Priyamvada Natarajan, wrote about black holes:
How do you think about black holes?
They’re crazy objects, no question; they’re bizarre. There are three ways to think about them, and you can choose. One way is that stars, when they exhaust their fuel, have a violent end, and they leave behind — like a dead nuclear reactor — these black holes.
So black holes are compact inner parts of the stars that have gravitationally collapsed and have become unbelievably dense.
There’s no analogue. It’s not lead; it’s nothing we can think of. Then these stellar remnants build up. Gas falls in. They become bigger.
I want a certain depth of understanding that comes with people who think mathematically.
Another way is to think about the fact that not even light can escape from a black hole.
If you want to launch a rocket that has to escape the gravitational grip of the Earth, we have to shoot it out at 11.6 kilometers per second. That’s 33 times the speed of sound, so it’s pretty fast.
Now imagine a rocket going out at the speed of light, 300,000 kilometers per second, and it still can’t escape, because the gravitational grip is so strong.
That’s a black hole.
The third way is if you picture space-time as a sheet, then a black hole is a pinch in that sheet. An anomaly in the shape of space.
I have many problems with the above.
My first objection was that defining the same concept in three different ways and then choosing one depending on the context amounted to casuistry. But Ms. Natarajan replied that this was hot the case:
Nope — it’s not — I don’t use these definitions as needed.
These are three different ways to think about black holes – that are – enigmatic, complex and have defied a single definition — this is just how it is — like it or not!
I’m sorry but I take this seriously. First of all words like “bizarre”, “crazy”, “enigmatic” and “complex” as qualities of black holes says nothing to me. Second, you say there are three definitions of black holes and “you can choose.” But when I say “you choose one as needed” you deny that you choose one depending on the problem. This is not clear to me. Are there three types of black holes with different characteristics? Are these independent definitions? One definition you offer is that a black hole is an object from which even light cannot escape. Is this valid for all three definitions of black holes?
Physicists define a black hole as an infinitely dense mathematical point, then objectify it as a sinkhole from which even light cannot escape but then they invent countless loopholes in order to do physics with these supernatural objects. After all, if it were true that no light could escape from a black hole, no physics could be done with such an object.
By definition, a black hole excludes electromagnetism and therefore it is a non-physical object. It cannot even be an “object” because an object is something that obeys physics. So in order to make black holes to play physics, physicists let black holes grow hair, they let them collide and merge. All these thermodynamical interactions happen but light cannot escape! How so? I think the best definition of a black hole would be this: A black hole is a suspension of disbelief.
I also take issue with your third definition. You tell us to think about a black hole as a “pinch” on the space-time defined as a sheet. Then you forget that you said “space-time” and say that a black hole is an anomaly of “space”. Where do black holes live? In spacetime or in space?
To ask us to imagine spacetime as a sheet is an insult to our intelligence. You know and we know that spacetime is not a sheet. So why are you telling us to assume that spacetime is a sheet and black hole is a pinch in that sheet? The sheet metaphor is just a metaphor and explains nothing. It hides the true explanation, if there is any.
You say “I want a certain depth of understanding that comes with people who think mathematically.” But mathematics can be used to quantify even absurd and bizarre objects. The fact that you can study an object mathematically does not prove that that object exists. We know that Mickey Mouse does not exist. But you can define his weight, height and age and study his properties mathematically. But Mickey Mouse will still be a fictional object. Same with black holes. Unless you have a single physical definition of a black hole that applies to all black holes, what you have will be sophistry. Sophistry or doubletalk happens when a concept is defined many times.
Three definitions of black holes:
1. Stars exhaust their fuel and have a violent end and turn into black holes. I think this type of black hole is assumed to be an infinitely dense mathematical point. Which is absurd.
2. We call a black hole an object from which light cannot escape. It’s strange because this black hole is so dense and small but it harbors light in it and this light cannot escape from it. But you are not talking about light per se but a rocket going with the speed of light. So a black hole is an infinitely dense and infinitely small mathematical point which said to be an “object” and we are talking about a rocket escaping from this objectified mathematical point. We don’t even know if a black hole has a surface from which a rocket can be fired. So we are really in the realm of speculative thought experiments presented as physical truths. We are building absurdity upon absurdity and no one is worried about all these absurd reasoning.
3. Think about a black hole as a metaphor. This is the classic “spacetime as a sheet” metaphor. A black hole is a “pinch” on that sheet. What a meaningless metaphor! It explains nothing. Effectively it means “take my word for it. Believe what I say. I’m an expert on black holes and you are not.” So you are asking us to believe your authority without question.
So what do we learn from these three definitions of black holes?
A black hole is an infinitely dense mathematical pinch in the fabric of spacetime (or space) from which light cannot escape. Where does this light reside in an infinitely dense mathematical point? That is absurd. We defined it as infinitely dense. It may even be pure gravity. It can contain no light. But it is defined in terms of light.
From this I conclude that absurd is legal in physics. We are living in an absurd world. The more absurd the better.
— Casuistry or case-based reasoning, is a method in applied ethics and jurisprudence, often characterised as a critique of principle- or rule-based reasoning. https://en.wikiquote.org/wiki/Casuistry
— Black holes is said to form with gravitational collapse. But what physicists call gravitational collapse is nothing more than lifting oneself up by shoestrings, that will not happen. Gravitational collapse fairy tale violates all of the laws of thermodynamics: