James Everitt blogs Quantum Physics and Mechanics as he discusses Heisenberg’s uncertainty principle

 

Werner Heisenberg’s uncertainty principle is most likely one of the most famous elements of Quantum Physics there is. While quite a simple idea compared with many other elements of Quantum Mechanics it has many other far more complicated applications which could perhaps serve as the topic for a future blog.

The uncertainty principle states that we can never precisely measure the position and velocity of an object at the same time. This principle is often used to explain something that we can’t explain using simple Newton-like physics. It also means that almost everything that we measure is not a fact but a probability.

A fundamental part of quantum mechanics is that everything is both a particle and a wave. Due to this there the location and momentum of a particle will always be a probability. This is because the more accurately we know one the less accurately we must know the other. This is because when you measure something as a particle its location is definite but to measure its momentum we must measure it as a wave. This is because somethings momentum is linked to its wavelength, they are inversely proportional to one another. This means that the higher somethings momentum the lower its wavelength. But as I said earlier to measure the velocity of something which we know from its momentum it must be measured as a wave but when measured as a wave we can’t be certain of its position. This is because a wave is like the ripples on pond there is no certain place where it is just probabilities of where it might be.

This can be demonstrated in the real world. We often measure things by using small massless particles (which are also waves) to measure the position and velocity of an object. For example, we measure the velocity and position of a football that has been kicked. Now imagine that we are measuring the velocity and position of an electron. This is where the uncertainty principle is shown. It would be like kicking a football at the football to measure where it is and how fast it is going. It would measure the electron at the point of impact and we wouldn’t know where it went afterwards and by simply measuring something we have effected its course and therefore we no longer know where it is and how fast it is travelling. So simply by observing something we will always affect it in some way that means we can never know its position and velocity at the same time.

In conclusion, this principle states that anything that we measure we influence and therefore don’t know that what we measured is true once we have measured it. In the everyday life, we don’t notice these things as the margins of error are so small but when measuring things on quantum scale it can have a huge impact and explains many mysteries of the sub-atomic world.

James Everitt, Year 11 Scholar, October 2017.