163 replies to this topic

[jaydfox]

"A black hole's surface is large enough in scale..."

Black holes have no surface. You of course pepper your remarks with personal attacks but that has always been your trademark. I will not address you further.

You're right, the event horizon isn't a tangible surface, in the sense that as matter is falling into it, it doesn't suddenly know that it has crossed through some physical "membrane". However, its location is well-defined (from any given reference frame), making it effectively a 2-dimensional "surface" within 3-D dimensional space. (Yes, including the fourth dimension with the local Lorentzian neighborhood, it's actually a 3-D "hypersurface".)

So, if you'd prefer more precise language, I should have said, "The circumference (or area) of the event horizon of a black hole is large enough in scale..."

If the density of the known universe at one time was close to infinite, then clearly the conditions necessary to form a closed system were present.

Wow, you must be really smart. Because hundreds of the world's most brilliant minds have tackled with the theories of general relativity, quantum mechanics, and the known observations of cosmology, and they don't seem to conclude with such clarity that the universe must be closed. Why on earth are they pouring so much effort into trying to determine whether the universe is open or closed if "clearly the conditions necessary to form a closed system were present"? You should be teaching physics postdocs what you know, because apparently they must be complete idiots.

[jaydfox]

It seems to me that gravity cannot be particle-based (i.e. graviton) merely by the fact that gravity itself "escapes" a black hole. Instead, it seems to me that gravity itself doesn't exist, just as there is no time particle. Gravity and time are both high-level manifestations.

That's the conclusion I always seem drawn to, but I haven't studied theories of quantum gravity at anything more than a very high level, so I'm not sure how they reconcile this seeming paradox. I assume they have some mechanism to reconcile it, since it seems rather obvious.

[Lazarus Long]

We had this discussion before, gravity is not escaping the BH, space/time is warping so extremely that everything falls toward the event horizon. Think of it as how the object outside is attracted *to* the BH and being of smaller mass/density moves toward the larger mass more.

However IMHO it is still a mistake to consider gravity as an emanating force at all because what you are really observing is not a force acting *on* spacetime as much as a distortion of spacetime acting as a force on matter.

[bgwowk]

Remember, guys, that black holes can have mass, angular momentum, and CHARGE. We know from quantum electrodynamics that charge forces are mediated by photons, and yet black holes can exert charge forces. So there is no reason that gravitational forces from black holes couldn't be mediated by gravitons. The expectation is that the field equations of General Relativity will ultimately be shown to be an approximation of quantum gravity in the same sense that the field equations of Maxwell's Equations are an approximation of quantum electrodynamics.

As an interesting point of trivia, it was shown many years ago that a charged black hole (Reissner-Nordstrom black hole) with sufficient charge loses its event horizons, becoming a naked singularity.

http://72.14.209.104...lient=firefox-a

Don't ask me to explain it. I know what Schwartzchild black holes, Kerr black holes, Kerr-Newman black holes, and Reissner-Nordstrom black holes are. But how these things are calculated, and how they can have one, two, or zero event horizons is an example of knowing what I don't know. For us mere mortals that have never studied graduate General Relativity, there are more things in heaven and earth than are dreamt of in our philosophy.

P.S. When in 1997 Stephen Hawking lost his bet that a naked singularity could ever be formed in any kind of practical way (the charge method has practical problems), but still expressed skepticism, Dr. Preskill replied:

''Stephen, I'm surprised to hear you, of all people, say that. There's one naked singularity that we all agree existed: the Big Bang. The universe itself.''

Edited by bgwowk, 14 November 2006 - 10:14 PM.

[DukeNukem]

We had this discussion before, gravity is not escaping the BH, space/time is warping so extremely that everything falls toward the event horizon. Think of it as how the object outside is attracted *to* the BH and being of smaller mass/density moves toward the larger mass more

Well yes, and that's why I do not think gravitons exist. I do not think there's a particle of gravity, as there is with the other three fields.

Of course, I'm purely a layman on this topic.

[xanadu]

LL wrote:

" We had this discussion before, gravity is not escaping the BH, space/time is warping so extremely that everything falls toward the event horizon. Think of it as how the object outside is attracted *to* the BH and being of smaller mass/density moves toward the larger mass more.

However IMHO it is still a mistake to consider gravity as an emanating force at all because what you are really observing is not a force acting *on* spacetime as much as a distortion of spacetime acting as a force on matter."

LL, those are very good points you brought up. You can say it's the space time warping that causes the attraction and that nothing leaves the BH. But, there is a clear cause and effect relationship between the matter inside the BH and the gravity felt outside it. The warpage in spacetime is caused by the mass inside the BH. You do not need particles to mediate this effect, IMO. I agree it seems to be a higher order function than electromagnetism, for example. If there was no mass inside the BH, there would be no gravity felt outside.

You could say that no information can leave a BH and that would have some truth to it but not be totally true under all conditions. Good point, whoever made it, about dropping matter into a BH. It would increace the mass and gravity of the BH which gives us info. We can instantly find out the total mass of a BH so gravity seems to be the one exception to the rule. If dropping a mass into a BH caused gravity waves that could be detected outside it, that would be very interesting.

As for those other strange beasties that no one has ever seen, two headed BH's or what was it, two event horizons? Yeah right.

Duke, I dont think there is a gravity particle either. Unless someone says so on an authoritative website then we all will swear it's a fact. All except a few.

[bgwowk]

As for those other strange beasties that no one has ever seen, two headed BH's or what was it, two event horizons? Yeah right.

This is an elementary result of General Relativity known since the early 20th century. Black holes with angular momentum are Kerr black holes, and Kerr black holes have two event horizons and a ring shaped singularity. Since angular momentum is ubiquitous, virtually all black holes in the universe, certainly stellar black holes, are Kerr black holes with two event horizons.

How can you continue to make assertions about physics with sarcastic force when you understand so little about what is already known?

[bgwowk]

dukenukem wrote:

Well yes, and that's why I do not think gravitons exist. I do not think there's a particle of gravity, as there is with the other three fields.

It's true that gravitons have not yet been discovered. However it is almost universally expected by physicists that gravity is a quantized force like all the others. It is expected that at the end of the day the General Relativity model of mass bending space and time will be an approximation of another process happening at a deeper level of reality, and that process may itself explain space and time.

[xanadu]

No doubt each black hole has a multitude of event horizons nested within each other. For an object with a speed of 1000 mph, the event horizon of a BH is fairly large and if the object strays within it, it will be drawn in. For a greater speed it can come closer and for a lesser speed it must follow a trajectory that will take if farther from the BH at the closest point. The EH that counts the most is the one for light. Are you saying the so called double EH has two both of which are for light and if so, how does that work? Obviously you don't know.

bgwowk wrote:

"Black holes with angular momentum are Kerr black holes, and Kerr black holes have two event horizons and a ring shaped singularity. Since angular momentum is ubiquitous, virtually all black holes in the universe, certainly stellar black holes, are Kerr black holes with two event horizons."

Spin pertaining to what, the mass inside the singularity? And you believe this causes a ring shape + 2 EH's why? Maybe it does but why do you believe uncritically things you don't understand just because an authority figure told you about it? I claim no such authority or understanding but we all have the right to question what is presented to us. Those who doubted that the earth was the center of the universe a few centuries ago were treated with much the same scorn you heap upon doubters right now. People now as then were expected to accept many things on faith.

If a BH has an event horizon and this seems to be a requirement for a BH, then any light or object inside that no matter it's speed will be drawn in. A second EH inside the first implies that there is a range between the inner EH and the outer one in which light would not be drawn in. If so, then the outer EH is not a true EH. If the outer EH is what we call an EH, that it does pull in light, then anything inside that also can not escape so a second EH inside that is little more than a mental excercise.

Ring shaped singularity? I thought we were told singularities were supposed to be points? A point has no shape, last I heard. A point has no volume. A ring shaped EH might be possible.

I read on one of those sites that a "naked singularity" was supposed to exist. Hawking is said to have paid off a bet when someone convinced him they were real. Maybe so but that begs the question of what is a singularity. If it is a point with infinite or near infinite density, then at some distance from it, gravity will be strong enough to do the light bending trick. Gravity falls off as the inverse square of distance so at a micron or some other very short distance from this supposed point of matter, gravity would be extremely strong and right at the point it would be nearly infinite. That is just simple logic. If there are factors that we have not discussed and or do not know about, then that could easily change things. It seems that none of us knows what these factors might be. Perhaps no one does. Rather than let fly with another round of scorn, ridicule and personal attacks, try coming up with facts or just pretend you didn't notice.

[bgwowk]

No doubt each black hole has a multitude of event horizons nested within each other. For an object with a speed of 1000 mph, the event horizon of a BH is fairly large and if the object strays within it, it will be drawn in. For a greater speed it can come closer and for a lesser speed it must follow a trajectory that will take if farther from the BH at the closest point. The EH that counts the most is the one for light. Are you saying the so called double EH has two both of which are for light and if so, how does that work? Obviously you don't know.

Obviously.

[jaydfox]

No doubt each black hole has a multitude of event horizons nested within each other. For an object with a speed of 1000 mph, the event horizon of a BH is fairly large and if the object strays within it, it will be drawn in. For a greater speed it can come closer and for a lesser speed it must follow a trajectory that will take if farther from the BH at the closest point. The EH that counts the most is the one for light. Are you saying the so called double EH has two both of which are for light and if so, how does that work? Obviously you don't know.

You're confusing escape velocity with the event horizon concept. It is true that for an object that starts with an initial velocity of 1,000 mph, there is a certain critical circumference (of a sphere centered around the black hole) from which that object would not be able to "escape" (in the sense of never falling back into the hole).

However, such an object could then try to accelerate away from the black hole, using rockets or whatever, and it would be able to escape. For any distance from a black hole's event horizon, there is a certain critical speed below which an object could not escape, faster than which an object could escape. That critical speed would be the "escape velocity". However, it must also be pointed out that at any distance outside a black hole, for an object travelling at any speed less than the escape velocity (including sitting still, just before freefalling into the hole), that object could exert some level of acceleration (perhaps a very large, but finite amount of acceleration) and escape the black hole.

At the event horizon, it's not just the fact that the "escape velocity" is the speed of light. This fact in and of itself doesn't fully capture the essence of the event horizon. What really matters is that, at or inside the event horizon, no amount of acceleration could change the fate of that object: it will never escape. For an object at 1.0001 times the critical circumference (of the event horizon), it could escape if it could expend enough energy. For an object at 1.0000000001 critical circumference, it could escape if it could expend enough energy. The fraction of energy that would have to be expended would be over 99% of the object's rest mass energy, but it could be done. But at and within the event horizon, no amount of energy could be expended to get the object out. There is only one event horizon in this sense, for a spinless, chargeless black hole. Many escape velocities at various circumferences, but only one event horizon.

I claim no such authority or understanding but we all have the right to question what is presented to us. Those who doubted that the earth was the center of the universe a few centuries ago were treated with much the same scorn you heap upon doubters right now. People now as then were expected to accept many things on faith.

The first difference you seem completely ignorant of was that those who doubted that the earth was the center of the universe had good reasons to. You play the part of the skeptic for skepticism's sake, not because you have good reasons to doubt anything. So far you haven't presented anything that might be confused as an educated objection to the current understanding of physics. You've only displayed your unerring faith in your own ignorance to help you understand the world. I pity you, and I don't say that to be mean. Honestly, what is your intention here? It's certainly not a pursuit of the truth.

[jaydfox]

Ring shaped singularity? I thought we were told singularities were supposed to be points? A point has no shape, last I heard. A point has no volume. A ring shaped EH might be possible.

A singularity (in the black hole sense; there are many connotations of "singularity") is anything which loses one or more of its dimensions. A volume that comes so flat it turns into a 2D sheet (not just "very" thin, but infinitely thin) would be or have a singularity.

In the case of a ring singularity, the 3D mass of the collapsing star becomes a 1-dimensional ring. It is not a 3D object: the ring itself has no thickness whatsoever, so it's truly a singularity. Even a "disk" could be a singularity, if it were infinitely thin (as opposed to "very" thin).

[Luna]

on the first page, some replies make it sounds as if the creation of the universe is the opposite of a black hole function.

[valkyrie_ice]

Ring shaped singularity? I thought we were told singularities were supposed to be points? A point has no shape, last I heard. A point has no volume. A ring shaped EH might be possible.

A singularity (in the black hole sense; there are many connotations of "singularity") is anything which loses one or more of its dimensions. A volume that comes so flat it turns into a 2D sheet (not just "very" thin, but infinitely thin) would be or have a singularity.

In the case of a ring singularity, the 3D mass of the collapsing star becomes a 1-dimensional ring. It is not a 3D object: the ring itself has no thickness whatsoever, so it's truly a singularity. Even a "disk" could be a singularity, if it were infinitely thin (as opposed to "very" thin).

Many matters of considerable importance follow immediately from the principles of physics. For example, nature has no singularities. If it did, matter could disappear from the universe, violating the no demise ad nihil principle while also violating the finite cannot become infinite. The continued action of an external gravitational field after the cause of that field has permanently ceased to communicate with the outside universe is an effect without a cause. And the strange temporal properties of black holes have led to the proposal of “worm holes”, which violate the no time reversal principle. Black holes and worm holes are fun science fiction concepts, and are much touted and discussed by mathematical relativists. But no physicist who understands the logical necessity of the principles of physics as descriptors of reality can take such concepts literally.

It follows from these principles that there are no black holes in the traditional relativity sense of event horizons centered on a singularity. This does not preclude highly collapsed states of matter generating a high redshift for light, or possibly no light escape at all. But such objects would continue to have normal gravitational and electrostatic forces and be in two-way communication with the rest of the universe. Some of the fantastic properties of black holes will therefore turn out to be fantasies after all.

Perhaps even more importantly, the physical principles immediately imply that there was no Big Bang at the origin of the universe. The “Big Bang” also violates several physical principles: an effect with no antecedent, proximate cause; no singularities in nature; and no creation ex nihilo. If the universe really is expanding - an assumption very much in doubt [ref. 1, 1999 ed., chapter 22; reprinted from ref. 4] - then something must limit how far back that expansion can be projected.

Of course, religions have long taught that the creation of the universe is at least the one major exception to no creation ex nihilo. This approach suffers from the difficulties mentioned earlier in connection with ascribing causes to acts of God. As long as it remains clear that viable explanations do exist that require no “acts of God” [ref. 1, chapters 1-2], science will always prefer these because they make reality testable and ultimately predictable, at least to the limits of our understanding.

http://www.metaresea...sPrinciples.asp worth reading regardless of your opinion on physics.

[Teixeira]

Alright]


I speak as a non-scientist, so I don't know what is the faster thing, why or how, these are merely thoughts.

-Infernity

where our theory stands, the speed of light is but a natural constant. It is a core axiom for Einstein's "Torat Ha'yacha'sut". Why is it 3x10^8 m/s ? - -for the same reason there is this unusual force we call "gravity" and all other natural phenomena and laws. how come all these laws and known phenomena are as they are? -because.

Nature has its hidden reasons, or no "reasons" at all all as we know and define em' ;-)

Where we stand, the fastest speed measured of travelling information is the speed of light... - so, until we find other empirical facts - this is where our scientific "knowledge" stands.

the tachyon theory is practically groundless in comparison to the research made in the field of relativity.

-D S

"the speed of light is but a natural constant"
The speed of light may not be constant. That´s what a portuguese scientist is triyng to demonstrate in his thesis. So, for the moment, we cannot be so sure about that.

[medicineman]

something can possibly exist that is faster than light, assuming it started off that speed.... Brain greene, a theoretical physicist and a string theorist states that relativity does not place a limit on anything which existed as fast or faster than light from the start, but no discovery of any such particle or agent was observed.

Edited by medicineman, 13 January 2010 - 11:25 PM.

[medicineman]

man, some bright people on this forum.....

This has been an informative, and quite confusing read.....

[SiliconAnimation]

Because it's the final product of material decomposition?

[Cameron]

What I'd like to know is why gravity|gravity-waves move|propagate at the speed of light.(Since some believe space can expand|warp far faster than the speed of light.)

[Brain_Ischemia]

Yeah, I know the OP posted almost 4 years ago...

Alright, isn't it obvious that if black holes swallow light, something must be faster than light? [huh]

Black holes don't swallow light, they warp spacetime to the point where light *falls into them* and cannot escape.

What I'd like to know is why gravity|gravity-waves move|propagate at the speed of light.(Since some believe space can expand|warp far faster than the speed of light.)

You could google this you know...
http://curious.astro....php?number=573

http://www.metaresea...sPrinciples.asp worth reading regardless of your opinion on physics.

Nah, about as worthwhile as any other whackjob, tinfoil-hat, loonytune conspiracy theory; just because he took the time to type out a gigantic essay of text doesn't make him right anymore than it makes the "Loose Change" 9/11 wingnuts right just because they took the time to make a video or the "I was kidnapped by aliens" people or the "free energy" people or the "flat earth" people or the "anti-gravity device" people.

Giant walls of fallacious and fanciful text typed out by self-absorbed conspiracy mongers is a dime-a-dozen on the internet.

Edited by Xanthus, 30 January 2010 - 05:31 AM.

[Cameron]

What I'd like to know is why gravity|gravity-waves move|propagate at the speed of light.(Since some believe space can expand|warp far faster than the speed of light.)

You could google this you know...
http://curious.astro....php?number=573

That still does not seem to answer it. If space can warp faster than light as some believe under the ideas of inflation|warp, why would there be a limit to its warping|gravity-propagation by a mass?

While the article does mention that there's still no agreement on gravity's speed having been measured, it is likely that it cannot surpass light speed. If it could surpass the speed of light it seems like it could be used to transmit information faster than light by moving a suitably massive object. Assuming it is true that gravity's speed is light speed what reason could there be for this under the ideas of it being the result of a warp in the fabric of spacetime? Unless one assumes that proving gravitons means disproving the idea that gravity is the result of differences in the fabric of spacetime.

Or are we going to use some sort of dualistic explanation, that is catches light because it is warping of spacetime(warps that can affect massless objects rapidly), but it only goes at light speed because it is the result of gravitons(Could such particles catch up to light despite moving at the same speed ?).

Edited by Cameron, 31 January 2010 - 09:49 PM.

[Brain_Ischemia]

That still does not seem to answer it. If space can warp faster than light as some believe under the ideas of inflation|warp

You have a basic misunderstanding.
Inflation does not imply that space is "warping faster than light", indeed according to Inflationary theory, the speed of light was NEVER locally violated.

Even if the space between two points once expanded at a rate faster than the speed of light, nothing between those two points was ever traveling faster than light. Think of the universe as the surface of a balloon being blown up. The rate at which the balloon expands has nothing to do with the speed at which you, I, or anything else on the surface of the balloon are capable of traveling. Indeed, while the balloon is expanding faster than the speed of light you and I could be standing perfectly still, or running at 10mph. Our local speed is separate from the speed at which the space we move in expands.

The fringe theory VSL (Variable Speed of Light) is the *exact opposite* of Inflation; according to VSL the speed of light *was* locally violated.

Essentially, both theories predict the same outcome; at some early period in the universe's expansion, either space itself expanded faster than light (but nothing *within* that space did) or light itself had a higher speed limit in the past (VSL).

Assuming it is true that gravity's speed is light speed what reason could there be for this under the ideas of it being the result of a warp in the fabric of spacetime?

You're forgetting that since gravity is the result of actions that take place inside of our local universe (ie; on the surface of the balloon), that means they're the result of actions that cannot take place faster than the speed of light. Think of gravity as dimples on the surface of the balloon.

Unless one assumes that proving gravitons means disproving the idea that gravity is the result of differences in the fabric of spacetime.

Or are we going to use some sort of dualistic explanation, that is catches light because it is warping of spacetime(warps that can affect massless objects rapidly), but it only goes at light speed because it is the result of gravitons(Could such particles catch up to light despite moving at the same speed ?).

Even a verified theory of Quantum Gravity has to end up being consistent with the [solidly established and well proven] observational evidence supporting General Relativity. Gravitons may very well end up proven not to exist at all. Exactly how Gravitons would be reconciled with Gravity as the result of spacetime geometry is not a completely settled issue yet, but keep in mind that gravity wouldn't be the "result" of Gravitons since AFAIK Gravtions essentially are *particles of spacetime*.

Edited by Xanthus, 12 February 2010 - 09:09 PM.

[ken_akiba]

I have thought about this, I mean, why is the speed of light the fastest speed achievable? Then I quicky gave up and instead began to think about, if I am to create a universe, why would I implement this limit? Imo, the answer is right there: To impose limit (to... most likely to ensure its equilibrium state, whatever that means). Then maybe I would like to impose limit on mass too, the limit of which, actually exists in our universe. Then my mind wanders around to quantum entanglement: Why in unverse would I want to implement this? Then I came to this possible use: To keep our universe seperate from other universes i.e. quantum entanglement is somewhat of an 'ID scan system' to see if this matter in question indeed belongs to the given universe, and naturally, existance of other universes or multiverses is a prerequisite to this daydream. Any thoughts?

:-)

Edited by ken_akiba, 17 May 2010 - 02:26 PM.

[chris w]

I have thought about this, I mean, why is the speed of light the fastest speed achievable? Then I quicky gave up and instead began to think about, if I am to create a universe, why would I implement this limit? Imo, the answer is right there: To impose limit (to... most likely to ensure its equilibrium state, whatever that means). Then maybe I would like to impose limit on mass too, the limit of which, actually exists in our universe. Then my mind wanders around to quantum entanglement: Why in unverse would I want to implement this? Then I came to this possible use: To keep our universe seperate from other universes i.e. quantum entanglement is somewhat of an 'ID scan system' to see if this matter in question indeed belongs to the given universe, and naturally, existance of other universes or multiverses is a prerequisite to this daydream. Any thoughts?

:-)

There is a God then

[ken_akiba]

Yes, I believe in a creator or creators (But I do not believe in God(s) in religion because I believe religion is created by man :-)

Edited by ken_akiba, 17 May 2010 - 04:13 PM.

[chris w]

Yes, I believe in a creator or creators (But I do not believe in God(s) in religion because I believe religion is created by man :-)

Wait, I'm a little confused by this, could You elaborate ? So You think that in the end there is / was some intelligence who created and governed the laws of universe or not ? Or something different even ?

Edited by chris w, 17 May 2010 - 04:50 PM.

[ken_akiba]

"So You think that in the end there is / was some intelligence who created and governed the laws of universe..."
Yes (but I don't know about "govern" part. I think the creator created it and then let it be :-)

[chris w]

"So You think that in the end there is / was some intelligence who created and governed the laws of universe..."
Yes (but I don't know about "govern" part. I think the creator created it and then let it be :-)

Ok, so You' re a Deist. I guess this is the closest that I could come to some sort of religion. The question "why is there anything at all ?" I could never dismiss just right away, it makes you look for the first cause wheter you want or not. Cheers.

Edited by chris w, 17 May 2010 - 05:35 PM.

[DukeNukem]

Yes, I believe in a creator or creators (But I do not believe in God(s) in religion because I believe religion is created by man :-)

And so are gods, my friend. Do yourself a favor, and read this book:
http://is.gd/cdwG1

[ken_akiba]

You meant "And so are creator(s)." And as to the book, Read it. Frankly boring. But to be fair, all, well at leat most books I read on this subjest, are big bore. And do yourself a favor, do not tell anyone, "Do yourself a favor, and read this book." Plain condescending, director or not. And one more thing, not that I believe in God(s), actually I don't, I believe in creator(s), but you need to realize you do not have right to crush others' belief, because believe me or not, what you believe is truth on this matter, may as well turn out to be a belief.

Edited by ken_akiba, 17 May 2010 - 08:04 PM.