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Author Topic: How do Black Holes form?  (Read 4891 times)

Offline Dharmansh

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How do Black Holes form?
« on: 08/11/2011 07:39:15 »
How is Black Hole formed?I have read many books some say it is made up of two dwarf planet and some say it is made of defective solar system or defective Galaxy what is it exactly made up of? And can we find out where is Black Hole? Coz i think we can By it's radio emission.With Radio emission we found that there was or is a Black Hole in M87. And what is Radio  Emission?Please tell me in easy way or with easy words.....n m confused ??? ??? ???please help me.
« Last Edit: 08/11/2011 08:19:26 by chris »


 

Offline Soul Surfer

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Re: How do Black Holes form?
« Reply #1 on: 08/11/2011 08:27:59 »
Most black holes are formed from large stars when they have used up all the hydrogen fuel available to them to keep shining.  They continue to collapse under gravity and a lot of their mass is ejected as a super hot supernova explosion while part of it is compressed to form a black hole.  In the early days of the universe the very large black holes in the centres of galaxies could have formed directly by the collapse of almost pure hydrogen and helium under gravity because it is much more difficult for pure material like this to form normal stars.

Radio emission is just what it says.  It is emission from vast clouds of gas at the radio frequencies that are ejected by material falling towards the black hole.  we use these  frequencies for transmitting TV and mobile phones.  if you have an old fashioned analogue TV and look at the noise when the stations have stopped broadcasting some of this noise comes from deep space.
« Last Edit: 08/11/2011 08:30:49 by Soul Surfer »
 

Offline Dharmansh

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Re: How do Black Holes form?
« Reply #2 on: 08/11/2011 14:30:27 »
so what is in the center of Black Hole is there any planet or nothing? And how can black hole swallow full solar system?
« Last Edit: 08/11/2011 14:38:15 by Dharmansh »
 

Offline Soul Surfer

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Re: How do Black Holes form?
« Reply #3 on: 09/11/2011 00:03:42 »
A black hole is extremely small for its mass a black hole with the mass of the sun is about one mile 1.6 Km across (compared with the size of the sun which is about 1.4 million KM across  They grow linearly as the mass gets greater so a two solar mass hole is 2 miles across and a 100 solar mass hole is 100 miles across.  The very biggest black holes at the centre of some galaxies weigh a few billion solar masses and are about as big as the orbit of Uranus.

As for black holes swallowing stars and solar systems.  It is quite difficult to fall into a black hole (particularly the smaller ones) things just get very hot and torn apart first so at least half of the matter is radiated away as energy in one form or another.  These are seen in the early universe as Quasars.

No one knows what is inside a black hole and it is not possible to find out experimentally because you can never send any sort of probe and get information out of them.  Most of the theoretical physicists call it a "singularity" which means a mathematical point containing infinite energy but that just does not make sense, so it is just another way of saying we don't know.

I would lay bets that it is another universe just as big and similar to ours (black holes are a bit like a Tardis they can be bigger on the inside than outside!) but no one will prove me right or wrong. 

Given a decade or two I reckon the theoreticians will come round to my way of thinking.
 

Offline Airthumbs

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Re: How do Black Holes form?
« Reply #4 on: 09/11/2011 00:14:02 »
A Blackhole would not exist without a singularity.  This object has such immense density it creates a gravity well around it.

Once this has been formed the point at which the gravity is strong enough to even prevent light from escaping is called the event horizon. 

The singulaity itself is most likely spinning at almost the speed of light and maybe even faster until proven otherwise.  ;D

 

Offline JP

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Re: How do Black Holes form?
« Reply #5 on: 09/11/2011 01:26:20 »
Additionally, outside of the event horizon (which is the very small thing Soul Surfer mentioned), the gravity is the same as if there were a star of the same mass as a black hole.  If we replaced the sun with an equivalently massed black hole, the orbits of the planets wouldn't change, since they'd see the same gravity. 
 

Offline JP

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Re: How do Black Holes form?
« Reply #6 on: 09/11/2011 01:34:52 »
Also, I suspect black holes are filled with unicorns, as no one can prove me wrong.
 

Offline Soul Surfer

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Re: How do Black Holes form?
« Reply #7 on: 09/11/2011 09:11:50 »
Too true JP everyone to their own taste as the old woman said when she kissed the cow.   

Airthumbs a black hole would not exist without putting a lot of gravitating matter into a small space so that its escape velocity exceeded the velocity of light.  however this  event horizon is not a "singularity".   As JP pointed out whatever is inside the event horizon can arrange itself how it likes.  The mathematical physicists like to cop out  with the simplest possible mathematical solution based on the orbits of point particles that do not interact and say they all end up at one point and call it a "singularity"  which is a mathematical point if zero size and infinite energy.  This makes absolutely no physical sense and is just about the only thing that I am prepared to say is NOT inside a black hole!

Tho take this further even if you had point particles with large random velocities heading towards the singularity point interacting only by gravity they would continually deflect each other from reaching this ideal point of "singularity" at the same time and you would end up with some sort of ultra high energy fuzzball.  As to the sort of particles in our universe the results would be much more complicated, very interesting and analysable a lot of the way completely without "quantum gravity" getting involved.  Its very sad that no one seems to want to give it a go.  I could give you lots of suggestions from standard physics what would happen but to do so would co beyond the limitations of standard theory.
 

Offline yor_on

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Re: How do Black Holes form?
« Reply #8 on: 09/11/2011 13:16:06 »
I don't know. Black Holes are infinitely confusing and there exist several solutions to what they might be like inside that event horizon, depending on how you define your 'coordinate system', and, what type of Black Hole you're describing. The truth is that we have never even seen a event horizon, although there are some experiments with light that is expected to be close analogues, maybe?

The simplest solution is the one for a non rotating black hole.

"It is spherically symmetric - a so-called Schwarzschild black hole, after Karl Schwarzschild who, in 1915, was the first to write down the equations defining and describing such a black hole; a special solution of Einstein's equations of general relativity. (However, it took physicists more than fourty years to come to understand the weird spacetime geometry that Schwarzschild's equations imply!) As has already been mentioned, this type of black hole is eternal - it has always been there, and will always be there. More realistic black holes with a definite beginning (for example those produced by the collapse of a massive star) or eternal black holes which rotate all have a somewhat more complex inside structure."

As for if we know what they have inside a event horizon?

In my book 'times arrow' is of one direction. If I assume that a black Hole can accrete mass by 'gravity' and that the event horizon can grow by that, then I don't see how times arrow can behave differently inside.

If I assume that 'gravity' exist both inside as well as outside the event Horizon, and attract, then they are not 'outside' this universe in any way.

If I assume that a free falling observer can pass the Event Horizon, in a for him measurable time, then the 'apparent Event Horizon' doesn't define something 'closed', instead it seems more of a 'one way street', that we all can take. The thing we can't do though, is to get our observations back, to outside that Event Horizon.

That said, here's a 'easy' description/explanation for a Schwarzschild black hole. The problem is the way mathematics freely throw around descriptions like 'negative time', and in this case, time and space changing 'axis' without explaining how they get to those ideas. It gives people a lot of strange ideas, not validated anywhere, except in the mathematical definitions and theory's describing them.

Changing Places.
« Last Edit: 09/11/2011 13:17:45 by yor_on »
 

Offline CZARCAR

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Re: How do Black Holes form?
« Reply #9 on: 09/11/2011 19:38:56 »
BH slows down time?
 

Offline syhprum

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Re: How do Black Holes form?
« Reply #10 on: 09/11/2011 21:48:04 »
A normal Neutron star can come quite close to producing an event horizon but if in some reason it becomes more dense and actually produces one we talk about it becoming a singularity not as a fairly normal object all be it one that has sufferred a further compression.
 

Offline CZARCAR

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Re: How do Black Holes form?
« Reply #11 on: 09/11/2011 22:01:19 »
BH slows down time?
BH can suck in light?& C is the speed limit
 

Offline Soul Surfer

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Re: How do Black Holes form?
« Reply #12 on: 10/11/2011 10:56:09 »
It does not exactly suck in light. The only light that goes in is what hits the horizon.  Light going close just does a tight orbit and goes away deflected.
 

Offline CZARCAR

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Re: How do Black Holes form?
« Reply #13 on: 10/11/2011 16:24:33 »
a laser is pointed @ a BH, photon approaches but cant exceed C? Q= will the wave of the photon stretch into a lower frequency?
 

Offline imatfaal

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Re: How do Black Holes form?
« Reply #14 on: 10/11/2011 16:39:45 »
a laser is pointed @ a BH, photon approaches but cant exceed C? Q= will the wave of the photon stretch into a lower frequency?

As it falls it will be gravitationally blueshifted - if it was trying to get out it would be red-shifted

http://en.wikipedia.org/wiki/Gravitational_redshift
 

Offline CZARCAR

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Re: How do Black Holes form?
« Reply #15 on: 10/11/2011 16:49:49 »
a laser is pointed @ a BH, photon approaches but cant exceed C? Q= will the wave of the photon stretch into a lower frequency?

As it falls it will be gravitationally blueshifted - if it was trying to get out it would be red-shifted

http://en.wikipedia.org/wiki/Gravitational_redshift
blue is a higher frequency?
 

Offline imatfaal

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How do Black Holes form?
« Reply #16 on: 11/11/2011 10:10:41 »
a laser is pointed @ a BH, photon approaches but cant exceed C? Q= will the wave of the photon stretch into a lower frequency?

As it falls it will be gravitationally blueshifted - if it was trying to get out it would be red-shifted

http://en.wikipedia.org/wiki/Gravitational_redshift
blue is a higher frequency?

Quote
Electromagnetic radiation that has passed "downhill" into a gravity well (a region of stronger gravity) shows a corresponding increase in energy, shorter wavelength, higher frequency and is said to be gravitationally blueshifted.
from the wikilink
 

Offline Dharmansh

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How do Black Holes form?
« Reply #17 on: 13/11/2011 09:40:40 »
how can black hole have gravity that it can even Attract light?
 

Offline CZARCAR

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How do Black Holes form?
« Reply #18 on: 13/11/2011 16:36:00 »
thanx, does a solar panel heat up or make electric from IR moreso than UV?
 

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How do Black Holes form?
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