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"It has always struck me as kind of bizarre that we make assertions about what is beyond the event horizon of a black hole at all." Careful readers and writers

by jerf 3y ago

"It has always struck me as kind of bizarre that we make assertions about what is beyond the event horizon of a black hole at all." Careful readers and writers will observe that we do not. What physicists actually say is "IF this theory is true, THEN we can say this and that about what lies within a black hole." Since at the moment we do not have any satisfactory theory that accurately describes black holes, every such if-then statement is known to be flawed, and a careful thinker will recognize these as being exploratory examinations of what theories imply, and a search for testable predictions, rather than dogmatic declarations of the true nature of the universe. Sometimes, for instance, you can explore a theory and determine that it makes contradictory predictions, which means you can toss that one out. Exploring mathematical hypotheses is a perfectly sensible use of research time. However, careless readers, writers, and thinkers abound. I think it is the general sense of physicists in general that there probably isn't a singularity in a black hole. There is almost certainly something there that is sensible under some theory. Extreme, sure, but sensible. It is relativity and derived theories that specifically yield singularities, but we also know relativity is not a complete description of the universe. Even this article, if read carefully, is not saying "black holes do not in the real universe have singularities". It is saying something much more like "Previously physicists have accepted that IF the mathematics of Einsteinian relativity is true, THEN black holes have singularities. However, if you analyze the mathematics more carefuly, this IF-THEN does not in fact follow from the mathematics." It actually isn't a claim about the real universe, which is already known to not be purely described by Einsteinian relativity, but a claim about Einsteinian relativity qua Einsteinian relativity as a mathematical theory. Of course, the whole reason anyone talks about singularities in black holes at all is precisely Einsteinian relativity in the first place. Quantum mechanics isn't the reason, nor any other alternate Theory of Everything that I know of. So if they are removed there, we are left with no reason to suspect singularities exist in any sense. That still doesn't mean that we positively know what goes on under the event horizon. It would merely eliminate one "IF relativity THEN singularity" from our current discussion. Still progress in its own important way, but perhaps not as groundbreaking as a popular press treatment might claim.

corethree 3y ago
First off no statement in science can be proven true. It's just the nature of what science is, even Einstein knew this. In science and therefore reality as we know it, things can only be falsified. I talked about this in this thread through other posts. Second, was general relativity falsified or are you referring to generally accepted speculation? If it was falsified, do you have a source?
- jerf 3y ago
  The incompleteness of both relativity and quantum mechanics as a theory of everything is actually so obvious it can be hard to see: Relativity only has mass and gravity, and no electromagnetism, etc., and QM has no gravity. Therefore, it's quite obvious neither of them are the actual Theory of Everything. They also don't agree about the nature of the universe; relativity runs on classical space time on real numbers and QM says you can't just treat space as homogeneous on all scales. They can't both be right. I'm not making some whacky fringe claim here; this is actually completely mainstream physics. It just isn't as well understood by the laymen as it ought to be. The previous paragraph is a summary and you can get into lots of nuances and details and such, but in the end the underlying fact remains that at the moment nobody knows how to put relativity and QM together. We have several theories, none proved and all with problems, and there was even a new entrant this very week. Relativity and QM are two of the best theories we've ever had in the world, in terms of the number of digits of precision they are accurate to... and in some sense that is one of the biggest problems with them. We know they don't go together as written, but to know how to weave them into something that covers both domains correctly, we either need real-world phenomena that they do not correctly predict, or the ability to do experiments in the regime where they disagree (which is why black holes are so interesting to physicists), and we're basically empty handed for both those things.
Aerroon 3y ago
>That still doesn't mean that we positively know what goes on under the event horizon. Could the inside of a black hole be an "observable universe"? I ask because our observable universe is a little smaller than its Schwarzschild radius. Ie could our edges be an event horizon too?

by jerf 3y ago

corethree 3y ago

First off no statement in science can be proven true. It's just the nature of what science is, even Einstein knew this. In science and therefore reality as we know it, things can only be falsified. I talked about this in this thread through other posts. Second, was general relativity falsified or are you referring to generally accepted speculation? If it was falsified, do you have a source?

jerf 3y ago
The incompleteness of both relativity and quantum mechanics as a theory of everything is actually so obvious it can be hard to see: Relativity only has mass and gravity, and no electromagnetism, etc., and QM has no gravity. Therefore, it's quite obvious neither of them are the actual Theory of Everything. They also don't agree about the nature of the universe; relativity runs on classical space time on real numbers and QM says you can't just treat space as homogeneous on all scales. They can't both be right. I'm not making some whacky fringe claim here; this is actually completely mainstream physics. It just isn't as well understood by the laymen as it ought to be. The previous paragraph is a summary and you can get into lots of nuances and details and such, but in the end the underlying fact remains that at the moment nobody knows how to put relativity and QM together. We have several theories, none proved and all with problems, and there was even a new entrant this very week. Relativity and QM are two of the best theories we've ever had in the world, in terms of the number of digits of precision they are accurate to... and in some sense that is one of the biggest problems with them. We know they don't go together as written, but to know how to weave them into something that covers both domains correctly, we either need real-world phenomena that they do not correctly predict, or the ability to do experiments in the regime where they disagree (which is why black holes are so interesting to physicists), and we're basically empty handed for both those things.

Aerroon 3y ago

>That still doesn't mean that we positively know what goes on under the event horizon. Could the inside of a black hole be an "observable universe"? I ask because our observable universe is a little smaller than its Schwarzschild radius. Ie could our edges be an event horizon too?