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What were Einstein and Bohr arguing about? Why did Einstein publish the EPR paper

by Zheng to 2 months ago in history
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At the beginning of the 20th century, Einstein and Bohr engaged in a debate in the field of quantum mechanics for nearly half a century. Do you know what they were arguing about?

In order to facilitate our thinking, we replace the microscopic particles with apple, for example, if there is an apple on the table, through the observation in a place, I found that apple apple before the question now is: "I have observed in which position", it is such a seemingly simple question, but in the quantum mechanics scientists eyes has caused great controversy. They believe that before the observation, the apple is nowhere, the apple is in the superposition of any possible position, the moment of observation to randomly explore a certain position, this is the core idea of quantum mechanics superposition principle.

Bohr of Copenhagen School believed that in the microscopic world, the characteristics of particles are in superposition state before measurement, for example, the spin of an electron is always in superposition state up and down, until you measure and observe the moment of his spin, he will explore the definite value for up or down. Bohr believed that reality was inherently uncertain, but Einstein believed that the spin of an electron was determinate, and that neither measurement nor observation affected the direction of the electron's spin. The measurement just captures the information.

By the 1930s, while the older generation of physicists, such as Bohr and Einstein, were still arguing about it, the younger generation of physicists began to lose interest in quantum mechanics, because it was a waste of time to talk about the nature of things in an age of miracles. Ever since Heisenberg made his breakthrough in atomic stack theory, smashing atomic nuclei with accelerators has been an endless gold mine. In an age when you can bend over and pick up gold, no one is doing this kind of thankless research.

In addition to Einstein, on May 15, 1935, Einstein, together with two of his assistants, published a paper known as the EPR, the title of which was "Can the physical reality described by quantum mechanics be considered complete?" To this question, the paper gives a straightforward answer: "No" describes a thought experiment in which a particle with zero spin decays into two particles, A and B, whose spins must be opposite due to conservation laws. At this time, we send particle B to Proxima Centauri, 4.2 light years away. According to the Copenhagen interpretation, before measurement, The spin of particle AB is in a superposition of up and down, and we measure particle A, assuming that the random spin exploration of particle A is up, because of the conservation law, the spin exploration of particle B must be down. Now, the question is how does particle B know that particle A is spinning up, so that its spin instant exploration is down? If there were some sort of super-distance connection between them, it would be faster than the speed of light, which defies relativity.

The publication of the epR paper in 1935 caused consternation at the Copenhagen School, and Arbitrage immediately wrote to Heisenberg asking for a statement lest the EPR paper confuse other physicists. Heisenberg later wrote a draft but did not publish it, as Bohr had already spearheaded a rebuttal. On October 15 of the same year, Bohr's paper was published in the same physics journal with a copy of the EPR paper in the title, and an interesting thing happened.

Bohr's answer to the same question, published in the Journal Physical Review 47 and 48, is a crisp yes. But Bohr acknowledged in his paper that Einstein and his team had managed to peek into the state of particle A, that is, observing a without causing mechanical disturbance to particle B, but still having some effect on the predicted behavior of particle B, so the observation to explore theory is still valid.

Bohr emphasized that this kind of indirect information interference is not physically real action at a distance, so it does not violate relativity. This magical explanation drove all physicists crazy, and Einstein called it Bohr's sorcery knife, a ghostly interplay. Schrodinger later used the word entanglement in his letter discussing EPR with Einstein. Scientists separated the two examples and still kept entanglement, which is called quantum entanglement. Scientists' scrutiny of the EPR paper has unwittingly led them into the mysterious world of quantum entanglement.

To further the demolition of the Copenhagen interpretation, Schrodinger moved in the name of the physics super monster, Schrodinger's cat. Put a cat in an airtight container with a small amount of radium and poison, and the radium atoms may decay, releasing a neutron that triggers a mechanism that kills the cat by tipping over the highly toxic bottle. According to the Copenhagen interpretation, atoms should be in a superposition of decay and undecay, resulting in poisons in a superposition of overturned and unoverturned. Bloodtop raised questions to the Copenhagen school.

Was the cat in a dead and alive superposition before the observation? Schrodinger's cat was already at the top of his game before the hype, eclipsing the likes of Max Bib and Laplace Yao. The real question facing scientists is, are there really any cats that are both alive and dead? After weighing the pros and cons, the Copenhagen school finally recognized the cat as both dead and alive, but it raised a series of problems. Since the cat was in a superposition of dead and alive before the observation, who is this observer? An instrument or a physicist? Did the cat not observe inside before opening it?

The spectre of Schrodinger's cat gnawing at the fragile nerves of physicists, even Hawking, who spent his whole life thinking, once said, "When I hear schrodinger's cat, I want to grab a gun." Today, the originator of this debate has long since passed away, but the debate continues, and the great debate of the century, with the most powerful intelligence, has not found the ideal, clear, single answer, but has dug up countless mysterious tunnels into the unknown. It makes it all the more clear that quantum theory is not as weird as we thought, but even weirder than we thought.


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Zheng to

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