Sep 2023

Do Quantum Effects Occur at the Atomic Scale or All Scales?

September 13, 2023
Do Quantum Effects Occur at the Atomic Scale or All Scales?

When learning about quantum physics, those with curious minds may wonder if quantum effects are solely confined to the atomic level. In reality, quantum effects can also show up on a much larger scale. You may remember your physics tutor in Singapore explaining that quantum physics deals with energy and matter behaving like both particles and waves, although it’s more complex than just that.

Quantum vs. Classical Physics

In our vast universe, everything, from distant stars to the tiniest atoms, follows the rules of quantum physics. However, in many everyday situations, like throwing a baseball, both quantum physics and classical physics give us the same results. That’s why we often prefer to use classical physics because it’s easier to understand and work with.

But even when we use classical physics for something like a baseball throw, quantum physics is still working in the background. In those cases, we call it “non-quantum” because we can’t see its effects. We only say something is “quantum” when we notice its unusual behaviour, even though it was quantum all along. Quantum effects are things that classical physics can’t predict well, but quantum theory can.

In classical physics, matter is thought of as small, solid particles. When these particles start behaving like waves, that’s when we see a quantum effect. Classical waves, like ocean waves and sound waves, aren’t considered quantum because the particles making them up are still solid “balls,” even though they move in wave-like patterns. To have a quantum effect, these particles themselves must act like waves.

The Nature of Quantum Effects

Quantum effects aren’t restricted to the atomic scale, but they’re more common there. This is because, for a large-scale quantum effect, the tiny particles must behave like waves in an organised way. If all these tiny bits of matter acted like waves randomly, their waves would cancel each other out on a larger scale.

In physics, we call this organised and wavy behaviour “coherence.” The more particles act like waves together, the more the whole system behaves like a wave. Think of kids playing in a pool. If each one splashes randomly, the water waves they create will be all over the place and not very noticeable. But if they all splash simultaneously every few seconds, the small waves they make will add up to create one big noticeable wave. This is just an analogy; the pool waves are not quantum, they’re classical. To be truly quantum, the particles of matter must align both in their movements and their quantum wave behaviours.

The important thing to remember is that to see a large-scale quantum effect, all the particles must align and create coherence. This is less likely if the particles behave randomly. For example, when you roll five dice together, there are many ways to get different numbers, but only a few ways to get all the same numbers in one roll.

In short, we can observe quantum effects on a larger scale when each particle and its quantum wave behaviour align and create coherence. Here are some examples:

  • Superfluidity

Once cooled enough, the atoms in certain materials can spread into coherent wave states resistant to surface tension, enabling the material to flow like liquids with zero viscosity.

  • Superconductivity

When certain conducting materials are super cold, their electrons will disperse into large-scale coherent wave states capable of flowing past atoms and impurities undisturbed. This allows them to flow through the material without any resistance, leading to fascinating effects like the Meissner effect and quantum levitation.

  • Bose-Einstein Condensates

At extremely low temperatures, the atoms in certain materials spread out into one gigantic coherent wave state. A macroscopic mass of matter that becomes condensed in this manner behaves like a wave and exhibits its inherent properties like interference.


To sum it up, quantum physics affects everything in the world, not just tiny things. And while its laws do not limit “quantumness” to the atomic level, quantum effects become vanishingly small to the point that they become unobservable in practice for larger objects. Nevertheless, quantum behaviour does exist at the macroscopic scale and has been observed.

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