black hole?

Question

i have heard many scientists refer to the singularity inside a black hole as "infinitely dense"... its kind of pathetic that they do not seem to grasp what that word means.... if something were infinitely dense... that means it must either be an infinite amount of matter(everything), at a constant size....... or..... be a finite amount of matter, but be infinitely small.. which would not exist...

are they simply using the word wrong to help convey the magnitude of density? or are they really stupid?

by the way.. space-time warping is a bunch of sh1t.... we still have no idea what causes gravity.. ya.. time is warping... i love alberto's deterministic ways, but he f'ed up on that one.

Answer 1

"be a finite amount of matter, but be infinitely small.. which would not exist..."

That's actually exactly what they are saying...

As to time warping... The mistake there is believe that Time is a dimension of it's own rather than the phenomenia caused by change in spacial dimensions and human observations being linear...

Answer 2

Whew! Let's start by defining terms. We gotta speak the same language before we can communnicate, right?

Black hole:
World War I was raging around him and a disease which would soon kill him left him weak and in pain, but German military officer Karl Schwarzschild was pondering one of the most profound scientific ideas of 20th-century science: Albert Einstein's theory of General Relativity.

Einstein eschewed earlier theories of gravity, which described it as an attractive force, and instead visualized it as a "warp" in space -- a curvature caused by matter. According to General Relativity, heavier and denser objects -- like planets, stars, and galaxies -- produce a greater warp in space, in essence giving them a stronger gravitational pull.

When Schwarzschild, a 42-year-old mathematician who was in charge of a German military weather station, read Einstein's new theory, which was published in 1916, he used it to make some calculations of his own. Schwarzschild found that if you squeezed enough mass into a small enough volume, its gravity would become almost infinitely strong. It would warp the space around it so strongly that nothing could escape from it -- not even light. In essence, the object would be invisible to the outside universe: matter and energy could fall into it, but nothing could come back out.

Schwarzschild's mathematical calculations provided the scientific basis for the concept of black holes. Today, astronomers suspect that millions of black holes populate our own Milky Way galaxy, and that supermassive black holes may inhabit the centers of the Milky Way and most other galaxies.

These black holes come in a variety of masses and sizes. The smallest are a few times as massive as the Sun and only a few miles in diameter. The largest are a few billion times as massive as the Sun and big enough to swallow our entire solar system. Yet all are fundamentally the same.

Most of what astronomers know about black holes themselves is based on theoretical models. These models say that a black hole consists of a SINGULARITY--an almost infinitely dense pinpoint of matter that contains the black hole's entire mass--and a horizon, which to the outside universe forms the black hole's surface. It is not a physical surface, however, but the point at which the black hole's escape velocity--the speed at which matter or energy must travel to get away--exceeds the speed of light. Anything passing within the horizon can never come back out: It is trapped in a black hole forever.

So, a SINGULARITY, then is a point where some property is infinite--a point where you cannot define any mathematical function. For example, at the center of a black hole, according to classical theory, the density is infinite (because a finite mass is compressed to a zero volume). Hence it is a singularity.

Similarly, if you extrapolate the properties of the universe to the instant of the Big Bang, you will find that both the density and the temperature go to infinity, and so the universe, at that instant, was also a singularity.

In terms of your question, it is the latter scenario that is more correct, i.e., a finite amount of matter which is infinitely small--but which does exist, at least as we can measure it indirectly.

Also, the black hole is a dynamic system, growing by the millisecond as more and more matter is fed into it. Do you agree that, essentially, the Universe contains an infinite amount of matter? If so, then eventually could all the black holes merge to form one huge gigantic mother-of-all-the-black-holes? Wouldn't THAT black hole (which could not exist if the universe IS infinite) be infinitely large and have infinitely gravity, all at once?

Would we then be back to the singularity that formed our own Universe 13.7 billion years ago?

In any case, they--those rat-basta*d scientists are not using the word "infinite" incorrectly, nor are they really stupid. They are using the word "infinite" in its mathematical sense.

We cannot see black holes or singularities. We can only measure them indirectly or infer them using mathematics. It's all we've got for now.

I love this stuff.
(-:

Answer 3

Maybe they use the term infinitely dense because a black hole could hold everything if it's gravitational pull was strong enough. If there was a black hole big enough it could swallow everything in this universe.

Space-time warping is not a bunch of **** as you put it. It doesn't matter what causes gravity to exist but gravity does effect time and space. Space is warped by gravity and so is time.

Answer 4

A black hole is made of the stuff the universe was made of before the big bang
(PS just a guess!) Oh, and space-time warping is actually real

Answer 5

you certainly sound very sure of yourself, especially about such an elusive subject as a black hole, that can not be observed by whatever means scientists can employ today.

Answer 6

Black hole
One of the end points of gravitational collapse, in which the collapsing matter fades from view, leaving only a center of gravitational attraction behind. General relativity predicts that if a star of more than about 3 solar masses has completely burned its nuclear fuel, it should collapse to a configuration known as a black hole. The resulting object is independent of the properties of the matter that produced it and can be completely described by stating its mass, spin, and charge. The most striking feature of this object is the existence of a surface, called the horizon, which completely encloses the collapsed matter. The horizon is an ideal one-way membrane: that is, particles and light can go inward through the surface, but none can go outward. As a result, the object is dark, that is, black, and hides from view a finite region of space (a hole). See also Gravitational collapse; Relativity.

The possible formation of black holes depends critically on what other end points of stellar evolution are possible. There can always be chunks of cold matter which are stable, but their mass must be considerably less than that of the Sun. For masses on the order of a solar mass, only two stable configurations are known for cold, evolved matter. The first, the white dwarf, is supported against gravitational collapse by the same quantum forces that keep atoms from collapsing. However, these forces cannot support a star which has a mass in excess of about 1.2 solar masses. The second stable configuration, the neutron star, is supported against gravitational collapse by the same forces that keep the nucleus of an atom from collapsing. There is also a maximum mass for a neutron star, estimated to be between 1 and 3 solar masses.

It would appear from the theory that if a collapsing star of over 3 solar masses does not eject matter, it has no choice but to become a black hole. There are, of course, many stars with mass larger than 3 solar masses, and it is expected that a significant number of them will reach the collapse stage without having ejected sufficient matter to take them below the 3-solar-mass limit. Further, more massive stars evolve more rapidly, enhancing the rate of formation of black holes. It seems reasonable to conclude that a considerable number of black holes should exist in the universe.

The black hole solutions of general relativity, ignoring quantum-mechanical effects, are completely stable. Once massive black holes form, they will remain forever; and subsequent processes, for example, the accumulation of matter, only increase their size. Steven Hawking showed that when quantum effects are property taken into account, a black hole should emit thermal radiation, composed of all particles and quanta of radiation which exist. Since a radiating system loses energy and therefore loses mass, a black hole can shrink and decay if it is radiating faster than it is accumulating matter. However, for black holes formed from the collapse of stars, the ambient radiation incident on the black hole from other stars, and from the big bang itself, is much larger than the thermal radiation emitted by the black hole, implying that the black hole would not shrink. Even if the ambient radiation is shielded from the black hole, the time for the black hole to decay is much longer than the age of the universe, so that, in practice, black holes formed from collapse of a star are essentially as stable as they were thought to be before the Hawking radiation was predicted.

Because black holes themselves are unobservable, their existence must be inferred from their effect on other matter. Such is the case with the binary x-ray star system Cygnus X-l. There are a number of binary x-ray systems known. The model which best explains the data is one in which a fairly normal star is in mutual orbit about a very compact object. Because these two are so close, mass flows from the star onto an accreting disk about the compact object. As the mass in the disk spirals inward, it heats up by frictional forces. Because the central body is so compact, the matter heats to a temperature at which thermal x-rays are produced. The only compact objects known that could accomplish this are neutron stars and black holes. The existence of very short-time bursts of radiation also points to an object of small diameter, that is, compact. In some of these binary x-ray systems, there is also a regular pulsed component to the x-rays, indicating a rotating neutron star (by reasoning similar to that given for pulsars). In these systems, the compact object could not be a black hole because that would imply a more complicated structure than a black hole would allow. In other systems, however, there are only irregular pulsations or fluctuations; they are candidates for possible black holes.

The crucial evidence comes from the mass determination of the compact object. Because the inclination of the orbit is not known, a range of masses is found; however, there will be a typical mass obtained by assuming that the orbit is not in an extreme orientation. For three x-ray binaries, Cygnus X-1, LMC X-3, and A0620-00, the typical mass of the compact body is about 10 solar masses, much larger than the maximum mass of a neutron star. In fact, the compact objects in the first and third binary systems are more massive than the maximum mass of a neutron star, no matter what orientation the orbit is assumed to have. Assuming that general relativity is the correct theory of gravitation (and this assumption is now supported very well experimentally), there can be no compact objects of such a mass other than a black hole. In this sense it can now be said that black holes exist.

While the evidence is less direct and more model-dependent, there is growing acceptance of the idea that supermassive black holes exist at the cores of nuclei of active galaxies, including quasars and radio galaxies. Here, the black hole is assumed to interact with accreting matter in such a way as to provide a source of energy to power these ultraluminous objects.

Black holes are thought to exist in the nuclei of other galaxies as well, their presence not giving rise to amounts of radiation as spectacular as for active galactic nuclei only because of differing conditions near the black hole. In the Milky Way Galaxy, observations of the proper motions of stars within a fraction of a parsec of the galactic center demonstrate unambiguously that a central mass concentration of 2 × 106 solar masses is present in a region so compact that no explanation other than that of a central black hole is feasible. Similar, although less convincing, observations of the presence of central black holes have been made for several nearby galaxies. The existence of supermassive black holes is virtually certain.

Answer 7

And you are qualified to say this because...

Answer 8

The concept of a body so massive that even light could not escape was put forward by the English geologist John Michell in a 1784 paper[2] sent to Henry Cavendish and published by the Royal Society. At that time, the Newtonian theory of gravity and the concept of escape velocity were well known. Michell computed that a body with 500 times the radius of the Sun and of the same density would have, at its surface, an escape velocity equal to the speed of light, and therefore would be invisible. In his words:

If the semi-diameter of a sphere of the same density as the Sun were to exceed that of the Sun in the proportion of 500 to 1, a body falling from an infinite height towards it would have acquired at its surface greater velocity than that of light, and consequently supposing light to be attracted by the same force in proportion to its vis inertiae (inertial mass), with other bodies, all light emitted from such a body would be made to return towards it by its own proper gravity.

Michell considered the possibility that many such objects that cannot be seen might be present in the cosmos.

In 1796, the French mathematician Pierre-Simon Laplace promoted the same idea in the first and second edition of his book Exposition du système du Monde. It disappeared in later editions. The whole idea gained little attention in the nineteenth century, since light was thought to be a massless wave, not influenced by gravity.

In 1915, Albert Einstein developed the theory of gravity called General Relativity. Earlier he had shown that gravity does influence light. A few months later, Karl Schwarzschild[3][4] gave the solution for the gravitational field of a point mass and a spherical mass, showing that something we now call a black hole could theoretically exist. The Schwarzschild radius is now known to be the radius of the event horizon of a non-rotating black hole, but this was not well understood at that time. Schwarzschild himself thought it was not physical. In a remarkable coincidence, the name Schwarzschild actually translates into black shield. In another coincidence, only a few months after Schwarzschild, a student of Lorentz, Johannes Droste, independently gave the same solution for the point mass as Schwarzschild had and wrote even more extensively about its properties.

In 1930, Subrahmanyan Chandrasekhar argued that special relativity demonstrated that a non-radiating body above 1.44 solar masses, now known as the Chandrasekhar limit, would collapse since there was nothing known at that time that could stop it from doing so. His arguments were opposed by Arthur Eddington, who believed that something would inevitably stop the collapse. Both were correct, since a white dwarf more massive than the Chandrasekhar limit will collapse into a neutron star. However, a neutron star above about three solar masses (the Tolman-Oppenheimer-Volkoff limit) will itself become unstable against collapse due to similar physics.

In 1939, Robert Oppenheimer and H. Snyder predicted that massive stars could undergo a dramatic gravitational collapse. Black holes could, in principle, be formed in nature. Such objects for a while were called frozen stars since the collapse would be observed to rapidly slow down and become heavily redshifted near the Schwarzschild radius. The mathematics showed that an outside observer would see the surface of the star frozen in time at the instant where it crosses that radius. However, these hypothetical objects were not the topic of much interest until the late 1960s. Most physicists believed that they were a peculiar feature of the highly symmetric solution found by Schwarzschild, and that objects collapsing in nature would not form black holes.

Interest in black holes was rekindled in 1967 because of theoretical and experimental progress. In 1970, Stephen Hawking and Roger Penrose proved that black holes are a generic feature in Einstein's theory of gravity, and cannot be avoided in some collapsing objects.[1] Interest was renewed in the astronomical community with the discovery of pulsars. Shortly thereafter, the use of the expression "black hole" was coined by theoretical physicist John Wheeler,[5] being first used in his public lecture Our Universe: the Known and Unknown on 29 December 1967. The older Newtonian objects of Michell and Laplace are often referred to as "dark stars" to distinguish them from the "black holes" of general relativity.


[edit] Evidence

A (simulated) Black Hole of ten solar masses as seen from a distance of 600 km with the Milky Way in the background (horizontal camera opening angle: 90°).
[edit] Formation
General relativity (as well as most other metric theories of gravity) not only says that black holes can exist, but in fact predicts that they will be formed in nature whenever a sufficient amount of mass gets packed in a given region of space, through a process called gravitational collapse; as the mass inside the given region of space increases, its gravity becomes stronger and (in the language of relativity) increasingly deforms the space around it, ultimately until nothing (not even light) can escape the gravity; at this point an event horizon is formed, and matter and energy must inevitably collapse to a density beyond the limits of known physics. For example, if the Sun was compressed to a radius of roughly three kilometers (about 1/232,000 its present size), the resulting gravitational field would create an event horizon around it, and thus a black hole.

A quantitative analysis of this idea led to the prediction that a stellar remnant above about three to five times the mass of the Sun (the Tolman-Oppenheimer-Volkoff limit) would be unable to support itself as a neutron star via degeneracy pressure, and would inevitably collapse into a black hole. Stellar remnants with this mass are expected to be produced immediately at the end of the lives of stars that are more than 25 to 50 times the mass of the Sun, or by accretion of matter onto an existing neutron star.

Stellar collapse will generate black holes containing at least three solar masses. Black holes smaller than this limit can only be created if their matter is subjected to sufficient pressure from some source other than self-gravitation. The enormous pressures needed for this are thought to have existed in the very early stages of the universe, possibly creating primordial black holes which could have masses smaller than that of the Sun.

Supermassive black holes are believed to exist in the center of most galaxies, including our own Milky Way. This type of black hole contains millions to billions of solar masses, and there are several models of how they might have been formed. The first is via gravitational collapse of a dense cluster of stars. A second is by large amounts of mass accreting onto a "seed" black hole of stellar mass. A third is by repeated fusion of smaller black holes.

Intermediate-mass black holes have a mass between that of stellar and supermassive black holes, typically in the range of thousands of solar masses. Intermediate-mass black holes have been proposed as a possible power source for ultra-luminous X ray sources, and in 2004 detection was claimed of an intermediate-mass black hole orbiting the Sagittarius A* supermassive black hole candidate at the core of the Milky Way galaxy. This detection is disputed.

Certain models of unification of the four fundamental forces allow the formation of micro black holes under laboratory conditions. These postulate that the energy at which gravity is unified with the other forces is comparable to the energy at which the other three are unified, as opposed to being the Planck energy (which is much higher). This would allow production of extremely short-lived black holes in terrestrial particle accelerators. No conclusive evidence of this type of black hole production has been presented, though even a negative result improves constraints on compactification of extra dimensions from string theory or other models of physics.


[edit] Observation

Formation of extragalactic jets from a black hole's accretion diskIn theory, no object beyond the event horizon of a black hole can ever escape, including light. However, black holes can be inductively detected from observation of phenomena near them, such as gravitational lensing, galactic jets, and stars that appear to be in orbit around space where there is no visible matter.

The most conspicuous effects are believed to come from matter accreting onto a black hole, which is predicted to collect into an extremely hot and fast-spinning accretion disk. The internal viscosity of the disk causes it to become extremely hot, and emit large amounts of X-ray and ultraviolet radiation. This process is extremely efficient and can convert about 10% of the rest mass energy of an object into radiation, as opposed to nuclear fusion which can only convert a few percent of the mass to energy. Other observed effects are narrow jets of particles at relativistic speeds heading along the disk's axis.

However, accretion disks, jets, and orbiting objects are found not only around black holes, but also around other objects such as neutron stars and white dwarfs; and the dynamics of bodies near these non-black hole attractors is largely similar to that of bodies around black holes. It is currently a very complex and active field of research involving magnetic fields and plasma physics to disentangle what is going on. Hence, for the most part, observations of accretion disks and orbital motions merely indicate that there is a compact object of a certain mass, and says very little about the nature of that object. The identification of an object as a black hole requires the further assumption that no other object (or bound system of objects) could be so massive and compact. Most astrophysicists accept that this is the case, since according to general relativity, any concentration of matter of sufficient density must necessarily collapse into a black hole.

One important observable difference between black holes and other compact massive objects is that any infalling matter will eventually collide with the latter at relativistic speeds, leading to emission as the kinetic energy of the matter is thermalized. In addition thermonuclear "burning" may occur on the surface as material builds up. These processes produce irregular intense flares of X-rays and other hard radiation. Thus the lack of such flare-ups around a compact concentration of mass is taken as evidence that the object is a black hole, with no surface onto which matter can collect.


[edit] Suspected black holes

Location of the X-ray source Cygnus X-1 which is widely accepted to be a 10 solar mass black hole orbiting a blue giant star
An artist depiction of two black holes merging.There is now a great deal of indirect astronomical observational evidence for black holes in two mass ranges:

stellar mass black holes with masses of a typical star (4–15 times the mass of our Sun), and
supermassive black holes with masses ranging from on the order of 105 to 1010 solar masses.
Additionally, there is some evidence for intermediate-mass black holes (IMBHs), those with masses of a few hundred to a few thousand times that of the Sun. These black holes may be responsible for the emission from ultraluminous X-ray sources (ULXs).

Candidates for stellar-mass black holes were identified mainly by the presence of accretion disks of the right size and speed, without the irregular flare-ups that are expected from disks around other compact objects. Stellar-mass black holes may be involved in gamma ray bursts (GRBs); short duration GRBs are believed to be caused by colliding neutron stars, which form a black hole on merging. Observations of long GRBs in association with supernovae[6][7] suggest that long GRBs are caused by collapsars; a massive star whose core collapses to form a black hole, drawing in the surrounding material. Therefore, a GRB could possibly signal the birth of a new black hole, aiding efforts to search for them.

Candidates for more massive black holes were first provided by the active galactic nuclei and quasars, discovered by radioastronomers in the 1960s. The efficient conversion of mass into energy by friction in the accretion disk of a black hole seems to be the only explanation for the copious amounts of energy generated by such objects. Indeed the introduction of this theory in the 1970s removed a major objection to the belief that quasars were distant galaxies — namely, that no physical mechanism could generate that much energy.

From observations in the 1980s of motions of stars around the galactic centre, it is now believed that such supermassive black holes exist in the centre of most galaxies, including our own Milky Way. Sagittarius A* is now generally agreed to be the location of a supermassive black hole at the centre of the Milky Way galaxy. The orbits of stars within a few AU of Sagittarius A* rule out any object other than a black hole at the centre of the Milky Way assuming the current standard laws of physics are correct.


The jet emitted by the galaxy M87 in this image is thought to be caused by a supermassive black hole at the galaxy's centreThe current picture is that all galaxies may have a supermassive black hole in their centre, and that this black hole accretes gas and dust in the middle of the galaxies generating huge amounts of radiation — until all the nearby mass has been swallowed and the process shuts off. This picture may also explain why there are no nearby quasars.

Although the details are still not clear, it seems that the growth of the black hole is intimately related to the growth of the spheroidal component — an elliptical galaxy, or the bulge of a spiral galaxy — in which it lives.

In 2002, the Hubble Telescope identified evidence indicating that intermediate size black holes exist in globular clusters named M15 and G1. The evidence for the black holes stemmed from the orbital velocity of the stars in the globular clusters; however, a group of neutron stars could cause similar observations.