012 013 the profound peculiarity of quantum mechanics begins. By actively observing the path of each electron, you will find that they will no longer form the interference pattern shown above but will instead form two individual strips. It is as if the electrons know they are being observed and do not want to be caught in the act of quantum mischief, resulting in the electrons behaving as ordinary particles. This seemingly magical phenomenon, which has been aptly named ‘nature’s conjuring trick’ by physicist Jim Al-Khalili, appears to have no rational explanation and comprises the ‘measurement problem’ of quantum mechanics. We will come back to this ‘measurement problem’ later, but for now we need to have a clear understanding of certain key concepts surrounding the quantum world. Indeterminism and Heisenberg’s Uncertainty Principle Have you ever wondered whether some things are just meant to be? You may believe in the idea of fate, or that all actions taken are pre-determined right down to the quantum level. This ideology is known as determinism and is commonly associated with Isaac Newton. Newton argued that every particle in the universe should obey the laws of motion, and that no matter the intricacy of the system, all processes should follow a predictable path. This appears to be a plausible argument, however, Newton later accepted the fact that the future can be pre-determined only if we have complete information on the present (i.e. information on the current location and momentum of every particle in the universe). This, in practice, is of course impossible and so led to the idea of indeterminism (the opposing view to determinism). But what has all this got to do with quantum mechanics? Well, to be able to explain this all, we need to have an idea of what a wavefunction is. Taking its definition from ‘Britannica,’ it is stated that a wavefunction is a variable quantity that mathematically describes the wave characteristics of a particle. For all we are concerned with, these wave characteristics can solely be its momentum and position. Now the groundwork has been laid out, it can be stated that a significant consequence of the indeterminism of a wavefunction is the concept of indeterminacy. Ok, please bear with me here. I know that there are quite a few fancy terms being thrown around that may seem incomprehensible, but I assure you that this idea is quite simple. Although indeterminacy and indeterminism appear to be remarkably similar, it is vital to not confuse them with one another. Indeterminism relates to the notion that the knowledge of certain characteristics of a particle at one point in time does not mean that its future characteristics can be known with certainty. On the other hand, indeterminacy states that we can never know with total precision all the characteristics of a system simultaneously. All clear so far, right? This is where Heisenberg’s uncertainty principle comes in. In essence, it states that we cannot simultaneously know the position and velocity of an electron at any point in time. To expand upon this, let us imagine we have an electron trapped in a room of microscopic scale. As we know with certainty that this electron lies somewhere in this small area, we can say that the position wavefunction of this electron is ‘localised in space.’ Moreover, using a mathematic method known as the ‘Fourier Transformation,’ we can use the position wavefunction of the electron to calculate its momentum wavefunction. Now, the catch is that a localised position wavefunction will always bring about a spread-out momentum wavefunction, and vice versa. This links back to the idea of indeterminacy, and how we can never know with total precision all the characteristics of a system simultaneously. To end, perhaps Heisenberg’s uncertainty principle could help to uncover the magic of the dual-slit experiment. By observing the precise location of the electron during the dual-slit experiment, we greatly narrow down its position wavefunction. Hence, we necessarily cause the momentum wavefunction of the electron to become more spread out – leading to uncertainties in its velocity. Although this explains why observing an electron may alter its initial path, it certainly does not explain why the electron behaves like a particle after it has been observed. Bibliography Jim Al-Khalili, Quantum: A Guide For The Perplexed Brittanica: Science & Tech - wave function https://www.britannica.com/science/wave-function Physics in a minute: The double slit experiment https://plus.maths.org/content/physics-minute-double-slit-experiment-0 he electron then undergo superposiCon, before recombining and hiQng the screen as a localised Ccle. w, this theory could easily be evaluated by placing a detector before the two slits. This detector would either observe ch slit the electron passes through, or whether the electron es through both slits simultaneously. However, this is where profound peculiarity of quantum mechanics begins. By vely observing the path of each electron, you will find that will no longer form the interference pa:ern shown above will instead form two individual strips. known with certainty. On the other hand, indeterminacy states that we can never know wi precision all the characterisCcs of a system simultaneously. 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