Ian Sample

speaker

1,923 appearances 27 recordings 3 series first heard Apr 2026 last heard 5d ago

Ian Sample’s voice in public audio — every appearance, attributed to the second.

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recordings per month · last 12 months

Recordings per month over the last 12 months — 27 in all, peaking in Jun 2026 with 8.

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Two people who are really key in getting some understanding of dark matter out there. voice-verified

The first is a guy called Fritz Zwicky. voice-verified

He was a Swiss-born astronomer. voice-verified

And in 1933, he started looking at clusters of galaxies. voice-verified

And he noticed that there wasn't enough visible matter in these clusters of galaxies to prevent the galaxies from just flying apart. voice-verified

And he said, oh, maybe there's this stuff called, he called it dunkle materiae. voice-verified

That didn't have a massive impact at the time. voice-verified

But about 40 years later, in the 70s, a US astronomer called Vera Rubin, she looked at individual galaxies. voice-verified

So she zoomed in on individual galaxies and looked at the speeds of the stars, especially around the periphery of those galaxies. voice-verified

And she worked out that the speeds of those stars at the edges of those galaxies just didn't make sense unless there was... voice-verified

some other matter there that wasn't visible, but that was exerting a gravitational force on those particles. voice-verified

And so now the sort of thinking is that galaxies are forming and exist within these kind of clouds of dark matter. voice-verified

Dark matter is thought to make up about 85% of the matter of the universe, okay? voice-verified

That would leave, you know, what we call normal matter, the stuff of you and me, making up about 15%. voice-verified

It's extraordinary that we don't know what makes up the vast majority of the matter of the universe. voice-verified

That is staggering. voice-verified

And so to understand this is an enormous question in physics. voice-verified

It's all clearly a bunch of particles that are unobservable to us, at least directly, but we don't know what's there. voice-verified

And that is super intriguing. voice-verified

Yeah, so not only is dark matter invisible, voice-verified

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