I'm Rory Stewart and I grew up wanting to be a hero and I'm still fascinated by the ideas of heroism.

In my new series, I'm taking in the long sweep of history from Achilles to Zelensky and asking, what is a hero?

Simply doing your job, being a decent human being.

A true hero is someone who just kind of shines by

their own light and that light is to be recognised by others. The long history of heroism with me,

Rory Stewart. Listen on BBC Sounds. My guest today has quite an unusual relationship with

gravity. While she spent her career exploring its fundamental nature,

much of her free time has involved trying to defy it,

from scuba diving in the Indian Ocean to piloting small aircraft over Canadian waterfalls.

Her ultimate dream was to escape gravity's clutches altogether and become an astronaut,

a dream that was

snatched away by an unlikely twist of fate. But Claudia Duram has no regrets. I've had to defy

gravity for most of my life, she says, in an effort to understand it. As Professor of Theoretical

Physics at Imperial College London, she now grapples with deep mathematics, where the fields of particle physics, gravity and cosmology meet, on a quest to understand how the universe really works.

She's a pioneer in a subject called massive gravity, which might take us beyond even Einstein's theory of relativity, and shed light on why

the universe is expanding at an ever-increasing rate. Claudia de Ramm, welcome for the Life

Scientific. Hi, Jim. Very good to be here. Now, here on Earth, we all experience gravity every day

and we can't escape its clutches. So what is this mysterious thing we call gravity? That's one of the

most profound question there is. What's really, to me, beautiful and fundamental is that it's actually

very universal. Even if in outer space, we can't escape gravity. It's always there. People will be

familiar with the experiment where you drop a hammer and a feather, and of course they fall at different speeds. So it does seem like gravity is acting in different ways, but that's not the case, is it? That's not the case. In fact, there's lots of different things happening. There's the friction of the air. But if you were to do the same thing on the moon, not because gravity is any different on the moon, it's just the same, but there's none of the other distractions like atmosphere on the moon.

And so that has been done, actually, during the Apollo missions, an astronaut dropped a feather and a hammer, and they fall exactly at the same rate.

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