DAVID KIPPING: I think it's an interesting question to ask, why do we actually want to look for these worlds? Why do we want to maybe even one day visit them and colonize these exoplanets in the far future? For me, I think what we're doing right now is a bit like being the map makers. If you go back 400, 500 years, we really didn't know what the shape of the globe was or where the continents were, and people were voyaging out into the unknown and drawing the first maps of what might be out there. And I think a lot of what we're doing right now is kind of similar as astronomers. We are map makers, essentially. We are looking out and trying to draw, not the continents, but the maps of the exoplanets that our distant descendants might one day visit and perhaps even build colonies on. How to colonize a galaxy? Now the question is why do we have this urge? I think it's something fundamental to us as human beings. Ever since we left Africa, we've had this compulsion to explore, to go over the next hill, over the next mountain, cross that river, and see what might lie beyond. There is the promise of a better life, more resources, building a more advanced civilization. That core for exploration is somehow just built into our spirit, I think, to wanna do this. Ultimately, there is a practical reason for doing it as well, which is of course, having all of our eggs in one basket here on the earth is a fairly risky strategy. It would only take one giant asteroid to strike the earth and knock us all out of existence. Or of course it could be a gamma ray burst or a supernova. The universe has no shortage of ways of exterminating life on the earth. And so if we can put our presence on other worlds, it perhaps gives us a better chance of survival. However, one thing we have to be very cautious with this idea of expanding human presence is of course there could be living creatures or even living beings, civilizations out there on these worlds already, and we really don't have any more right than they do to put our presence out there onto these worlds, especially if there's someone already there. So there is interesting ethical questions about how we should actually conduct ourselves in such an exploration phase. If we want to explore beyond our solar system and visit even the nearest exoplanet to us, which is Proxima Centauri b, 4.2 light-years away, it would take even our fastest spacecraft many thousands of years to cross that distance using chemical propulsion technologies, which is what we have relied on so far. These distances are so great compared to human technologies that there's no way a human lifetime could ever last long enough to survive the journey and expect a step foot on the other side on these planets. So how do we solve this problem of one day visiting these other worlds? Is there a way that we could get over chemical propulsion and reduce that journey from thousands of years to maybe decades or even years? Now, unfortunately, we can't really think of a way of doing that with a human being on board, but we can think of ways of doing that with very small spacecraft, even micro spacecraft. So as ideas to use solar sailing or even really light laser sailing to push a spacecraft not only to nearby planets in the solar system, but beyond two exoplanets, many light-years away. The idea here is to have a very, very light spacecraft. Think of an aluminum sheet that is just maybe even 20, a hundred atoms thick, a very, very thin sheet of material, and yet it is huge, maybe many meters across, and you shine a gigawatt laser at that large sheet of aluminum. It will be propelled by light pressure to very high velocity. Now, of course, the payload is gonna be very small. We're talking about a microgram payload onboard this thing that's gonna be something like a very small ChipSat essentially on board. It's not gonna be able to do a lot, but it could probably take a photo, it could probably have an AI ChatGPT loaded on board that could maybe interact with people on the other side. But the idea of putting a human being on board, one of those things is completely impossible. Just a mass of a human is far too heavy for these vehicles to work in that way. So I think the most realistic proposal I'm aware of, of getting a human being to actually physically step foot on another exoplanet within sort of a hundred years timescale would probably, you don't actually have a human being on board the spacecraft. Instead you just have embryos, frozen embryos that perhaps are even genetically engineered to be well suited for the destination planet they're arriving at. Now, of course, there has to be something on board that's gonna unpack those embryos and grow them into human beings. And so you can imagine having a robot on board that would accomplish that goal. In fact, this idea was recently explored in Ridley Scotts' "Raised by Wolves" series, and I think it is most realistically the best way I can imagine of seeing a human being on another exoplanet in let's say the next century. It's difficult to imagine exactly what a astronaut arriving on an exoplanet is really gonna expect, because after all, with our current technology, we only have very limited information about what these exoplanets are truly like. We know their mass, their size, we know their chemical composition, but we don't truly know much more beyond that. So one of the things they might encounter, one of the problems might be there might not even be a solid surface on these worlds. There are these types of plants which are in between the size of the earth and Neptune. We sometimes call them super earths, we sometimes call them mini neptunes, but really we don't know. They could have a non-solid surface, which would obviously be a challenge for astronauts to build a colony in the way that we would normally recognize. On top of that, we don't even know really what the conditions would be like for a national in terms of the gravity or the terrain. The gravity could be much stronger than none of the earth. Of course, on the earth we have 1G of gravity, and if you go into an airplane and you're a fighter pilot, you experience maybe 2, 3, 4Gs of pressure on your body, and that's fine for a few seconds, but to live that way would be extremely stressful for the human body. I can't really imagine a human being coping with 4Gs of gravity for a prolonged period of time. On an exomoon, there'd be other challenges, of course, you would have this beautiful giant planet potentially in your sky many, many times larger than what we see the moon in our own sky. It would mean at nighttime there really wasn't a nighttime. You'd still have essentially a kind of afternoon level of light even during the middle of the night because of all the reflected light coming off your giant exoplanet around you. And that would raise some interesting questions about potentially what the biosphere itself would be like. Would animals have developed to live differently to nocturnal creatures on our own planet? It could be a very hazardous place to be an astronaut if we are not very careful. But you know, this is the human spirit to go to a new place explore, and I'm sure the people who are willing to do that will be very aware that they're taking a huge risk and are probably accepting of that risk because that's something built into us, at least some of us, to wanna go to those places and take the risk anyway. One of the interesting cultural questions about a civilization which spreads out between the stars is that space is very, very big. In fact, if you spread out far enough, you could end up on one side of the galaxy to the other, which is a hundred thousand light-years across. So that would mean that simple messaging limited by the speed of light would take a hundred thousand years. It's very difficult to imagine how a culture could remain monolithic over such a long distance, that in fact these cultures would splinter off and perhaps even forget their origins, as is often explored in the sci-fi books and the movies "Dune", where civilizations really aren't sure where the original planet even is anymore. So I think a question we often have when we think about the looking for aliens is that we kind of assume there'll be a monolith. We assume they'll all act the same way, but truly, even if they spread out from a singular source, the sheer distance scale will ultimately force them to fracture into a diverse range of civilizations and cultures, and that's interesting when we think about looking out that we are not gonna encounter just maybe one single galactic federation, but really a menagerie of different beings. Personally, I think the idea of humans expanding and colonizing other planets is feasible in our own solar system, but is a stretch to imagine really happening for exoplanets just because of the sheer distance to them. The sheer challenge of traveling that long in space with a human body is gonna be very difficult to imagine overcoming. I never say never, but just it's not my bet that that would be a likely thing to happen, but I do think I can imagine a human presence across the solar system in the far future and having an extended human presence in the form of AI agents, robots and machines, children, if you like, spreading out to those more distant outposts and sending us back information and being ambassadors to the greater part of the galaxy.