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mohamed amine
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can we find causality in quantum mechanic like the classical physics ?
mohamed amine said:can we find causality in quantum mechanic like the classical physics ?
A specific example, please. For instance, photons are quantum particles. IR wavelengths or energy levels are absorbed by CO2. There are certain vibrational modes that are excited by this absorption. In the atmosphere, this energy may then be converted to kinetic energy of other molecules in the gas.DrChinese said:
As PeterDonis says, causality in quantum physics does not follow some classical concepts. Specifically:
1. Measurement outcomes are expressed as an expected probability amplitude. The outcome of any specific measurement is random. There is no known "causal agent" responsible for that specific outcome. In the classical world, there is determinism in every outcome when the appropriate setup parameters are known.
2. The classical world is local realistic, while the quantum world is not. Trying to explain "local realistic" itself would be a separate topic, but here is a link that might help:
https://en.wikipedia.org/wiki/Principle_of_locality
itfitmewelltoo said:A specific example, please. For instance, photons are quantum particles. IR wavelengths or energy levels are absorbed by CO2. There are certain vibrational modes that are excited by this absorption. In the atmosphere, this energy may then be converted to kinetic energy of other molecules in the gas.
So there is a causal chain. ...
So, where in there do we see find the predominantly quantum physics (not so classical) process as you've described and the classical physics we are accustomed to?
As @DrChinese has said there is indeterminacy in quantum processes. But we can recover something like classical causality by summing many quantum effects. For instance with Brownian motion we can say that the motion of the pollen grain is caused by pressure fluctuations in the fluid. Those fluctuations are composed of many random molecular motions.mohamed amine said:can we find causality in quantum mechanic like the classical physics ?
Thank you for making a very clear distinction.vanhees71 said:One has to clearly distinguish causality from determinism
The concept of causality in quantum physics refers to the idea that every event has a cause and effect relationship. This means that for every observed effect, there must be a preceding cause that can be determined and predicted.
The uncertainty principle in quantum physics states that it is impossible to know both the position and momentum of a particle with absolute certainty. Causality still applies in this scenario, as the unpredictable nature of a particle's position and momentum is caused by the inherent uncertainty in quantum mechanics.
There are some theories in quantum physics that suggest that causality can be violated, such as the concept of non-locality. However, these theories are still highly debated and have not been proven to be true. In general, the principle of causality is a fundamental concept in physics and is not easily violated.
Entanglement is a phenomenon in quantum physics where two particles become connected in such a way that their states are dependent on each other, even when separated by large distances. This can appear to violate causality, as a change in one particle's state can instantly affect the state of the other particle. However, it is important to note that the initial cause of entanglement still follows the principle of causality.
The concept of causality in quantum physics plays a crucial role in our understanding of the universe and how it operates. It allows us to make predictions and explanations for observed phenomena, and helps us to develop new theories and technologies. Without the principle of causality, our understanding of the universe would be limited and chaotic.