Dec 7, 2023 12:34 AM
https://bigthink.com/starts-with-a-bang/...-roy-kerr/
KEY POINTS: Way back in 1963, Roy Kerr became the first person to write down the exact solution, in general relativity, for a realistic, rotating black hole. 60 years later, it's still used everywhere. Although Roger Penrose won the Nobel Prize in physics just a few years ago for demonstrating how black holes come to exist in our Universe, singularities and all, the subject isn't closed. We've never peered beneath the event horizon, and have no way of detecting what's inside. Using a powerful mathematical argument, Kerr argues that singularities shouldn't physically exist. He may be right.
EXCERPTS: . . . the question of what spacetime looks like if you have a mass that rotates is much more complicated. Indeed, many brilliant physicists worked on this problem and were unable to solve it: for months, years, and even decades.
But then, in 1963, New Zealand physicist Roy Kerr finally cracked it. His solution for the spacetime describing realistic, rotating black holes — the Kerr metric — has been the gold standard for what relativists have used to describe it ever since.
[...] Instead of a single, spherical surface describing the event horizon and a point-like singularity at the center, the addition of rotation causes there to be several important phenomena that aren’t apparent in the non-rotating case.
However, demonstrating a counterexample to your attempted proof, both physically and mathematically, is an excellent way to falsify any assertion that gets made. With Kerr’s latest work — a full 60 years after first deriving the Kerr metric — we have to reckon with the sober fact that our best “singularity theorems” that argue for their necessity at a realistic black hole’s center are based on an invalid assumption.
Furthermore, once you cross over to be inside the inner event horizon in Kerr spacetime, it once again becomes possible to travel in any direction between the theorized ring singularity and the inner event horizon. The “trapped surface” only exists between the inner and outer event horizons, not interior to the inner event horizon: where the ring singularity allegedly exists. Who knows what exists in that region? The problem is that there are enormous numbers of mathematical solutions to this problem, and “a singularity” is only one of them. There might indeed yet be a singularity inside, but there also may be something entirely different. Kerr, currently at the age of 89, has no problem telling us what he thinks, writing that he:
“has no doubt, and never did, that when relativity and quantum mechanics are melded it will be shown that there are no singularities anywhere. When theory predicts singularities, the theory is wrong!”
What we can be certain of is that the long-accepted “proof,” that rotating black holes must have singularities, can’t be counted on any longer. You can download and read Kerr’s latest paper for free here. ...... (MORE - missing details)
KEY POINTS: Way back in 1963, Roy Kerr became the first person to write down the exact solution, in general relativity, for a realistic, rotating black hole. 60 years later, it's still used everywhere. Although Roger Penrose won the Nobel Prize in physics just a few years ago for demonstrating how black holes come to exist in our Universe, singularities and all, the subject isn't closed. We've never peered beneath the event horizon, and have no way of detecting what's inside. Using a powerful mathematical argument, Kerr argues that singularities shouldn't physically exist. He may be right.
EXCERPTS: . . . the question of what spacetime looks like if you have a mass that rotates is much more complicated. Indeed, many brilliant physicists worked on this problem and were unable to solve it: for months, years, and even decades.
But then, in 1963, New Zealand physicist Roy Kerr finally cracked it. His solution for the spacetime describing realistic, rotating black holes — the Kerr metric — has been the gold standard for what relativists have used to describe it ever since.
[...] Instead of a single, spherical surface describing the event horizon and a point-like singularity at the center, the addition of rotation causes there to be several important phenomena that aren’t apparent in the non-rotating case.
- Instead of a single solution for the location of the event horizon, as in the Schwarzschild case, the equation you wind up with in the Kerr case is quadratic, giving two separate solutions: an “outer” and “inner” event horizon.
- Instead of the event horizon marking the location where the timelike component of the metric flips sign, there are now two surfaces that are different from the inner and outer event horizons — the inner and outer ergospheres — that delineate those locations throughout space.
- And instead of a zero-dimensional, point-like singularity at the center, the angular momentum present smooths that singularity into a one-dimensional surface: a ring, with the rotational axis of the black hole passing perpendicular through the center of the ring.
However, demonstrating a counterexample to your attempted proof, both physically and mathematically, is an excellent way to falsify any assertion that gets made. With Kerr’s latest work — a full 60 years after first deriving the Kerr metric — we have to reckon with the sober fact that our best “singularity theorems” that argue for their necessity at a realistic black hole’s center are based on an invalid assumption.
Furthermore, once you cross over to be inside the inner event horizon in Kerr spacetime, it once again becomes possible to travel in any direction between the theorized ring singularity and the inner event horizon. The “trapped surface” only exists between the inner and outer event horizons, not interior to the inner event horizon: where the ring singularity allegedly exists. Who knows what exists in that region? The problem is that there are enormous numbers of mathematical solutions to this problem, and “a singularity” is only one of them. There might indeed yet be a singularity inside, but there also may be something entirely different. Kerr, currently at the age of 89, has no problem telling us what he thinks, writing that he:
“has no doubt, and never did, that when relativity and quantum mechanics are melded it will be shown that there are no singularities anywhere. When theory predicts singularities, the theory is wrong!”
What we can be certain of is that the long-accepted “proof,” that rotating black holes must have singularities, can’t be counted on any longer. You can download and read Kerr’s latest paper for free here. ...... (MORE - missing details)