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Why is Light the Fastest?


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#61 jaydfox

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Posted 10 November 2006 - 12:30 AM

Here's another example to help give an intuitive feel for how little damage a nano-black hole can do. Imagine that a black hole is like an eraser. How long would it take to erase a chalkboard that covered the entire surface of the earth, if you had an eraser the size of a pinhead. I'll even let you move the eraser across the surface of this giant chalkboard at the speed of light. But it can only erase a strip with a width of a few hundred microns. So you'd have to go back and forth, or around and around, trying to get every square millimeter of the chalkboard.

Now, when you're done, you have to do it again about 10 million times, to simulate going down in depth a few hundred microns at a time, to erase the next level.

So, how long will it take to erase the earth like this?

#62 xanadu

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Posted 10 November 2006 - 12:35 AM

Duke wrote:

"A BH doesn't grow fast -- I takes a LOT of matter to make any significant growth. A BH with an event horizon the size of a grain of sand (as opposed to a BH made from matter the equivalent to a grain of sand, which would likely be smaller than a proton) would suck down very little matter on it's 30 hour journey falling to the center of the earth, where it would get stuck, barely making any impact on it's surroundings. (At least, this is my guess.)"

If it can absorb whatever matter touches it, then it's going to grow very fast. At the center of the earth, liquid iron would be under huge pressures. That's like having a high pressure hose feeding you water. It will fall into the BH rapidly. I don't care how large the event horizon gets, it's the rate of matter absorbtion that is worrying.

Jay wrote:

"A black hole with 1% of earth's mass would be about 200 microns across. By virtue of its mass (i.e., regardless of the fact that it was a black hole), it would increase gravity at the earth's surface by 1%, which would have some pretty noticeable consequences (pressures would increase at all depth by 1%, and even more near the core), which would compress and shift material around and cause seismic activity."

How could a BH increace the gravity of the earth or increace gravity at the earth's surface? The earth is not getting any heavier, it is just transfering matter from itself to the BH. Conservation of mass, you know.

"The seismic consequences of a black hole that big dropping from the earth's surface to the core are far worse than the prospect of material disappearing into the black hole."

We are not talking about a giant BH at the earth's surface. We are talking about a tiny one forming and becoming large. Once it had any appreciable mass it would immediately head for the earth's center. We just have to hope that very tiny BH's are unable to absorb matter. All it would take would be an electrical or atomic force that tended to repel normal matter and it would never grow. Once it did start to grow it would tend to do the things I spoke of.

#63 jaydfox

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Posted 10 November 2006 - 12:55 AM

We are talking about a tiny one forming and becoming large. Once it had any appreciable mass it would immediately head for the earth's center. We just have to hope that very tiny BH's are unable to absorb matter.

Why are we hoping that very tiny BH's are unable to absorb matter, again? Even if they can suck matter in at the speed of light, I've already shown that they are still essentially harmless, at least until they have any appreciable mass, which would take billions if not trillions of years to amass in the first place.

"A black hole with 1% of earth's mass would be about 200 microns across. By virtue of its mass (i.e., regardless of the fact that it was a black hole), it would increase gravity at the earth's surface by 1%, which would have some pretty noticeable consequences (pressures would increase at all depth by 1%, and even more near the core), which would compress and shift material around and cause seismic activity."

How could a BH increace the gravity of the earth or increace gravity at the earth's surface? The earth is not getting any heavier, it is just transfering matter from itself to the BH. Conservation of mass, you know.

It was a thought experiment. If an black hole with a mass of 1 nanogram were created out in space and then brought to earth and dropped on the earth, it would do essentially nothing. If a black hole with 1% of the earth's mass were brought here and dropped on the earth, the seismic consequences would be the major problem we'd have to deal with, not the sucking in of matter.

If we tried to create a black hole with 1% of the earth's mass, there would be a big hole about 2700 km in diameter, which would be pretty devastating in its own right. It doesn't make sense to speak of a black hole that big, so I imported the mass for illustration's sake. In any and all practical circumstances, a black hole formed here on earth will either
A) be completely harmless, or
B) be destructive for a variety of reasons completely unrelated to the fact that the black hole is also consuming small quantities of the earth's mass.

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#64 jaydfox

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Posted 10 November 2006 - 12:57 AM

"A BH doesn't grow fast -- I takes a LOT of matter to make any significant growth. A BH with an event horizon the size of a grain of sand (as opposed to a BH made from matter the equivalent to a grain of sand, which would likely be smaller than a proton) would suck down very little matter on it's 30 hour journey falling to the center of the earth, where it would get stuck, barely making any impact on it's surroundings. (At least, this is my guess.)"

If it can absorb whatever matter touches it, then it's going to grow very fast.

(my emphasis)
Xanadu, I think if you can get this one point, the rest of your objections will begin to fall away:
A black hole the size of an atom can't touch very much mass at all. Even if a black hole could suck in all the matter it touches at the speed of light, that's still very little matter.

#65 bgwowk

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Posted 10 November 2006 - 12:58 AM

Planets can never be consumed by wandering black holes. A wandering black hole that fell toward a planet would necessarily hit the planet at greater than planetary escape velocity, pass through the planet, and then head back on its merry way into space on a hyperbolic orbit never to be seen again. The mass-to-size ratio of a black hole is so great that friction cannot affect it.

Any black holes created by particle accelerators would evaporate before they could ever grow, and there is no mechanism for gravitionally unbound black holes to become bound. It is therefore physically impossible for the earth to ever be consumed by a black hole. Even a stellar mass black hole, being only a few miles wide, would only consume a negligible fraction of the earth as it passed through. Of course the damage done by gravitational tidal forces by a large black hole would be severe.

#66 caston

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Posted 10 November 2006 - 01:00 AM

Any possible way to contain a blackhole? Electromagnetic / static shielding etc?

A artifically created blackhole and an exhausted sun blackhole could be entirely different beasts.

regards,

Chris

Edited by caston, 10 November 2006 - 01:12 AM.


#67 jaydfox

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Posted 10 November 2006 - 01:04 AM

Any black holes created by particle accelerators would evaporate before they could ever grow, and there is no mechanism for gravitionally unbound black holes to become bound.

Playing into the idea of a lack of Hawking radiation (for xanadu's sake), wouldn't a lab created black hole, if created at a standstill, essentially oscillate? Wouldn't it fall to the far side of the earth, then fall back, and so on?

Edit: Yes, I realize that achieving a standstill is virtually impossible, reflecting a precision of one part in billions or trillions with respect to kinetic energy of the colliding objects (assuming counter-rotating streams of particles, as opposed to smashing one stream of particles into a stationary target).

Edited by jaydfox, 10 November 2006 - 01:15 AM.


#68 jaydfox

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Posted 10 November 2006 - 01:09 AM

there is no mechanism for gravitionally unbound black holes to become bound.

By the way, wouldn't one method of binding a black hole be the reduction in speed as it accumulates mass that was effectively sitting still? The linear momentum would not change, but the mass would increase, so the velocity would necessarily decrease ever so slightly. The decrease in speed is small, but if the black hole was going right at escape velocity, then wouldn't it pass through and be at just below escape velocity? Granted, it would take a long time to fall back, but at least it's a start...

One hitch to this is that the masses have changed, which changes the escape velocity, so it'd depend on whether the black hole was heavier or lighter than the object passed through, etc...

#69 eternaltraveler

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Posted 10 November 2006 - 02:32 AM

One hitch to this is that the masses have changed, which changes the escape velocity, so it'd depend on whether the black hole was heavier or lighter than the object passed through, etc...


the escape velocity would not change because the relative mass of the two body system would not change, correct?

#70 eternaltraveler

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Posted 10 November 2006 - 02:51 AM

err i guess it would be the same relative kinetic energy, not really the same velocity.

#71 jaydfox

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Posted 10 November 2006 - 03:04 AM

the escape velocity would not change because the relative mass of the two body system would not change, correct?

Well, the escape velocity is measured relative to either body. The escape velocity from the earth is about 11.2 km/s, to some level of precision. After having a some miniscule fraction of its massen eaten up, the escape velocity would drop by a correspondingly miniscule amount, to a first approximation.

The question is, if the escape velocity drops by a miniscule amount, but the black hole is also slowed by a miniscule amount, then what's the net result? Qualitatively, we know both quantities got smaller, so the naive assumption is that nothing has changed, and the black hole will still escape. However, this probably depends on the relative masses of the two bodies. Perhaps if the black hole is less massive than the earth, then the difference is enough to tip in favor of capturing the black hole. Or perhaps it's the other way: if the black hole is more massive than the earth, it tips in favor of capture. Maybe it always tips in favor of capture. Maybe it never does.

Only way to find out is to run a calculation. This one's a bit more complicated; I'd probably need an excel spreadsheet to get a good approximation. But maybe Brian knows the answer off the top of his head?

#72 caston

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Posted 10 November 2006 - 03:05 AM

A blackhole is often called a a singularity. Imagine if someone tried computing evolved AGI inside a blackhole!

#73 jaydfox

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Posted 10 November 2006 - 03:09 AM

Imagine if someone tried computing evolved AGI inside a blackhole!

Wouldn't do any good. Time dilation makes the computer run slower compared to the rest of the universe, not the other way around. A computer in orbit around earth would run a tiny bit faster than a computer here on earth, due to the smaller time dilation.

If you're looking to take advantage of relativity to make a computer run faster, you're looking for an opposite effect to time dilation. A computer moving near the speed of light, or running close to a neutron star or black hole, will run slower, not faster, so there's no real benefit.

A computer out of the gravitational field of nearby masses (such as in deep space, preferably deep intergalactic or intercluster space), will run the tiniest bit faster than a computer in our solar system. The effect is small enough that the time necessary to move the computer to the distant location would make the difference moot.

#74 eternaltraveler

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Posted 10 November 2006 - 03:26 AM

The escape velocity from the earth is about 11.2 km/s, to some level of precision.


Perhaps if the black hole is less massive than the earth, then the difference is enough to tip in favor of capturing the black hole. Or perhaps it's the other way: if the black hole is more massive than the earth, it tips in favor of capture. Maybe it always tips in favor of capture. Maybe it never does.


if the body, in this case a black hole, were any reasonable fraction of the mass of the earth (or greater than the mass of the earth for that matter) the escape velocity is going to be greater than 11.2 km/s between the two body system. The only reason we assume the escape velocity from the earth to be a constant is because generally the mass of the second body is utterly insignificant when compared to the earth itself. But in reality the escape velocity of a paper clip weighing one gram, a rock weighing 1000 kilograms are going to be different, as the mass of the rock will attract the earth to itself more than the paper clip will do so.

#75 eternaltraveler

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Posted 10 November 2006 - 03:32 AM

Even a stellar mass black hole, being only a few miles wide, would only consume a negligible fraction of the earth as it passed through.


in this case we wouldn't be terribly concerned with the escape velocity of the earth, as that would be fairly insignificant, but the escape velocity of the stellar mass black hole. Which even at distance of 695 000 kilometers would still be 617.54 km/s (the radius of the sun, and the escape velocity at the surface of the sun respectively). So chances are if we ran into a stellar mass black hole the earth would not escape unless the black hole was moving at quite a considerable velocity indeed.

#76 jaydfox

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Posted 10 November 2006 - 03:43 AM

if the body, in this case a black hole, were any reasonable fraction of the mass of the earth (or greater than the mass of the earth for that matter) the escape velocity is going to be greater than 11.2 km/s between the two body system. The only reason we assume the escape velocity from the earth to be a constant is because generally the mass of the second body is utterly insignificant when compared to the earth itself. But in reality the escape velocity of a paper clip weighing one gram, a rock weighing 1000 kilograms are going to be different, as the mass of the rock will attract the earth to itself more than the paper clip will do so.

Yes, now that I think about it, the escape velocity is probably with respect to the barycenter (center of mass) of the two-body system, not with respect to either body. As mass is transferred from one to the other, the escape velocity would not change, nor would the center of mass. So the reduction in speed of the black hole would be sufficient to put it just under escape velocity, assuming it initially struck exactly at escape velocity.

Thanks for bringing that to my attention.

#77 jaydfox

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Posted 10 November 2006 - 03:47 AM

By the way, another way a black hole could be captured is in a multi-body system. A so-called gravitational slingshot, if doen in the proper fashion, could sap kinetic energy from the black hole, allowing it to become bound to another object. If the binding allows the black hole to periodically pass through the other object, then it will have multiple opportunities to either devour the other object or become trapped within it, depending on whether it can lose enough speed to get "stuck inside".

#78 bgwowk

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Posted 10 November 2006 - 04:54 AM

Yes, if you created a black hole that was stationary at the Earth's surface (and that didn't evaporate), it would oscillate from one side of the Earth to the other for a long time.

Yes, if you dropped a black hole from infinity so that it hit the Earth at *exactly* escape velocity, the small amount of friction it experienced would make it a bound object. But, depending on the amount of friction, the bound orbit might have an initial period of millions of years. The question is rather academic. The point stands that it's very difficult to make a black hole coming from far away into a bound object that can devour the Earth. I suspect you'd need another massive third body participant to do it.

So chances are if we ran into a stellar mass black hole the earth would not escape unless the black hole was moving at quite a considerable velocity indeed.

No, the Earth would escape from an interloping stellar mass black hole just fine (except for being squashed into hot dust by the tidal force, that is). In this case, the Earth is in a hyperbolic orbit around the black hole. Again, there is no mechanism to make the Earth (or the rubble that was the Earth) into a bound object. At least not that I can think of, offhand.

#79 caston

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Posted 10 November 2006 - 09:30 AM

Wouldn't do any good. Time dilation makes the computer run slower compared to the rest of the universe, not the other way around. A computer in orbit around earth would run a tiny bit faster than a computer here on earth, due to the smaller time dilation.

If you're looking to take advantage of relativity to make a computer run faster, you're looking for an opposite effect to time dilation. A computer moving near the speed of light, or running close to a neutron star or black hole, will run slower, not faster, so there's no real benefit.

A computer out of the gravitational field of nearby masses (such as in deep space, preferably deep intergalactic or intercluster space), will run the tiniest bit faster than a computer in our solar system. The effect is small enough that the time necessary to move the computer to the distant location would make the difference moot.


What we need then is Reverse Time dilation

#80 xanadu

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Posted 10 November 2006 - 07:14 PM

I'm glad to see people are thinking about this and coming up with ideas. Jay, you have a good point about the fact that if a BH was very tiny, it would be hard for it to absorb matter at first due to it's size. If it was unable to attract matter to it, it would depend on random collisions with atoms and particles as well as absorbing radiation. However, you consistantly ignore it's steady growth. If it's area of absorbtion was a few microns wide at first, it would necessarily widen as it became larger. Also, it's large density would cause it to move towards the center of the earth and encounter matter on the way. Once at the center, it would be in a high pressure zone which would accellerate the growth even further. To grow from subatomic size to a size that could accelerate growth at a rapid pace might take a long time. We just don't know.

bgwowk, I'm glad to see you are talking again.

"Planets can never be consumed by wandering black holes. A wandering black hole that fell toward a planet would necessarily hit the planet at greater than planetary escape velocity, pass through the planet, and then head back on its merry way into space on a hyperbolic orbit never to be seen again."

As has been already pointed out, it would be escape velocity from the BH, not from the earth that is the factor. There are many other factors you are potentially overlooking

"The mass-to-size ratio of a black hole is so great that friction cannot affect it."

Ordinary friction is not going to affect a BH. It is, far as we know, a point. What we have to be concerned with is it's ability to interact with matter around it which would act in a way far greater than friction on a normal object. Friction is a product of electrical interactions of molecules moving in close proximity to each other. BH's, far as we know, do not have an ordinary surface. Friction between a BH and surrounding ordinary matter would not take place mediated by electric charges and other ordinary factors. We know this because electric fields and other forces can not pass beyond the event horizon.

"Even a stellar mass black hole, being only a few miles wide, would only consume a negligible fraction of the earth as it passed through. Of course the damage done by gravitational tidal forces by a large black hole would be severe."

You have a talent for understatement. Severe indeed. I'm sure you are aware of the accretion discs around known black holes and the x ray and gamma radiation coming off them. A BH of that mass coming within even a few thousand miles of the earth would destroy it entirely although it would not absorb all of the earth.

"Any black holes created by particle accelerators would evaporate before they could ever grow,"

Your faith in the unproven Hawking radiation is touching. Or do you propose some other mechanism for this evaporation?

caston wrote:

"A artifically created blackhole and an exhausted sun blackhole could be entirely different beasts."

You are correct. We don't know for sure if an extremely small (light) BH can interact with surrounding matter or not. Larger ones do without a doubt.

bgwowk wrote:

"Yes, if you created a black hole that was stationary at the Earth's surface (and that didn't evaporate), it would oscillate from one side of the Earth to the other for a long time."

You are again making many assumptions. You assume a BH could pass through the earth with little to no resistance and that is patently false. Gravitational effects alone mean it would interact strongly with the earth as well as the fact Jay pointed out that it would absorb matter on the way which was at rest and would have to be accelerated to the velocity of the BH. If you are assuming a sub atomic sized BH of very tiny mass that would not have significant gravity, you are still assuming it can pass through matter without interacting with it. On what do you base this assumption? Oh I forgot, you don't answer questions.

Time dilation might be useful if it was harnessed in some way because it could be used as a form of time machine. Unfortunately, it would only go forward. You could see the year 3000, get back in and check out 10,001 or try for a few million years in the future. It would have to be fascinating. I think many people would choose to take the journey particularly if they believed they had little time left to live.

#81 bgwowk

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Posted 10 November 2006 - 09:43 PM

xanadu wrote:

Your faith in the unproven Hawking radiation is touching.

It is because of statements like that that I have no interest in talking to you. I could do a rigorous calculation setting upper limits on the frictional force experienced by black holes moving through matter, and you would dismiss it with the same swagger you dismiss so much other physics you don't understand. You don't know what you don't know. There is therefore nothing I could tell you that you don't think you already know.

#82 jaydfox

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Posted 10 November 2006 - 09:47 PM

You assume a BH could pass through the earth with little to no resistance and that is patently false.

Patently false? How so? Did you prove it? Or did you just make another uneducated guess.

Friction cannot affect a black hole by definition, because there's nothing to push back. Friction is caused by equal-and-opposite forces. As I push a chair along the floor, the floor pushes on the chair, and the chair pushes back. A black hole never pushes back, it just attracts, attracts, attracts! No friction.

Similarly, viscosity cannot affect a black hole. The analog here is a submarine moving through the ocean. The front of the hull pushes the water out of the way, and the mass of the displaced water has momentum that was initially stationary but is now moving. That momentum is pulled from the sub's momentum.

A black hole doesn't push anything out of its way. It just attracts, attracts, attracts!

Friction and visocity are both irrelevant to a black hole, by definition!!!.

The only force that's relevant, that could slow the black hole down, is the picking up of matter along the way. That matter was initially motionless, but now its moving at the same speed as the black hole. This is slightly analogous to the sub pushing on the water, where the water ends up matching the speed of the sub, and the sub's speed is reduced. However, the analogy is somewhat flawed, since the water wouldn't ordinarily become "stuck" to the sub. A better analogy is a baseball thrown at 100 MPH, and splatting a housefly in mid-flight. The fly would stick to the baseball, and the baseball would slow ever so slightly from the impact.

If a black hole manages to gobble up a sizeable fraction of its own mass on the way through the planet, it could lose a similarly sizeable fraction of its speed. However, if it takes millions of years for nanoscale black hole to gobble up a significant amount of mass (significant enough to affect its size), then it's going to gobble up very little in the few seconds or minutes it takes to pass through the earth.

#83 jaydfox

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Posted 10 November 2006 - 09:53 PM

However, you consistantly ignore it's steady growth. If it's area of absorbtion was a few microns wide at first, it would necessarily widen as it became larger.

Ignored? I don't know how many different ways I can explain it. You obviously have a conceptual or mathematical block somewhere. Please explain to me what you aren't understanding, and I'll try again. But I'm not going to take a shotgun approach and hope I figure out what detail it is that escapes you.

#84 jaydfox

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Posted 10 November 2006 - 10:14 PM

"Planets can never be consumed by wandering black holes. A wandering black hole that fell toward a planet would necessarily hit the planet at greater than planetary escape velocity, pass through the planet, and then head back on its merry way into space on a hyperbolic orbit never to be seen again."

As has been already pointed out, it would be escape velocity from the BH, not from the earth that is the factor. There are many other factors you are potentially overlooking

Good point. However, that depends on what exactly we're discussing. If it were a black hole created in a lab here on earth, it would be escape velocity of the earth, due to the insignificant mass of the black hole. And as I sort of pointed out, a black hole created on the earth would most likely be travelling well in excess of escape velocity when it was created, probably a large fraction of c.

For a large black hole (roughly stellar mass, as Brian suggested), then you're correct, it would be the escape velocity of the black hole. Of course, where did the black hole come from? If it came from somewhere else in the galaxy, then by the time it reaches the earth, it would already be moving faster than escape velocity, because the earth (and everything else in the solar system) would have been gravitationally pulled towards it. In other words, earth would be falling towards the black hole at greater than the BH's escape velocity, then barrel right past it and escape on the other side. Brian talks about a hyperbolic path, but from a comoving frame of reference to the black hole, the black hole would hardly have shifted direction, and it's the earth that would have the hyperbolic trajectory.

If we were talking about a wandering "primordial" black hole (i.e., a really small one), then it would be the earth's escape velocity that mattered, and again, if the black hole were just passing by, it would accelerate towards the earth and hit it at a speed in excess of escape velocity. A gravitational slingshot could slow it down before it got here, the way we use slingshots to slow down probes we send to Mercury. But those trajectories require a great deal of precision, so the most likely scenario would be a black hole falling from outside the solar and hitting us with an escape velocity greater than that of the sun-earth system, which is something like 3-5 times earth's escape velocity. So even a little friction would be moot: the speed could get cut in half and it would still be more than escape velocity.

#85 xanadu

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Posted 10 November 2006 - 10:42 PM

bgwowk once again indicates he could easily answer all questions if only the questioner assumed the proper pose of reverence. He assumes "swagger" on the part of the questioner and therefore will not give out any of his wisdom. I'll have to remember that one when someone asks me a question I don't know the answer to. But I'd probably just say I don't know the answer and propose one or two possibile theories to explain it.

"I could do a rigorous calculation setting upper limits on the frictional force experienced by black holes moving through matter,"

I believe you could come up with something and it would be rigorous. But, you know I would question your assumptions and you are none too sure of them so your argument would fall apart. You've already seen that happen. Call that swagger if you wish but answering tough questions instead of dismissing them with a wave of your hand is the hallmark of modern science. Church leaders in the past could get away with an answer like "because it's god's will" or refuse to answer because the person was a heathen and did not beleive the same way they did. It's much harder to get away with that nowdays. Take note that I have never insulted you, I merely expressed skepticism for some of your statements and demanded answers. Perhaps that is considered being too pushy. I apologise if I hurt your feelings along the way. But if you constantly run from the tough questions, people will assume you have no clue. I assume you have been trained in some branch of science though when I asked you, you once again gave no answer.

Jay wrote:

"QUOTE
You assume a BH could pass through the earth with little to no resistance and that is patently false.

Patently false? How so? Did you prove it? Or did you just make another uneducated guess."

Gravitational interaction with surrounding matter, for one thing. Slowing of momentum as it absorbs matter for another. Possible interactions by means of electrical charge or other forces. All of this was already discussed, did you miss it?

"Friction cannot affect a black hole by definition,..."

I already said as much about conventional friction and BH's. Did you miss that too?

"If a black hole manages to gobble up a sizeable fraction of its own mass on the way through the planet, it could lose a similarly sizeable fraction of its speed. However, if it takes millions of years for nanoscale black hole to gobble up a significant amount of mass (significant enough to affect its size), then it's going to gobble up very little in the few seconds or minutes it takes to pass through the earth."

Now you're getting into an area where you may be correct. We don't know how a subatomic BH behaves so no one can answer that. But, a somwhat larger BH which does attract and swallow matter would not act as you proposed. Since we don't have any data to base our theories on how micro BH's behave, I'm not going to try to debate that with you no matter how sure you think you are. You assumed a lab created BH would have escape velocity when created and not interact with normal matter. And you base that on what exactly? <-- do try to answer that one.

#86 DukeNukem

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Posted 10 November 2006 - 10:51 PM

Well, for one thing, a basketball-sized black hole would weight about 15 times as much as the earth, give or take

Jay, I'd love to know how you figured that out, so I don't have to make wild-ass guesses in the future! ;-)

That seems like a lot of mass to make such a small event horizon. Upon more considered thought, though, it now seems to make sense.

#87 jaydfox

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Posted 10 November 2006 - 11:02 PM

Jay, I'd love to know how you figured that out, so I don't have to make wild-ass guesses in the future! ;-)

An earth-mass black hole would have a diameter of 2 cm, give or take. It's useful to remember that little factoid.

Diameter scales linearly with mass, so a basketball is about 10-15 times bigger than 2 cm (I don't know exactly how big a basketball is, somewhere around 10-12 inches, give or take). So that's how I pulled that number out of thin air!

#88 xanadu

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Posted 10 November 2006 - 11:02 PM

What do we know about BH's that can be extrapolated from? Keep in mind this is just speculation but we do know that BH's are extremely dense and by definition have an "event horizon" that prevents light, matter and other radiation from escaping. If a micro BH was formed, it would have to have these properties. It has been stated that gravity would play little or no role in the life of a sub micro BH because of it's tiny mass. I say that is not true at all, gravity would play a central role. True, it would not be able to attract matter at a distance and pull it in let alone create an accretion disc heated by tidal forces. But, at sub atomic distances, gravity would be very strong.

How would a black hole of whatever size look if you had one close enough to look at? We will neglect for the moment the danger of falling in and gravitational effects harming the observer. Most people likely visualise a black marble like object but that is not what you would see. You would not be able to see the event horizon at all. The BH would act like a free floating lense and magnify whatever is behind it. We've already seen this in the form of dense galaxies and other dense objects forming a gravitational lense in the sky magnifying faint and distant galaxies behind them. Since the BH bends space and time, light flowing past it would be bent. None of this is my own personal conjecture, this has been observed. We just haven't seen any close up.

If the micro BH had an event horizon of 1 nanometer, to pick a number at random, one would expect it to bend space and time within that radius to the point that nothing can escape. Beyond the event horizon (EH), it would also bend space but at a lesser degree. Anything coming "close" would be captured by that gravity and either go into an orbit or fall in and release some form of energy on the way. I don't know how far this sphere of influence would extend but it would clearly be much farther than the EH extends. Radiation of all kinds would be bent and tend to fall into the micro BH. What would the BH do when it got close enough to an atom to influence it? I don't know but it seems likely that the BH would begin to absorb electrons and finally the atom itself. It may be able to draw a number of atoms at a time into orbit and slowly bring them down and devour them. This may indeed take a very long time before it gets big enough to be dangerous. Who knows?

As for hawking radiation, let me know when you find some.

#89 xanadu

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Posted 10 November 2006 - 11:06 PM

Jay, would you give us your calculations that you used to come up with your figures? I'm too lazy to look it up.

You wrote:

"Diameter scales linearly with mass,"

I don't think so. Neglecting the fact that BH's are likely points and not solids, diameter does not scale linearly with mass with any object. Volume varies as the cube of the radius, as I recall. Perhaps you meant it a different way?

#90 bgwowk

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Posted 10 November 2006 - 11:27 PM

xanadu wrote:

Take note that I have never insulted you.

You have as much to learn about human relations as you do about physics.

I assume you have been trained in some branch of science though when I asked you, you once again gave no answer.

Credentials are immaterial since you show no respect for them, as evidenced by your general contempt of any physics that doesn't suit your preconceptions.




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