When quantum mechanics was first formulated, the authors started with the mathematical definition of a 'measurement', namely projecting the wavefunction of the system on to a certain eigenvector.
It is not at all clear what counts as a 'measurement' of a quantum state. You have touched on something of an unsolved problem in physics or philosophy of physics (depending on who you ask). I suggest looking up the double slit experiment if you would like a visual example of this. The converse is true too, that if you measure it's position you have an inherent uncertainty in the momentum. It is not too difficult to find the momentum of a wave, but by measuring this you know that it is a wave, and lose information about where it is. Think of a particle existing along a wave. There is a wave particle duality that goes on in qm. Observing is actually an act of measuring. This is the problem with quantum mechanics (and is misinterpreted by many people). This means that if we know the position exactly then we don't know the momentum. For a one dimensional case involving momentum and position it would be as follows. This "observation" is actually just a more simple way to state the uncertainty principle. There is no need for a human observer, and so no paradox - the wavefunction of the radioactive decay collapses when it interacts with the detector and the cat in the closed box, meaning that the cat is already either alive or dead when the box is opened. The radioactive decay that is to trigger the release of cyanide and kill the cat can exist in two states only as long as it interacts with nothing else. It is interesting to apply this explanation to Schrodinger's Cat. (the uncertainty principle by contrast is the same whether or not the photon is observed) That interaction causes the photon's wavefunction to collapse, and the quantum effect of the two slit defraction to cease. However, any attempt to try to watch it going through both slits at once will require something to interact with that photon, whether that be a human observer or simply the matter that makes up a piece of apparatus. In two slit defraction, a photon can go through two separate openings at once and then in effect "bump" into itself on the other side. However, if you try to to observe the photon being in two places at once, then the wavefunction "collapses", and the photon will appear in only a single place. Wavefunctions can allow the superposition of several states - for instance a photon's wavefunction can allow it to be in two places at once, and even to interfere with itself. The effect is similar - you can't know what you want to know - but the underlying phenomena is different) For instance, the more one knows about the momentum of an electron, the less one can know about its location, and vice versa.
That states that certain complementary metrics cannot be known with complete accuracy at small scales. (this is entirely different from the uncertainty principle. The point of these wavefunctions is to describe the world in terms of probability - for instance, one cannot talk about an electron being in a particular place, but rather only of the probability of it being there. When they interact with anything else - even as small as another electron - they can experience "wavefunction collapse".Ī "wavefunction" in quantum mechanics is the maths used to describe how something behaves (and that means everything, though there is no point trying to work out a wavefunction for say a bus, as it would be a) impossibly complex, and b) quantum effects are so unlikely and so minuscule at that scale as to be irrelevant, so physicists only talk about wavefunctions for tiny things, such as an electron). To this paradoxical conclusion, known as the observer effect, or measurement problem, Albert Einstein retorted, quite rightly, that the moon continued to exist, undisturbed, even when nobody was watching it! But to what extent can we say that our observations can create our own reality? And is it really true that quantum mechanics would have reached the same conclusions as some mystical-religious philosophies, which claim that the universe is a product of the consciousness?ĪB - According to the orthodox interpretation of quantum mechanics, no phenomenon can be such if not first observed, and reality cannot exist in the absence of observation."Observation" means interaction with anything, which might be a sentient being or might simply be matter.Īt very small scales (sub-atomic) particles can exist in several states at once. N2 - According to the orthodox interpretation of quantum mechanics, no phenomenon can be such if not first observed, and reality cannot exist in the absence of observation.
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