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Comment by mabbo | Hacker News Reader

Let's set aside the part that making a planet where we could live is hard. Just presume we did that, to start.

Let's talk Logistics.

Presume there are only 1 billion people left on Earth when we decide it's time to go. How do you get them there? The gravity well holding us here (and holding the air down so we can breath it) is pretty darn strong. Today we're hoping to get cost-to-orbit down to around $100/kg. I weigh a bit less than 100kg, so that's $10,000 just for my mass- not including the life support system I need.

And then I'm just in orbit.

If I'm moving to some kind of spin-gravity station in orbit, that's not too far away. But Mars? Mars is a months long trip in a best case.

And don't get me started on planets on other stars. Even the most optimistic generation ships would be taking 10s of thousands of years to get there- longer than all of human history so far. If each ship held 100,000 people, you'd need 10,000 of them. And what power source would you use to move that massive ship, and keep the light and heat on between stars? (Antimatter, I guess?)

If we can make Mars habitable, we can make Earth habitable for far less cost.

I'm entirely in favour of building spin-gravity stations, Mars habitats, even terraformation of Mars and Venus. I just feel like it's never going to be the case that anything more than a tiny fraction of humans will leave Earth to go see those things.

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The idea of finding another Earth is not so much about moving everyone from Earth to somewhere else, but rather about "backing up" our species and civilisation in additional places. If an asteroid is going to wipe out Earth, we can't evacuate 8 billion people, or even 8 million people. but if we had a few generations of colonists in domes on Mars, or floating in the clouds on Venus, or somewhere else, the species itself would hopefully survive.

We only have one Earth, and its the best home we could hope for. But we're crazy to keep all of our existential eggs in a single basket and hope it all works out.

> If we can make Mars habitable, we can make Earth habitable for far less cost.

That said, I absolutely love this sentence.

Although I would say, the technology we ultimately have to develop to survive on Mars or the moon will certainly help us keep Earth habitable.

> But we're crazy to keep all of our existential eggs in a single basket and hope it all works out.

While the cost to colonize elsewhere is "mine the earth to a wasteland" it does make sense to preserve the basket we have. At least until we can afford to buy another basket without ruining the original.

> While the cost to colonize elsewhere is "mine the earth to a wasteland"

I'm not sure where this idea is coming from. I think the idea of most modern colonisation plans is to use materials at the location to build habitats etc, by 3d printing using martian soil or lunar regolith, not ship millions of tons of natural resources into space.

That's just magic woo though. You can't just "3D print" a clean room to build semiconductors or furnaces to smelt metal. Pretty much all heavy industry on Earth that makes all our high technology runs on petroleum products in some fashion. You can't just "3D print" lubrication and good luck building heavy industrial pieces without it.

Luckily space is already clean, the trick will be converting current production processes to work in microgravity - process heat offtake without convection etc. LEO or higher orbit based manufacturing will probably occur before 2050, once that is solved then deploying infrastructure onto the Martian surface will become relatively trivial.

That's just a string of nonsense. There's not a single aspect of deploying infrastructure anywhere in space is trivial.

> You can't just "3D print" a clean room to build semiconductors or furnaces to smelt metal.

The idea isn't that you'll <<just "3D print" a clean room to build semiconductors>>. But yes, the idea is to "3D print" furnaces to smelt metal (basic furnaces are prehistory-era tech) using heat provided from the solar, wind and/or nuclear power you arrived with. Then use that to mine more ore to smelt more metal to "3D print" more... and so on, and so on, adapting production processes to local environment piece by piece, until you eventually reach basic self-sustainability, and yes, eventually you may be able to build a clean room using entirely local resources and processes.

(Of course, there's the matter of whether people living on other planets will want to go for full self-sufficiency, and then if Earth even allows it. There's a potential for trade here, but the flip side of that is political power. E.g. as long as a Mars colony depends on Earth for complex organics or high-tech industry products, they're effectively under control / at the mercy of Earth.)

> Pretty much all heavy industry on Earth that makes all our high technology runs on petroleum products in some fashion.

It didn't until recently, though. I imagine that between those older techniques from early-to-mid XX century, and modern advances in organic chemistry, you'd be able to eliminate some of the hydrocarbons used and synthesize others, without a need to dig dead plants/dinosaurs out of the ground.

> You can't just "3D print" lubrication and good luck building heavy industrial pieces without it.

That's all part of the R&D work for off-world habitats and industrializing space.

> basic furnaces are prehistory-era tech)

Which require water and air in huge quantities, and ore, none of which you have on Mars.

> That's all part of the R&D work for off-world habitats and industrializing space.

You might as well say "magic" - it would be more plausible.

One thing to remember is that our guessing how things would work out has always been laughable with [say] 5 insanely complex problems we didn't see coming for every 1 thing turning out much less complicated than anticipated.

How much of what we did just the last 100 years was accurately anticipated and how much of it is down right magical?

In hind sight, how complicated an idea was it really to heat water, get it to expand and do work? I think execution was hard but the idea was kinda obvious.

Most stuff we build is made of stone/rocks? It seems we can dig caves, just ship the front door an we can start our usual hoarding :)

> How much of what we did just the last 100 years was accurately anticipated and how much of it is down right magical?

How much more of what we did failed but nobody died (somebody died, but not always) because those failure happened in a hospitable environment for life?

We didn't just "magically" progress, we failed 99% of the times to evolve the process until it succeeded.

Now imagine launching 100 projects on Mars, most of which could lead to an explosion, and predict that 99 of them will fail (and probably explode)

Would you still believe "everything's gonna be fine"?

The Martian is just a good SCI-FI movie.

> In hind sight, how complicated an idea was it really to heat water, get it to expand and do work?

steam engine was well known 2,300 years ago.

https://en.wikipedia.org/wiki/Aeolipile

It took > 2,000 years to perfect it.

And we have free water and oxygen on Earth but no water nor oxygen on Mars.

> Now imagine launching 100 projects on Mars, most of which could lead to an explosion, and predict that 99 of them will fail (and probably explode)

Well I'm just picking holes now, but in the Martian atmosphere is 95% CO2 - nothing will explode

> Would you still believe "everything's gonna be fine"?

Nobody said "everything's gonna be fine". The argument for sending people to Mars, at great peril, is that sitting _at home_ on Earth, and saying "everything's gonna be fine" is a bad idea.

It's going to be a tremendous struggle and we might not succeed. Mistakes will be made, people will die. We will have to push our abilities to the limit and beyond our known capabilities. We will learn new things (like working together) and every new answer will come with 20 new questions.

This is so much our thing (perhaps culturally) that we build our entire civilization to endlessly progress or implode.

I wouldn't mind living in a cave, scavenging and hunting for food but that is not what we are doing atm, I didn't choose this formula nor do I have to like it but if this is what we are doing lets do it.

Some of us questioning the sanity of the project is also important. We might chose to do something else one day. Until that day we might as well be good at what we do.

Hmmm.

While I would be actively surprised if the Moon, for example, had every element necessary for semiconductors, one of the things I absolutely do expect to be possible on its surface is 3D printing an extremely clean clean-room.

Furnaces? Well, I think it would take a polishing step after printing, but if you have aluminium you can do a rough parabola out of it and focus sunlight on a patch of regolith. Can you turn that molten alumina into aluminium and oxygen only by carbon rods and electricity? Or would electrolysis still work if you used a high-current election beam?

(I genuinely don't know, I didn't do material science).

Don't get me wrong, even if this is ultimately all fine without petrochemicals, I expect there is a lot of postgraduate research between now and any significant space manufacturing.

> electrolysis

That's a process that involves drawing ions through solution towards a cathode and anode. A direct beam won't do.

A solar furnace would suffice for the first half of the smelting process if you have access to ore which is not pure alumina, as well as melting the cryolite flux. Actually separating out the aluminum from alumina requires PV panels, high temperature rods and some means of synthesizing the cryolite or similar solvent / flux.

> That's a process that involves drawing ions through solution towards a cathode and anode. A direct beam won't do.

OK, thanks for the info. Can you go into more depth about this specific part, or is this a thing where I need to do the whole degree to understand the answer?

> one of the things I absolutely do expect to be possible on its surface is 3D printing an extremely clean clean-room.

My understanding is that there is lots of very fine dust near the surface of the moon. It's continually being bombarded with micrometeorites that kick up the dust.

So perhaps a moderately cleanish room.

In addition to that, not 'well rounded' by erosion like sahara sand, instead still very sharp edged, abrasive. And electrostatically charged by being bombarded with particles over long times. Creeping into every seam and seal. Not good to breathe in at all.

There was a scene in https://en.wikipedia.org/wiki/For_All_Mankind_(TV_series) S02E01 where a solar storm surprised some astronauts on the surface, where they couldn't make it into shelter in time. One got toasted, another barely made it into a cave, and watched from there.

It looked like invisible drops of torrential rain, splashing down hard, and stirring the dust up, like in slow-motion capture of a drop of water, impacting, and stirring things up.

I don't know how realistic that is, but I liked it as a conceptual visualization, at least.

Edit: Think of something like a https://en.wikipedia.org/wiki/Cloud_chamber at large scale. Where the medium is stirred up dust.

Edit: A there it is: https://www.youtube.com/watch?v=YzlP403rUGA

> While I would be actively surprised if the Moon, for example, had every element necessary for semiconductors

As I understand it, the currently accepted theory about how the moon formed is the giant-impact hypothesis, which is that a very large object hit the proto-Earth and the moon is the material that was "splashed" off when this happened. As such it seems at least plausible that the moon would have a similar set of elements available for semiconductor production as Earth does.

We have been to the moon and collected samples. Regardless of the why, we know it has a similar composition to the Earth. At least at the surface; seismic data suggests, for instance, that its iron core is comparativly smaller than Earth's.

All of this is inputs that led to the impact model of moon formation.

It doesn't matter if the moon has required elements to build semiconductors. Getting from sand to a solar panel or computer chip takes literal tons of infrastructure and precursor materials. Most of that infrastructure can't come from 3D printers. It's non-trivial to spin up a chemical factory on Earth with access to all of our infrastructure. Building one in space is orders of magnitude more difficult even if all of the technology required to do so already existed.

3D printers aren't Star Trek replicators. You can't take a manufacturing flowchart, add a "3D printer" node in the middle, and then consider your manufacturing problem solved. Even if you had a magic 3D printed that could print pipes and fasteners and ducting, it would still need to be assembled and the facility processed to get it clean enough to build semiconductors. Then you'd need smelters/factories processing raw materials to get the necessary feedstocks. Then you'd need reprocessing facilities that could recycle wastewater to be reused and catalyze waste chemicals to reuse.

While you're obviously correct to say you can't just pop them in at a random manufacturing node, "3D printers" are a category, not a specific tech.

Similarly, semiconductors don't only mean the really good ones we use now (though once you have the capacity to make an appropriate factory, obviously you should do that), there are also relatively easy but also mediocre options like copper oxide.

Looking at the tech timeline, the first (semiconductor) PV predates quantum physics: https://en.wikipedia.org/wiki/Timeline_of_solar_cells

Edit:

If it takes merely literal tons of pre-made equipment from Earth to bootstrap, that's easy. Musk's (for all I know paper napkin) stated intent of a million colonists is 50,000 to 100,000 tons just of human biomass.

> if you have aluminium

Where are you going to get that, or any other raw material? Robot miners? We don't have those on Earth yet.

How do you purify it? All our chemical processes require huge quantities of free air, and of very cheap water, neither of which you have on Mars.

Where do you get the power for all of this? Solar panels don't behave well during sandstorms, the sun isn't very bright there, and how many solar panels can we really fly to Mars?

It's a pipe dream. We will destroy our ecosystem long before we manufacture even one thing on Mars.

> Where are you going to get that, or any other raw material?

Bootstrap with whatever the initial mission payload is. It's not like anyone is proposing magically teleporting there without stuff, IIRC even Musk's optimistic idea is still several no-humans flights for each passenger flight.

> Robot miners? We don't have those on Earth yet.

Sure we do. TBMs. Not all of which are manned. A few of the missions on Mars right now are taking rock samples with drills.

(Honestly, I'm mainly thinking of the moon, but Mars has moons too. No idea if any of Mars, Demios, or Phobos have significant easy access to aluminium oxides).

> Where do you get the power for all of this? Solar panels don't behave well during sandstorms, the sun isn't very bright there, and how many solar panels can we really fly to Mars?

Sure, PV. They do suffer as you say, but that's not a critical failure when bootstrapping a colony or whatever, especially when you're in the "robotic labor only" phase that (a) is a prerequisite and (b) Optimus Prime or whatever random pop culture reference Musk named that middling demo after. While I don't have any reason to actually trust Musk's "million people" number as anything more than a nice round number, at that kind of scale you necessarily have a lot of PV. Like, "tens of square km" is the minimum baseline. How much is made locally vs sent by Starship depends what can be made locally vs. what can't.

Plus, a Mars colony is one of the few situations where orbital solar via microwave isn't obviously worse than "a big wire to the other side of the planet".

As Starship has ~100T payload, and this PV is 120 W from 5.2g, given 50% reduction in sunlight relative to Earth, even if all the semiconductors have to be shipped from Earth, it's only a few flights out of what you need just to get the people, never mind the other bootstrap equipment you also want: https://spectrum.ieee.org/ultrathin-solar-cells-for-lightwei...

> Sure we do. TBMs. Not all of which are manned.

To ignore the massive difference in scope and scale between a space probe with a tiny rock drill and a tunnel boring machine, TBMs require literal tons of lubricants/coolant to operate. Even if you had a 100% electric TBM none of its parts are going to move without lubrication. Even "unmanned" TBMs aren't fully autonomous, they have a small army of squishy people in hard hats adjusting fasteners, checking feed lines, repairing damage, and generally maintaining the machine.

TBMs also going to be orders of magnitude more difficult to build for use on the Moon or Mars. They're incredibly dry environments, dryer than most places on the surface of the Earth. The dust is electrostatically charged and literally creeps along surfaces into seams and seals. The dust is also incredibly abrasive. Machinery does not like dust, machinery will hate Lunar and Martian dust.

In actual operation machinery does not look showroom pristine. It gets dirty and needs to be bathed in lubricants and coolants. Dust, dirt, and shavings get everywhere except in the cleanest of cleanroom environments and those take tons of effort to maintain.

Everything around you was manufactured with a very long tail of infrastructure. You can't just build a PV factory on Mars. You need to first build the infrastructure to build infrastructure before you can lay the first 3D printed brick for a factory. Even if you've got that infrastructure and factory you need a whole supply chain of refined materials to feed the factory to get solar panels.

It's not a handful of unmanned Starship missions, it's a hundred missions with no failures landing billions of dollars of basic infrastructure just to start building more infrastructure. The whole endeavor also needs to use technology like autonomous robotic mining rigs and autonomous mining rig support robots that don't even exist on Earth. I honestly don't understand trivializing the amount of infrastructure and complexity required to manufacturer things here on Earth let alone anywhere else in the solar system.

> You need to first build the infrastructure to build infrastructure before you can lay the first 3D printed brick for a factory

While I disagree with the specific claim here (bricks are easy mode, sand sintered with a fresnel lens brought from Earth), for the general point you're otherwise making:

Yes, and?

Depending on which bit you're pointing at, "a few" was just for the PV for everyone, or just per manned flight. For the "million colonists" (again, no idea if that's a well thought out number) that's thousands to tens of thousands of manned flights, and 3000 to 50000 unmanned flights each with about 100 tons of payload depending on which random early stage wild guess you use to calculate from.

5 million tons of stuff from Earth may or may not be enough to bootstrap, I wouldn't know. (Does anyone?)

But your specific criticisms… don't feel like they're aware of the scale Musk is aiming for.

On a separate point:

I have read of both liquid CO2 and graphite (which can obviously be made from that) being used as lubricants, but I'm emphatically not suggesting they're drop-in replacements. Obviously one would have to design mining equipment specially to use them, likewise for thermal issues.

Given who owns The Boring Company, this is probably already being researched.

It's space. Orbit is in all likelihood cleaner than your average clean room. Planets/moons add dust and thin atmospheres as concerns, but that's quite obviously easier to mitigate than the "dust and much thicker atmosphere and microbes and moisture" that Earth-based clean rooms have to mitigate.

As for bootstrapping industry beyond Earth, the amount of Earthborne equipment and supplies to build a self-sustaining extraterrestrial supply chain is far below necessitating stripmining the Earth bare - obviously, since we were able to bootstrap terrestrial industry just fine without (yet) doing so.

> the amount of Earthborne equipment and supplies to build a self-sustaining extraterrestrial supply chain is far below necessitating stripmining the Earth bare - obviously, since we were able to bootstrap terrestrial industry just fine without (yet) doing so.

Considering how quickly industrialization has damaged Earth's ancient ecology I sincerely doubt industry could be sustainably stood up on a planet like Mars.

You may be underestimating how special Earth is as a home, and vastly overestimating how suitable Mars would be for carbon-based life.

> Considering how quickly industrialization has damaged Earth's ancient ecology I sincerely doubt industry could be sustainably stood up on a planet like Mars.

There is no ecology (at least to anyone's knowledge) on Mars to destroy in the first place, nor is there one in orbit or on the Moon or anywhere else other than Earth. "Sustainability" is therefore not a factor except in the sense of raw resources - and in the infinity of space that's a lot of raw resources at our disposal.

> You may be underestimating how special Earth is as a home, and vastly overestimating how suitable Mars would be for carbon-based life.

What makes you think I may be underestimating or overestimating (respectively) anything? Earth is special, which is precisely why we should be maximizing the preservation of the one thing that makes it special: its biosphere. That maximization entails moving everything that is even merely irrelevant (let alone actively harmful) to said biosphere off of Earth; anything less than literally all human industry (and all human population aside from non-industrialized peoples and maybe conservationists/biologists and their support staff) being moved to orbit and beyond represents a failure to achieve such maximization and puts that one special thing in jeopardy.

The Earth is a giant ball of resources and we have only just begun to scratch the surface.

Ultimately, you will protest and we will build. And we will both get what we want: we will get our rockets and you will get your protests. Everyone is happy.

If the real cost of the rockets is an uninhabitable Earth, and an uninhabitable Mars, then everyone is some combination of unhappy or dead.

Sure, but it's not. Which everyone knows but some people will pretend it is so that they can get the thing they want: the protesting. So we'll just let them say that and pay the increased costs so we can "recognize the contributions of the original habitants of this land: the stripe tailed gecko" and we'll launch the rockets. They'll take the money and buy a bigger office to go after the next target.

And everyone is happy and alive.

> Which everyone knows but some people will pretend it is so that they can get the thing they want: the protesting.

Just want to say what a repugnant and mocking answer this is.

There are real issues here. You can't deal with them, so you resort to rudeness.

This sort of ever-escalating pearl clutching is exactly what I mean. Fine, this is your domain. Enjoy it whole. I shall return to mine.

And when the time comes we'll pay the toll. But we've got work to do, so don't seek too high a rent.

Bad idea. I want us to actually get to Mars.

Protesters are generally sincere about their dislike of whatever they protest about. To echo your own language, they will cost a lot more than mere rent, if you don't talk them down.

I think their sincerity can be handled with inducements. But there's nothing wrong with a multi-pronged approach. Eager to see the outcomes your approach generates.

> the real cost of the rockets is an uninhabitable Earth

I've seen more than one person here express this opinion - what about rocket launches makes you think they will render the Earth uninhabitable? They certainly aren't very clean, but the emissions they produce are dwarfed by commercial aviation and ICEs. Why all the rocket hatred?

To me, this feels more like a waste of resources just for something that is cool. It's completely useless to send people to Mars, just an expensive artistic performance.

Meanwhile life on Earth is dying, because of the human activity. Some things are difficult to change (forcing everyone to use bikes all the time would be a big problem: how do you bring food into cities without trucks?), and others seem very easy: just don't put all those resources into useless Mars, and instead try to save life on Earth.

> just don't put all those resources into useless Mars, and instead try to save life on Earth.

_instead_ is the word I have a problem with. the idea that we must do one or the other. that either we fix climate change OR we go to Mars.

Small note: climate is only part of the problem. The current mass extinction has nothing to do with Climate Change, but is rather due to loss of habitat. Now of course, this will add to the problem big time.

But the other thing is energy. Our entire society depends on fossil fuels, which are not only causing the climate problem, but are also limited. Planning to go to Mars in 50 years assumes that we will have enough energy to live on Earth and to launch rockets. Let's be honest: right now we don't have a replacement for fossil fuels.

We mostly have hope, based on "promising tech" oversold by startups surfing on the green economy idea. Wind/solar is growing a lot, but thanks to fossil fuels. Nuclear plants take a lot of years to get built, and in many places in the world we are more closing them than building new ones.

So it is quite likely that we will have a critical energy problem before we manage to send people to Mars. The climate/energy problem is not something that we can solve later, because we are slowly running out of time. And it feels like all the resources that we put in advanced projects like Mars could be (or even should be, at this point) put somewhere else. Because that's a lot of money and competent people. Also it goes with over-consumption: it's not that one such project in itself is too much, but rather that we should start cutting into many of those superfluous projects, to survive.

> the emissions they produce are dwarfed by commercial aviation and ICE

You're comparing the emission of something that carried few dozen people over 60 years to something that carried 40 millions people in 2019 alone

Politeness costs little. I guess not having an argument makes you resort to rudeness.

If you could go back to your building instead of writing that kind of comments, I would be happy.

> While the cost to colonize elsewhere is "mine the earth to a wasteland" it does make sense to preserve the basket we have.

The cost of keeping human civilization on Earth is currently "(eventually, at this rate) mine the earth to a wasteland". We need to get as much of humanity's industry as possible into orbit and beyond if we want to avoid mining the Earth into a wasteland. That industry includes agriculture if we want to avoid clear-cutting the Earth into a wasteland, while we're at it.

In reality this is just a fantasy. It is not possible for a healthy human to really care about survival of human race in case of something catastrophic happening and wiping out humanity.

Why?

Healthy people care about having descendants they'll never meet.

Survival of human race is very different then caring about descendants. Yet as you are live witnessing right now some people barely care about that and most people do not even think about it. If earth to be wiped out by a meteor and there was a ship with limited space to colonize another planet people would fight for that space even if it would mean decreasing success chance of mission.

People have other reasons of going. You don't colonize during the asteroid event, you colonize long before. You won't have people fighting to go to save themselves, you'll have them wanting to go for various reasons, legacy, reputation, isolation, etc.

That being said, I don't agree with your premise that you can't be a healthy person and care about the human race. You haven't added enough to support that claim.

It was an example to point out that people may behave vicious to increase survival chance of their children or themself even if conflicts with survival chance of human race in total.

Because you don't, and you can't imagine you're not an exemplar of health?

Because i am very objective person and this is just hard fact. It may be healthy to think that way but just not the reality.

That's the essence of Elon's philosophy. It's NOT about Mars. It's about preventing existential risk. That's why his technical focus is actually heavy lift to low Earth Orbit for a Brilliant Pebbles program,

https://wikipedia.org/wiki/Starlink#Military_capabilities

The idea is not to replace earth but to have a second earth inhabitting both concurrently.

Hence, keeping earth inhabitable is important, since you don't want to give up your fallback easily.

> rather about "backing up" our species

First we need to stabilize the Earth, dealing with the threat coming in decades, before we deal with threats that come millions of years apart.

They say that necessity is the mother of invention. I think the best way to learn how to stabilise the Earth is for some of us to have to cope with stabilising something much worse, something unforgiving on a timescale where there are personal consequences to getting it wrong.

Not like here, where the consequences are separated by decades or continents, or where a big pile of money can make up for any personal pain.

> ... but rather about "backing up" our species and civilisation in additional places.

It would certainly cease to by "our civilization" within a very short time frame. It could eventually cease to be our species also. Without at least faster-than-light communication, there is no keeping humanity in sync between star systems.

I genuinely don't get the "save the human species" argument. We are living a mass extinction which is caused by the human species. So one species (humans) is essentially destroying most of the variety of life.

If you care about preserving humans, why don't you care about preserving life? Of all the miracles of evolution, ending up with a few humans surviving on Mars is not a success in my book.

Humans would clearly bring other life with them to Mars just as we have to almost every part of the earth.

In contrast to this worldview that humans are the agents of mass-extinction, it's much more likely that humans are the only ticket to survival for every species on earth. No other species has been able to escape Earth's massive gravity well, nor has come anywhere close to harnessing the energy required to do so.

> just as we have to almost every part of the earth.

Do you have an idea of the ratio between the species human has been moving around vs the number of species in existence?

> In contrast to this worldview that humans are the agents of mass-extinction

Wait wait wait. This is a fact. We are living a mass extinction now, it is acted. We, human, have removed 2/3 of trees, 2/3 of mammals, and 2/3 of insects from Earth. Mostly because of the loss of habitat (not Climate Change, this still has to come as a bonus, and definitely won't help).

It is not hypothetical, it is not a worldview. It is a fact. Of all the species that lived on Earth at the same time as humans, the number of species that got decimated because of humans is so much higher than the number that humans may bring to space (should we ever succeed, which is far from certain) that it feels absolutely wrong to consider that "humans are the only ticket to survival for every species on earth". Pretty much every species on Earth would be better off without humans.

And again: preserving life on Earth is much easier than bringing it to space (and we are failing at it right now). The asteroid scenario is completely ridiculous: again it's far easier to prevent the asteroid from colliding with Earth than to send a few species to survive in space.

Even if an asteroid does not destroy the earth, the sun ultimately will

Not sure what your point is :).

The earth is doomed, it's up to humans to get them off this rock that will eventually burn up in one way or another.

Do you realise that the Sun "threat" is not for another few billions of years (with a "b")? Dinosaurs appeared what, 250 millions years ago (with an "m")?

And there's more: the closest star, Proxima Centauri, is more than 4 light-years away. It means that if you want a chance to survive the Sun, you don't need engineering; you need theoretical physics. You need a fundamental discovery in physics to make that kind of travel realistic. At which point the engineering you will have put to go to Mars will possibly don't apply at all.

Again: there is no planet B unless you make a fundamental discovery in theoretical physics. People need to stop pretending that going to Mars is a need. It is an artistic performance. It is cool, but mostly useless.

Why do we care about our species having a "backup" if it isn't us? "It sounds hard and I am bored" is a reason I can at least understand, but arguing we would be "crazy to keep all of our existential eggs in a single basket" implies some objective inherent value to humanity existing in the abstract that we all must be willing to sacrifice for, and that requires a lot more explication.

It's not just humanity, it is all of life. It is possible that complex multicellular life does not exist anywhere else in the universe.

Almost everyone agrees that life, not just human life is important and meaningful.

Another way to look at it is consider the opposite bet. Suppose that you could improve every Earth organism's life by 10%, but at the cost of requiring all life to stay on a single volcanic island in Hawaii. Would you ever take that bet?

> If an asteroid is going to wipe out Earth, we can't evacuate 8 billion people, or even 8 million people. but if we had a few generations of colonists in domes on Mars, or floating in the clouds on Venus, or somewhere else, the species itself would hopefully survive.

The problem with this reasoning is that even in the case of a dinosaur-busting asteroid impact earth will be still much more liveable than mars.

the proof being that earth got a dinosaur-busting asteroid impact few millions years ago and that life continued there but didn't appear on mars

> but rather about "backing up" our species and civilisation in additional places

If that's the goal, we should find a safe place to store the backup, or it's just hoping for the best in the worst situation possible.

> Presume there are only 1 billion people left on Earth when we decide it's time to go

The scenario that leads to have only 1B left from where we're at would entail such a catastrophic meltdown of society that even building a rocket would likely not be feasible, let alone anything significant for a human exode.

Think about it, you're fighting against something that killed 7B people, be it the end of fossil fuels, climate change, a massive and deadly pandemic, a war or another type of catastrophe. There are probably global food shortage, areas that can't be lived in anymore. The global supply chain doesn't exist anymore, and government is much more localized, very different. Being down to 1B is probably not the bottom line of your decline, 1B people is still a lot. Your priorities are based on survival, you're trying to figure out how to grow enough food, gather enough water. You don't have enough reserve capacity that you can spare it on projects like building a lot of rockets and colonizing another planet.

Rockets are a thing of complex societies with abondant energy ; not a last minute effort to preserve the human race.

The GP was just setting a lower bound of 1B to establish a basis for calculating the cost to move humanity offworld. The cost for 5B people or 7B people would be even more cost prohibitive.

But also the shrinkage would not have to happen abruptly. In theory you might be able to get to a population of 1B over the course of 200 years without the kind of catastrophic meltdown you're describing.

I completely agree this would happen over a long time, barring a disaster like nukes or asteroids, which does not seem like the most credible scenario (I dont think I said anything to the contrary)- and I'll confess to a pessimistic vision of the future, when our demise is self inflicted.

But look at Covid for a reference point. I mean all things considered this was still too mild to reduce humanity to 1B. This almost immediately (in the span of a year) led to big issues with the supply chain. Products removed from the shelves, years long backlogs on cars. People getting sick all around you and hospitalized, and yet there were societal debates on whether the disease actually existed, whether we should wear masks, or take the vaccine. Climate change is in the same line, people denying change with snarky remarks every time we receive a snowflake, and any step forward being accompanied by two steps backwards (look at the Paris accords). What I mean there is that there is no change witnessed without actual pain, and the change required for something truly threatening for humankind (e.g climate) won't see any actual action till we're already greatly suffering, and probably beyond the point of repair.

Now imagine a large chunk of the population disappearing, even over the course of decades, and whether that would leave society in a state where it can afford a significant "gtfo of here" space program. My personal opinion, and that is only an opinion, is that this is not systemically possible ; and therefore I don't believe in GP's base assumption, even if that's departing from the motivation of simplifying that they made :)

In any case, beyond cost, short of inventing completely new physics, I doubt earth even has enough resources to catapult us all into and then out of orbit.

The most likely scenario to me is a handful of elites (which fortunately for them are fewer and fewer) embarking on rockets, accompanied with scientists and engineers to give them a fighting chance, plus a bunch of slaves to do the grunt work and die, because surviving ain't worth it if you can't enjoy life.

(once again, I confess is a pessimistic vision, and is also departing a bit from the initial statement from GP)

> If we can make Mars habitable, we can make Earth habitable for far less cost.

I think the main thing there is that Mars is a blank slate, unclaimed and fairly uniform. We can't terraform Earth because we can't get everyone aligned with the same goals. Moving away from fossil fuels means that a lot of individuals, corporations and countries have to make investments and sacrifices, or lose their grounds for existence entirely.

I mean this was only achieved once, when banning CFCs. There's been other agreements - like let's not use cluster bombs or chemical weapons - but those have been ignored without major consequences.

Why would you not expect these exact same challenges to develop almost immediately on Mars? It's not like one country will own Mars and even if it did, one country generally cannot agree on environmental policy even internally. I fully expect Mars, at best, to be a terrible version of Earth with all the same problems and way fewer benefits.

When has "This is too hard, let's do a full rewrite" ever worked?

Economics is how we align goals. When using clean energy is better and cheaper than fossil fuels then people don't need to be coerced into adopting it. It's rapidly reaching that state and already is there for many.

We can't terraform earth because we don't know how to terraform, and foe the same reason we can't terraform mars

> If we can make Mars habitable, we can make Earth habitable for far less cost.

I'd put it slightly differently. If we can't keep earth habitable, when we're standing right here on it, what hope do we have of making Mars habitable?

Never mind logistics, look at the billions of years of evolution that led to billions of interdependent organisms. We are one of those organisms, but in our guts alone live countless more. As a tech person, have you ever built system A, then built system B which depends on system A. And then, when the both up and running, accidentally modified A to depend on B? And that's just 2 systems. Scale to billions. How the hell do you cold-boot that?

> I weigh a bit less than 100kg, so that's $10,000 just for my mass- not including the life support system I need.

That doesn't seem all that unreachable, honestly. The average middle-class income could swing that with a payment plan (said incomes commonly cover car payments already), and even for those who can't afford it, an enterprise seeking workers could surely cover that as part of an employment contract. We could also probably slash the costs - and multiply the scale - even further with non-rocket launch systems like skyhooks or launch loops.

Yes, people don't realize how expensive transatlantic travel was even as recently as the steam age (1850). A steerage (lowest class ticket) was £3.50 while avg. annual wages were something like £17.

It's crazy to think that going to Mars will soon be about the same relative cost as a trip across the Atlantic.

If you really want to get a billion off earth quickly, you'd use a non-rocket system like a launch loop ($3/kg) or an orbital loop ($0.05/kg).

I kinda agree that most humans won't leave Earth, at least for the foreseeable future, even if those things were magically built this year: even in 2019, international tourism was only 1.466 billion people, less than 20%.

While I don't see that mentioned very often I do think off-Earth settlements could have many benefits even for the Earth population - say research commoning from experience of living in space environments could have application on Earth. Also many asteroid strikes could be much more likely to be detected and averted using in-space instruments and infrastructure.

Even more exotic stuff like dropping first responders from orbit to disaster areas might be useful, but would not ever be doable without infrastructure in place for supporting space operations.

> Just presume we did that, to start.

While I'm fully on board with the thrust of your post, I think skipping this obvious first question is kind of missing the point. Terraforming Mars would be such an enormous, slow, expensive, intensive process that any other problems with "logistics" would be long solved before we ever got past that initial challenge.

> If we can make Mars habitable, we can make Earth habitable for far less cost.

Ultimately this summarises it best: I don't really think logistics would be a problem if we solved making Mars habitable - I just don't think doing that is worthwhile to begin with.

Well the first thing that we'll need to do is compute this in terms of actual resources, rather than money - which is a tokenised abstraction from value, and arguably an inflated one.

So the raw material and energy requirements to leave the planet carrying people and everything they'll need on the other side.

Things will be different once there's been a reasonable build up, but if it's an evacuation we won't have time for that.

And things on Earth will be falling apart evironmentally, politically and geopolitically.

And what of the political systems on the other side? Work 80 hours or get out of my bubble?

> And what power source would you use to move that massive ship, and keep the light and heat on between stars? (Antimatter, I guess?)

Fusion. If nobody made it obvious until now, well, fusion is the ultimate interstellar power source. Fuel is everywhere, the ISP is huge (a few orders of magnitude smaller than antimatter, but well, antimatter doesn't exist everywhere), and it's far from the hardest thing to build for a ship like that.

Anyway, there is still space to cut orders of magnitude on the cost-to-orbit. But you are correct in that none of that will solve any of our current problems.

> Even the most optimistic generation ships would be taking 10s of thousands of years to get there

https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls...

Nuclear bombs make for pretty good propulsion systems and can propel incredible mass at a decent speed. In a "the planet needs evacuation" type of scenario you don't worry about the fallout either.

I agree with everything you said and everything in the article, except for the number of people. There are 8B people now, and, if nothing changes, by 2100 there will be 16B people. But I would not be surprised if this thing with the mice getting younger is developed rapidly for people in the next 20 years or less, and 20 years after that it's a staple of comprehensive health care, and by 2100 there's instead 32B people.

My thing is, whomever wants to colonize space and Mars and distant exoplanets around other stars... let them go. Let whomever wants to go, go. Encourage them to go. The rest of us can clean up the Earth and work to create a future society that doesn't use 175% of the available resources every damn year, work to find a balance that preserves diversity and honest to goodness Nature, stop expanding development and deforestation, finds some equitable solution to birth control, prevent stupid people from constantly breeding, support and encourage LGBQ and celibate priests, solve crime, and stop polluting the air, water, land and the food everything eats. Colonizing space and other worlds only helps Earth and everything living or that will live on it, because while there are very smart people, humanity as a whole is a complete idiot, so the best thing we can do is reduce and limit the number of people here without cruelty or genocide. Think of space as a suicide booth, and let people be free. We shouldn't let insurmountable odds deter them. People will lotteries. Throw enough spaghetti at a wall and sooner or layer, it will stick.

> so the best thing we can do is reduce and limit the number of people here without cruelty or genocide. Think of space as a suicide booth, and let people be free.

Unrealistic and honestly pretty cruel sounding despite your caveat. If space is a death trap, you will never get more than a few small caravans to give it a shot. No way that would put a dent in your 32B, a number you pulled from nowhere, loosely based on one recent study about improving longevity in mice.

140M people are born every year, but only 60M people die every year. We'll need to do something if the birth rate keeps increasing or even stays steady, or even slows down, but the death rate stops.

"if the birth rate keeps increasing" is another of your assumptions that most demographers find unrealistic. Rising incomes have solved this problem (perhaps too well) in every single advanced economy on Earth.

Is your assumption that certain developing societies aren't capable of this? Or won't do this? If that's the case, why? Why are we extrapolating current birth rates in places like West Africa 100 years into the future? That didn't happen anywhere else.

> Rising incomes have solved this problem (perhaps too well) in every single advanced economy on Earth.

This is an unrealistic fantasy. 90% of all the available wealth is held by the top 1%. Cost of living increases have never matched inflation. The most advanced society Earth has ever seen is sliding slowly backwards. Few are getting richer, nearly everyone is getting poorer. Your solution is elusive.

> Is your assumption that certain developing societies aren't capable of this? Or won't do this? If that's the case, why?

What are you talking about? Look around. I don't see this utopia of yours anywhere now or before, so why do you expect it will just materialize in the future?

> Few are getting richer, nearly everyone is getting poorer. Your solution is elusive.

The material science necessary for pitchforks and guillotines has been well understood for centuries. Extreme inequality had the same outcome across human cultures and generations.

It would be far more equitable and cleaner to vote the conservative minority holding the country hostage into oblivion. All we need to do is convince everyone to ignore all irrelevant distractions like gun rights and abortion, and vote in their personal economic interests. If everyone would only and always do that, no Republican would ever hold office again, economic advancement would occur, and the economy would boom.

Wonderful article about overcoming Earth's gravity well available here

https://what-if.xkcd.com/7/

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