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Author Topic: about black hole and vent horizon  (Read 5942 times)

Offline qazibasit

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about black hole and vent horizon
« on: 19/05/2005 14:41:12 »
why the light which is at the event horizon is not dessipating and why cant we say that a normal star is also a black hole coz a burning star also has a very high gravitational force.


 

Offline DoctorBeaver

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Re: about black hole and vent horizon
« Reply #1 on: 20/05/2005 11:53:28 »
A black hole is black because light cannot escape its gravitational field. A normal star is visible so obviously ITS light CAN escape.
 

Offline neilep

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Re: about black hole and vent horizon
« Reply #2 on: 20/05/2005 14:29:02 »
Black Hole : Black= BLACK...Hole=HOLE...that's two things which stars are not...unless you take a piccy and look at the negative ;-)

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Offline qazibasit

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Re: about black hole and vent horizon
« Reply #3 on: 20/05/2005 16:55:08 »
ok do you agree that if you stop the path of photon it will become a particle then why the light constitute of photon is not becoming particles at the event horizon
 

Offline Ultima

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Re: about black hole and vent horizon
« Reply #4 on: 20/05/2005 17:28:02 »
All gravity distorts/is a result of distorted space so the light coming from a star is also bent by the stars gravitational field or any other gravitational field. Black Holes distort space so much it folds back in on itself so once something enters, if it continued in a straight line it would just end up back where it was when it entered (The Event Horizon).... at least this is how I was taught to understand it. In fact the idea that light's path is distorted by gravity was proven by looking at the gravitational effect from our own Sun by measuring the difference in position of a distant star that was visible close to the Sun during an eclipse.

Astronomers use this nice effect to do all sorts of crazy things... If you know enough about each part of the lensing setup you can calculate some other things such as the mass of objects etc.
http://www.iam.ubc.ca/~newbury/lenses/research.html

wOw the world spins?
« Last Edit: 20/05/2005 17:40:18 by Ultima »
 

Offline DoctorBeaver

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Re: about black hole and vent horizon
« Reply #5 on: 20/05/2005 19:17:14 »
Ultima - I thought the bending of light by gravity was proven by observing Mercury passing behind the sun. As it emerged it was shown that it's apparent position was different from its actual position by almost exactly the amount predicted by Einstein.

gazibasit - light behaves as both a wave & as particles. Which of the 2 it appears as depends on the way you observe it.

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Offline gsmollin

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Re: about black hole and vent horizon
« Reply #6 on: 20/05/2005 21:00:33 »
quote:
Originally posted by DoctorBeaver

Ultima - I thought the bending of light by gravity was proven by observing Mercury passing behind the sun. As it emerged it was shown that it's apparent position was different from its actual position by almost exactly the amount predicted by Einstein.

gazibasit - light behaves as both a wave & as particles. Which of the 2 it appears as depends on the way you observe it.

It wasn't me - a big boy did it & ran away



That was starlight bending as it passed near the sun. The star was visible because of a solar eclipse. This was the first important verification of the general theory of relativity, and had been suggested by Einstein. The Mercury connection was the precession of the perihelion of Mercury. Einstein had also suggested that experimetal verification of GR, but it has never been verified to a satisfactory precision. The problem is that most of the precession is due to the oblateness of the sun, and that has also not been determined to satisfactory precision.
 

Offline DoctorBeaver

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Re: about black hole and vent horizon
« Reply #7 on: 20/05/2005 22:03:20 »
Are you sure the Precession is the right word? I was under the impression that it meant a gradual movement around the sidereal sphere. Surely the Mercury eclipse was not anything to do with that.
I must admit that all i really know about it is that Einstein predicted it & observation verified his prediction to within 1% - and that was at variance with the contemporary Newtonian prediction

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Offline chimera

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Re: about black hole and vent horizon
« Reply #8 on: 20/05/2005 22:13:12 »
I think you mean the Michelson-Morley experiment.

http://www.drphysics.com/syllabus/M_M/M_M.html



The living are the dead on holiday.  -- Maurice de Maeterlinck (1862-1949)
 

Offline DoctorBeaver

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Re: about black hole and vent horizon
« Reply #9 on: 21/05/2005 23:24:51 »
Yes, Rob - that's the beastie. Am I right in saying that was nothing to do with precession but merely orbit?

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Offline chimera

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Re: about black hole and vent horizon
« Reply #10 on: 22/05/2005 10:21:45 »
There was also the 1919 Eddington eclipse observation:

http://www.simonsingh.com/1919_Eclipse.html

which showed that Einstein was correct in his prediction (albeit off by a factor of exactly two, which sure p*ssed off our dear Albert bigtime) of the 'bending' of star light passing close to the gravitationall well of the sun.

Those are often mixed up in hagiographies. I've a suspicion this one fits your bill better.

The living are the dead on holiday.  -- Maurice de Maeterlinck (1862-1949)
 

Offline gsmollin

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Re: about black hole and vent horizon
« Reply #11 on: 22/05/2005 23:50:02 »
quote:
Originally posted by DoctorBeaver

Are you sure the Precession is the right word? I was under the impression that it meant a gradual movement around the sidereal sphere. Surely the Mercury eclipse was not anything to do with that.
I must admit that all i really know about it is that Einstein predicted it & observation verified his prediction to within 1% - and that was at variance with the contemporary Newtonian prediction

It wasn't me - a big boy did it & ran away



Yes, that is the word- precession of the perihelion. It IS a gradual movement through the sidereal sphere. It has nothing to do with any Mercury eclipse. Actually, as far as I know, Mercury does not eclipse anything. When it passes in front of the sun, it is known as a transit. The 1% accuracy is about right, however, and that is the main problem with this experiment: Poor precision. Much better precision is required to verify GR than that. Fortunately, other methods are in use, and have verified GR to much better precision.
« Last Edit: 22/05/2005 23:52:56 by gsmollin »
 

Offline DoctorBeaver

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Re: about black hole and vent horizon
« Reply #12 on: 23/05/2005 10:41:40 »
quote:
Originally posted by gsmollin

quote:



Actually, as far as I know, Mercury does not eclipse anything. When it passes in front of the sun, it is known as a transit.



In the experiment I was referring to Mercury passed behind the Sun & its re-appearance was observed
 

Offline gsmollin

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Re: about black hole and vent horizon
« Reply #13 on: 23/05/2005 19:56:12 »
Except for such observations being used to track the precession of mercury's orbit, I don't know about any experiment where the reflected light from mercury bending as it passed near the disk of the sun was used to verify GR. That experiment was the light from a distant star. If you have a source for this, I'd be glad to look at it.
 

Offline DoctorBeaver

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Re: about black hole and vent horizon
« Reply #14 on: 23/05/2005 21:02:23 »
quote:
Originally posted by gsmollin

If you have a source for this, I'd be glad to look at it.



I'll try to find something
 

Offline DoctorBeaver

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Re: about black hole and vent horizon
« Reply #15 on: 23/05/2005 21:06:26 »
OK, it looks as if I was getting the 2 experiments confused. My apologies [:I]
 

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Re: about black hole and vent horizon
« Reply #15 on: 23/05/2005 21:06:26 »

 

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