What Is.. Gravitational Collapse? too much gravity?

[Madkat-Z 0]

I'm seeing what seems to be a lot of mistaken information here... Here's the scientific truth about black holes from an avid astronomer:1) Black Holes Do Exist - as stated, scientists are not sure of their nature, but we know they are very, very, very dense. If you collapsed the entire Earth into a sphere 1 in. (2.5 cm.) in diameter it would be as dense as a black hole.
2) No light can escape from black holes. Also, a black hole is usually created when a super gigantic star collapses in a hypernova (like a really big supernova) or whatever's more powerful than a hypernova... some type of last-breath explosion
3) White dwarf stars are not that dense, and neither are brown dwarfs or whatever the heck type of dwarf you want to talk about.
4) What you might have been thinking of, MadKat-Z, is the Neutron star - a really, really, really dense star which wasn't quite large enough to become a black hole when the original star exploded, or their kin, the Quark Star...

I've probably not made much sense but hopefully this sheds some light on the situation...

You might be right, it has been awhile since I've studied astronomy. I tend to get my words mixed up rather easily, but still. Can't there be a Neutron Star that is large enough and dense enough create something that may look like a black hole? There are alot of strange things and really large things out there in space you know.

[gaurdro 0]

It is a simple matter of definition that a black hole cannot be a white dwarf. it is possible that a white dwarf may turn into a black hole but once light stops escaping it ceases to be a white dwarf and becomes a black hole. it is more probable that black holes don't go away because there is no net radiation from the hole. therefore all the matter(remember e=mc2) and energy is contained and in most cases added to. they do emit "Hawking Radiation" but this is even below the level of background noise in the universe so there is still a net influx of energy.

[Madkat-Z 0]

It is a simple matter of definition that a black hole cannot be a white dwarf. it is possible that a white dwarf may turn into a black hole but once light stops escaping it ceases to be a white dwarf and becomes a black hole.
it is more probable that black holes don't go away because there is no net radiation from the hole. therefore all the matter(remember e=mc2) and energy is contained and in most cases added to. they do emit "Hawking Radiation" but this is even below the level of background noise in the universe so there is still a net influx of energy.

See I agree with you once a white dwarf can turn into a black hole. However, I'm no space physicist. So some of what you are saying I kind of understand but at the same time I don't. Anyway the whole White dwarf/ Neutron Star theory is what it is, just a theory and like any theory it has its faults.

[iVTEC 0]

Gravitational Collapse is a collapse in the gravitional force wicth cause's us humans and other things to loose control and float away.Sincerly,iVTEC

[Sharn 0]

from what I undersood reading an article of science, gravitational collapse is like a gravity so higth that even light can't escape.
But it's hard for mr to understand.

Beacause I imagine gravity as froce created from a mass that attire other mass. So the Earth can attire me because of her mass. the moon can attire less, because her mass is lower.
So to have a gravity force such in a gravitational collapse, we should have a very very very big mass.
The problem is, when we talk about black-holes as gravitational collapses. In a black hole we don't have such very big mass.

It's steel unknown, what is the black-Holes mass, and probably, they have no mass. Some one says that they are a no-mass zone. SO how can we (or nature) create a gravitational collapses?

To start at the very beginning of this thread. No offense, but you obviously have no idea what mass is. Mass has nothing to do with actual size of the object. Well, I guess you could say it does, but a thing the size of a.... cheerio, for example, could have more mass than our earth. (VERY VERY unlikely, but possible) So, size does not determine mass.

A black hole, as said above could *probably* be made by compacting our earth to the size of a small bounty ball. (Wonderful comparison, no?) A white dwarf is still much less dense than would be needed to make a black hole. It would have to be much more compact also... Anyway, that's my two cents.

~Sharn

[tdktank59 0]

Allright

 

We cannont directly "see" black holes becase they bend light so we cna see them with other methods such as infared and other types of detection

 

one of the biggest hints to it would be the destruction it causes swollowing up whole stars, planets all sorts of things like that.

 

The next closest thing to a black hole is a nuetron star wich has a mass of 1.3-2+ solar masses, and whats really screwy is that as they shrink there masses get bigger. they are about the size of a city (chicago for example) and are as massive as a a few sons together...

 

back to black holes

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.

 

heres an example of G.C.

 

so in all gravitational collapse is when the force inside cannot push out anymore and it falls in onits self thus making a big object with mass mass into a small object with the same mass

 

mass cannot be created or destroyed in otherwords...

 

Black holes donot destroy mass it rips it apart and (im speculating from this point on) compresses it with all the other stuff the blackhole decides to "eat"

[Kioku 0]

Black Holes have a singularity in which they pull everything towards their center. Gravity works like a trampoline. It's not exactly a force, but a spacial distortion. If one were to place a bowling ball on top of it, marbles would be drawn towards it. If more force were applied by lets say a pole or something, pushing it way down, it would pull everything to that central position where the force is being made.As for Black Holes, they let out sub atomic particles slowly in the form of Hawking Radiation slowly until it seemingly evaporates.

[salamangkero 0]

Actually, it's not gravity that is like a trampoline but space-time.

 

Many have imagined space-time as a flexible rubbery fabric. If it were to be supposed so, an object, say a marble, placed on this fabric will distort the surface, depressing the nearby areas. Any stellar dust, marbles or particle affected by such a depression will be attracted to, or "gravitate", towards the marble.

 

A more massive object, like a bowling ball will create a deeper depression and affect a larger area. If, however, this hypothetical bowling ball were to be compressed further into the size of a pea, a small, massive object creates an even deeper depression. Such is a blackhole.

 

In other words, ordinary objects are like marbles; they do have their own influence over the rest of the univesre but their power of attraction is almost insignificant. Massive objects, like stars, are like bowling balls. Even our own sun has enough gravity to bend light, a phenomenon best observed during solar eclipses. Now, if a blue giant were to be compressed into something small, the gravity of all its particles will still "summon" eveything else to them.

 

However, it's not exactly solely about blackholes; the topic is gravitational collapse. Methinks it is the crushing, implosive action of a blue giant on it's deathbed, which may eventually lead to a blackhole anyway. It is understood, of course, that these giant bodies have accumulated quite a lot of mass. Probably the only thing that keeps it from falling apart by itself is the constant "push" or pressure emanating from the fuel burning within.

 

When the star has finally squandered all its fusion fuel, it begins to burn off the by-products of its earlier reactions. In doing so, heavier elements like helium and, eventually, iron, are formed. When, finally, the star has nothing left to burn, the outward "push" ceases and the gravitational pull of the matter deep within may be sufficient enough to attract those on the surface, metaphorically "pulling the roof down", hence the term gravitational collapse.

 

This doesn't always happen, though. As stars die, they shed off shells, or fragments of themselves, and it is hypothesized that it will have to take a really large blue giant to decay into a blackhole.

 

By the way, to one who said blackholes are dead stars and dead things cannot die anymore, that is so not true. Blackholes may be, metaphorically speaking, dead but corpses do not always remain intact. Blackholes may not ressurect into stars but they do decay, eventually, and fade away. A big question, however, is where does all that matter go?

[Voidless_Shadows 0]

There was another thread like this from some time back, I posted someting about negative energy, not entirely relative, but sorta, I'll find it an quote it.

There's a theory in quantum physics that a black hole can be destroyed by doses of negative energy.Negative energy is essentially a space with less than nothing... Hard to explain and while most of what I learned in physics and quantum physics largely escapes me, density can be a negative number, therefore creating negative energy.
Negative energy is suppose to be highly versatile, allowing for traversable wormholes, warp drives, time machines, perpetual-motion machines, or destroy black holes.
The laws in quantum physics that allow for negative energy also limit it.
So I guess why I'm mentioning this is that so many things related in the study of these cosmic forces are...such paradoxes unto themselves...We know they exist and yet we also know some of them couldn't because the laws that make them work make them not work? Yet we do know they exsist, isn't it perplexing? Or are our definitions of how things work screwed and wrong? Are there really any limits as to what can happen?
When you think about this it really proves and disproves everything we know about science...

[Kioku 0]

Actually, it's not gravity that is like a trampoline but space-time.

Stop warping my post. I broke it down to how gravity is a space-time curvature because I didn't feel like going into detail. Geesh.

Black Holes evaporate slowly. They give off Hawking Radiation.
Edited September 3, 2006 by Kioku (see edit history)

[cangor 0]

which is named after Hawking becuase scientists have egos, too. And big ones. Anyways, white dwarfs are dense, but nowhere near as dense as a black hole. While a white dwarf has a density of roughly 1x10^9 g/cm^3, a black hole, though it essentially has infinite density, technically has a density of something like 1.8x10^16 g/cm^3, and a Neutron star is about 1x10^14g/cm^3

[Voidless_Shadows 0]

Hehe, one day I will discover something cool and call it "The Neil Effect" (that's my name) or something...Of course first I have to work on my amazing discoveries... :DAnyways, there's a distinct difference between, black holes, black dwarfs, white dwarfs, neutron stars, the theoretical white holes, singularities, etc...etc...They're related...in ways, but the same no, I think we've established that, other than that, anyone else have anything else they know/found out about Black holes today?

[turbohead 0]

Sorry, but I think maybe you have mixed the concept of MASS and GRAVITY. MASS is constant wherever you are. But GRAVITY, it's the resultant of centripetal force and gravitation you affected on a celestial body. If you stand on moon, the GRAVITY you affected is different from earth, but your MASS is constant(unless you gained or losed some weight )

Edited September 26, 2006 by turbohead (see edit history)

[wacky_stu 0]

First of all: BLack Holes are not only theory they have been proved through observations using the hubble telescope.The other day in science we watched a 20 minute long video deatiling the universe. Also I have recentley read a book called "A short history of time". Both of which talk about how black holes are formed. Light and time are subject to the pull of gravity just as much as matter. The greater the density or "mass" of an object the greater its gravatational pull. When a sun dies it implodes and pulls in large amounts of nearby matter. Eventually once the density or mass is high enough, it will have enough gravatational pull to draw in any nearby light "photons". Once nearby light has been drawn in, the sun becomes invisible. And the area of space which used to be occupied by a star is now dark. Thus scientist can prove that there is a black hole there because although the surrounding area is light the area where the black hole resides is vacant.