to somehow withstand and overcome the impossibly massive forces of this stream, sparing no expense for this ultimately pointless and futile mission), could it get past the event horizon (and be uselessly destroyed by tidal forces) this way? Or would it be pulled down into the orbital plane of the accretion disk before reaching the horizon?

If the ship remained perfectly positioned in the middle of the jet stream, would it basically be split at the center with each part of the ship pulled down into its corresponding section of the accretion disk?

At what point would this happen?

Does this change based on the type of black hole?

In fact, does a non-rotating black hole HAVE an accretion disk? Or is it more like a cloud?


The Department Of Interstellar Colonization And Human Expansion thanks you for your responses,
Jack
 ArghStopItYouStupidDuck
Joined: 4/2/2011
Msg: 196
Black holes...help!
Posted: 5/14/2011 7:52:28 PM

Can black holes explode at some point?

Also, can black speres have "galaxies" and "universes" even in its sphere?

Can someone explain just how can a black hole evaporate if it is so dense after consuming matter for centuries (it could be for thousands of years too) ...

Once "evaporated" what is the contents of the "molecules" once evaporated?

Just wondering.


There's people here far more qualified to answer these questions than I, but I'll try to do the best I can...

There's a theoretical form of radiation known as Hawking radiation (named after Stephen Hawking, this is why you keep hearing about him being such a brilliant scientist) emitted by black holes. It is minuscule compared to the amount of matter/energy drawn into the "hole" and expelled through the jets, however if the theory is correct it is present and continuous.

Eventually no matter how large the black hole is, if it is continually radiating out this tiny amount energy it will use up its entire mass and disappear. This is what people mean when they refer to black holes evaporating. In addition it is believed that a black hole might "explode" once the last minute bit of energy is being evaporated, but this would be more of a tiny puff rather than a bang (as if it had enough mass/energy to produce a big bang, it would have enough to hold itself together and not explode) .

As an interesting side note, it is estimated that it will take around a googol years for a supermassive black hole to evaporate. A googol is one with a hundred zeroes behind it, and this is the basis of the word Google, i.e. the search engine. A one with a googol zeroes behind it is known as a googolplex (and the headquarters of Google is known as the Googleplex as well!)

As far as universes inside of black holes, there are theories and such out there, such as this one asking if we are living inside of a black hole:

http://www.popsci.com/science/article/2010-07/we-might-be-living-black-hole-scientist-says

And finally, regarding the contents of the molecules that are evaporated, I believe they would be the same as the contents of the molecules that were pulled into the black hole, except in a higher energy state from the gravitational effects. However that's a total guess and I'm sure that others here with more knowledge about the subject could give you a more accurate answer.


Hopefully all of this isn't TOO far off,
Jack
 ArghStopItYouStupidDuck
Joined: 4/2/2011
Msg: 197
Black holes...help!
Posted: 5/14/2011 8:49:31 PM
Oh and just realized that I never actually addressed your question of how the black hole can evaporate other than simply stating that it was called Hawking Radiation..

Again, this is way, way out of my league as far as knowledge of the subject goes but I'll throw this out there in hopes that someone more educated on the topic can confirm or deny the accuracy of it..

First of all, remember that mass and energy are different forms of the same thing.

Now, let's take a single particle zooming through space at the black hole, but not quite at an angle that would put it within the event horizon. So it flies around, right outside of the event horizon, speeding up due to the gravitational slingshot effect.

It then rockets out away from the black hole, moving even faster than it was in the first place due to the gravitational boost. The energy required for it to move faster came from somewhere, as energy cannot be created nor destroyed.

Where did the energy come from? The black hole itself. In essence the particle "stole" some of the energy from it and used it for acceleration.

Since the black hole no longer possesses this energy, it is the same as if you took a tiny, insignificant amount of mass away from it. When this happens, it's own gravitational field weakens a minute amount, allowing other particles to escape (ones that were previously trapped in orbits around the hole). These particles also "steal" some of the hole's energy in the process of escaping, repeating the process. Eventually enough mass/energy is stolen that the field degrades to the point that the event horizon shrinks, allowing the particles that are actually "part of" the black hole to escape.

Obviously, the black hole has an incredible amount of gravitational force, so the amount of radiation escaping is very tiny, but the process is continuous and ultimately fatal for the black hole.


Again, I'm putting this out here as much for my own edification as to provide an explanation, but hopefully if I'm off somewhere a more knowledgeable poster can clarify what really happens..

Jack
 abelian
Joined: 1/12/2008
Msg: 198
Black holes...help!
Posted: 5/15/2011 6:22:58 AM
Can black holes explode at some point?

No, but black holes can evaporate. They will evaportate faster as they get smaller and the smaller they are, the hotter they are.

Also, can black speres have "galaxies" and "universes" even in its sphere?

In principle, yes, although the size of the black hole would have to be enormous. What you are calling ``its sphere'' is the region of spacetime bounded by the event horizon. The event horizon is the boundary such that once anything crosses it, it must move toward the singularity and cannot return to any point outside the horizon. However, there is nothing special about the horizon other than that. The gravitational field at the horizon could be the same as the earth's gravitational field if the black hole was large enough. (Off the top of my head, I think this is about 10^42 solar masses - a 10 with 42 zeroes behind.) If you were to fall into one that large, as you crossed the horizon, you would feel nothing any different than you would feel free falling on earth.

Black holes are not dense. There is plenty of space inside. The matter all ends up at the singularity.
Can someone explain just how can a black hole evaporate if it is so dense after consuming matter for centuries (it could be for thousands of years too) ...

That is actually quite difficult to explain in a simple way. To do so, requires relativistic quantum field theory. However, a somewhat oversimplified explanation is the following:

In a region of spacetime where there is no matter, no gravitational field, you have nothing but empty space. The space is not really ``empty.'' Particles and antiparticles are created in pairs and anihilate with each other all the time. This is called the quantum vacuum state. These particle pairs are created and anihilated very quickly, so that they have no effect on anything. They can't without violating conservation of energy. (They do play a role in quantum field theory, but for this purpose, that is not germane.)

On the other hand, at the horizon of a black hole, things are different. If a particle anti-particle pair is created at the horizon, one member of the pair may escape the gravitational field, in which case, the other must fall into the black hole. To conserve energy, if the outgoing particle has a positive enery (which it must), the ingoing particle must have a negative energy. That negative energy decreases the mass of the black hole. (One might equally well ask why the negative energy particle in the pair always falls inside. The answer is that the explanation is that isn't quite how it works and a detailed explanation would fix this minor defect, but then making clear what's really happening would get mathematically complicated.) Suffice it to say that if you treat the particles and anti-particles correctly in a curved spacetime, it doesn't matter which falls in. All that matters is that one member of the pair crosses the horizon and one does not. )

Since photons are massless, photons will be the most likely types of particles produced, in which case, the blcak hole evaprorates by producing ordinary electromagnetic radiation. It's actually a perfect blackbody and produces a blackbody radiation spectrum. However, the temperatures of even a pinhead sized black hole are so low that, the radiation would extremely difficult to observe and the time required for it to evaprorate would exceed the lifetime of the universe.

Once "evaporated" what is the contents of the "molecules" once evaporated?

Photons. In principle, other particles could be produced, but the heavier the particle, the less likely it is to produce them. There are some other factors that would surpress heavier particles even more.
 ArghStopItYouStupidDuck
Joined: 4/2/2011
Msg: 199
Black holes...help!
Posted: 5/15/2011 6:58:00 AM
^

Woohoo! It's one of the aforementioned way out of my league posters!!


But he never answered my questions...

Jack
 chrono1985
Joined: 11/20/2004
Msg: 200
Black holes...help!
Posted: 5/15/2011 7:44:32 AM
One concept of a black hole you rarely hear about, which is yet another function of them that media like to ignore. Even space falls into a black hole. This is why light can not escape, because the space it's falling toward is falling at the same rate. It's like if you jumped off your chair and all of a sudden the ground started to fall, so that you were always 1ft above the ground.

The disc you see on a black hole with spin is formed by that key component of a black hole. It occupies the area called the ergosphere, an area where space is pull along with the black hole. Anything falling through that space now must travel the curvature of space formed by the rotation of the black hole. Keep in mind though that not all black holes spin.
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