PHYSICS

He just waved (he’s a particle) 👋

Light is everywhere. It lets us see, it keeps us warm (thanks Sun), and it can travel up to billions of light-years away straight to our eyes. But what actually is light?

For centuries now, scientists have battled with this question. At times it behaves like a wave: spreading out, interfering, and diffracting. Other times, it behaves like a stream of particles: bouncing off surfaces and arriving in distinct packets. So, which is it? It can’t be both, can it? It can.

Light exhibits what is known as wave-particle duality. In the famous double-slit experiment first performed by Englishman Thomas Young in 1801, light creates an interference pattern, displaying clear wave behaviour. But, if you detect which slit the light passes through, the interference pattern disappears. Instead of spreading out, like a wave, light behaves like individual particles hitting the screen one at a time. It is as if the light ‘knows’ it is being watched and decides to behave differently, like how you act differently when you’re alone in your bedroom singing Taylor Swift songs into your hairbrush versus when someone unexpectedly walks in. This challenges how we understand reality itself, blurring the boundary between observer and observed.

💡 Things to consider

• Can it be both? At the same time?: In our everyday world, things have identities: a cat is a cat, a wave is a wave, and a particle is a particle. But in quantum physics, entities like light can behave both as a particle and as a wave, depending on the situation. This challenges our notion of a fixed, objective reality. Does reality exist independently of observation, or is it somehow shaped by it?

• Imagine light: Our brains have evolved to be able to understand the world in which we exist, not the quantum world. Light doesn’t behave in ways we can easily visualise; it is unlike anything we experience directly. Every time we describe light as either a “particle” or as a “wave”, we are using metaphors that best describe light in a way we are familiar with. Could there be a more accurate way of understanding light that doesn’t force it into familiar categories? Is it possible that wave-particle duality is a convenient framework rather than the true nature of light? How should we distinguish between accuracy and utility in scientific modelling?

• Techno-logies: Wave-particle duality has consequences in the real world, outside of the laboratory. Understanding light has allowed us to create lasers, which rely on controlled photon emissions. Photovoltaic cells work because photons can knock electrons loose to generate electricity. Fibre optics use the wave behaviour of light to transmit data globally. However, just as past technologies brought both benefits and consequences, should science apply more caution in designing devices that manipulate quantum phenomena?

🔎 Find out more

• Simulate Young’s double slit experiment with this powerful tool here

• Watch this video hosted by Prof. Jim Al-Khalili to find out more about wave interference here

• Enjoy a long read of this article diving deeper into the effects of the experiment here

🍒 The cherry on top

• 🧠 Can You Outsmart Your Own Brain?: Ever wonder if you could trick your brain into thinking differently? This article from Psychology Today delves into cognitive biases and how they shape our decisions. Understanding these biases can lead to better decision-making in everyday life, and may even help you improve your critical thinking. A great read for those interested in Psychology.

• 🌐 The Big Idea Behind Blockchain: Here’s a short and clear explainer video from Encyclopaedia Britannica on what blockchain is - the technology behind crypto‑assets but with broader implications for transparency, decentralisation and trust in digital systems. A worthwhile watch for anyone interested in Computer Science and Economics.

• 📚 Education & Critical Thinking: The History and Meaning of “Critical Thinking”: This article from the Stanford Encyclopedia of Philosophy takes a deep dive into how the concept of “critical thinking” has evolved, how the term is used in education, and why it matters. This is a fascinating read for anyone interested in History, Education, or Philosophy.

👀 Keep your eyes peeled for…

• Wednesday 22nd October

  • Churchill College Cambridge Arts, Humanities and Social Sciences Interview Webinar

  • University of Sheffield Biosciences Taster Session

  • University of Sheffield Chemistry Taster Session

  • University of Sheffield English Language and Linguistics Taster Session

  • University of Sheffield Mechanical Engineering Taster Session

  • University of Sheffield Psychology Taster Session

  • University of Sheffield Sociological Studies Taster Session

• Thursday 23rd October

  • UEA English Literature Webinar

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