Uncertainty Principle

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GERMANY - CIRCA 2001: A stamp printed in Germany shows Werner Heisenberg circa 2001

Quantum chemistry tells of a world that is based on probability. Every action and event has a value of probability associated with it and nothing is impossible, only too improbable. As such, the microscopic world has many fascinating principles and laws that govern the systems existing on the scale. One of those principles is the uncertainty principle which was put forth by the German physicist Werner Heisenberg and hence it is also called Heisenberg’s uncertainty principle.

To err is observerr

Human beings are very subjective and whenever we are introduced to something new, we tend to assimilate the information that is provided to us in a way with which we are most comfortable. It is believed that this effect takes place when are making observations or taking measurements as well, though the latter might be because of the method or the measuring tool. Whenever we measure a certain system there is something known as an observer effect that takes place due to the interaction. As per this observer effect, we cannot take the measurement without affecting the system that we are actually measuring in some or the other way and so we obtain an incorrect or biased measurement. Due to deep-seated misconceptions, when Heisenberg proposed his uncertainty principle, most people argued that it is another example of the observer effect.

What is uncertainty principle?

The uncertainty principle states that in the quantum world, it is difficult to have precise information about the position and the momentum of a moving particle simultaneously. The principle puts an upper limit on the precision up to which these two pieces of information can be determined. The effect that the uncertainty principle tells about arises because of the wave-like nature of all quantum objects and their interaction with the macroscopic world. It is irrelevant that a measurement is taken or not, the quantum world behaves on the uncertainty principle and it is an inherent property of the system.

Electrons don’t move in orbits

In most illustrations it is shown that electrons are moving around the nucleus in fixed orbits. This is only done for illustrative purposes and in reality the electron are sort of cloudy masses that keep jiggling in their permitted space. The reason why electrons do not move in well-defined orbits is because classical mechanical concepts break down when dealing with the quantum systems. Quantum systems like to exist in discrete levels and there is no real continuity. Energy change also takes place at discrete levels. Energy changes are associated with frequency jumps and the permissible frequencies which operate in the quantum world do not mingle with the classical world. It is impossible to predict where an electron will go and form a trajectory of its path.

Einstein’s reluctance

Albert Einstein strongly opposed the fundamental principles of quantum mechanics and kept on devising thought experiments to put down the rules which the quantum world is said to obey. He came up with several examples in which the uncertainty principle could be disproved, only to be proven wrong himself in his assumptions. Though the uncertainty principle is still an important concept in quantum chemistry, it is being challenged by modern observations.

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