[palata]

Not sure why you got downvoted :-/.

I am always surprised by how people tend to completely ignore the scale of the universe. People get excited by claims to "go back to the Moon, then Mars, then who knows?", but the truth is that given our current understanding of the world, sending humans on another solar system is theoretically impossible. Just look at those distances: we just can't, period.

Of course, we may discover new fundamental physics that would change that. But that's a fundamental problem, not an engineering problem. Instead of wasting money and energy on the engineering required to send humans to Mars (which is an artistic performance at this point), we should pay fundamental physicists to attempt to revolutionize our understanding of the world (wishing them luck) and spend those resources into something that is actually important for life: preserving life on Earth.

Right now we as a civilization are failing to survive on Earth. It seems reasonable to consider that other civilizations may have the same problems.

[mr_mitm]

I agree. The only way to colonize other solar systems is using some sort of cryogenic technology or generation ships. And even then, no one alive will ever witness the ship arriving at the destination. Which, to me, raises the question why you should even do this. There is no benefit. Just for the solace of knowing that there is a chance your species might survive the demise of your civilization? That's not much considering the immense cost. Civilizations that do this must have some strong biological urge or have founded a suitable religion that compels them to colonize other solar systems.

That's not even considering secondary colonies. The time it takes for the passengers of a generation ship to start a new civilization and gather the resources to launch another generation ship is mind boggling. They have to ensure not to lose any knowledge or the will to colonize more solar systems. By the time they've done this a few times, it's probably not even the same species anymore.

[gcanyon]

The "time it takes for the passengers of a generation ship to start a new civilization and gather the resources to launch another generation ship" is minuscule compared to the time to make the journey in the first place. Here's a Kurzgesagt video that essentially proposes using our solar system itself as our "generation ship" and getting from one star to the next would take on the order of a hundred thousand years, while the time to set up to travel that way seems reasonable to create in tens of thousands, or even thousands, of years.

https://www.youtube.com/watch?v=v3y8AIEX_dU

[mr_mitm]

Good point. So unless they freeze themselves, whoever arrives might not even be the same species as the ones who left.

[shiroiushi]

>Which, to me, raises the question why you should even do this. There is no benefit. Just for the solace of knowing that there is a chance your species might survive the demise of your civilization? That's not much considering the immense cost.

For the people on the generation ship, it can be a good deal. If the ship is large enough and comfortable enough, it can be a better lifestyle than many people live today.

[palata]

> If the ship is large enough and comfortable enough, it can be a better lifestyle than many people live today.

Surely if it is comfortable enough, nobody is even remotely considering sending poor people there, right?

Then again: what about improving life on Earth instead? Because if you look out there, it's great (at least in those places that humans have not completely destroyed).

[shiroiushi]

>Then again: what about improving life on Earth instead?

Because it's politically impossible.

Your question is like going to a prison full of psychopathic murderers (not just regular murderers, but the ones who really like murdering) and asking them why they can't just be normal, good citizens.

[nojs]

It’s not theoretically impossible, it’s just really hard. If we go fast enough, we can even do it within the current lifespan of a human (from the perspective of that human).

https://en.m.wikipedia.org/wiki/File:Roundtriptimes.png

[palata]

Well, it starts with "assuming we had something we don't have (i.e. the capability to accelerate at 1G for 100 years)"...

I meant it's theoretically impossible with the theory that we have now. Of course if we make breakthroughs in the theory, then the theory will change and it may become possible.

But SpaceX going to Mars is not exactly revisiting this theory. They are just having fun with the current state of the theory, which says that they won't bring humans further, period.

[jonahrd]

I don't mean to be nitpicky, but you specified the difference between a theoretical impossibility and an engineering impossibility in your parent comment. I assume the reply is just referring to the fact that technically getting to a star system within the 10s of light-years away is an engineering feat, not a break-the-known-rules-of-the-universe feat. I don't take it that they're actually claiming it's a realistic feat that may be accomplished soon.

[palata]

Sure, I guess I shouldn't have used the word "theoretically". My point was that with our current knowledge and capabilities, it is completely unrealistic to consider it remotely possible to achieve such a thing. We are orders of magnitudes more likely to disappear as a civilization in the short term than to achieve any kind of meaningful space travel.

[ianburrell]

Continuous acceleration to relativistic speeds is impossible without magic. Reasonable drives require impossibly enormous amounts of fuel. Antimatter drives require impractically enormous amounts of fuel.

Relativistic speeds require too much energy, too much reaction mass, and too much fuel. None of the reaction drives are good enough. It would only be possible with magic reactionless drive, and magic source of power.

[pfdietz]

Or with beamed propulsion.

[shiroiushi]

>People get excited by claims to "go back to the Moon, then Mars, then who knows?", but the truth is that given our current understanding of the world, sending humans on another solar system is theoretically impossible. Just look at those distances: we just can't, period.

1. Colonizing and exploiting the resources of our star system is mostly separate from traveling to other star systems. We can do one and never do the other.

2. It's not impossible at all. It's just an engineering problem: we could build large "generation ships" and send those to other star systems if we really wanted to. No, this isn't the same as traveling to other systems in your lifetime and returning, but it is possible for humans to travel to other stars.

>we should pay fundamental physicists to attempt to revolutionize our understanding of the world (wishing them luck) and spend those resources into something that is actually important for life: preserving life on Earth.

Fundamental physicists can't help you with this project. We already know the fundamental physics we really need for this. The problem is social and economic and governmental. If you want to preserve life on Earth, you have to get humans to live in a way that's more compatible with the biosphere, but humans don't want to do that.

[palata]

> It's just an engineering problem

Famous last words :-)

[shiroiushi]

Sure, it's obviously an enormous challenge and totally beyond our current capabilities, but my point is that it's not at all impossible, it's just a matter of priorities. Humanity could do it if they really wanted to. The physics aren't that hard or in the realm of sci-fi. (I'm not sure the resulting ship would survive, but that's another matter. They'd really need to make many of such ships to make sure at least one survives the trip.) It would require developing significant capabilities for space-based construction of course, which means mining operations in space, manufacturing, etc., none of which we currently possess, so it's not even something that could be done in a decade like the Apollo moonshot, but if humanity really wanted to do this, it could be done in a century I think.

Humanity doesn't really want to do a project like this, however.

[russdill]

It's ok, just wait a while. Other solar systems will pass by our stellar neighborhood

[TomSwirly]

I expected to be downvoted! It's a grim idea, that this is there is and there isn't some huge prize of "a whole galaxy" a thousand years down the line.

I would have resisted it when I was a kid, myself.

About fifteen years ago, I made an attempt to figure out how much it would cost to set up a self-sustaining colony on Mars. My target was a Mars that could make its own pressure suits because terraforming would take centuries and making your own pressure suits is a precursor to that.

I realized that you had to essentially re-invent almost every industrial process humans have today, from baking to smelting steel, because all of them rely on unlimited, free air, and large quantities of cheap water.

You need to recreate most of the chemical industry, just to create new computer chips, each one of which relies on hundreds of chemical compounds available at very very high purities and affordable prices.

After a lot of work, I was unable to come up with a figure. My best guess was $3 to $30 quadrillion dollars, if it were even possible!

And all of that to have a bunch of miserable real estate in a cold, dark, arid, lifeless, airless, radioactive desert characterized by fine, abrasive, statically charged, poisonous dust. Antarctica is nicer in every way - much warmer, much brighter, has breathable air, endless quantities of water, etc - and yet no one lives there.

[gcanyon]

If you're trying to calculate "how much it would take" for a project that size, it seems silly to try to calculate in dollars. What you want to consider is how many people it would take: what population would you need, with reasonable bootstrapping equipment, to establish a self-sustaining colony on Mars?

I'll hand-wave away whether Mars has the necessary resources (I suspect it actually doesn't, but that's just a guess) so if we assume that Mars has the raw materials we need, and is just lacking an atmosphere, then it seems likely (just spit-balling here) that a million people could get the job done, or to be conservative, ten million. For comparison, North Korea has something like 25 million -- they're not as isolated as a Mars colony would be, but they're also not organized well.

If we really want to translate that back into dollars, it seems unlikely that we should budget over a billion dollars per person, but maybe?

[palata]

> so if we assume that Mars has the raw materials we need, and is just lacking an atmosphere, then it seems likely (just spit-balling here) that a million people could get the job done

Hmm... I don't get how it seems likely that a million people could get the job done. I mean really, we are destroying the conditions necessary for our survival on Earth. It's not like we know how to survive in a place (Earth) that just requires us to change nothing. Why would we be able to survive in a place (Mars) that requires us to create from scratch the very conditions we can't seem to maintain on Earth?

[gcanyon]

I'm not sure I understand your point. I'm not an expert, but "conditions necessary for our survival" == about 7 things in (rough) order of immediacy:

   1. Breathable air
   2. Survivable temperature
   3. Shelter from solar radiation
   4. Drinkable water
   5. Food
   6. Energy to support the previous 5
   7. Raw materials to support the previous 6

I postulated the 7th item, so let's take the previous 6 in order:

   1. We know how to generate breathable air and keep it under pressure. We do this in nuclear submarines.
   2. We know how to insulate habitats. We cope with a roughly equivalent temperature at Antarctica.
   3. We know how to protect against solar radiation. We (somewhat) do this at the ISS, and we have plans to do it on lunar base.
   4. We know how to produce water as long as we have raw materials to work with.
   5. We can grow food in pretty much any environment we ourselves can survive in.
   6. We can generate power in almost any environment if we have raw materials.

We are not "destroying the conditions necessary for our survival on Earth." -- we are significantly changing the environment on Earth, that is true, but not such that we will all die. Has any credible person presented evidence for that outcome?

[palata]

> I'm not sure I understand your point.

I guess my point is that though we know how to make a few humans survive in space (with constant support from the Earth) and we may know how to make a few humans survive on Mars without constant support from the Earth, I am not at all convinced that we know how to make millions of people survive on Mars.

Take point 6 for instance: power. One of the biggest problems we currently have on Earth is that we don't know how to replace fossil fuels, and fossil fuels are not unlimited. It's currently unsolved, and it will impact our lives heavily in the next few decades.

> We are not "destroying the conditions necessary for our survival on Earth."

We are, most definitely. Where the air humidity is saturated (so take a strip around the Equator), if the air temperature goes higher than the skin temperature, we can't regulate our own temperature anymore (by sweating). So we can't live outside without life support.

If we reach an average increase of 4 degrees, then 1/3 of the world population will be located in places where humans cannot survive outside without life support. And right now we are most definitely going for those 4 degrees.

Now you may not care because you don't live around the Equator, but... imagine a world where 1/3 of the population must relocate in order to... regulate their body temperature properly. And I am not even talking about the impact on agriculture in the rest of the world where you can still regulate your body temperature (because at some point you need to eat). In such a world, if you are lucky enough to be in a livable location in terms of temperature, you may just not have food. Definitely global instability and wars.

Not everyone will die, but you have to realize that everybody will be affected greatly.

[gcanyon]

Fossil fuels are becoming less and less necessary to human life, and we have solar and nuclear in pretty reasonable shape to make synthetics as long as we have the raw materials.

Sorry, I took "destroying the conditions necessary for our survival on Earth" to mean in general, as in universally. We're certainly not doing that.

Just as a rough guess something like 15 percent of the land surface of the Earth is near-completely inhospitable to humans, and we're increasing that by 1-3% per century? (both guesses) I don't find it difficult to imagine 1/3 of the earth's population relocating over the course of a few centuries.

I'm an optimist, but I think "everybody will be affected greatly" is pessimistic. Technology and affluence make up for a great deal of negative environment (check out the growth around Phoenix) and the world is becoming more affluent.

[bluGill]

Note that mars is the most likely candidate to make self supporting. I too am not sure if we can, but everywhere else in our solar system is harder.

[pfdietz]

> but the truth is that given our current understanding of the world, sending humans on another solar system is theoretically impossible. Just look at those distances: we just can't, period.

Of course it's theoretically possible. We couldn't do it at relativistic speeds, but that's hardly necessary. We could even do it with chemical propulsion (especially if the Oberth effect were exploited by close solar/stellar flyby). Granted, the trip would take a long time, the scale of the vehicles would be very large, and the humans who arrived would not be the ones who left.

[gcanyon]

It depends on what time scale you're talking about. Here's a Kurzgesagt video that describes how to do it over the course of millions of years: https://www.youtube.com/watch?v=v3y8AIEX_dU

That's a loooong time, obviously, but it's not "theoretically impossible"

[palata]

Sure, but it assumes technology we don't remotely have. Maybe I should not have used the word "theoretically" here. It's just ridiculous to seriously consider it at this point.

It is nice to think about it, of course. But I just don't get how people support wasting so many resources into sending people to Mars where it's basically useless (though exciting, I get it!) and we have much bigger problems to solve on Earth (e.g. the survival of our species in acceptable conditions).

[gcanyon]

I think the word you misused is "impossible," not "theoretically."