11. COSMIC HITCHHIKERS
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We've come a long way and where do we go next? Who will we meet along the way?
The season fades out as we imagine ways to travel beyond our solar system...Thanks for the ride.
Irina Mullins is a Professor of Physics and Astronomy at Houston Community College. She is also the creator of the ‘Cosmic Hitchhikers Hypothesis’.
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We’re in a large cave, there is a slow descent. Moisture everywhere: you can hear it, dripping, gurgling. You continue to move down the water flecked slope. You stumble on some slime covered rocks. You feel the space around you change, open up, and beneath your feet the slippery stone gives way to pebbles. There is the slow slap of water falling onto land.
The air changes temperature. It’s obvious you’ve just stumbled out into a vast, open space. Sand now under foot. You look up ahead into the gloom and see that there is some kind of lake or sea even ahead of you, and above you where there should be sky is the cavernous, monstrous expanse of a hollowed earth. Your feet wobble at the sheer inverted vertigo of this blind sea, this vaulted, paved firmament.
Where are you and how did you get here? Deep below the surface of a roving planet, untethered from the gravitational pull of any one star or its system. On a worldship passing rapidly through the interstitial realms of interstellar space. You’re a subsurface, cosmic hitchhiker. You are a tourist.
This episode is about Irina Mullins’ theory of cosmic hitchhikers, it’s called a theory but it just as well could be called a story. In fact, this episode is about a number of stories, and what they might reveal to you, to all of us:
Irina Mullins: So, let me first tell you a story. Once upon a time, there was a cloud. there was an interstellar cloud of gas and dust that travelled in a distant far galaxy for millions and millions of years, and once completely accidentally it encountered the shock wave from a supernova. And as a result of the accidental event, the it triggered collapse, contraction of the cloud. And that's how the sun in our solar system came into existence. So that's one of the theories accepted right now by scientists.
IM: This is sometimes is called in science is called a frozen accident. Physicist Gelman discussed it in the 1990s, I believe, in his essay. So a frozen accident in science, it's accidental events that may happen may not happen. But if it happens, it produces far reaching and long lasting consequences. So another story another example, there was some planet in the solar system, it also by the size of Mars, it was orbiting the sun just minding its own business. And once one day accidentally it collided with Earth. And as a result, the Moon was formed from the collision. And so this is the Giant Impact theory, which is commonly accepted right now by scientists.
IM: Again, that was a frozen accident, because it just happened by accident. But as a result we have, we have Moon and the moon. It has its own impact on the development of life on Earth. For example, the moon stabilises the excess rotation of Earth, and as a result, it creates conditions more favourable for development of multi celled organisms. The moon also exerts tidal forces that mix up oceans and end effect in the development of life.
IM: Another example, is dinosaurs. So about 65 million years ago, the comet or asteroid striked Earth and as a result, like 75% of all life forms on Earth they became extinct, including dinosaurs. That was another Frozen accident, if it didn't happen, we still would have dinosaurs roaming our planet probably. Which means that our existence and our, well humans dominating this planet, is a result of chain of very large number of frozen accidents. And if you're talking about comets, or asteroids, I would say making dinosaurs extinct. But it also had in the past, and in distant past of our planet, we had comets and asteroids striking our planet, and they will actually bring in water and carbon based molecules to our planet.
IM: And those were required building blocks for life for creation of life on our planet. Which means in other ways, I can say that our universe is very, our universe is very creative, when it's producing conditions to support the origin and evolution of life, all conditions to destroy life. And everything that we can find on our planet is the result of chain of frozen accidents. Now, if you look at the great filter, so the idea of the Great Filter is that there is a chain of stages that lead to the emergence of technologically advanced civilizations. So first, you need to have one important stage, you need to have the right star with the right planet in the habitable zone, then you need the emergence of simple life forms, then the emergence of complex life forms, then the emergence of species that can actually make tools, and then the emergence of technologically developed civilizations that can produce some kind of activity that we can observe.
IM: And the great filter tells us that probably some of those stages or transitions from one to another is very unlikely. And if it's unlikely that may explain why we don't see, let's say why we wouldn't find complex life forms elsewhere, or why we wouldn't find technologically advanced civilizations. Well in a way this is just a method to explain the Fermi Paradox, because the Fermi Paradox tells us that, okay, if there are civilizations out there, why don't we find them in our solar system?
IM: And why don't we find them elsewhere in the galaxy? And there are three approaches how to explain the Fermi Paradox. So one is that they're just not there. They don't exist. And that's, that's the idea of the great filter, because the Great Filter tells us you know they just don't exist, there's some kind of cut off event that just prevents the interruptions. Another approach is that they do exist extraterrestrial civilizations exist, but we don't know exactly how to look for them and where to look for them. Maybe we're looking in the wrong places.
IM: Maybe we're looking for, Maybe they can, or their activity can produce some kind of techno signatures that we don't recognise. And the third approach is that the civilizations, they may be out there, but they're intentionally hiding they may be a reason that they don't want to be discovered. Or, for example, they may be just exisiting on the planets in the habitable zones. And they found ways to live in harmony with their worlds, so they don't really produce something that we can actually observe in interstellar distances. So if we go back to the great filter, as I said, it's basically the way to explain the Fermi paradox in terms of they're just not there.
IM: And the great filter tells us there is some of those stages in the development of life or transition from one to another, which is highly unlikely. And it's something that is common for pretty much every planet that happens to have life on it. But remember, I told you about those frozen accidents. So there's so many of them that I highly doubt, that there is just one cut off event for all life forms everywhere in the galaxy.
IM: I started thinking about it several years ago. And my first question was when free floating planets were discovered, and free floating planets are planets that are not gravitationally bound to stars, they just travel in the galaxy on their own. And I was thinking, what about if they will just one of them will just pass through the solar system, what would happen? Of course, the answer depends where it will travel through the solar system, like in our solar system? or in our cloud? So would it affect us negatively or not? But then later, as though the civilizations, for example, face some kind of existential threats, for example, a nearby supernova explosion, or their star is dying.
IM: So how would they evacuate the whole population, because for some time, the idea of worldships, spacecraft that would pick up the whole civilization and carry it to another planetary system was sort of popular, but then if you look close it closer, it has problems, because if you have to carry hundreds of 1000s of members of a civilization, or maybe millions of them, you also have to carry all the resources, all the supplies, you have to create biosphere, you have to have a defence protection from space radiation. So that will be gigantic, gigantic spacecraft, that will have to travel for at least several centuries, to another planetary system. And if something goes wrong, then basically they don't have any way to get resources anywhere else, they cannot just go by somewhere to pick it up. And that would mean, you know, any pandemic, any social unrest, or any just something breaks down, and they're doomed. So basically, you know, how did they say that life happens when people make plans, right?
IM: So they can make plans. But something can definitely happen over the course of several centuries, that can actually result in their complete demise. So they will not reach another planetary system. And then I returned back to that idea of free floating planets. And I thought, well, maybe if a free floating planet is based in, and that planetary system just based on what is causing it, the planetary system where civilization exists, they can actually transfer all their infrastructure and their population on the planet or another planet free floating planet, and I just use it as a means of transportation to reach another planetary system.
IM: And actually, their idea of the question of how many free floating planets are out there in the galaxy, it was investigated by many researchers and the estimates are from for example, 2.5, Earth- like planets per star, or, for example, Lingam and Loeb, they have an article which is called "subsurface exolife." And in the net research paper they estimated the number of free floating planets with the radius by more than 0.3 of radius of earth shouldn't be like 30 times the total number of stars in our galaxy.
IM: So we'll have 33 floating planets for each star. So number is very large, and Lingum and Loeb they also estimated that even right now we may have a free floating planet basin through our solar system at some distance maybe a one , well 2000 astronomical units or a little bit more, which is in our age of the oort cloud. Like right now, they also said, you know, if they're here, we really need to send like small spacecraft with solar cells to investigate them. And so if there's so many of them, that means that can pass planetary systems pretty frequently, maybe like every 20/30,000 years, which means the civilization are just looking for ways to escape, you can actually prepare to transition to that free fortune planet and to fly away.
IM: But another way also if there is no right planet coming by, they can create their own free floating planet. So they can pick up like stenotype type object or goblin type and type object, which is getting pretty close, like semi astronomical units from the sun, for example, and travel on them toward the inner age of the oort cloud. And then from there, they can use gravity assist event events just to fly away from from the planetary system. And once they approach another one, they cannot really get exactly the inner part of the another planetary system, but they can reach the oort cloud of the planetary system and then gradually over a long, long time, they will just travel through the inner part of the planetary system that they will reach.
IM: Otherwise, then we choose just to leave to remain in the outer parts and outer regions of that planetary system. For example, if that planetary system already has its own civilization, it has some kind of fly forms and they don't want to interfere, you know, they just they will say, Okay, we'll just stay in the outer regions of the planetary system. And we will not interact with those species. Or, for example, over many, many years of their travel among the stars, they can get accustomed to conditions on the free floating planet, and they will prefer the cold and distant regions of the planetary systems.
IM: Another also, consequence of this would be that there might be freefloating planets captured by planetary systems, they might have extraterrestrial species or might have extra extraterrestrial artifacts, so alien artifacts present now.
IM: Well, they might be in hibernation, but I don't think all of them would want to be in hibernation. And they could use sources of energy, for example like controlled nuclear fusion. Because we know scientists on Earth are already working on achieving a controlled nuclear fusion. So those extraterrestrials they would have to be advanced, they would have to be at least a few 1000 years in the development of humankind, because they would need to have spacecraft to transfer them from their planet to stenotype or goblin type objects. They would have to build infrastructures to live on those objects central to reach the oort cloud.
IM: They would have to have perhaps propulsion systems and some methods of navigation to use gravity assist events in the oort cloud also to leave the oort cloud or to intercept the free floating planet so they would have to be a few 1000 years ahead of us in development, and then they would have to build some kind of subsurface habitats on the free floating planet. Now, what is important here is that standard is demonstrated that some free floating planets, they may have subsurface oceans, and those advanced extraterrestrials that can actually get to those subsurface oceans and build their habitats there.
IM: Because water protects from space radiation. And space radiation is very, very harsh in the interstellar space. So that's one of the advantages of using free floating planets. So unlike a spacecraft that has very, very limited resources, on the free floating planets they will have protection from space radiation, if they reside in subsurface, they have a huge number of resources. They have some gravity surface gravity, which is also very important because if you ever heard there's something called gravitational biology, so It studies the effect of gravity on a living organisms on Earth, and our bodies and all the cells of all living organisms on Earth. They're very finely tuned to gravity.
IM: Worldship, it's another name for a very large spacecraft that would carry 10s of 100s of 1000s of people or some kind of members of civilizations. So basically, you can have, it is possible to build an interstellar spacecraft to carry small and medium groups of some extraterrestrial, or human travellers. However, worldship means spacecraft, which is so huge, it can carry large populations
IM: To become cosmic hitchhikers who first will have to learn how to colonise cold worlds in our solar system, for example, like the moons of Jovian planets located further from the sun objects in the Kuiper Belt. And we would really have to expand up the distance of like 70/80 astronomical units away from the sun. And so then they'd have just in we could think about that we would have to learn how to build infrastructure, subsurface structures, we are not ready for that. But if you think about the future of humankind, so probably because of the nuclear reactions happening in the sun inside the sun, the sun is gradually changing and it's evolving.
IM: As a result, probably in one, 2 billion years from now, it will make conditions on Earth inhabitable, so we'd have to go somewhere else. And but it's the good news is that we have at least several 100 million years to think about it. You don't have to worry about it right now.
You see grandparents take photos of their grandchildren playing in autumn leaves.
Delivery vans take the place of rubbish trucks, behind them fire brigades, ambulances, an Amazon-contractor Hyundai van. Unprotected building sites. Bridges spanning the mouths of off-colour rivers
You see processes you have no name for. A quark entanglement, a rocket engine fighting the tyranny of gravity. Farms for life that seem hard to fathom, you can’t quite make out the dinner that will be on the table that night. The children born a safe death.
From street level in town, behind the swirls of plastic garbage, the tentacles of lights at night in dark countryside, beyond the line of seashore, ships sailing. Beyond that a mountain of tall buildings. Walls and the irradiation of past hydrogen bombs on Pacific atolls. The adventures of polynesian explorers, sailing into the unknown.
Below you now a plane, cruising altitude. The spaceship `earth itself, hurtling through the void. Pull your loved ones out of the car crash. Jump into the river. There next, starlinks rush by, and above you satellites. The Sea of Tranquility. A flagpole. Etienne! Slow down.
Where do you think you’re going? At 67,000 miles per hour. How silly tribes and personalities are until you’re alone. Or all together. Below the subsurface, existing. A tourist, a cosmic hitchhiker.
John Holten: Thank you to Irina Mullins for taking the time out from looking after her tomato plants in the hot Austin, Texas sun. You can find a link to her fascinating and imaginative paper on Cosmic Hitchhikers in our shownotes.
Eva Kelley: This episode was written and produced by John Holten with additional writing by myself, Eva Kelley.
JH: Sound editing and design was by David Magnusson
EK: Mundi Vondi is our executive producer, and also created the artwork for this episode in collaboration with midjourney.
JH: Additional research, script supervision, and fact checking was by Savita Joshi.
EK: Follow us on social media and subscribe for more wherever it is you listen to your podcasts.
JH: We’d be delighted to hear from you.