Quantum mechanics is a fascinating field of physics. You might’ve heard people say it’s the future and that it will revolutionise many industries—but chances are, you don’t know much about it. This blog is meant to be a simple and accessible introduction to quantum mechanics. I’ll be focusing on the physics and logic behind it, rather than diving into the heavy maths and boring equations. The goal here isn’t to make you an expert in quantum mechanics. Instead, I want to help you start thinking like a quantum physicist rather than a classical one—and hopefully spark a lifelong curiosity about the subject. Ideally, you’ll walk away from this having learned something new and be inspired to keep learning.

To begin talking about quantum physics, we first need to talk about classical physics. It’s only by comparing the two that we can start to appreciate the quantum perspective.

Classical physics is what most people learn in middle or high school. You’ve probably come across concepts like Newton’s laws of motion or Maxwell’s equations. Even if you haven’t, that’s fine. In general, classical physics describes most everyday objects—things like balls, cars, or aeroplanes. You can talk about the position of a ball, its momentum (which is just velocity times mass), the forces acting on it, its initial conditions, and so on.

This is why classical physics is deterministic. If you have all the possible information about an object—like I mentioned earlier—you can accurately predict where it will be in the future, or figure out where it was in the past. For example, if I took two identical balls in a vacuum (to eliminate air resistance) and pushed them with the same force in the same direction, they would behave in exactly the same way.

Now let’s talk about quantum mechanics. Quantum mechanics deals with particles that are extremely small—like atoms, or even smaller particles such as electrons.

This brings us to the biggest difference between classical and quantum physics: quantum mechanics is probabilistic. Even if you know everything you could know about a particle, you can only predict the likelihood of different outcomes—not the exact outcome itself. So, if you have an electron, you can’t say for sure where it will go next. All you can do is calculate probabilities. For example, you might say there’s a 50% chance it’ll be in position x, a 30% chance it’ll be in position y, and a 20% chance it’ll be in position z. This is, of course, a simplified analogy—I’ll explain the real nuances later.

You might be wondering why we have two different types of physics, and how both can be correct at the same time. The answer is that physics is just a tool we use to describe the world around us. Classical physics is essentially an approximation of quantum physics that works well on larger scales, but it breaks down at very small scales. Quantum mechanics is currently our best description of reality—but it’s usually too complex to apply to large objects in everyday situations.