How big is a rainbow?

How big is a rainbow?

Author: BBC World Service November 28, 2025 Duration: 29:03

When listener Sakura’s husband came home from his morning walk in Cambridgeshire, UK, he told her about a massive rainbow he’d seen. But when he showed her a picture, she didn’t think it was particularly large. So how big is a rainbow really? Are they always the same size? And if some are bigger than others, is there a limit?

To find the answers, presenter Marnie Chesterton meets independent rainbow expert Philip Laven in a pitch-black studio to simulate how a rainbow is formed. He demonstrates how they are created by sunlight, reflecting and refracting in millions of little water droplets.

But what does that mean for their size? Raymond Lee, retired professor from the US Naval academy, says that rainbows are not objects and don’t have a linear size, just a specific angular size that’s relative to the person seeing it. But Marnie doesn’t give up so easily – some rainbows still look bigger than others.

In her journey to discover other ways to size up a rainbow, Marnie hears from Australian aerial photographer Colin Leonhardt who stunned the world with a beautiful picture. Next, assistant professor Ping Wah Li from The Chinese University of Hong Kong explains why it’s possible to come across more than one rainbow at a time.

And finally, atmospheric scientist Harald Edens shares another way to consider size, as well as how much he struggles to explain the complexity of rainbows to his four-year old daughter.

Presenter: Marnie Chesterton

Producer: Florian Bohr

Editor: Ben Motley

Photo: Rainbow of Dreams - stock photo stock photo Credit: Laurent Fox via Getty Images)


Curiosity drives discovery, and CrowdScience from the BBC World Service is built entirely on that principle. Each episode begins not with a scripted lesson, but with a question sent in by a listener from anywhere in the world. These aren't simple queries with easy answers; they are the wonderfully complex, often quirky puzzles about everyday phenomena and cosmic mysteries that make us all stop and wonder. What does silence sound like? Could we ever photosynthesize like plants? How does a crowd's mood physically spread? The team then embarks on a genuine investigative journey, tracking down the specialists at the very edge of our understanding-neuroscientists, ecologists, physicists, and engineers-to piece together credible, compelling answers. Listening to this podcast feels like having a direct line to the labs and field sites where knowledge is being created. The conversations are deep yet accessible, transforming abstract concepts into relatable stories. It’s a collective exploration where listener curiosity sets the agenda, making each episode a unique and democratic look at the machinery of our world and beyond. You become part of a global community pondering life, Earth, and the universe, one thoughtful question at a time.
Author: Language: English Episodes: 50

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