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Posted

do or dont black holes exsist.if so is it true that a black hole is a exploded star or planet that exploded under its own gravity. and has shunk to a small spec in space and has the gravity of 1000 times that of earths.

Posted

Do. The original object must be at least 3 solar masses (3 times as much stuff as our sun), and thus has to be a star. When it collapses, it throws off a bunch of stuff, but its still going to be almost as big as it was before it started in mass, which yes, is going to be much more than "1000 earths" but is going to be at least as big as the original object. There is good evidence that the center of our and many other galaxies have supermassive black holes that have sucked in lots of other gunk over time, so they are really, really, unbelievably big, big, big.

 

Cheers,

Buffy

Posted

Thats right,Buffy. I remember watching the Discovery channel last month and they explained how it was discovered that many known galaxies (including Andromeda) have blackholes at the centre.These black holes have mysteriously stoped sucking in gases from space.

 

There are even some theories saying that these black holes are the objects responsible for the 'birth' of galaxies.

 

 

See you later,

Vishesh

Posted

Interesting things, black holes.

 

One thing that I don't quite get, though, it that seeing as nothing can escape a black hole, ever, according to the Laws of Nature, how is the Big Bang scenario possible? 'Cause the idea is that all the stuff in the Universe was compressed into a little speck which exploded, and... you all know the story. That just means that either the Laws of Nature evolved together with the Universe, say, in the first couple'o seconds, or stuff can actually escape a black hole. 'Cause if everything was in the original singularity, that must have just been one hell of a black hole?

Or could there be mass limits to black holes? Say, a black hole can have 10,000 solar masses, for the sake of the argument, but at 10,001 some sort of repulsive force will blow it apart, overcoming the gravitational attraction?

The only thing I can think of, if the Big Bang hypothesis is to be believed, is that the Laws of Nature must somehow have been in flux initially. That's probably why we can't say for sure where all the stuff came from in the first place, cause there's no way to experiment with the original set of Laws.

Hmmmmmmm... :)

Posted
The only thing I can think of, if the Big Bang hypothesis is to be believed, is that the Laws of Nature must somehow have been in flux initially. That's probably why we can't say for sure where all the stuff came from in the first place, cause there's no way to experiment with the original set of Laws.

 

This is basically correct. In standard cosmology the laws of nature are a result of the Big Bang, so they would not have been the same before.

 

However, in string theory things are slightly different (for example, they have no singularity at the beginning of time) so they even talk about t-x (ie, the time before the Big Bang).

Posted
Interesting things, black holes.

 

One thing that I don't quite get, though, it that seeing as nothing can escape a black hole, ever, according to the Laws of Nature, how is the Big Bang scenario possible? 'Cause the idea is that all the stuff in the Universe was compressed into a little speck which exploded, and... you all know the story. That just means that either the Laws of Nature evolved together with the Universe, say, in the first couple'o seconds, or stuff can actually escape a black hole. 'Cause if everything was in the original singularity, that must have just been one hell of a black hole?

Or could there be mass limits to black holes? Say, a black hole can have 10,000 solar masses, for the sake of the argument, but at 10,001 some sort of repulsive force will blow it apart, overcoming the gravitational attraction?

The only thing I can think of, if the Big Bang hypothesis is to be believed, is that the Laws of Nature must somehow have been in flux initially. That's probably why we can't say for sure where all the stuff came from in the first place, cause there's no way to experiment with the original set of Laws.

Hmmmmmmm... :)

 

Good point Boerseun, that same question has crossed my mind on more than one occasion. If this is what is going on in our universe, maybe there was in fact not really a Big Bang, but rather at unpredictable intervals, many smaller Bangs. Taking this concept to it's limit, one might view the universe as eternal.

Posted
If this is what is going on in our universe, maybe there was in fact not really a Big Bang, but rather at unpredictable intervals, many smaller Bangs. Taking this concept to it's limit, one might view the universe as eternal.

 

I agree..."maybe there was in fact not really a Big Bang"

 

..."many smaller Bangs" ...ask littleBang, maybe he (she?) knows.

 

To make a short story long...the boundary condition (with or without a singularity) is a place (or time) where (and when) the laws of physics break down. The Schwarzschild or Kerr presumption that black holes are hidden behind an event horizon is just as pathological, artificial, and surreal as the presupposition that airplanes and boats will disappear in the carnal voracity of the Bermuda triangle. This scientific game of hide and go-seek is the perfect glossolalic expression of the physicist’s creative ability—especially when considering its derivation as ‘sanctuary.’

 

I love the concept of black hole, but like Einstein, I don't swallow it...

Posted
Good point Boerseun, that same question has crossed my mind on more than one occasion. If this is what is going on in our universe, maybe there was in fact not really a Big Bang, but rather at unpredictable intervals, many smaller Bangs. Taking this concept to it's limit, one might view the universe as eternal.

 

I agree. I'm much more comfortable with the idea of an eternal universe than one with a fixed beginning and end. But that's just because it makes sense to me, and we know the universe is filled with things that don't make sense. :)

Posted

What will happen to a star that is 100 times bigger and is made completely of pure Uranium.

 

 

This is my guess :

Uranium is used to extract energy. So when their atoms collide in the star there will be fusion and energy and the star will never collapse and all the atoms will be converted into energy ?

Posted
What will happen to a star that is 100 times bigger and is made completely of pure Uranium. This is my guess : Uranium is used to extract energy. So when their atoms collide in the star there will be fusion and energy and the star will never collapse and all the atoms will be converted into energy ?
When you're talking about star-sized masses, gravity alone drives fusion of atoms: it does not really matter what element the atoms are. Most of the matter in the universe is Hydrogen. The early stars were basically all hydrogen, through fusion, helium and then heavier elements were formed. When they exploded in a nova/supernova, it spit out these heavier elements, and eventually you had enough heavier elements to form planets made of iron and other elements.

 

Now *waaaaaay* of in the future, there's going to be a lot more of these heavier elements around, and its possible you'd end up with a lot of Uranium, but its highly unlikely that you'd get "pure" uranium, partly because at lower densities, uranium undergoes fission, which *splits* the uranium atoms into lighter elements like cesium, strontium, iodine, etc. meaning you'd get quite a mixed soup of stuff in the process of bringing together the uranium in the process. All these elements will undergo fusion, and the pressure of the reaction will maintain a certain size for a while, but eventually it will go through the same stellar evolution that all stars go through and collapse, explode, and spread the stuff out all over the place, leaving an incredibly dense core. Depending on how big the total mass was to begin with it will end up a brown dwarf, neutron star, or black hole....

 

Cheers,

Buffy

Posted
What will happen to a star that is 100 times bigger and is made completely of pure Uranium.

 

 

This is my guess :

Uranium is used to extract energy. So when their atoms collide in the star there will be fusion and energy and the star will never collapse and all the atoms will be converted into energy ?

 

Anomalous, the example you give would have long before collapsed into what we call a Black hole. We find examples of even more massive objects at the center of galaxies. You use the element Uranium in your questioning thought, but the matter which goes into such an object weather Uranium or otherwise would have first changed to a neutron soup long before collapse. So it really dosen't matter what you build a star with, it will end up consisting of the same stuff.

Posted
Okay...but can somebody pleeeeeeeze :) tell me how the original universe avoided being a black hole?

 

There are some theorists that believe that there was no beginning, that the universe just is, was, and forever shall be. To understand this line of thought one needs to redefine what a Black Hole is. It may be that a Black Hole will only reach a certain mass after which it will transform into what is called a White Hole. A White Hole will inturn begin to spurtforth matter and energy back into the universe. This is a brief description of what some would call a steady state universe. As you can see, this discription of how some view universal evolution avoids a singularity for a Big Bang. Therefore, not requiring a Black Hole to start things in motion. String theory also avoids the issue of a universal singularity.

Posted
There are some theorists that believe that there was no beginning, that the universe just is, was, and forever shall be. To understand this line of thought one needs to redefine what a Black Hole is. It may be that a Black Hole will only reach a certain mass after which it will transform into what is called a White Hole.

 

What the hell is a White hole?!?!?!?!?!

 

Pleeeeeze explain! This sounds kinda cool!

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