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  Inviato da: Wakinian Tanka  Mostra tutti i messaggi di Wakinian Tanka
Titolo: La MQ
Newsgroup: it.scienza.fisica
Data: 26/02/2018
Ora: 21:12:52
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  26/02/2018 ore 21:13<br /> <br /> Secondo voi &egrave; giusta questa frase:<br /> <br /> <br /> &lt;&lt;In quantum mechanics the kind of certainty about the future characteristic of classical mechanics is impossible because the initial state of a particle cannot be established with sufficient accuracy&gt;&gt; ? <br /> <br /> Il contesto &egrave; il seguente (Beiser - Concepts of Modern Physics - sixth edition - paragrafo 5.1):<br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> &quot;The fundamental difference between classical (or Newtonian) mechanics and quantum mechanics lies in what they describe. In classical mechanics, the future history of a particle is completely determined by its initial position and momentum together with the forces that act upon it. In the everyday world these quantities can all be determined well enough for the predictions of Newtonian mechanics to agree with what we find. Quantum mechanics also arrives at relationships between observable quantities, but the uncertainty principle suggests that the nature of an observable quantity is different in the atomic realm. Cause and effect are still related in quantum mechanics, but what they concern needs careful interpretation. In quantum mechanics the kind of certainty about the future characteristic of classical mechanics is impossible because the initial state of a particle cannot be established with sufficient accuracy. As we saw in Sec. 3.7, the more we know about the position of a particle now, the less we knowabout its momentum and hence about its position later.The quantities whose relationships quantum mechanics explores are probabilities. Instead of asserting, for example, that the radius of the electron&rsquo;s orbit in a ground-state hydrogen atom is always exactly 5.3*10^(-11) m, as the Bohr theory does, quantum mechanics states that this is the most probable radius. In a suitable experiment most trials will yield a different value, either larger or smaller, but the value most likely to be found will be 5.3*10^(-11) m.&quot;<br /> <br /> <br /> <br /> Scusate, ma non erano /le osservabili/ e non /lo stato/ che &egrave; impossibile stabilire con sufficiente precisione (in generale)? Una volta che un sistema quantistico viene preparato in modo appropriato, il suo stato (puro) &egrave; perfettamente stabilito, e di conseguenza anche gli stati successivi, per mezzo dell'equazione di Schroedinger, se conosciamo l'hamiltoniana del sistema. <br /> <br /> Non &egrave; cos&igrave;? <br /> Grazie <br /> <br /> --<br /> Wakinian Tanka  

Il thread:
da leggere Wakinian Tanka 26/02 21:12
La MQ
   da leggere Giorgio Bibbiani 01/03 18:42
Re: La MQ
   da leggere Elio Fabri 05/03 17:32
Re: La MQ
 

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