Re: la forza di gravità...
Inviato da RedPill il 26/7/2011 18:24:07
Beh, in realtà la fisica quantistica non è dimostrabile con esempi concreti. E' una contraddizione in termini dire che il paradosso di EPR è un esempio concreto.
Una semplificazione dell'esperimento (semplice da capire anche a quelli come me che non sono degli addetti ai lavori) è questo:
A perfect example is the case of the neutral pion. A pion is a subatomic particle (very small, see Quantum Physics Is. . .) that decays into two photons, each with opposite spins. These are difficult concepts to understand, but all you really need to know is this:
The pion has no spin. Imagine a baseball just sitting there, not spinning. Pretty simple.
When the pion decays (a common occurrence in the subatomic world) it no longer is a pion. It splits into two photons that shoot away from each other in opposite directions.
Photons have spin, but these two photons came from a pion with no spin. So, since you know the spin of one photon, you can find out the spin of the other photon because their spins have to add up to no spin at all. Imagine our baseball that was not spinning all of the sudden flies apart into two golf balls, each spinning in opposite directions.
Because the photons came from a single pion, it is said that they are entangled. You'll see what I mean.
One of the photons flies to the right. You first measure it's spin along the x-axis with absolute certainty (quite possible). But, alas, quantum mechanics won't let you measure the y-axis spin, since you already know the x-axis spin. So you go to the second photon that flew to the left. You already know its x-axis spin without even measuring it: it is the exact opposite of the other photon. The paradox is this: Can you measure the y-axis spin of the second photon with absolute certainty even though you already know it's x-axis spin without measuring it?(Blanton)
Duh, of course you can, says Einstein. How would the second photon "know" you measured the first photon? But quantum mechanics says you can't measure the y-axis spin with absolute certainty. It doesn't matter if the two photons were separated by an inch or 10 miles, the very instant you measure the first photon's x-axis spin, the y-axis spin of the second photon is impossible to measure. Relativity says that the "knowledge" of the measurement of the first photon can only travel the speed of light. But quantum mechanics requires the "knowledge" of the measurement to be instantaneous, because they have been entangled. Einstein called it "spooky action at a distance".
Quindi capisci che la "misurazione" è solo postulata e non effettuata realmente.
Quindi il concetto di "locale" è un concetto quantistico (comunque una spina nel fianco per le teorie relativistiche) ma non è una realtà tangibile, quindi tanto meno un esperimento "sperimentabile".
Non so se mi sono fatto capire... la velocità del fotone si può misurare, i dati del paradosso EPR non si possono misurare.
Comunque sono convinto che la teoria della relatività sia un punto di partenza e non di arrivo.
Peace
RedPill
Una semplificazione dell'esperimento (semplice da capire anche a quelli come me che non sono degli addetti ai lavori) è questo:
A perfect example is the case of the neutral pion. A pion is a subatomic particle (very small, see Quantum Physics Is. . .) that decays into two photons, each with opposite spins. These are difficult concepts to understand, but all you really need to know is this:
The pion has no spin. Imagine a baseball just sitting there, not spinning. Pretty simple.
When the pion decays (a common occurrence in the subatomic world) it no longer is a pion. It splits into two photons that shoot away from each other in opposite directions.
Photons have spin, but these two photons came from a pion with no spin. So, since you know the spin of one photon, you can find out the spin of the other photon because their spins have to add up to no spin at all. Imagine our baseball that was not spinning all of the sudden flies apart into two golf balls, each spinning in opposite directions.
Because the photons came from a single pion, it is said that they are entangled. You'll see what I mean.
One of the photons flies to the right. You first measure it's spin along the x-axis with absolute certainty (quite possible). But, alas, quantum mechanics won't let you measure the y-axis spin, since you already know the x-axis spin. So you go to the second photon that flew to the left. You already know its x-axis spin without even measuring it: it is the exact opposite of the other photon. The paradox is this: Can you measure the y-axis spin of the second photon with absolute certainty even though you already know it's x-axis spin without measuring it?(Blanton)
Duh, of course you can, says Einstein. How would the second photon "know" you measured the first photon? But quantum mechanics says you can't measure the y-axis spin with absolute certainty. It doesn't matter if the two photons were separated by an inch or 10 miles, the very instant you measure the first photon's x-axis spin, the y-axis spin of the second photon is impossible to measure. Relativity says that the "knowledge" of the measurement of the first photon can only travel the speed of light. But quantum mechanics requires the "knowledge" of the measurement to be instantaneous, because they have been entangled. Einstein called it "spooky action at a distance".
Quindi capisci che la "misurazione" è solo postulata e non effettuata realmente.
Quindi il concetto di "locale" è un concetto quantistico (comunque una spina nel fianco per le teorie relativistiche) ma non è una realtà tangibile, quindi tanto meno un esperimento "sperimentabile".
Non so se mi sono fatto capire... la velocità del fotone si può misurare, i dati del paradosso EPR non si possono misurare.
Comunque sono convinto che la teoria della relatività sia un punto di partenza e non di arrivo.
Peace
RedPill
Messaggio orinale: https://old.luogocomune.net/site/newbb/viewtopic.php?forum=54&topic_id=4027&post_id=198772