Instant Genius - How our planet connects to the Solar System around it

Episode Date: February 16, 2026

We often think of our planet as an isolated island, solitary and cut off from the cosmic ocean it resides in. But the truth is, Earth is intimately connected with the Universe surrounding it. What’s more, by learning more about the Solar System around us, humanity has changed its own view of the world as well. Dr Dagomar Degroot from Georgetown University spoke to us to explore this idea in more detail. Learn more about your ad choices. Visit podcastchoices.com/adchoices

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you'll hear the world-leading scientists and experts talking about the most fascinating ideas. in Science and Technology today. I'm Ezi Pearson, commissioning editor at BBC Science Focus. Today, I'm talking to environmental historian Dr. Dagamore de Gru from Georgetown University. We often think of our planet, Earth, as an island completely cut off and isolated

from the ocean of the universe surrounding it. But in reality, our planet is tightly interconnected to the motions and changes of our solar system. The sun, planets, moons and even other space rocks have helped to shape our world and even human culture. Dagamore explores these ideas in his latest book, Ripples on the Cosmic Ocean, and is here with us to discuss them. Hello, Dagamara, and welcome to Instant Genius.

Well, thank you so much. It's so fun to be here. This idea that not just Earth, but our entire human culture, is intimately connected with the universe, is really fascinating. But how long has humanity been influenced by the heavens? How long has that connection been going? Well, I guess if you define humanity as our species, so homo sapiens, then I guess it's since the beginning. It's since 300,000 years ago. And that influence has been direct and indirect.

So probably the most direct influence has been climate change, you know, since we evolved 300,000 years ago. We've had to cope with some pretty big ones, some pretty huge climatic changes. Extreme glacial periods when the ice sheets marched south. from the Arctic or expanded out of mountains and covered a huge chunk of the earth. The earth was just much, much, much, much colder and drier and dustier during glacial periods that we had to live through, and then warmer sort of interglacials. And these were paced by changes in the Earth's rotation and in the ellipticity of its orbit around the sun. So like how circular it is.

So these were like thousand year cold and warm periods or like dry and wet periods. But then there were also like really short and abrupt and extreme climatic shocks. Like I mean, it's unbelievable. I just get really excited about them because they involve just massive breakdowns in Atlantic Ocean circulation. Like the thing just kind of shuts off because of meltwater coming from ice sheets. and it's just like it's like you're flipping a switch and a huge part of the northern hemisphere, at least just kind of cools down. So, I mean, our ancestors had to live through the most extreme climatic changes.

Some of them even bigger than the ones we're probably going to have to cope with, unfortunately, in the coming century. That's an example of like really direct and profound impacts on our distant ancestors of changes in the solar system and how Earth moves through the solar system. system. But of course there were also indirect changes like so much of ancient culture, so much of the kind of cultural building blocks that our civilizations are built on today and kind of be traced back to how people try to understand the heavens and what they were seeing there, how the heavens were changing, from the regular cycles of the planets to the occasional

appearance of comets. So the solar system and its changes are sort of baked into what we are beginning 300,000 years ago. And you mentioned there that the sun causes these huge changes in global climate and the motion of the earth as well creates these huge changes. Is there been other smaller climatic changes that have started somewhere out in space? Yeah, there's a great question. Can I break that down a little bit more like the big changes. Actually, I've got this like multimedia project called the Climate Chronicles, and so right now I'm doing a lot of this kind of work. So yes, changes in Earth's rotation and its orbit around the sun, they're responsible for these glacials and interglacial periods that we had to live

through. Right now we're in an actually in an interglacial period, and we're kind of wrecking everything obviously with our greenhouse gas emissions. But, you know, why were these changes able to affect us? It's because actually because of plate tectonics. And that goes back, that story actually goes back 45 million years ago when the Indian plate crashed into the Eurasian plate while the Antarctic plate, or just before the Antarctic plate kind of moved to its current location. And what all that did is to start a process of global cooling

that lasted for like 45 million years. And only as of about 2.5 million years ago that the Earth become cool enough for these cycles, in Earth's rotation and in the ellipticity of its orbit to be able to cause glacial periods. So the upshot is that there's a lot of different things happening at the same time, and they're happening on this, like, vast scale, right? Like the Earth is changing profoundly, the solar system is changing, and it's all interacting. And it's really, I think, quite a profound illustration of how intimately connected

Earth is to the rest of the solar system. Now, those are the really, really megacized changes. You asked about the opposite. So the smaller changes. And yeah, so we're now in an interglacial, but even in an interglacial period where things are generally warmer and wetter than they are during a glacial period,

you can still get climatic changes. On a global scale, small ones, on a regional scale, sometimes much bigger. So as an example, in the Holocene, which is what we call our interglacial period, began about 11,700 years ago. The Sahara, actually, for most of it, was a grassland. It was a green Sahara. And only as of about 5,000 years ago did it turn into the world's second largest desert, the world's biggest hot desert. And so that's a megacized, regional climate change. And it's caused by a shift in the strength

of the monsoons. On the global scale, these changes, are a lot smaller. One of the biggest ones is called the Little Ice Age. And this is a period of climatic cooling that's really, really complicated. It's often misrepresented. In fact, it's difficult to get an accurate picture of it in popular media. But the upshot is things start to cool down by about the 13th century, maybe the 14th century. And then there are these waves of cooling in the northern hemisphere that eventually become sort of global and are associated with drought in some places, heavier precipitation in others, instability, the instability of weather, and a lot of it can be tied back to changes in solar output. So just really, really tiny changes in how much radiation

comes to us from the sun, but then also explosive volcanic eruptions. So you need like a real, really, explosion and not all volcanoes are like this. You can think of the Hawaii volcanoes, right? They're just oozing lava. No, you need a big explosion because what has to happen is you have to send a whole bunch of sulfuric gases into the upper atmosphere. You can only do that with a huge amount of force. And then the sulfuric gases start to create these aerosols like dust particles. They scatter incoming solar radiation. And that pools. the lower atmosphere, warms up the upper atmosphere, cools down the lower atmosphere. And so those are the two big forces, probably responsible for the little Ice Age, a small decline in solar

output, and then clusters of big volcanic eruptions. And this lasts all the way through the middle of the 19th century. Then we get, of course, the beginnings of global warming. One of the things you bring up in the book is that we can learn about what's happened with our own planet and possibly what we're doing to our own planet by looking elsewhere in the solar system and at Venus. What exactly can we learn by studying the planets around us? There's a whole field called comparative planetary climatology. And it's possible because we've got rocky bodies in the solar system that have atmospheres beyond Earth. So of course, Earth is, no, you know our atmosphere. And we've got one more rocky body in the solar system that has an atmosphere.

just as thick as ours, which is the moon Titan. It's an awesome place. You've got oceans of methane on the surface of Titan, and you've got oceans probably of water under the surface of Titan, and then you've got this thick, complex atmosphere. And one of the missions at NASA that has not been canceled yet is being sent to Titan to explore this ocean. And, you know, who knows there might be life there.

It's one of the coolest places that we know of in the universe. But, okay, so those are two rocky bodies that have the same density of atmosphere. Then you've got another rocky body that has a much thinner atmosphere. In fact, 100 times less dense than Earth's, and that's Mars. And then you've got another one that has a much thicker atmosphere than Earth's. In fact, 100 times thicker than Earth's, and that's Venus. And, you know, until really quite recently, until like the 19th, 1940s or even 50s, scientists believe that there was probably life on Venus, on the surface

of Venus and probably on the surface of Mars. And the assumption was that both of these planets, yeah, you know, their climates might be different from that of Earth's, but not that different, right? Like Mars is a bit cooler. Venus is maybe a bit warmer, but, yeah, maybe Venus is kind of like a swamp planet, you know, like Earth used to be during the time of the dinosaurs. And maybe Mars is like a glimpse of Earth's future. So it's going to be colder and drier.

But basically, you can have plants on both worlds. And it was one of the surprises, the great surprises of the early space age, that turns out Venus is a hell world, basically, right? It's as I put it in the book. It's not only as hot as an oven. It's hot enough to melt the oven. It's not where I'd be heading on my holidays. I'm going to tell you that. If I'm going on a space holiday, I'm not going to Venus.

Well, I'm going to pitch it to you maybe in a second. But the upshot is that this is a real mystery, right? So how in the world, Venus is on the inner edge of what we call the habitable zone. Maybe a little bit closer to the sun than the habitable zone is now. But the habitable zone is traditionally defined as the part of a star system where it's warm enough that you can have liquid water stable on a planet's surface. So that's the habitable zone. Earth is in, obviously, in the habitable zone.

Mars is on the outer edge, and Venus is maybe a little bit inside the inner edge. So, I mean, it's really shocking then that Venus is actually harder than Mercury. How do you explain that? And it really was one of the most important discoveries, I think, of the space age. And it was first proposed, really, by Carl Sagan, you know, a great planetary scientist, exobiologist. space communicator, that there is a possible reason that Venus is that warm, and it's something

that we call the greenhouse effect, right? Atmospheres can actually trap radiation from the sun. And so a lot of the people who then worked on Venus and its greenhouse effect ended up ringing the alarm about what we were doing to the Earth, because of course by releasing carbon dioxide and other greenhouse gases like methane and nitrous oxide, we were strengthening Earth's greenhouse effect. So James Hansen is a great example. One of the most important climate scientists, a pioneering climate scientist who rang the alarm about global warming in the 80s. And he was a Venus scientist. He was a Venus specialist who decided, you know what, this effect wrecked Venus. I'm going to make sure it doesn't wreck the Earth. And he was

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Visit focal powered by name.com for more information. So looking at these other planets, it definitely sounds like making analysis. between our world and these other worlds has been incredibly useful. But has there been other times when looking at other planets and trying to make those sort of similarities has led people down a slightly wrong idea about what might be going on in our universe. Yeah, slightly wrong is one way of putting it. So, you know, a big part of the book, but my favorite parts of the book, honestly, are about the apparent discoveries of extraterrestrial life based on the assumption that what's

happening on other worlds is what happens on Earth. And a large part of that is astronomers for like, I don't know, 400 years, 300 years, seeing changes on other worlds. And this is actually why the book kind of starts with the invention of the telescope right around that time, because, you know, people with the telescope are able to see these points of light in the night sky, planets, as being, you know, disks, right, as being real worlds. And they can start to see that those worlds change. And then, of course, the question is, well, what might Earth look like if viewed from those worlds, right? Like, if you're standing on Mars and you've got a little telescope and looking at the Earth, what makes Earth Earth, basically, right?

Like, what are the first things you notice? And what reveals Earth to be a living world? Well, it's the movement of water, basically, right? It's clouds going about their day, right? Moving across the surface of the Earth. it may be how coastlines are changing. It certainly is the ice gaps expanding and retreating, right? Sea ice, really, in both the Arctic and Antarctic, expanding and retreating with the passing

of the seasons. So Earth, when viewed from afar, has to be a dynamic place. And its dynamism reveals the ingredients of habitability. And if you really had a good telescope, then you can see even more important, telling things. You could see vegetation changing in different hemispheres as the seasons change. You could see the tillage of huge tracks of farmland. You could see the construction of cities, electrification, all of these things, right? So you could see dynamism on Earth that reveals it to be habitable and then a different kind of change of dynamism on Earth that reveals it to be

inhabited by intelligent life. So it really is a kind of, I think, a thing. fascinating thought experiment that these people have to do. And so it's totally understandable why they would then look for similar changes elsewhere. And many of them ended up thinking that they found it, right? They thought they'd found cities on the moon. They thought they'd found swarms of insects on the moon, right? There was even a hoax in the 1830s about finding manned bats, which really cracks me up. We've seen man bats on the moon and there's some man bats are better than others and they live in different and all this kind of stuff. But then I think the most interesting one is the discovery of so-called canals on Mars.

And then for like 50 years, thousands of people end up seeing these canals on Mars and there attempts to explain them. And it turns out, yeah, because Mars is older and drier than Earth, it's a dying world. And a civilization that has evolved there now has to try and cope with that drying. and so the only way they're able to stave off extinction is to build a global network of canals that siphons water from the last place it exists on the planet, the poles down to the equator,

where it can go into fields. And there's like this whole Mars world system, this beautiful sort of idea of what it would take to survive on a dying world. And it's all wrong, obviously. But it does generate some fascinating debates and ideas and people coming up with the kind of principles of interplanetary, inter-civilizational communication. And so actually one of the things that I'm really passionate

about about this book and just in general is rehabilitating people who are wrong, who come up with these big ideas, these dreams. And they're wrong now. We know they're wrong. But sometimes it's those big ideas. And it's people who are. are bold enough to be wrong, who end up moving things forward. And it's almost actually, to be honest, for me, I almost don't like to think of them in terms of being right or wrong. It's more like, you know, how are you contributing to the conversation that is, you know, scholarship and our broader sort of discussion about space.

That was one thing I really enjoyed was all of the different stories about the individuals and the various different characters that were involved. in this, you know, the story of us learning about what was going on and how us and the planets were all connected. Are there any other favorite stories that you'd like to highlight? Well, I have a few, if you'll humor me. I can discuss not only stories about people, but it's just some ideas. And I think the first one I want to go to is back to Venus. Because I'm pretty passionate about this. I teach a class on space history. And this semester, A semester we just had, I had a class on Venus.

And I came in hot, and I, you know, I told my students all about the prospects for Venus colonization. And none of them were convinced. Nevertheless, it's in the book. And so the thing is, if you fill a balloon with Earth's atmosphere, and you send it off to Venus, presumably you'll be blowing it up, actually, when you get to Venus rather than before. But so you do that. And then the balloon ends up floating around the cloud tops of Venus. And why is that?

Well, it's because, of course, the atmosphere of Venus is 100 times denser than out of Earths. So you fill up a balloon with Earth atmosphere, and you're going to float way above the surface of Venus. And where are you going to float? Where you're going to float in a part of the Venusian atmosphere, where the temperature is about as warm as it is here in Washington, D.C. in the summer. If you've ever been in Washington, D.C. During the summer, you'll know it's too hot, but you can survive.

It is survivable. And it's rough mostly because it's so human. Well, there's no water on Venus. So you're actually going to be in a pretty comfortable place. What happens if the balloon is breached, right? If there's a hole in the balloon, well, that's okay. You just have to patch it up. You've got quite a bit of time to do it.

It's good because of the atmosphere inside of the balloon. balloon is about the same as the atmosphere outside of it, you're not going to have a lot of leakage, so it's not a huge problem. Can you build anything because you can't mine, obviously, on the surface? It's too hot, so can you build anything there? Well, yeah. You can condense stuff out of the atmosphere. It's so thick and it's full of really good chemicals you can use. Like if you can capture the gases and condense that and distill it into liquids and solids, then you can actually build with it. And it's just a, it's a really fascinating, to me, idea from the 20th century, you know, after the discovery of what Venus is actually

like, it's a fascinating idea because it just gives you a glimpse of what it might be like to actually settle on another planet. You'd have to try and think like a Venusian and do things that are completely alien to us here, right? Like, what do you mean? You live your entire life on a floating city. What do you mean you can't actually mine things like rocks and stuff? You have to mine things from the atmosphere.

like that just sounds weird. But really, the cloud tops of Venus are probably the most benign environment in the solar system outside of the earth. And it's just completely, to me at least, that's, it's completely, was not expected when I started writing the book, put it that way. The top of the Venus atmosphere.

Like the further down you get, it starts getting really, really bad, but the top is fine. You don't want to go lower. Yeah, yeah. Do you not want to fall. Whatever you do, Do not fall.

You're going to fry before anything else. But yeah, so that's just an idea from the book that I think is I really enjoyed writing about. Specific story about people. One of the ones that stands out is about Nikola Tesla. And, you know, Tesla is this fascinating figure in general. He's brilliant, obviously, and he's really ambitious, and he's constantly casting about for the next big thing, right? And he, I mean, it's fascinating to think about because he is harnessing this entirely new power, right, the power of electricity. And he is realizing that with this power, he can sort of, he can explore new dimensions of reality.

And he can harness abilities, really, that humanity never has had before. So just imagine being in that kind of mindset, right? Like in a laboratory, you've got like huge spark. of lightning flying all around you, right? And what that must be like every day to wake up and, you might actually have species altering discovery on that day, right? And it's such a just a fascinating idea. Anyway, late one night, he's there with his receivers and his instruments, and he thinks he

hears a message, some sort of message from another planet. It's a repeating message. It's kind of like what we're looking for with SETI. search for extraterrestrial intelligence now, right? We've got all these efforts to listen for radio signals from outer space. It's a little bit like that. This is the late 19th century. He's already thinking in these terms, listening for a repeating message.

He thinks he hears one. And really, this shapes the rest of his life. Because for decades, he's sort of chasing after this discovery. He thinks he's heard a message from ours. And he builds these huge machines to try and send a signal back. He insists he's heard one. He thinks it's the next big thing that the rest of the 20th, like the 20th century

is going to be defined by interplanetary communication in the solar system. And what he probably heard was an interaction between Io, the moon of Jupiter and Jupiter itself. So like sulfur arising from the volcanoes of Io, getting trapped in the Jovian magnetic field, which is much stronger than Earth's,

and generating a repeating signal. So he did hear an extra, a terrestrial message probably. Just he thought it came from the wrong source. And so it's an example of how this perception of change in the solar system, how it can shape the lives of even like really prominent people. So I really like that story. Another story that I like, just the last one then, is about the path towards what we now

call planetary defense, so protecting our world from asteroids and comets. and just, you know, I'm a historian, and this is a really interesting example to me of how history comes to change. And, you know, in the 1980s, the threat of asteroid and comet impacts is known to a small group of scientists. And there's like really, like, limited, poorly funded efforts to deal with it. But then, by the time you get to the early 2000s, for sure, planetary defenses it's now called is NASA's most popular priority. It's ingrained within the things that NASA does. There's like asteroid detection networks and systems being set up. And people are planning asteroid deflection missions, which you've now done. So there's a in 20 years or so,

there's a huge shift from this being kind of a totally niche concern that nobody takes seriously to it being something that probably actually the existential risk, the sort of species threatening danger that we've handled best. So in a way, it's a really happy story because we now have a much better handle on the threat. In another way, for me, it's a huge problem. Like, how did this happen in 20 years? What caused it? And so in the book, I go through everything from, you know,

comet impacts on Jupiter to near misses around Earth. the end of the Cold War, changes in NASA's crude space program, cultural changes, like all these things, all coming together in just the right way, allows for this, you know, really a successful effort to deal with an existential risk.

But all the pieces had to be aligned. And that's what I like about that story. Thank you for listening to this episode of Instant Genius, brought to you by the team behind BBC Science Focus. That was Dr. Dagamar de Groot. To discover more about the topics we've just discussed, check out their latest book, Ripples on the Cosmic Ocean,

available from the 26th of February. If you liked what you just heard, then please consider subscribing to Instant Genius on your preferred podcast platform. If you'd like to see our guests and hosts in person, why not check out our YouTube channel at Science Focus. The current issue of BBC Science Focus is out now. Pick up a copy wherever you buy your favourite magazine

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