| Rate of Acceleration & Relativity ala Black Hole
Posted: 10/8/2007 11:32:23 AM | The power described when scientists discuss theoreticized calculations of a black hole would lead ordinary people to imagine that they're very chaotic and destructive, but may the laws of relativity prove otherwise?
I've never seen an actual drawing of a blackhole that really includes data about the blackhole such as surface area and how wide reaching the gravitational pull is. | |
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| Rate of Acceleration & Relativity ala Black Hole
Posted: 10/8/2007 11:53:18 AM | Gravity has no limit to its reach, though its influence is a function of distance. There's nothing special about the gravity of a black hole as compared to the gravity of a toy truck. The difference is mass. More mass, more gravity. Same mass, same gravity. If a red giant and a black hole have the same mass, you will experience the same gravitational effects at the same distance from their cores.
A critical difference here is that the black hole is more dense, more compact. If you make your measurements relative to the surface of a black hole, this will put you FAR closer to its center. 100 miles above the surface of a black hole, converted to distance to center, would put you deep inside the red giant. If you maintain the surface distance, you would then be much further from the center of the red giant than the center of the black hole. Farther from center = less gravitational effect.
So there's nothing remarkable about the gravity of a black hole. That's determined entirely by its mass.
Regarding surface area, I suspect you've seen no illustrations because it's more or less impossible to determine. The mass of a black hole can be measured by its observed effects. This also allows the determination of a maximum possible size. Anything smaller with the same mass would have the same effects, leaving no way to know what the surface area is, nor even if it HAS a surface. Since nothing escapes the gravity well, there's no way to directly observe it. | |
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| Rate of Acceleration & Relativity ala Black Hole
Posted: 10/8/2007 8:23:00 PM | FrogO_Oeyes is quite right. However, there are significant differences:
1) You can see the red giant shining its light from way off, and avoid it. You cannot see the black hole at all. Even if you shine a torch on it, the light gets caught, so all you see is empty space. Same for radio waves, microwaves, X-rays, and any other form of E-m waves. You cannot pick in up even with sound waves like sonar, because they only work in close masses, and the black hole sits in empty space. The only way that I know of that you can detect a black hole is that if the black hold sits between you and a star, then the light coming from the star that would normally stream away from the star on either side of the black hole, can be bent around the black hole, and the black hole acts as a lens in space. If you have instrumentation that is designed to constantly measure such anomalies, you can pick them up. Otherwise, you could fly straight into one, and never see it coming. until it's too late.
2) Even if you get close to a red giant, your exposure to its gravity is limited as a maximum to the surface of the red giant. If you tunnel into the red giant, the gravity of what is above you mostly counteracts the extra gravity below. So it never gets greater than the surface.
With a black hole, when you reach the Event Horizon, nothing can escape its gravity. The Event Horizon is far outside of the surface, so you can get stuck permanently way before you get close to the surface of the black hole.
3) When you're caught by the gravity of the red giant, you're pulled quickly close to the ground. When you're caught by the black hole, it's been theorised that the gravitational force is so intense that the distance between your head and your feet can experience differing amounts of gravity, that are different enough that the part nearest the black hole is being pulled in quicker than the part farthest away. So you're slowly being pulled apart, until you slowly rip in two, and then in four, etc, etc. Also, it's also been theorised that you'll get pulled so quickly that time can slow down by Relativity, and you take forever to slowly be ripped apart. Not a pleasant way to go.
4) The gravity of a red giant is the same all over. It has also been theorised that the energy of a black hole is pulled in closer and closer, and ejects in invisible streams at North & South poles, in near vertical streams. You cannot detect them unless you are directly over a North or South pole, and if you get hit, you get hit by an incredibly dense stream of energy, that would rip you apart in an instant.
IMHO, black holes are like invisible space monsters that slowly rip you apart or instantly disintegrate you at either end. Deadly to meet, and currently very difficult to avoid. That's why I think that we'll need black-hole detectors before we can effectively make interstellar travel a real possibility. | |
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| Rate of Acceleration & Relativity ala Black Hole
Posted: 10/8/2007 10:50:07 PM | Yeah...I figured my explanation might be hard enough to get without adding to it.
1) That's the size factor at work. Because the black hole is packed into a smaller volume, closer proximity to the surface is also closer to the core, and gravity's effect is thus greater. Light will never experience that effect from the red giant, though at a distance, the effects should be identical. Otherwise, there's nothing special about the gravity - there just happens to be enough of it to trap photons.
2)I thought of the internal differential effects, though it came up in another thread [hollow earth?], and I wasn't sure of the veracity.
3)Again, not a special feature, but a consequence of scale. Accurate though.
4)I thought of the x-ray jets, but it's my understanding that these are generated at the event horizon by particles being drawn in. They are not discharged from the black hole itself, and are focused at the poles by the magnetic field of the accretion disk. Apparently, it isn't gravity which is the final doom, but the accretion disk itself! Gravity draws matter into orbit, but the angular momentum is too great for anything to actually be drawn in. However, inner layers apparently shed energy as electromagnetism. This offsets the momentum, allowing gas to be drawn in. [http://www.space.com/scienceastronomy/060621_bhole_magnetic.html] | |
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| Rate of Acceleration & Relativity ala Black Hole
Posted: 10/17/2007 8:56:24 PM | One great analogy to think of gravity is this:
Take a sheet and have a couple friends hold onto the corners, and pull it tight. Then, toss a basketball on the sheet. You see how the sheet bends and deforms around the basketball, making a dip? That dip is gravity - the deformation of space (the sheet) around mass.
A blackhole is that deformation taken to an extreme. So much mass in such a small place will deform space to the point where light will travel into it, and cannot continue out of it. Mathematically speaking, there is no surface area of a black hole - just the event horizon. The event horizon is the exact distance from the center of the black hole where space has become so misshapen that light cannot exit. One millionth of a meter further, and light can leave. One millionth of a meter closer, and it's trapped in the black hole forever.
In reality, there are two ways to find a black hole: Through its accretion disk, and through gravitational lensing.
The accretion disk is matter that has basically formed a whirlpool around the black hole - as it gets closer and closer to the event horizon, it gets more and more compact, heating up until its glowing in all wavelengths. This disc is quite visible to astronomers.
Gravitational lensing is more of a lucky hit - if a black hole (from our point of view) crosses in front of a more distant star, some of that star's light will be bent around the black hole (like light travelling through a lens is bent around the glass). Based on the distance and brightness of the star, it is possible to deduce the amount of gravitational lensing observed, and thus the amount of mass that would be required to exhibit that effect. | |
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| Rate of Acceleration & Relativity ala Black Hole
Posted: 10/23/2007 11:34:07 PM | Lots of good information, but two things aren't quite right, at least not the way they were stated.
A black hole does not necessarily sit in empty space. Due to their intense gravitational pull, they tend to attract matter. It's now thought that black holes reside at the center of many (if not all) galaxies.
And it's not strictly necessary for an object to be a black hole for its gravity to tear other objects apart. | |
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| Rate of Acceleration & Relativity ala Black Hole
Posted: 10/25/2007 2:06:26 PM | | Large Hadron Collide at CERN accelerator in France hopes to make a black hole when its up and running. The smaller a black hole is the less it sticks around. The one they hope to make at CERN posses little risk do to its size. They also hope to confirm or deny the exists of the Higgs boson particle. Inside the event horizon of a black hole there isn't any space, time or mass, all have collapsed into a singularity. | |
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| Rate of Acceleration & Relativity ala Black Hole
Posted: 10/25/2007 8:35:54 PM | | The speculation regarding Black Holes is, that they are matter with such a strong gravitational pull that they do not allow light to escape. All of the bodies we see, are due to the fact that the light they emit (or reflect) reaches the earth. Black holes emit no light; thus are black (black is the absence of light). We can only speculate, that the reason an area appears black is because it does not reflect light...the concept of it's tremendous gravitational pull on light is just a theory and appear to be the only plausible answer, however we do not know that for a fact. Speculation does not equal fact unless it is proven without a reasonable doubt. | |
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| Rate of Acceleration & Relativity ala Black Hole
Posted: 10/25/2007 10:01:49 PM |
the concept of it's tremendous gravitational pull on light is just a theory
First correction: the phrase "just a theory" is one that creationists are fond of. I think you mean "just an hypothesis". It's not a theory until it's fairly well-supported and has no viable alternative explanations, making the phrase "just a theory" something of an oxymoron.
The more salient point - the gravitational influence on light is demonstrated, via the gravitational lensing of light from distant galaxies. Certain anomalous images of very distant space were odd because they showed sets of images arranged opposite each other in a circle. These were found to be identical images of a far-distant object, actually located directly behind the center of the circle. The invisible black of the circle being a black hole, and the multiple images being the result of the distant light being lensed around the black hole by its gravity. Highly corroborated theory, not a mere hypothesis, yet not definable as "fact". About as close as you can get though. | |
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| Rate of Acceleration & Relativity ala Black Hole
Posted: 10/25/2007 11:12:23 PM | | Pressure is one consequence of gravity, but gravity isn't the only cause. The more mass above you [ie, you're between it, and the center of mass], the greater the pressure. Increase in pressure causes increase in density and increase in temperature, and a decrease in pressure does the reverse. The exact results will vary according to circumstances. | |
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| Rate of Acceleration & Relativity ala Black Hole
Posted: 10/25/2007 11:21:36 PM | Don't photons give off an amount of heat when they hit and reflect off of an object?
How much heat do they exert when they're sucked into a blackhole comparatively and do they have any mass? | |
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| Rate of Acceleration & Relativity ala Black Hole
Posted: 10/26/2007 12:37:21 AM | Well modern physics breaks down at the event horizon of a black hole.
1)Photons have no mass. They exhibit the dual qualities of both a particle (photon), and wavelength (light frequency). This is just the fundamental nature of light.
2)At a black hole, we can't tell how hot it is - no light (which we use to observe) escapes the black hole. So, it could be infinitely hot, infinitely cold, or something in between - we can't tell.
Photons don't reflect off a black hole. A black hole isn't a solid thing, per se. It's more of a boundary (the event horizon) plus a singularity (a point at the "center" of the black hole).
Space in between (and approaching the event horizon) is so warped that light can't escape. It's no so much that there is a "pull" to the center, so much as the path in is warped so extremely that light, once it falls down the hole, can't "climb back out" so to say. | |
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| Rate of Acceleration & Relativity ala Black Hole
Posted: 10/26/2007 5:17:21 AM | | The theory behind Bekenstein-Hawking radiation predicts that some mass will leak from a rotating black-hole, and I think Chandra has recently observed what is believed to Bekenstein-Hawking radiation being emitted from a large black hole in the center of a distant galaxy. | |
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| Rate of Acceleration & Relativity ala Black Hole
Posted: 10/26/2007 9:10:05 PM | I despise the term "Leaking"
The force required produced by some physics/chemical reaction to emit any mass away from a black hole would have to be something of tremendous value. I believe that leaking is hardly a befitting term for this occurence. | |
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| Rate of Acceleration & Relativity ala Black Hole
Posted: 10/26/2007 9:29:23 PM | Tangent thought...
You're traveling through space and you want to get from A to B.
Could you "slingshot" around the gravitational field of a black hole or would it be too unstable to calculate and about how much velocity could you expect to gain? | |
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| Rate of Acceleration & Relativity ala Black Hole
Posted: 10/27/2007 5:33:32 AM | | Like any gravitational body, you could sling shot from a black hole, the closer you got to it the faster you would sling shot. You probably end up quite a bit taller though. | |
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| Rate of Acceleration & Relativity ala Black Hole
Posted: 10/28/2007 11:50:39 PM | It depends. Technically, yes. However, depending on the mass of the black hole, you may have to take into account the difficulties of extreme tidal forces and also the frame-dragging effect.
for a black hole close to the Schwartzchild limit (of approx 3 solar masses), by the time you get to the event horizon, the tidal forces would have ripped you into your constituent atoms. However, for a mass of, say, a galaxy (several hundred thousand solar masses), you could probably not feel any tidal effect at all right near the horizon.
So, pick your black hole well! :) | |
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| Rate of Acceleration & Relativity ala Black Hole
Posted: 8/17/2009 10:54:49 PM | I think I know why the OP has never seen a realistic drawing of a black hole.
I had a really good one once but I put it down and now I can't find it, despite setting up a telescope in my loungeroom and looking for anomalies.
Once complete they're hard to see...
But thinking about the speed of light.... as you do
What if you looked back, when travelling at 101% the speed of light? Would it appear as if you were being chased by a Black Hole? Or would the Black Hole seem to be in front of you? Would 'front' and 'behind' still have any meaning at that point anyway, since you've out run the light needed to give you a reference point?
mmm... OK... still thinking about the speed of light.
Imagine two points that are 299,274kms apart. Person A (at point a) has a torch and person B (at point b), who synchronised his/her watch with person A earlier, is waiting for person A to turn it on.
Between the 2 points (a and b) there is also a very long rod... heh heh
So person A turns on the torch and simultaneously gives the end of the rod a whack, causing it to jump forward 1cm.
Person B meanwhile, would notice the end of the rod move followed one second later by a flash of light off in the distance.
Can person B's end of the rod, specifically that 1cm movement, be said to have arrived faster than the speed of light?
If that movement was a message of some sort, binary for instance (using 2 rods), could it not be said that transmission had exceeded light speed?
Is there a simple explanation for this? | |
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| Rate of Acceleration & Relativity ala Black Hole
Posted: 8/17/2009 11:48:02 PM | The gravitational field of a Schwarzchild black hole described by the metric:
ds&2 = -(1 - 2m/r)dt^2 + dr^2/(1-2m/r) + r^2 (dtheta^2 + (sin(theta) dphi)^2)
for r 0 as r-> infty, leaving the metric of special relativity). The surface area of the black hole is defined by the area of the event horizon. If the black hole is rotating or has an electric charge, the metric is more complicated, but the field still extends to infinity. However, there will be two horizons. The surface area is then defined by the outer horizon which is called the event horizon while the inner horizon (also called a Cauchy horizon) is a region of spacetime where it becomes impossible to predict the future from the initial conditions defined at the horizon. In other words, the spacetime becomes acausal and it's possible to traverse a closed timelike loop into the past.) This aspect is not well understood. | |
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| Rate of Acceleration & Relativity ala Black Hole
Posted: 8/18/2009 1:05:56 AM | Erm... cough , excuse me for the interruption but I feel that you very learned people become so immersed in your minds that you don't stop , breathe and think about life as we know it . It's not all mathematics you know ... we humans are much more complex and potentially poweful than that . As someone who loves the symmetry of mathematics , can I bring to your attention that sometimes non-mathematicians think about things too and one of my thoughts is that the black hole area is where we would find GOD if we could get into a spiritual frame of mind and certainly after we die . As you were , as it were .  | |
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| Rate of Acceleration & Relativity ala Black Hole
Posted: 8/18/2009 5:30:53 AM | Sometimes I find working theoreticians tend to get a little complicated over what seems a simple explanation.
The thing about a compact black hole which is really impressive are its tidal forces. It's no so much the strength of its gravity as the actual mass isn't all that much more than our Sun (where a simple degenerate stellar remnant). It's that the gravity is concentrated into such a small area for wont of a better term, that once you get close enough for it to affect you, it increases in such a steep curve that it pulls you apart, an effect known as spaghettification (from where we get the loving reference for God as a flying spaghetti monster).
As for the surface area of a black hole, it doesn't have one. This is because the mass of a black hole is so compact that the gravity at its surface breaks all subatomic bonds, so our current models of matter composition are completely taken apart, we just plain run out of demonstrable subatomic structures to work with.
The black hole metrics are models for exotic objects we simply don't have all the math for yet, but as has been mentioned we can astronomically witness their influence and theorise properties under given conditions. Black holes were after all theorised before they were observed (gaining credence by continuing the postulates of Chandrasekhar), which is a good sign theoretical astrophysicists are well on the right track.
String theorists suggest black holes are exotic black body objects of information potential (a raw quantum field), with a surface area equivalent to the swarzschild radius, and many but not all theoreticians have a leaning towards this idea.
For one the eventuation of naked singularities seem to be a strong argument against the Kerr and Reissner-Nordstr'm metrics, which are the only realistic ones for actual stellar bodies (the Swarzschild metric is a mathematical postulate never intended to represent a dynamic body, more to deal with some specific questions about theorum). | |
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