Yesterday 05:38 AM
(This post was last modified: Yesterday 05:39 AM by C C.)
https://www.yahoo.com/news/science/artic...00787.html
EXCERPTS: Superposition is an uncanny aspect of quantum mechanics that allows particles to be in multiple states at once-such as literally here and there simultaneously [...] A key aspect is that if you start with a state in a superposition, it remains in a superposition for all time: superpositions cannot be destroyed.
To appreciate the consequences of superposition, we must understand how waves are added and subtracted. [...] Throw a stone into the pond ... Wait until the surface is still again, then throw in a second stone at another position ... If you watch carefully, you will find that the result is just the sum of the two patterns that each single stone created.
If a wave crest from the first stone meets a wave crest from the second, they will combine to form a bigger wave crest, but if a crest and a trough meet, they will cancel each other out. These processes are called constructive and destructive interference, respectively. In this way, multiple solutions to a wave equation can be added together, and the result will still be a solution of the same equation. And it doesn't stop with two solutions-if you want the wave pattern of three stones, you just combine the three patterns, and so on.
[...] We know that superpositions can't be destroyed because Schrödinger's equation obeys the superposition principle. ... There can be no collapse according to Schrödinger's equation. [It's a brute add-on.]
[...] Everett's proposal is known as the Many Worlds interpretation of quantum mechanics. It's confusing, however, to call it an "interpretation." The Many Worlds interpretation and the Copenhagen interpretation are not really two different interpretations but two different theories. The former predicts the existence of a multiverse as an inevitable consequence of the superposition principle of Schrödinger's equation. The latter predicts a single universe by denying the universal validity of Schrödinger's equation.
Which theory is right? Is Schrödinger's equation universally valid, or does it apply only to microscopic systems such as atoms? [...] experimental progress over the past few decades shows that Schrödinger's equation is not valid only for minuscule particles. ... Although the multiverse sounds like science fiction, it is a real scientific prediction...
[...] If everything is described by the wave equation, why do so many things behave like classical particles? Why can't we interact with other branches of the multiverse?
[...] The answer is somewhat counterintuitive at first: we actually do see interference effects all the time but only from destructive interference. This is what physicists call decoherence -- the inability of many waves to show strong constructive interference.
Note that decoherence is not a new, fundamental law that we add to Schrödinger's equation to obtain classical behavior. It is a consequence of Schrödinger's equation that arises naturally once there are many interfering waves. In fact, decoherence is a universal phenomenon that we're already familiar with.
[...] Another clue is the fact that the universe appears highly fine-tuned: a slight variation in its fundamental parameters, such as the precise charge of an electron, the mass of a proton or the strength of the gravitational constant, would make life as we know it impossible. How can we explain the fact that these values seem almost chosen for their convenience for life? A popular answer is known as the anthropic principle: the fact that we are alive means we must find ourselves in a version of the universe compatible with life. We have essentially selected this universe from the array of all possible universes, which may be mostly hostile to life. But what does "select" mean? From which "selection of universes" are we choosing? Here the answer strongly depends on whether there is only one unique universe or a vast collection of them.
[...] The Many Worlds interpretation is gaining momentum as a candidate to solve the quantum measurement problem. Despite its seemingly weird prediction that our world is just one part of a multiverse, because of destructive and constructive interference, it is perfectly compatible with our sensation of living in one classical universe. Moreover, it opens possibilities for addressing fundamentally and technologically relevant questions.
Still, many challenging open questions must be answered before the Many Worlds interpretation can be accepted as our best explanation for the measurement problem..... (MORE - missing details)
EXCERPTS: Superposition is an uncanny aspect of quantum mechanics that allows particles to be in multiple states at once-such as literally here and there simultaneously [...] A key aspect is that if you start with a state in a superposition, it remains in a superposition for all time: superpositions cannot be destroyed.
To appreciate the consequences of superposition, we must understand how waves are added and subtracted. [...] Throw a stone into the pond ... Wait until the surface is still again, then throw in a second stone at another position ... If you watch carefully, you will find that the result is just the sum of the two patterns that each single stone created.
If a wave crest from the first stone meets a wave crest from the second, they will combine to form a bigger wave crest, but if a crest and a trough meet, they will cancel each other out. These processes are called constructive and destructive interference, respectively. In this way, multiple solutions to a wave equation can be added together, and the result will still be a solution of the same equation. And it doesn't stop with two solutions-if you want the wave pattern of three stones, you just combine the three patterns, and so on.
[...] We know that superpositions can't be destroyed because Schrödinger's equation obeys the superposition principle. ... There can be no collapse according to Schrödinger's equation. [It's a brute add-on.]
[...] Everett's proposal is known as the Many Worlds interpretation of quantum mechanics. It's confusing, however, to call it an "interpretation." The Many Worlds interpretation and the Copenhagen interpretation are not really two different interpretations but two different theories. The former predicts the existence of a multiverse as an inevitable consequence of the superposition principle of Schrödinger's equation. The latter predicts a single universe by denying the universal validity of Schrödinger's equation.
Which theory is right? Is Schrödinger's equation universally valid, or does it apply only to microscopic systems such as atoms? [...] experimental progress over the past few decades shows that Schrödinger's equation is not valid only for minuscule particles. ... Although the multiverse sounds like science fiction, it is a real scientific prediction...
[...] If everything is described by the wave equation, why do so many things behave like classical particles? Why can't we interact with other branches of the multiverse?
[...] The answer is somewhat counterintuitive at first: we actually do see interference effects all the time but only from destructive interference. This is what physicists call decoherence -- the inability of many waves to show strong constructive interference.
Note that decoherence is not a new, fundamental law that we add to Schrödinger's equation to obtain classical behavior. It is a consequence of Schrödinger's equation that arises naturally once there are many interfering waves. In fact, decoherence is a universal phenomenon that we're already familiar with.
[...] Another clue is the fact that the universe appears highly fine-tuned: a slight variation in its fundamental parameters, such as the precise charge of an electron, the mass of a proton or the strength of the gravitational constant, would make life as we know it impossible. How can we explain the fact that these values seem almost chosen for their convenience for life? A popular answer is known as the anthropic principle: the fact that we are alive means we must find ourselves in a version of the universe compatible with life. We have essentially selected this universe from the array of all possible universes, which may be mostly hostile to life. But what does "select" mean? From which "selection of universes" are we choosing? Here the answer strongly depends on whether there is only one unique universe or a vast collection of them.
[...] The Many Worlds interpretation is gaining momentum as a candidate to solve the quantum measurement problem. Despite its seemingly weird prediction that our world is just one part of a multiverse, because of destructive and constructive interference, it is perfectly compatible with our sensation of living in one classical universe. Moreover, it opens possibilities for addressing fundamentally and technologically relevant questions.
Still, many challenging open questions must be answered before the Many Worlds interpretation can be accepted as our best explanation for the measurement problem..... (MORE - missing details)
