Mar 15, 2024 06:25 PM
Do black holes explode? The 50-year-old puzzle that challenges quantum physics
https://www.nature.com/articles/d41586-024-00768-4
INTRO: In hindsight, it seems prophetic that the title of a Nature paper published on 1 March 1974 ended with a question mark: “Black hole explosions?” Stephen Hawking’s landmark idea about what is now known as Hawking radiation has just turned 50. The more physicists have tried to test his theory over the past half-century, the more questions have been raised — with profound consequences for how we view the workings of reality.
In essence, what Hawking, who died six years ago today, found is that black holes should not be truly black, because they constantly radiate a tiny amount of heat. That conclusion came from basic principles of quantum physics, which imply that even empty space is a far-from-uneventful place. Instead, space is filled with roiling quantum fields in which pairs of ‘virtual’ particles incessantly pop out of nowhere and, under normal conditions, annihilate each other almost instantaneously.
However, at an event horizon, the spherical surface that defines the boundary of a black hole, something different happens. An event horizon represents a gravitational point of no return that can be crossed only inward, and Hawking realized that there two virtual particles can become separated. One of them falls into the black hole, while the other radiates away, carrying some of the energy with it. As a result, the black hole loses a tiny bit of mass and shrinks — and shines... (MORE - details)
Swirling forces, crushing pressures measured in the proton
https://www.quantamagazine.org/swirling-...-20240314/
EXCERPTS: Physicists have begun to explore the proton as if it were a subatomic planet. Cutaway maps display newfound details of the particle’s interior. The proton’s core features pressures more intense than in any other known form of matter. Halfway to the surface, clashing vortices of force push against each other. And the “planet” as a whole is smaller than previous experiments had suggested.
The experimental investigations mark the next stage in the quest to understand the particle that anchors every atom and makes up the bulk of our world.
“We really see it as opening up a completely new direction that will change our way of looking at the fundamental structure of matter,” said Latifa Elouadrhiri, a physicist at the Thomas Jefferson National Accelerator Facility in Newport News, Virginia, who is involved in the effort.
The experiments literally shine a new light on the proton. Over decades, researchers have meticulously mapped out the electromagnetic influence of the positively charged particle. But in the new research, the Jefferson Lab physicists are instead mapping the proton’s gravitational influence — namely, the distribution of energies, pressures and shear stresses throughout, which bend the space-time fabric in and around the particle. The researchers do so by exploiting a peculiar way in which pairs of photons, particles of light, can imitate a graviton, the hypothesized particle that conveys the force of gravity. By pinging the proton with photons, they indirectly infer how gravity would interact with it, realizing a decades-old dream of interrogating the proton in this alternative way.
“It’s a tour de force,” said Cédric Lorcé, a physicist at the Ecole Polytechnique in France who was not involved in the work. “Experimentally, it’s extremely complicated.”
[...] They found that in the heart of the proton, the strong force generates pressures of unimaginable intensity — 100 billion trillion trillion pascals, or about 10 times the pressure at the heart of a neutron star. Farther out from the center, the pressure falls and eventually turns inward, as it must for the proton not to blow itself apart. “This comes out of the experiment,” Burkert said. “Yes, a proton is actually stable.” (MORE - missing details)
https://www.nature.com/articles/d41586-024-00768-4
INTRO: In hindsight, it seems prophetic that the title of a Nature paper published on 1 March 1974 ended with a question mark: “Black hole explosions?” Stephen Hawking’s landmark idea about what is now known as Hawking radiation has just turned 50. The more physicists have tried to test his theory over the past half-century, the more questions have been raised — with profound consequences for how we view the workings of reality.
In essence, what Hawking, who died six years ago today, found is that black holes should not be truly black, because they constantly radiate a tiny amount of heat. That conclusion came from basic principles of quantum physics, which imply that even empty space is a far-from-uneventful place. Instead, space is filled with roiling quantum fields in which pairs of ‘virtual’ particles incessantly pop out of nowhere and, under normal conditions, annihilate each other almost instantaneously.
However, at an event horizon, the spherical surface that defines the boundary of a black hole, something different happens. An event horizon represents a gravitational point of no return that can be crossed only inward, and Hawking realized that there two virtual particles can become separated. One of them falls into the black hole, while the other radiates away, carrying some of the energy with it. As a result, the black hole loses a tiny bit of mass and shrinks — and shines... (MORE - details)
Swirling forces, crushing pressures measured in the proton
https://www.quantamagazine.org/swirling-...-20240314/
EXCERPTS: Physicists have begun to explore the proton as if it were a subatomic planet. Cutaway maps display newfound details of the particle’s interior. The proton’s core features pressures more intense than in any other known form of matter. Halfway to the surface, clashing vortices of force push against each other. And the “planet” as a whole is smaller than previous experiments had suggested.
The experimental investigations mark the next stage in the quest to understand the particle that anchors every atom and makes up the bulk of our world.
“We really see it as opening up a completely new direction that will change our way of looking at the fundamental structure of matter,” said Latifa Elouadrhiri, a physicist at the Thomas Jefferson National Accelerator Facility in Newport News, Virginia, who is involved in the effort.
The experiments literally shine a new light on the proton. Over decades, researchers have meticulously mapped out the electromagnetic influence of the positively charged particle. But in the new research, the Jefferson Lab physicists are instead mapping the proton’s gravitational influence — namely, the distribution of energies, pressures and shear stresses throughout, which bend the space-time fabric in and around the particle. The researchers do so by exploiting a peculiar way in which pairs of photons, particles of light, can imitate a graviton, the hypothesized particle that conveys the force of gravity. By pinging the proton with photons, they indirectly infer how gravity would interact with it, realizing a decades-old dream of interrogating the proton in this alternative way.
“It’s a tour de force,” said Cédric Lorcé, a physicist at the Ecole Polytechnique in France who was not involved in the work. “Experimentally, it’s extremely complicated.”
[...] They found that in the heart of the proton, the strong force generates pressures of unimaginable intensity — 100 billion trillion trillion pascals, or about 10 times the pressure at the heart of a neutron star. Farther out from the center, the pressure falls and eventually turns inward, as it must for the proton not to blow itself apart. “This comes out of the experiment,” Burkert said. “Yes, a proton is actually stable.” (MORE - missing details)