Can we truly know the fate of objects in black holes?

[DaveC426913]

Please note though that I'm making an assumption that there is an objective, independent reality. I know of no way to prove that that reality exists. Physics is an incomplete body of knowledge because you cannot prove within physics that its basis, the physical world, exists. You would need to go beyond physics to prove that reality exists. To do so may be impossible.

You do not have to assume an objective, independent reaility.

You merely have to do several different tests on the same thing. You will discover that some of your tests lead to conflicting answers (the straw looks bent from one angle, yet straight from another angle) while some corroborate each other (I can stick a darning needle down the straw, I can pull the straw out and see it's not bent, I can apply optics to the problem and see why it looks bent but isn't).

Whether or not there is some "objective" reality, you can arrive at an internally consistent reality that has no contradictions.

Such as concluding that, say "the straw is straight; it's the light rays that are bent".

With all due respect, Christopher, why should I believe you rather than Scientific American?

Don't.

Instead, look for verification. You've come to a science forum to clear something up and they're refuting Sci Am. Is it plausible that SciAm was glossing over a point, and that, if given a chance, they would clarify?

 

[SpectraCat]

You should believe him because he is explaining to you the mainstream view of what happens when something falls into a black hole. I will add my name to the chorus of those who have never heard the terminology "incinerated" used to describe what happens at the EH of a black hole.

For example, consider this passage from the wikipedia article Black Holes (I cite it not because it is from Wikipedia so much as that it is properly attributed to external sources).

"To a distant observer, clocks near a black hole appear to tick more slowly than those further away from the black hole.[44] Due to this effect, known as gravitational time dilation, an object falling into a black hole appears to slow down as it approaches the event horizon, taking an infinite time to reach it.[45] At the same time, all processes on this object slow down causing emitted light to appear redder and dimmer, an effect known as gravitational redshift.[46] Eventually, at a point just before it reaches the event horizon, the falling object becomes so dim that it can no longer be seen.

On the other hand, an observer falling into a black hole does not notice any of these effects as he crosses the event horizon. According to his own clock, he crosses the event horizon after a finite time, although he is unable to determine exactly when he crosses it, as it is impossible to determine the location of the event horizon from local observations.[47]

The shape of the event horizon of a black hole is always approximately spherical.[Note 2][50] For non-rotating (static) black holes the geometry is precisely spherical, while for rotating black holes the sphere is somewhat oblated."

That is the description I am familiar with .. notice the lack of reference to any "incineration". I would suggest you choose another reference (preferably a physics or astronomy textbook), and read up on black holes there to decide for yourself whether or not "incinerate" is likely to be a correct description of what happens in the example you cited.

 

[disregardthat]

It strikes me that this is exactly equivalent to saying that when I drive down the highway and pass the 14 mile marker, you now get to say that I don't have a valid frame of reference because I have passed the 14 mile marker. It clearly doesn't make sense.

The event horizon is utterly irrelevant to a person falling into a black hole as he falls in, it's just a place where he no longer has the option of getting back out again. What's relevant is spaghettification and that that does not have anything to do with the EH. For big BH's it will happen inside the EH and for small ones outside.

I guess I am stuck with special relativity intuition, thanks to you and Dalespam for clarifying.

 

[Jagella]

With all due respect, Christopher, why should I believe you rather than Scientific American?

Because of what I said in the first line of my first post.

I don't believe we've made much progress. I ask you why I should believe what you've said, and you tell me to believe what you've said!

Laying all jokes aside, we are running into the same kind of problem when we judge the credibility of sources as we run into when we judge physics and its ability to give us information about reality. In order to judge the credibility of what you say, Christopher, it's not enough to rely on what you say. Anything you say to establish the credibility of what you say runs into the same problem: I'm still left wondering if what you're saying is credible. Your statements as a system is incomplete in that nothing you say, even if true, can establish the truth of what you say. We need to go beyond your mere statements to assess your credibility as a source of information.

Physics encounters the same problem. If we challenge physics as a source of truth about the real world, then any attempt to use physics to lend credibility to itself falls flat on its face. We get nowhere because any theory in physics, no matter how well tested, is still based on the assumption that physics is based on reality. You cannot sensibly assume what you are trying to prove. It's like saying that God must exist because he wrote the Bible.

But you don't have to take my word for it! Study physics yourself! It's fascinating, but you have to start with the boring stuff unfortunately.

I do study physics. The “boring stuff” I'm studying now is the thermal properties of matter. How many people know what causes a bubble to burst at the surface of boiling water?

Here is a quote from Stephen Hawking:

"I don’t demand that a theory corresponds to reality, because I don’t know what it is. Reality is not a quality you can test with a litmus paper. All I’m concerned about is that the theory should predict the results of measurement."

Yes, that sounds right to me. Physics works just fine in making predictions about what the measurement of something might be.

Jagella

 

[DaveC426913]

Physics encounters the same problem. If we challenge physics as a source of truth about the real world, then any attempt to use physics to lend credibility to itself falls flat on its face.

No. It is what is known as a preponderance of evidence. No one test or source of authority gets anywhere in science. It is an accumulation - a preponderance - that tells us one idea is much more likely to be correct than another. It is also why a competing theory gets trounced fairly quickly, and will stay in the sidelines until mounting evidence puts it in favour over the incumbent theory.

We get nowhere because any theory in physics, no matter how well tested, is still based on the assumption that physics is based on reality.

This line of reasoning has been explored many, many times both here on PF and throughout history (and in movies - a la The Matrix). It's a dead end.

Our reality is what we observe. If the whole universe were great big lie, it would not matter. We study what the universe gives us. That is our reality.

 

[Feeble Wonk]

As a non-physicist, I must side with Jagella... at least in one respect. We are looking to the "science" of physics to help us understand what REALITY is. It is not sufficient to simply balance the equations. It is not enough to make accurate predictions based on previously established patterns. I am not disputing the accuracy of the mathematics. Indeed... I marvel at the beauty and elegance. But, WHAT does it mean about the nature of existence?
I understand that this "looking at the deeper questions" is not necessary to pursuit of the scientific method. It might, in fact, act as a distraction to those that do this for a living. But those of us on the outside are depending on the professional physicists to explain what they mean. We are educated enough to accept that science is the route to the truth... and yet, we are still naive enough to believe that there IS a truth.

 

[Drakkith]

As a non-physicist, I must side with Jagella... at least in one respect. We are looking to the "science" of physics to help us understand what REALITY is. It is not sufficient to simply balance the equations. It is not enough to make accurate predictions based on previously established patterns. I am not disputing the accuracy of the mathematics. Indeed... I marvel at the beauty and elegance. But, WHAT does it mean about the nature of existence?
I understand that this "looking at the deeper questions" is not necessary to pursuit of the scientific method. It might, in fact, act as a distraction to those that do this for a living. But those of us on the outside are depending on the professional physicists to explain what they mean. We are educated enough to accept that science is the route to the truth... and yet, we are still naive enough to believe that there IS a truth.

You know, I had like 3 paragraphs a had written in response to this, but then I realized that it was pointless.

 

[Dale]

We are looking to the "science" of physics to help us understand what REALITY is. It is not sufficient to simply balance the equations. It is not enough to make accurate predictions based on previously established patterns.

Then you are looking in the wrong place. Science can never tell you anything other that whether or not the equations give accurate predictions. Anything beyond that is philosophy or religion, not physics.

 

[Feeble Wonk]

Perhaps I didn't express myself very well. I'm not expecting science to answer questions about the "meaning of life". I simply would like to have a more articulate description of the concepts being discussed. For instance, if theory defines a fundamental "particle" as having zero spatial dimension, what are you really describing. Is that supposed to be something that represents material reality? If not, what then?

 

[phinds]

Perhaps I didn't express myself very well. I'm not expecting science to answer questions about the "meaning of life". I simply would like to have a more articulate description of the concepts being discussed. For instance, if theory defines a fundamental "particle" as having zero spatial dimension, what are you really describing. Is that supposed to be something that represents material reality? If not, what then?

Science at any given point in history gives what is the best representation of physical reality that it is possible to have given the knowledge and assumptions of the time. Then, often, someone comes along and shows that there is a way of looking at things that gives a better picture of reality.

Excellent examples of this are

(1) the "epicycle" view of planetary motion being overtaken by the understanding that the orbits are elliptical. The epicycle view at the end of its life gave extremely accurate predictions about planetary motion, but betrayed a flawed understanding of the underlying reality. The newer theory gave a much better picture of reality AND provided even better fine-grain predictions.
(2)Newton's theory of gravity gave OUTSTANDINGLY good predictions about physical reality and was firmly believed to be a fundamental description of reality. Einstein didn't prove Newton wrong so much as he just showed the Newton's description was very limited and Special and General Relativity give a much better picture of a deeper understanding of reality and make accurate predictions in situations where Newton's law does not.

In Newton's time there was a strong belief that "final" answers were known, so "Newton's Law of Gravity" is called a "law" whereas now Einstein's theory of relativety is called a "theory". This is not because Newton's "law" is a more firm description of reality (quite the opposite is true) but because "law" has a presumption of finality that physicists wisely avoid these days, knowing as they do that the best current attempts to describe reality could well be subject to improvement tomorrow.

So all of that is a very longwinded way of saying that yes, the description that physicists give today of reality DOES represent reality to an extent, but perhaps not to the extent that you would like.

For example, relativity breaks down at the quantum level so is KNOWN to not be a final description. We need a quantum theory of gravity, and I believe that when we find it, it will not show that relativity is wrong, so much as just show (which we already know) that it breaks down in some situations and that the new theory extends our understanding. Will THAT theory be final? Good question.

So does a dimensionless particle represent reality? Hell, I don't know ... all I know is that yes it does, to the best of our abiltiy to currently describe reality. This brings us back to DaleSpam's statement "Science can never tell you anything other that whether or not the equations give accurate predictions. Anything beyond that is philosophy or religion, not physics. " which is not how I would have expressed it, but a statement that I would not take issue with.

 

[DaveC426913]

I simply would like to have a more articulate description of the concepts being discussed. For instance, if theory defines a fundamental "particle" as having zero spatial dimension, what are you really describing.

You're not looking for a more articulate description, you're looking for a less articulate description.

There is no concept you have that will cause a zero-dimensional particle to make sense. To make sense, you'll have to compare it to something you know, model it after something you know.

But there is nothing to compare it to. Any description will have to be flawed.

You would no expect to understand anything about genetics without learning the lingo would you? Same with physics, it's just the lingo is numbers.

 

[Christopher G]

Crap guys, looks like you might get incinerated after all...

http://arxiv.org/abs/0811.1926

BUT, you would be 'comfortably' within the outer horizon before this happens... So I guess we are still correct!

 

[phinds]

If I correctly understand the synopsis linked to then for a person falling into a black hole with nothing else infalling at the same time, this is irrelevant and there is no incineration. Am I missing something?

 

[Drakkith]

If I correctly understand the synopsis linked to then for a person falling into a black hole with nothing else infalling at the same time, this is irrelevant and there is no incineration. Am I missing something?

I think that covers it.

 

[Christopher G]

There is always something falling into a black hole. Dark matter, CMB radiation... Other stuff?

I may not have understood what you meant.

I'm pretty tired at this point, so I'm just going to read it tomorrow.