Meet our panel

Chris - With me this week is Will McMahon, who's a geologist at the University of Cambridge. He uses a variety of different geological techniques to study some of our most important periods in history since the planet was first formed about four and a half billion years ago. In your view then, Will, what is really the most important time in the earth's life?

Will - For me, it's got to be when plants were first colonising our continents. If we look around today, we have greenery everywhere. In fact, if you were to try and add up the biomass of all forms of life and put it on some big massive weighing scale, about 85% of the total would be made up by plant life.

Chris - So plants make up 85% of the mass of everything that's alive on earth?

Will - Everything - every kingdom of life, 85% of it.

Chris - And when did the first plants appear?

Will - So we're talking about 450 million years ago. It sounds like a long time, but bear in mind, earth is 4.5 billion years old. So 90% of earth's history, we actually had no plant life at all.

Chris - Thank you. Will also here, Xander Byrne, who's at the Institute of Astronomy. One of your interests is looking for exoplanets. That got a Nobel Prize, didn't it? These are planets that are not in our own solar system. They're planets orbiting stars elsewhere out there in space. How on earth do we find them?

Xander - That's all correct. So the problem with this is that planets don't usually emit very much of their own light. They're usually blinded by the light of the star that they're in orbit around. So we usually have to find them by the way that the star light is affected by the planet, whether that's the planet passing in front of the star and blocking out some of the starlight, or whether it's due to the planet's gravitational effect on the star causing it to wobble about and altering the kind of colours that we can see in the star's spectrum.

Chris - How likely do we think out there is another earth?

Xander - This is quite a difficult question to answer, but it's a bit of a numbers game, right? I mean, we think that pretty much every star that's out there has at least one or two planets around it. And in our own galaxy alone, there are 200 billion stars, something like that. And there are tens of billions of galaxies in the observable universe. So when you multiply these numbers up, it seems pretty inevitable that there would be something very, very analogous to earth out there somewhere.

Chris - Also with us this week, Charlotte Kukowski is a psychologist and she's at the University of Cambridge's Social Decision Making Lab, and she's also on the panel for a talk, which is happening at the Cambridge Festival, and that incidentally kicks off on March the 17th. And her talk is titled, "What Is For Dinner: The Future of Meat." So what are you going to say?

Charlotte - That event is going to be a conversation about how we can shift to diets that are sustainable for the planet, but also healthy and enjoyable for people.

Chris - There was a bit of controversy recently when the Cambridge University Student Union voted to make all of the meals at the University vegan, and there was a bit of pushback. Do you think that's a valid standpoint? How well received is that likely to be?

Charlotte - I did see that petition. What we see in the science, and what's often surprising for people to hear about, is that it really is about what we eat and not where that food comes from or how it's packaged. So the type of food, plant-based food in this case, and especially reducing red meat consumption, is really something that's highly impactful for the environment. And so plant-based options are a good way to go on with sustainable diets, but of course, they need to be accessible and available for people.

Chris - Thank you very much, Charlotte. Stefanie Ullmann's also here, she's a linguist and she also is going to be giving a talk at the Cambridge Festival, but your one's a little bit different?

Stefanie - I'm going to be talking about language-based artificial intelligence, something like social media, for example, and some of the phenomena that have been increasing on these platforms like harmful speech radicalisation.

Chris - And how does AI help with that?

Stefanie - Depends a bit how we use it. So a lot of these AI systems, a lot of the algorithms are of course part of the problem, but if we deploy them in a slightly different way, we can actually also use them to counter the harmful, the potentially dangerous content.