Whether there can be a cat live and dead at the same time? A macrocosm, habitual for us, a body only the one and only state at a given time hasB. For example, apple can lie on a plate or hang on a tree, the boxer can win a duel either lose it, or draw, the cat can be either live, or the dead. But in a microcosm such restrictions cease to work.
Quantum particles behave so as if they are in several places at the same time. And both apple, and a cat, and all other macroscopic bodies consist of quantum particles. It is one of bright paradoxes of the most exact modern theory - quantum mechanics.
The quantum mechanics perfectly explained those phenomena which occur at the level of elementary particles, but at the same time was inefficient concerning the description of systems of macroscopic scale in which the classical mechanics well worked. In turn, the classical mechanics could not explain adequately what is observed in the world of atoms, hadrons, electrons and protons. The theoretical physics was divided into two layers which did not wish to be coordinated among themselves in any way.
the Theory which it is difficult to submitof
In the history of science often happens so that the mathematical apparatus of the theory is developed earlier, than the understanding of its physical sense comes. So occurred and this time. Despite elegance of mathematical designs of quantum mechanics, there was an urgent need in its interpretation from the point of view of reality and even philosophy. In other words, it was required to make so that it was possible not only to count and paint the quantum world in formulas, but also to imagine.
And it, it is necessary to tell, very difficult occupation. To take at least the fundamental provision of quantum physics - the principle of uncertainty of Heisenberg. It says that what will most more precisely measure the speed of a quantum particle, it will be more difficult for that to predict its location and vice versa. If this principle was observed in everyday life, then it would turn out very unusual situation. Let`s say there is an offender on the car. This a grief - the racer can be afraid of nothing and at a full speed to go there where to it will take in head - it is worth recording car speed a radar as its situation right there will become uncertain. To the contrary, if to photograph the car that is to establish its location, then the awful error which will prevent to calculate speed will be shown. Such here funny things.
Elementary particles in quantum mechanics have no speeds and coordinates to which we so got used. Instead of them there is a wave function describing a so-called pure condition of system and defining probabilities of characteristics of a particle. At the same time the quantum object is not located in any concrete place and does not move to and fro. It as if is smeared in space and is at once everywhere and in all possible states at the same time. It is called superposition. At interaction of such particles the “confused“ states with uniform system and the general wave function are formed.
Before physics there was a number of questions: what is represented by quantum particles in reality? What will be with wave function at registration of quanta in a certain point? And the most important, what role in all this are played by the observer?
the Copenhagen interpretationin Copenhagen through joint efforts of Niels Bohr and Verner Heisenberg was formulated 1927 by
B interpretation of the quantum theory. In particular, it concerned such major questions as korpuskulyarno - wave dualism and, especially, measurement (supervision).
According to the Copenhagen interpretation, wave function contains all data on a condition of quantum objects. However it describes elementary particles not in itself, but their properties which are shown at the macrolevel. In particles there are no hidden characteristics which define when to them to break up or where to appear at registration. Wave function is influenced by only such processes as unitary transformation (proceeds from the Schrodinger equation) and supervision process.
A cornerstone of the Copenhagen interpretation is process of quantum measurement. When the experimenter observes a particle in the concrete place, probability of its stay aside - almost zero. That is wave function immediately concentrates in very small area. This event is called a collapse of wave function.
It is possible to give the following simple experiment as a bright example of a collapse. Let`s say we have a silvered glass plate reflecting and passing exactly a half of an initial light stream which on it falls. Let on this plate only one photon fall. Its wave function will be divided into the reflected and passed waves. If on this wave way to put two photosensors, then only one of them because the photon will appear or at the left, or to the right of the silvered plate becomes more active, that is either it will be reflected, or will pass through it. The probability of such registration - 50%, and is absolutely casual process.
Unfortunately, even the Copenhagen interpretation does not give the answer to a question what is wave function - real essence or the mathematical tool for the miscalculation of probabilities? But nevertheless this interpretation got the greatest popularity at physicists, and its monopoly lasted long enough. And now she is supported by most of scientists. Anyway, Niels Bohr considered that the main thing - to count and foretell results, and the rest - the reflection - belongs not to science any more, and to philosophy.
Shortcomings of quantum mechanics in relation to a macrocosm very much disturbed Ervin Shryodinger, one of creators of this theory. To show its incompleteness, he thought up mental experiment. If to try to explain with simple words an experiment essence, then the following will turn out.
In a safe-deposit box the cat is locked. The chamber contains the mechanism with the Geiger counter in which there is a radioactive material. Its quantity so scanty that in one hour only one atom can break up, but with the same probability can not break up. If the kernel breaks up, then the reading-out detector will transmit a signal to the relay activating a hammer which strikes a flask with hydrocianic acid. Therefore, at disintegration of a kernel the cat will die and if disintegration is not, then he will survive - is healthy.
The quantum mechanics shows that if over an atomic nucleus (and respectively, and over a cat) supervision is not made, then it stays in superposition. Only supervision can eliminate this uncertainty. But before the observer will open a chamber, the system “a cat - a radioactive element“ is in the “smeared“ state with identical probability of 50%. It turns out that the cat both is live, and it is dead at the same time. Certainly, actually it cannot be because there is no intermediate state between life and death, so, the quantum mechanics has defect.
The Copenhagen interpretation “gets out“ of this paradox thus: if to impose macroscopic wave function on a quantum state, then superposition collapses and the experimenter will see either a live, or dead cat. The choice of a condition of disintegration of a kernel (and conditions of an animal) happens not at the time of opening of a chamber namely when the kernel gets to the detector.
Criticizing quantum mechanics, great Albert Einstein somehow told: “God does not play dice“. Niels Bohr answered it: “Einstein, do not specify to God what to do“. Disputes in this respect continue. For the simple inhabitant the quantum theory let and successful, but unimaginable. Anyway, today in physics there is no other concept which could describe the amazing world of elementary particles more precisely. Isn`t that so?