Why light can't escape a Black Hole's gravity?

[juanrga]

Only matter is affected by gravity. And if light is made up of matter, why won't it destroy anything it goes through?

 

Would this answer be correct:

 

Black holes warp space-time so much that any particle that crosses the event horizon finds that simply moving forward in time also moves it toward the singularity at the center of the black hole. The only way anything could escape the black hole would be if it could travel faster than light. You can view an event horizon as being defined to be the boundary between an escape velocity that is lower than c and an escape velocity that has to be greater than c.

 

 

Another question that I can't answer is: Would light bounce between the event horizon and the mass? Because Professor Stephen Hawking says that not even a black hole is truly black.

So even in the slightest, light should reflect off the black hole but only to get sucked in again as it can't escape the event horizon.

 

It is not right that only matter is affected by gravity. Light is also affected. For instance light bends around Sun due to gravity.

 

Neither "light is made up of matter".

[morgsboi]

It is not right that only matter is affected by gravity. Light is also affected. For instance light bends around Sun due to gravity.

 

Neither "light is made up of matter".

 

This topic was a while ago. I did a lot of reading up on it. And no, light isn't affected as it is the light which follows the space-time (which has been warped by gravity).

[pmb]

It is not right that only matter is affected by gravity. Light is also affected. For instance light bends around Sun due to gravity.

 

Neither "light is made up of matter".

Physicists understand light to be a form of matter. This viewpoint started with Eintein when he wrote his papers on relativity. For example; in Einstein's 1916 paper which is a review on gravity. In section 14 Einstein writes

We make a distinction hereafter between "gravitational field" and "matter" in this way, that we denote everything but the gravitational field as "matter". Our use of the word includes not only matter in the ordinary sense but the electromagnetic field itself.

I had a rather new undergraduate physics text around here somewhere which defined the term in that way. I can't find it right now. But I know of no valid reason to use the term otherwise. In fact it makes sense to think of the electric field and magnetic field in this way too.

 

Neither "light is made up of matter".

On what basis do you make this assertion?

[juanrga]

This topic was a while ago. I did a lot of reading up on it. And no, light isn't affected as it is the light which follows the space-time (which has been warped by gravity).

 

And in general relativity, matter also follows the spacetime (which has been warped by gravity). One cannot say that matter is affected by gravity whereas light is not, when both are effected and 'bend'.

[pmb]

And in general relativity, matter also follows the spacetime (which has been warped by gravity). One cannot say that matter is affected by gravity whereas light is not, when both are effected and 'bend'.

What do you mean by matter also follows the spacetime ?

[juanrga]

Physicists understand light to be a form of matter. This viewpoint started with Eintein when he wrote his papers on relativity. For example; in Einstein's 1916 paper which is a review on gravity. In section 14 Einstein writes

 

I had a rather new undergraduate physics text around here somewhere which defined the term in that way. I can't find it right now. But I know of no valid reason to use the term otherwise. In fact it makes sense to think of the electric field and magnetic field in this way too.

 

On what basis do you make this assertion?

 

As shown in the other thread Einstein did many mistakes, his original thinking does not satisfy current scientific standards of rigour and precision (science has advanced a lot of since 1916), and his old quotes do not quality as an argument based in 'authority'.

 

The standard definition of matter can be found in chemistry and physics textbooks and shows that light is not usually considered a form of matter.

 

Feynman titled his book "QED: The strange theory of light and matter". Of course, he did not mean the strange theory of matter and matter

Edited April 16, 2012 by juanrga

[pmb]

As showed in the other thread Einstein did many mistakes, ...

And I said that everyone makes mistakes so the fact that Einstein made mistakes merely makes him human and nothing else and as such is insufficient reason for you to counter Einstein elsewhere.

...his original thinking does not satisfy current scientific standards of rigour and precision, and his old quotes do not quality as an argument based in 'authority'.

I merely quoted Einstein there for historical context, i.e. to show where the viewpoint "light has matter" started. To say that Einstein's thinking does not satisfy current scientific standards of rigour and precision is unjustified.

 

The standard definition of matter can be found in chemistry and physics textbooks and shows that light is not usually considered a form of matter.

The term "matter" is typically a vauge term which is never really defined in chemistry and physics textbooks.

[juanrga]

What do you mean by matter also follows the spacetime ?

 

That was my response to morgsboi and it seems evident that I am meaning the same than him when he wrote that "it is the light which follows the space-time". I have tried to state my point using his own wording for improving our communication. I was not trying to be technically precise and accurate.

 

And I said that everyone makes mistakes so the fact that Einstein made mistakes merely makes him human and nothing else and as such is insufficient reason for you to counter Einstein elsewhere.

 

I merely quoted Einstein there for historical context, i.e. to show where the viewpoint "light has matter" started. To say that Einstein's thinking does not satisfy current scientific standards of rigour and precision is unjustified.

 

The term "matter" is typically a vauge term which is never really defined in chemistry and physics textbooks.

 

Neither your claim that the term matter is not "defined in chemistry and physics textbooks" nor your deleting of my citation to Feynman book does surprise me, although the definition of the term matter can be found in standard textbooks .

 

However, your last claim that "matter is typically a vague term" after you initially stated that Einstein understood "light to be a form of matter" deserves some surprise .

[questionposter]

And I said that everyone makes mistakes so the fact that Einstein made mistakes merely makes him human and nothing else and as such is insufficient reason for you to counter Einstein elsewhere.

 

I merely quoted Einstein there for historical context, i.e. to show where the viewpoint "light has matter" started. To say that Einstein's thinking does not satisfy current scientific standards of rigour and precision is unjustified.

 

 

The term "matter" is typically a vauge term which is never really defined in chemistry and physics textbooks.

 

Einstein wasn't actually wrong. Both matter and energy distort the fabric of space, and in the newly developing world of quantum field theory, all of this "stuff", both matter and energy, can be described as various types of oscillations in various fields. Both a ball and a light beam are comprised merely of oscillating fields. I suppose it's more like it takes energy to oscillate, and that same energy will cause different oscillations in different fields, like matter fields or light particle fields.

Edited April 17, 2012 by questionposter

[Sanford]

The statement, “A black hole is a region of spacetime whose gravitational field is so strong that nothing which enters it, not even light, can escape”, taken from Wald, Robert M., General Relativity (1984) is dated. 21st publications clearly show this statement to be false. This is discussed by Aranoff in “Basic Assumptions and Black Holes”, Physics Essays 22, 559 (2009), and by Aranoff in Teaching and Helping Students Think and Do Better (2007). It is also discussed by Hynecek, “The Galileo effect and the general relativity theory”, Physics Essays 22, 4 (2009). This paper makes the following statement, “The Schwarzschild metric, which is the vacuum solution of Einstein field equations, is clearly a nonphysical metric and predicts the existence of such absurdities as black holes.”

 

It is surprising that people still accept old incorrect ideas!

 

The reasoning is simple. Due to time dilation, it takes forever to reach the black hole, and so it is meaningless to speak about the “inside”. The puzzle is that why then do so many discuss the inside. There is another solution of the equations for the viewpoint of an observer falling down the black hole. According to this solution, he enters the black hole in a finite time. However, this solution is not valid, as mathematicians have proven that at the center of the black hole there is a singularity, that is, the solution is not valid.

[MigL]

PMB and Juanrga can you guys stop arguing for a moment about the definition of matter ? Who really cares ?

Space-time affects mass-energy and compels it to follow its curvature, so yes photons and anything else with mass ( and don't start arguing about mass definitions either ) is affected by gravity.

Spyman lightspeed is c in all frames, strongly gravitating or not, even a far-off observer. Keep in mind that that speed is measured by arriving light signals which give distances travelled per unit time. Even light coming out of a black hole's event horizon is moving at c, although you'd never know it since it is red-shifted out of existence ( infinite wavelength and zero frequency ) upon escaping the event horizon.

As for Sanford, I think he has alot of misconceptions about the validity of GR inside the event horizon. It is only at very close distances to the possible singularity that GR must be modified by quantum effects. It is not meaningless to speak of the interior of the event horizon as time most certainly does not stop if you keep your frames straight.

[Spyman]

Spyman lightspeed is c in all frames, strongly gravitating or not, even a far-off observer.

Yes, agreed.

[granpa]

no.

 

to a far away observer, light near a black hole travels slowly.

 

but a local observer is equally time dilated so he would not notice.

 

light speed is constant only locally.

Edited May 30, 2012 by granpa

[swansont]

The statement, “A black hole is a region of spacetime whose gravitational field is so strong that nothing which enters it, not even light, can escape”, taken from Wald, Robert M., General Relativity (1984) is dated. 21st publications clearly show this statement to be false. This is discussed by Aranoff in “Basic Assumptions and Black Holes”, Physics Essays 22, 559 (2009), and by Aranoff in Teaching and Helping Students Think and Do Better (2007). It is also discussed by Hynecek, “The Galileo effect and the general relativity theory”, Physics Essays 22, 4 (2009). This paper makes the following statement, “The Schwarzschild metric, which is the vacuum solution of Einstein field equations, is clearly a nonphysical metric and predicts the existence of such absurdities as black holes.”

 

It is surprising that people still accept old incorrect ideas!

 

The reasoning is simple. Due to time dilation, it takes forever to reach the black hole, and so it is meaningless to speak about the “inside”. The puzzle is that why then do so many discuss the inside. There is another solution of the equations for the viewpoint of an observer falling down the black hole. According to this solution, he enters the black hole in a finite time. However, this solution is not valid, as mathematicians have proven that at the center of the black hole there is a singularity, that is, the solution is not valid.

 

!

Moderator Note

If you wish to discuss this further, please do so in in another thread. Publication in Physics Essays neither overturns nor establishes an idea as mainstream physics.

 

Response to this modnote should not happen in this thread.

[juanrga]

Space-time affects mass-energy and compels it to follow its curvature, so yes photons and anything else with mass ( and don't start arguing about mass definitions either ) is affected by gravity.

 

In general relativity, photons are considered massless particles. Photons are affected by gravity is because gravity curves spacetime and photons (or more correctly light signals if you want emphasize that general relativity is not a quantum theory) travel in a curved spacetime as any other object does, was massive or not.

 

Search "massless" in this introduction to general relativity and you will find the geodesics for light signals. And if you search the term again you will find the equation of motion for a massless particle in a Schwarzschild spacetime. This equation and the rest of the discussion therein explains why light cannot explain black holes (see also figure 2).

Edited May 30, 2012 by juanrga

[MigL]

Sorry Juan but I don't see the significance of your link, it doesn't negate anything I've said.

 

Light is affected by gravity because its energy is equivalent to mass. The zero 'rest mass' of a massless particle is a defined concept because massless particles only travel at c ( no matter what Granpa says ). They can never be at rest.

 

Oh no !! Now you've got me arguing about the definition of mass !

Edited May 30, 2012 by MigL

[descovery2time]

Only matter is affected by gravity. And if light is made up of matter, why won't it destroy anything it goes through?

 

Would this answer be correct:

 

Black holes warp space-time so much that any particle that crosses the event horizon finds that simply moving forward in time also moves it toward the singularity at the center of the black hole. The only way anything could escape the black hole would be if it could travel faster than light. You can view an event horizon as being defined to be the boundary between an escape velocity that is lower than c and an escape velocity that has to be greater than c.

 

 

Another question that I can't answer is: Would light bounce between the event horizon and the mass? Because Professor Stephen Hawking says that not even a black hole is truly black.

So even in the slightest, light should reflect off the black hole but only to get sucked in again as it can't escape the event horizon.

 

I believe in Hawkins universe when matter is suck into a blackhole it is crushed by gravity force so powerful that matter,time and space is literally crushed out of existance.Hawkins believes there are parts of the universe that is disappearing into nothing.Even the particle information is lost.

 

i dont know

[juanrga]

Sorry Juan but I don't see the significance of your link, it doesn't negate anything I've said.

 

Light is affected by gravity because its energy is equivalent to mass. The zero 'rest mass' of a massless particle is a defined concept because massless particles only travel at c ( no matter what Granpa says ). They can never be at rest.

 

Oh no !! Now you've got me arguing about the definition of mass !

 

I tried to explain that one can describe the behaviour of massless particles such as photons in presence of gravity, without any need to attribute to them a fictitious 'mass' (which is ill-defined and variable).

 

Notice that I never use the term rest-mass because it is a misnomer, specially for photons because they are never at rest are you correctly point!

[MigL]

Ok juan, sorry I'm a little dense sometimes. Thanks for the clarification.

[juanrga]

Ok juan, sorry I'm a little dense sometimes. Thanks for the clarification.

 

You are welcome