Nov 17, 2021 04:46 PM
(This post was last modified: Nov 17, 2021 06:48 PM by C C.)
Why can’t black holes be made of dark matter?
https://bigthink.com/starts-with-a-bang/...rk-matter/
KEY POINTS: If enough mass gathers together in one small volume of space, a black hole will inevitably form. Five-sixths of the mass in the Universe is made of dark matter, and just one-sixth is normal matter. And yet, we're quite certain that all black holes in the Universe formed from normal matter, not dark matter. Here's why... (MORE)
Wormholes may be viable shortcuts through space-time after all, new study suggests
https://www.livescience.com/wormholes-ma...-after-all
EXCERPTS: Wormholes, or portals between black holes, may be stable after all, a wild new theory suggests. The findings contradict earlier predictions that these hypothetical shortcuts through space-time would instantly collapse. The sea change comes because tiny differences in the mathematics of relativity, which is used to describe such wormholes, end up dramatically changing our overall picture of how they behave.
[...] Koiran's result is still interesting because it points out that wormholes aren't quite as catastrophic as they first appeared, and that there may be stable paths through wormhole tunnels, perfectly allowed by general relativity... (MORE - missing details)
How the best alternative to “quantum spookiness” failed
https://bigthink.com/starts-with-a-bang/...pookiness/
KEY POINTS: Until the discovery of radioactivity and quantum physics, every particle and interaction was thought to obey completely deterministic equations. Quantum mechanics can only yield an indeterminate probability distribution of outcomes. It cannot tell you what comes next. The leading deterministic interpretation, involving hidden variables, is called Bohmian mechanics. Its only distinct prediction was just falsified.
EXCERPTS: . . . In the early days of quantum mechanics, de Broglie gained fame for showing that it wasn’t simply light that possessed a dual nature of being simultaneously wave-like and particle-like, but that matter itself possesses a wave-like nature when subjected to the proper quantum conditions. His formula for calculating the wavelength of “matter waves” is still widely used today, and to de Broglie, it’s because we ought to be taking the dual nature of quanta literally.
In de Broglie’s version of quantum physics, there were always concrete particles, with definite (but not always well-measured) positions to them, that are guided through space by these quantum mechanical wavefunctions, which he called “pilot waves.” Although de Broglie’s version of quantum physics couldn’t describe systems with more than one particle, and suffered from the challenge of not being able to measure or identify precisely what was “physical” about the pilot wave, it represented an interesting alternative to the Copenhagen interpretation.
Instead of being governed by the weird rules of quantum spookiness, there was an underlying, hidden reality that was completely deterministic. Many of de Broglie’s ideas were expanded upon by other researchers, who all sought to discover a less “spooky” alternative to the quantum reality that generations of students, with no superior alternative, had been compelled to accept.
Perhaps the most famous extension came courtesy of the physicist David Bohm, who in the 1950s developed his own interpretation of quantum physics: the de Broglie-Bohm (or pilot wave) theory. The underlying wave equation, in this idea, is the same as the conventional Schrodinger equation, as in the Copenhagen interpretation. However, there’s also a guiding equation that acts on the wavefunction, and properties like the position of a particle can be extracted from the relationship of that guiding equation. It’s an explicitly causal, deterministic interpretation, with a fundamental non-locality to it.
But this interpretation posed its own difficulties...
[...] In many ways, pilot wave theory was more of an interesting counterexample to the assertion that “no hidden variable theory could reproduce the success of quantum indeterminism.” It could, as Bohm’s pilot wave theory illustrated, but at the cost of a fundamental non-locality and the difficult notion of having to extract physical properties from a guiding equation, whose results are not necessarily straightforward to work with.
[...] As the perfectly valid Copenhagen interpretation has long demonstrated, however, just because something is counterintuitive or even illogical doesn’t mean it’s incorrect. Physical behavior is often more bizarre than we’d ever expect, and that is why we must always confront our predictions with the harsh reality of experiments.
[...] What appeared to be random, in these experiments, wasn’t truly random at all, but rather provided a thrilling confirmation of the ideas of pilot wave theory.And then it all fell apart...
[...] We may not have the ultimate “right answer” to the question of how the Universe works, but we have knocked down a tremendous number of pretenders from the throne. If your predictions disagree with experiments, your theory is wrong, no matter how popular or pretty it happens to be. We have not yet ruled out all possible incarnations of Bohmian mechanics, or pilot wave theories, or quantum mechanics interpretations that have hidden variables. It may not ever be possible to do so. However, every attempt to construct a theory that agrees with experiment requires some level of quantum spookiness that simply cannot be done away with. The least spooky alternative has now been falsified, as a single, concrete reality cannot describe all that we observe and measure... (MORE - missing details)
https://bigthink.com/starts-with-a-bang/...rk-matter/
KEY POINTS: If enough mass gathers together in one small volume of space, a black hole will inevitably form. Five-sixths of the mass in the Universe is made of dark matter, and just one-sixth is normal matter. And yet, we're quite certain that all black holes in the Universe formed from normal matter, not dark matter. Here's why... (MORE)
Wormholes may be viable shortcuts through space-time after all, new study suggests
https://www.livescience.com/wormholes-ma...-after-all
EXCERPTS: Wormholes, or portals between black holes, may be stable after all, a wild new theory suggests. The findings contradict earlier predictions that these hypothetical shortcuts through space-time would instantly collapse. The sea change comes because tiny differences in the mathematics of relativity, which is used to describe such wormholes, end up dramatically changing our overall picture of how they behave.
[...] Koiran's result is still interesting because it points out that wormholes aren't quite as catastrophic as they first appeared, and that there may be stable paths through wormhole tunnels, perfectly allowed by general relativity... (MORE - missing details)
How the best alternative to “quantum spookiness” failed
https://bigthink.com/starts-with-a-bang/...pookiness/
KEY POINTS: Until the discovery of radioactivity and quantum physics, every particle and interaction was thought to obey completely deterministic equations. Quantum mechanics can only yield an indeterminate probability distribution of outcomes. It cannot tell you what comes next. The leading deterministic interpretation, involving hidden variables, is called Bohmian mechanics. Its only distinct prediction was just falsified.
EXCERPTS: . . . In the early days of quantum mechanics, de Broglie gained fame for showing that it wasn’t simply light that possessed a dual nature of being simultaneously wave-like and particle-like, but that matter itself possesses a wave-like nature when subjected to the proper quantum conditions. His formula for calculating the wavelength of “matter waves” is still widely used today, and to de Broglie, it’s because we ought to be taking the dual nature of quanta literally.
In de Broglie’s version of quantum physics, there were always concrete particles, with definite (but not always well-measured) positions to them, that are guided through space by these quantum mechanical wavefunctions, which he called “pilot waves.” Although de Broglie’s version of quantum physics couldn’t describe systems with more than one particle, and suffered from the challenge of not being able to measure or identify precisely what was “physical” about the pilot wave, it represented an interesting alternative to the Copenhagen interpretation.
Instead of being governed by the weird rules of quantum spookiness, there was an underlying, hidden reality that was completely deterministic. Many of de Broglie’s ideas were expanded upon by other researchers, who all sought to discover a less “spooky” alternative to the quantum reality that generations of students, with no superior alternative, had been compelled to accept.
Perhaps the most famous extension came courtesy of the physicist David Bohm, who in the 1950s developed his own interpretation of quantum physics: the de Broglie-Bohm (or pilot wave) theory. The underlying wave equation, in this idea, is the same as the conventional Schrodinger equation, as in the Copenhagen interpretation. However, there’s also a guiding equation that acts on the wavefunction, and properties like the position of a particle can be extracted from the relationship of that guiding equation. It’s an explicitly causal, deterministic interpretation, with a fundamental non-locality to it.
But this interpretation posed its own difficulties...
[...] In many ways, pilot wave theory was more of an interesting counterexample to the assertion that “no hidden variable theory could reproduce the success of quantum indeterminism.” It could, as Bohm’s pilot wave theory illustrated, but at the cost of a fundamental non-locality and the difficult notion of having to extract physical properties from a guiding equation, whose results are not necessarily straightforward to work with.
[...] As the perfectly valid Copenhagen interpretation has long demonstrated, however, just because something is counterintuitive or even illogical doesn’t mean it’s incorrect. Physical behavior is often more bizarre than we’d ever expect, and that is why we must always confront our predictions with the harsh reality of experiments.
[...] What appeared to be random, in these experiments, wasn’t truly random at all, but rather provided a thrilling confirmation of the ideas of pilot wave theory.And then it all fell apart...
[...] We may not have the ultimate “right answer” to the question of how the Universe works, but we have knocked down a tremendous number of pretenders from the throne. If your predictions disagree with experiments, your theory is wrong, no matter how popular or pretty it happens to be. We have not yet ruled out all possible incarnations of Bohmian mechanics, or pilot wave theories, or quantum mechanics interpretations that have hidden variables. It may not ever be possible to do so. However, every attempt to construct a theory that agrees with experiment requires some level of quantum spookiness that simply cannot be done away with. The least spooky alternative has now been falsified, as a single, concrete reality cannot describe all that we observe and measure... (MORE - missing details)
