Debunking Interstellar Travel: Separating Fact from Fiction

[newjerseyrunner]

I think the biggest problem with the whole "we have to save the species" idea is that I bet most of us simply don't care. Extinction is a natural thing and if humanity were on it's way out I'd probably rather accept it and enjoy my own life than worry about whether or not there even will be a next generation. For almost all of human history we've depended on a stable climate. We've known now for a generation that we're destroying that. As a whole, the species doesn't care.

 

[mfb]

Extinction is a natural thing

So is working on not going extinct. Extinction only happens if the species cannot save itself (or gets saved with the help of other species, as we do it today in some cases).

 

[nikkkom]

I think the biggest problem with the whole "we have to save the species" idea is that I bet most of us simply don't care. Extinction is a natural thing and if humanity were on it's way out I'd probably rather accept it and enjoy my own life than worry about whether or not there even will be a next generation. For almost all of human history we've depended on a stable climate. We've known now for a generation that we're destroying that. As a whole, the species doesn't care.

The survival doesn't happen on the scale of "the species as a whole".
Only those *individuals* who have children are participating in the survival (and evolution). Every single one of your ancestors had children. Only they "succeeded" as forms of life. Not *all* humans who lived before us.

Those who enjoyed their own lives and decided to not have trouble of raising children are irrelevant now, regardless of whatever arguments they may have raised as a rationale. They are dead. Their children do not exist.

And merely having children is not the end. A tribe can have lots of children, but fail to expand out of a small valley it lives in. A small valley which happens to sit nearly a dormant volcano, for example.

For "success as a life form", it makes sense to do more than just multiply in an existing niche.

 

[sophiecentaur]

I think the biggest problem with the whole "we have to save the species" idea is that I bet most of us simply don't care.

I totally agree. A project such as being proposed would demand every member of the human race to 'go without' for generations, just so that a small number of them (or their foetuses ) could be sent on a one way trip with never any feedback about success or failure. We cannot even get the influential majority of the Earth's population to take the subject of Climate repair seriously. Of course, they deny climate change because that keeps the status quo, with unchanged lifestyles for the wealthy (within their limited forward vision). There is no motivation to prevent looming local disaster, so why would attitudes change so that this Noah's Ark project could be funded?
The attitude of humans is to 'save me, my immediate family and possibly some more distant friends and relatives'. That is the same attitude that early tribal mankind evolved with. The difference is that we no longer live in tribes of a few dozen.
I cannot understand how the people who are excited by the possible technologies involved with such a project (me too, in many respects) seem to ignore the way that human nature works. There is no, even remotely, similar project in our history. It is not the slightest bit like crossing the Oceans in tiny boats or riding West on a wagon train. The Earth is small enough for a human to have traveled around it at least once in their lifetime and this has been true for centuries or even millennia. Going home has never been 'impossible' like it would be for this venture.
There are alternative strategies to prolong the life of humanity that are much more realistic - but they do not have the appeal of this grand idea. The same thing applies to schemes for terraforming our neighbours in the solar system. How could anyone possibly think that it could be done successfully when there is no inclination to look after the place that we evolved on?

 

[sophiecentaur]

The survival doesn't happen on the scale of "the species as a whole".

But the survival, in this case, would demand the involvement of 'the species as a whole'.
Who cares enough?

 

[phinds]

For "success as a life form", it makes sense to do more than just multiply in an existing niche.

Which does not in any way address the issue I brought up in post #147

 

[anorlunda]

Regarding @sophiecentaur 's point in #145. I can visualize the following conversation.

Astronaut : Here I am, back to report success of the generation mission to Kepler 134.
Politician : What the f* are you talking about?
Astronaut : You know. The generation star mission you launched 150,000 years ago to preserve the human species. Reporting back was a requirement for accountability of the money spent.
Politician : No I don't know. What's a human? What's a money?

 

[sophiecentaur]

Regarding @sophiecentaur 's point in #145. I can visualize the following conversation.

Astronaut : Here I am, back to report success of the generation mission to Kepler 134.
Politician : What the f* are you talking about?
Astronaut : You know. The generation star mission you launched 150,000 years ago to preserve the human species. Reporting back was a requirement for accountability of the money spent.
Politician : No I don't know. What's a human? What's a money?

I love it.
There is the inverse square law and there is the inverse relevance law of space distances.

 

[nikkkom]

But the survival, in this case, would demand the involvement of 'the species as a whole'.

Not necessarily. A sufficiently big part would do.

While some part of humanity mount a mission to Mars, and later, to Jovian moons, and then KBOs, and then Proxima, some other parts of humanity can still sit on a small peninsula (or small asteroid), half-starving, brainwashed by their tribe leader into thinking that everyone wants to kill them, and it's vitally important for them to put all efforts into having not 2, but 3 nuclear devices (instead of a mission to far away new worlds).

 

[CalcNerd]

With the very real prospect of never ever actually finding another Earth (even it one should actually exist) and the ever increasing abilities of gene modification, mankind will likely have to consider unmanned robotic missions with AI. These missions (done on the cheap with low cost especially in comparison with generational or hibernation technologies) would send out spacecraft with robotic systems that could terraform new planets that had possibilities for life (terraforming with genetically modified bacteria/algae, whatever..). The process could take millennia. Then genetically modify some humanoid that could survive on the resulting rock and move onto the next system. The time scale would be in tens of thousands to millions of years, but to a robot AI with a mission to populate as best as possible, mankind (in some genetically altered state best suited for each planet capable of life) could flourish.
.
I cannot imagine any other solution for space travel, unless there is some unforeseen space propulsion system discovered and developed. All current technologies, even when achieving theoretical perfection fall short due to energy requirements, fuel mass, and life support systems for any practical system.

 

[sophiecentaur]

I said
"But the survival, in this case, would demand the involvement of 'the species as a whole'."

Not necessarily. A sufficiently big part would do.

A sufficiently big part would impose the cost on all the others - so same thing. We still 'owe' the majority of the world a good (acceptable) living. We all know that those at the bottom of the pile would 'pay' for such a massive project - even thought it may not be admitted.

 

[phinds]

All current technologies, even when achieving theoretical perfection fall short due to energy requirements, fuel mass, and life support systems for any practical system.

Not JUST current technologies but any foreseeable extrapolations of those technologies. That's what the optimists keep overlooking (or are unwilling to accept). "Thinking out side the box" in this case seems to require getting so far outside the box that it is just nonsensical.

 

[nikkkom]

With the very real prospect of never ever actually finding another Earth (even it one should actually exist) and the ever increasing abilities of gene modification, mankind will likely have to consider unmanned robotic missions with AI. These missions (done on the cheap with low cost especially in comparison with generational or hibernation technologies) would send out spacecraft with robotic systems that could terraform new planets that had possibilities for life (terraforming with genetically modified bacteria/algae, whatever..). The process could take millennia. Then genetically modify some humanoid that could survive on the resulting rock and move onto the next system.

In 100-500 years, we run rather high chances of being partially or even completely "cyborgized". For one, today's prosthetic hands, legs, ... lungs... hearts... think where this road ends.

Spending millennia changing planets to be suitable for a particular kind of ape to live does not look smart. Changing the ape is faster.

I cannot imagine any other solution for space travel, unless there is some unforeseen space propulsion system discovered and developed. All current technologies, even when achieving theoretical perfection fall short due to energy requirements, fuel mass, and life support systems for any practical system.

Not really. This was raised in this thread already: traveling at "only", say, 15000km/s, gets you to another star in some 100 years - not really too long a time. Well established physics has nothing against accelerating macroscopic objects to 15000km/s.

 

[rootone]

... traveling at "only", say, 15000km/s, gets you to another star in some 100 years - not really too long a time. Well established physics has nothing against accelerating macroscopic objects to 15000km/s.

That's still 3 or 4 generations to get to the nearest star, and the alternative of 'hibernating' the crew is science fiction at present.
Consider also that the chances of an Earth-like planet existing at a star system which is one of the Suns close neighbours is very low.
Earth like planets may well exist within the scope of say 100ly, but to get to those the number of generations looks more like 50.

 

[mfb]

Dedicating your whole life so that someone ELSE can someday land on another planet while you spend your in a relatively small spaceship? Do NOT sign me up.

Don't worry, other people will sign up.

Only those *individuals* who have children are participating in the survival (and evolution).

What about a brother/sister helping the other one and their children? Thinking of species as a single tree is too easy. Every individual has some impact on the survival and reproduction of others.
In addition, genes are not the only thing we pass on - our ideas, values and so on are passed on as well, and they don't need a direct genetic link.

A project such as being proposed would demand every member of the human race to 'go without' for generations

Huh? Citation needed.

with never any feedback about success or failure

A 40-year trip to Proxima Centauri would certainly allow feedback.

It is not the slightest bit like crossing the Oceans in tiny boats or riding West on a wagon train. The Earth is small enough for a human to have traveled around it at least once in their lifetime and this has been true for centuries or even millennia. Going home has never been 'impossible' like it would be for this venture.

Some ocean crossings were one-way streets. The people never came back. And still some people went along this one-way street - without even knowing if there was a target to land! We are in a much better position - we can study the possible destinations from Earth.

How could anyone possibly think that it could be done successfully when there is no inclination to look after the place that we evolved on?

Our planet would look much worse if there would be no inclination to look after it. There is. In addition, it is mainly a political problem. You would not have this political problem on places like Mars: You would not have to explain anyone that the climate outside is not optimal for humans.

With the very real prospect of never ever actually finding another Earth (even it one should actually exist)

Wait, what? Kepler showed that Earth-sized planets in habitable zones are common, and it just looked at a tiny fraction of the sky, and only for transit-planets which is a tiny subset of all planets. TESS and PLATO should find some 4-digit number of them. JWST and E-ELT can do spectroscopy for the closest planets, so we can study their atmospheric composition. This is not science fiction, those are telescopes that will take data within 2-10 years.

I cannot imagine any other solution for space travel, unless there is some unforeseen space propulsion system discovered and developed. All current technologies, even when achieving theoretical perfection fall short due to energy requirements, fuel mass, and life support systems for any practical system.

Nuclear propulsion. There was a concept study for an interstellar spacecraft for 10% the yearly US GNP. Roughly the money the US spends on its military per year, and a nearly irrelevant number as global project.

Consider also that the chances of an Earth-like planet existing at a star system which is one of the Suns close neighbours is very low.

Depends on what you count as Earth-like. Roughly the mass of Earth, about the same amount of radiation? Then the nearest planet is at the same distance as the nearest star, because Proxima Centauri has such a planet.

 

[sophiecentaur]

Huh? Citation needed.

Do we really need specific citations for government spending affecting the fortunes of the poor? India receives international Aid on the grounds of its poor population but can afford vanity projects in Space. And it is by no means the only example.

 

[sophiecentaur]

Some ocean crossings were one-way streets. The people never came back. And still some people went along this one-way street - without even knowing if there was a target to land! We are in a much better position - we can study the possible destinations from Earth.

Of course there were many fatalities in ancient exploration but the timescale for a successful trip would have been well within a lifetime. Most exploration involved island hopping.
A significant proportion of astronauts fail to return too. (A very dangerous occupation by modern standards). There is no parallel here with multi-generational voyages. Alpha Centuri is not representative of the sort of trip that would be involved.

 

[rootone]

Depends on what you count as Earth-like. Roughly the mass of Earth, about the same amount of radiation? Then the nearest planet is at the same distance as the nearest star, because Proxima Centauri has such a planet.

I guess I mean a planet that could be habitable.
A planet on which it could be possible to at least place an enclosed and durable artificial habitat on the surface.
Essential commodities like water and some minerals, (metals?), being accesible

We have Venus in the solar system which is similar to Earth in terms of mass and radiation, but placing a habitat on the surface is a non-runner.

 

[nikkkom]

That's still 3 or 4 generations to get to the nearest star

...Which is not impossible. That's my point.

Consider also that the chances of an Earth-like planet existing at a star system which is one of the Suns close neighbours is very low.

Even the Proxima's planet can have regions suitable for humans to live, this possibility is not ruled out.

Earth like planets may well exist within the scope of say 100ly, but to get to those the number of generations looks more like 50.

Having 50 generations on a ship is not impossible. The poster I replied to thinks it's impossible, and he "cannot imagine any other solution for space travel" but a robotic terraformer with genetic seeds. Something makes him think people can't be born and raised on a ship. ?!

 

[sophiecentaur]

I really don't see the motivation for this project. A very few - either mature or foetal - 'colonists' would be involved. It could never be a rescue exercise for all of us. So why would the huge majority want to spend money on such an exercise? Exploration in the past was always based on economic factors. Ships were financed by a backer, expecting a return on their money. What return would you and I expect, for our 'investment' (hardly the right word)? Nothing would be worth bringing back to Earth.
Some of those left behind might experience a rosy glow about the whole thing. A pretty expensive ego trip.
I guess that there could be scientific data from such an expedition but even that would be bad value as it would involve the extra expenses involved with human cargo.

 

[mfb]

Do we really need specific citations for government spending affecting the fortunes of the poor? India receives international Aid on the grounds of its poor population but can afford vanity projects in Space. And it is by no means the only example.

No, I am interested in a reference showing that any project of interstellar travel would need huge efforts by generations of humans on Earth ("A project such as being proposed would demand every member of the human race to 'go without' for generations"). Especially as we have studies like Project Orion with cost estimates that are fundable within 10 years of 1% of the US GNP.

Alpha Centuri is not representative of the sort of trip that would be involved.

Alpha Centauri is a different star. A journey to Alpha Centauri would be interstellar travel. And it is reachable within a human lifetime with current (!) technology (although the price would go up for this sped-up trip).

A planet on which it could be possible to at least place an enclosed and durable artificial habitat on the surface.
Essential commodities like water and some minerals, (metals?), being accesible

That is even better than the habitable zone. Mars and various moons and asteroids would fit within our solar system alone.

It could never be a rescue exercise for all of us.

Neither was Columbus trip. See what happened later.

Exploration in the past was always based on economic factors.

What was the economic factor of going to the North/South pole? To the top of Mount Everest or the bottom of the Mariana trench? To the moon? What is the immediate direct economic factor of fundamental science? At least for now, humans can do science much more efficiently than robots. If robots can do science better than we can, then they can do nearly everything better and our society will change more than ever before anyway.

 

[rootone]

That is even better than the habitable zone. Mars and various moons and asteroids would fit within our solar system alone.

Then it would be a good idea to go with putting self sustaining colonies on those first before thinking of settlements in other solar systems.
(if the motivation is to have an established base of human habitation other than Earth)

 

[mfb]

Then it would be a good idea to go with putting self sustaining colonies on those first before thinking of settlements in other solar systems.
(if the motivation is to have an established base of human habitation other than Earth)

I don't think anyone wants to start interstellar missions before we got humans to Mars (to stay there) and at least research bases at a few other destinations in the solar system.

 

[mheslep]

...If and when Earth gets threatened by some imminent and inescapable disaster, the place we would be going would be along the lines of Mad Max and a very sad decline until the remnants all expire...

We have a good idea from history what happens after calamities. There's a mix of behaviors, but there's plenty of evidence that in the face of calamity human behavior most often follows the opposite of the 'Mad Max' theme. People quickly reach out to join small groups for support, become more adaptive, more social. Social divisions in place prior to the calamity fade in importance. There are also of course negative behaviors that manifest in the mix as well, but in most cases the positive wins out over the negative.

That's the way humans work and we need to accept that - but we won't.

Yes I grant that the apocalypse (Mad Max, Zombies, Rapture May 2011) has a house of horrors fascination to many, but the dogmatic, contrary to all evidence assertions that everyone must accept these predictions of the future as fact; that I find bizarre.

See e.g. http://wsnet.colostate.edu/CWIS584/Lori_Peek/Data/Sites/1/1-research/publicationpdfs/zahranetal2009.pdf

...Many studies of post disaster deviance and antisocial behavior draw on Fritz’s (1961) concept of the therapeutic community to explain why rates of crime decline (or increase only modestly) after a disaster event. Fritz (1961) argues that post disaster behavior is adaptive, prosocial, and aimed at promoting the safety of others and restoration of community life. Many reasons account for post disaster altruism and other community oriented behaviors. First, social divisions tend to dissolve in the aftermath of a disaster. Risk, loss, and suffering become public rather than private phenomena (Fritz 1961, p. 685). This relative equality of suffering promotes solidarity among disaster victims and sympathizers.1 Second, human survival needs are widespread and visible in the aftermath of a disaster (Fritz 1961, p. 684). Visible suffering increases empathy, inducing social cooperation to solve immediate problems like rescue and debris clearance. Third, natural disasters enable groups to introduce desired reforms into a social system (Fritz 1961, p. 685). For social entrepreneurs, disasters represent opportunities for social change.
...
According to Fischer (1998), looting is the most expected criminal response to a natural disaster. Logically, opportunities for widespread theft are said to increase following a disaster because private property is unprotected. Contrary to logical expectations, scholars find that incidences of looting in the aftermath of a disaster are empirically rare...

 

[Vanadium 50]

Interstellar travel with today's technology and physics is like jumping off a cliff with a garbage bag as a parachute.

Or maybe a sketch of a garbage bag as a parachute.

 

[mheslep]

Or maybe a sketch of a garbage bag as a parachute.

Occasionally, I get away with the excitement over the latest sketches and take them too far.

 

[sophiecentaur]

We have a good idea from history what happens after calamities. There's a mix of behaviors, but there's plenty of evidence that in the face of calamity human behavior most often follows the opposite of the 'Mad Max' theme. People quickly reach out to join small groups for support, become more adaptive, more social. Social divisions in place prior to the calamity fade in importance. There are also of course negative behaviors that manifest in the mix as well, but in most cases the positive wins out over the negative.
Yes I grant that the apocalypse (Mad Max, Zombies, Rapture May 2011) has a house of horrors fascination to many, but the dogmatic, contrary to all evidence assertions that everyone must accept these predictions of the future as fact; that I find bizarre.

See e.g. http://wsnet.colostate.edu/CWIS584/Lori_Peek/Data/Sites/1/1-research/publicationpdfs/zahranetal2009.pdf

I have to hope that you are right about this. But it is not likely to affect me, personally, nor any descendents that I know of. Time will tell.
But whatever you say about how 'communities' behave (well) in adversity, there are massive differences between the fortunes of the rich and of the poor (mostly in separate communities) and I can't see things getting better if resources get tighter. I would imagine that most PF contributors could be classified in the more favoured set of the population (easy access to a computer and a full education, for a start) so we have a possibly biassed view. The attitude in Europe to refugees from the Middle East conflicts shows that most of us are quite happy with the existence of places like the Calais Jungle. and refugee camps elsewhere. The reasonable that the jungle is being removed is not a humanitarian one - just that it is inconvenient and difficult to deal with, as it exists.
I guess my problem (?) is that, being an Atheist, I do not have the luxury of a belief that humans are basically nice and will do the right thing in the end. I am in the middle of Max Hastings' book on WW2 ("All hell let loose") and, whilst he is clearly biased against some major figures, he produces endless lists of documented examples of inhuman acts, carried out by all sides, en mass. My recent input to the thread could even explain my present skeptical view of this thread. Well, we're all human, aren't we?

 

[mfb]

Or maybe a sketch of a garbage bag as a parachute.

With aerodynamic calculations showing that the descend velocity is fine.

Didn't see that post earlier:

Currently (i.e. through 2200)

2200 is as far away from today as the discovery of electromagnetism. I think we made some progress since 1832. I think we made so much progress that any attempt of predictions for 2016's technology back then was pointless. Unless there is some global, long-lasting collapse, there is no reason to assume the world of 2200 would be in any way more familiar to us than today's world to someone from 1832. With the rapid increase in research, I would expect the same even for 2100.

 

[Rubidium_71]

Dedicating your whole life so that someone ELSE can someday land on another planet while you spend your in a relatively small spaceship?

We have humans that are perfectly willing to blow themselves up and commit mass murder for the sake of their superstitions. I would think there would also be people that would sign on to a project with more substantial goals and rewards. I wouldn't sign up either but that doesn't mean that no one would. When it comes to sacrifice for a greater good, look at some of our dedicated submariners. They spend a good portion of their adult lives in nuclear submarines. I've been on a sub, not the greatest situation to live in. But they do it. The main reason for nuclear subs to exist at all is to be sure we can launch a nuclear attack even if the US is nuked first. Signing up for a generation ship would be more altruistic than sitting on a clutch of nuclear warheads at the bottom of the Atlantic waiting to join in on WW3.

the immediate crew, personally pointless.

I disagree, Sir. People already care about their children and grandchildren because they like the idea of their lineage carrying on into the future. If you tell folks their progeny will be part of starting an off world colony, I think there would be interested parties.

My guess is interstellar travel remains jumping-off-a-cliff out of reach for the next century even with on trend, incremental but non-revolutionary improvements in technology.

I don't disagree, I think even the fanciful Mars missions being discussed would result in likely death and disaster. However, humans have a tendency to climb into a barrel and ride it off of Niagra falls, so if someone like Musk ever slapped together a ship for an interstellar try I think there would be interested people.
We certainly have enough time to let better technology develop. I think in the long run the only wrong answer is not to try at all.

 

[mheslep]

...
2200 is as far away from today as the discovery of electromagnetism. I think we made some progress since 1832...

I retract 2200 as too far out to extend any trend that I might perceive. I was vaguely looking for some point in time that seemed like a compromise between extension of current discovery trends and also being slightly over the horizon.

Still, my guess is that the distance between current capabilities (technical and political) and those likely to enable interstellar travel is much greater than the historical gap between now and electromagnetism. I'm more inclined to think the capablities gap is more like between now and Aristotle's four elements and Earth centric universe. Whether that gap is covered in 100 years or 2400 years I have no idea. Well, not no idea, I could hand waive some more.

 

[mheslep]

... most PF contributors could be classified in the more favoured set of the population (easy access to a computer and a full education, for a start) so we have a possibly biassed view.

Certainly. Everyone is capable of bias.

...I guess my problem (?) is that, being an Atheist, I do not have the luxury of a belief ...

My point was you placed a strong belief system on display in this thread, that everything *will* go to hell, and that anyone who disagrees is in denial. I only draw your attention to some contrary evidence, and not to a certainty that the unknowable future will be fine.

...I am in the middle of Max Hastings' book on WW2 ("All hell let loose") and, whilst he is clearly biased against some major figures, he produces endless lists of documented examples of inhuman acts, carried out by all sides, en mass. ...

Yes, by some measures the most calamitous event in history. Somewhere in Hastings book there's undoubtedly also some description of millions of people who, despite being far removed from harm, got involved at great cost to put a stop to it all. They won, and though they too were flawed humans, they were not equivalent to the tyrants they defeated.

 

[mheslep]

...
I don't disagree, I think even the fanciful Mars missions being discussed would result in likely death and disaster. However, humans have a tendency to climb into a barrel and ride it off of Niagra falls,

There is the foolish, self-destructive risk, like Russian Roulette, and then there is exploration inspired by an evidenced based theory that entails a considered risk.

 

[nikkkom]

I really don't see the motivation for this project. A very few - either mature or foetal - 'colonists' would be involved.

How did you reach this conclusion about "very few"? Why interstellar ship can't have a crew of 50, 100, 200?

It could never be a rescue exercise for all of us.

It does not have to be.

Exploration in the past was always based on economic factors.

Wrong.

 

[nikkkom]

The attitude in Europe to refugees from the Middle East conflicts shows that most of us are quite happy with the existence of places like the Calais Jungle. and refugee camps elsewhere.

What irritates me about this refugee situation and ME conflicts is that while there are callous people who don't care one iota about horrors somewhere far away, there are also "good people" who nevertheless don't try to understand what's happening, why it is happening, and unwilling to discuss what can be a working solution for this problem. The only thing these "good people" care is to placate their sense of "goodness". "Lets feed and clothe starving and homeless", and let's not figure out how to stop more people from starving and becoming homeless. Good plan. Almost on par with the plan to let entire Africa and ME immigrate into Europe. Evidently, some people think that's the solution.

 

[sophiecentaur]

How did you reach this conclusion about "very few"? Why interstellar ship can't have a crew of 50, 100, 200?
It does not have to be.
Wrong.

I would depend entirely what the terms of the project were. I can't see any point in sending fewer than many (tens of?) thousands of people on such a trip. It would be necessary to have an established community which could regulate itself and be capable of coping with many social problems. Failure of the expedition simply because a squabble amongst a small crew would always be a risk. This, again, shows how the proponents of this sort of scheme are only concerned with nuts and bolts and speeds. The whole project would have to have a 'reason'. It would need to be justified and funded and SOLD to the governments of the World.
In many ways, the practicalities are the least of the problems.

 

[nikkkom]

I would depend entirely what the terms of the project were. I can't see any point in sending fewer than many (tens of?) thousands of people on such a trip. It would be necessary to have an established community which could regulate itself and be capable of coping with many social problems.

Why? Can you try justifying your views and numbers instead of just having an opinion.

Regarding a viable minimal size of a multi-generational community. Before I formulate an opinion, I look for facts. In this case, facts are as follows.

For thousands of years, a typical unit of human society was a tribe. A village. Some 100-1000 people. They existed for hundreds of years, and were usually disrupted by wars / attacks by other human groups (which is not very likely to happen on an interstellar flight), not by internal strife.

Failure of the expedition simply because a squabble amongst a small crew would always be a risk.

True. There are many risks, this one is present too. However, squabble amongst a big crew is also possible. Why do you think it's less likely?

 

[phinds]

For thousands of years, a typical unit of human society was a tribe. A village. Some 100-1000 people. They existed for hundreds of years, and were usually disrupted by wars / attacks by other human groups (which is not very likely to happen on an interstellar flight), not by internal strife.

Uh ... you think maybe things were simpler back then and they didn't need to know the thousands of things that a high tech group will need if they are going to have a viable human ecosystem both on the trip and after arrival?

 

[sophiecentaur]

For thousands of years, a typical unit of human society was a tribe. A village. Some 100-1000 people. They existed for hundreds of years, and were usually disrupted by wars / attacks by other human groups (which is not very likely to happen on an interstellar flight), not by internal strife.

There is very little about this subject that's more than 'opinion' - apart from the Engineering aspects.
The tribal scale of life worked fine when there were many tribes about and if one failed, there would be others beyond the next hill, to continue the race. If the 'colony' is to have good chance of survival (after the investment that's been put into it) then it needs to be able to expand into the new world; hitting the ground running. You can't do that sort of thing on a tribal scale. They will need all kinds of specialists and the capacity for giving a complete education to any children they may have. That is my justification for the big numbers I suggested.
I repeat, this is nothing like Cristopher Columbus or a few intrepid Vikings. Explorations in those days could afford to fail on a regular basis. There was nothing at stake for mankind. Another group would be along in a few decades. And there was always the possibility of going home with a load of goodies. Modern 'Explorers' are not comparable with this. Their purpose is not to do with spreading humans around the planet- they are only self-sufficient for a limited time. Climbing Everest is a pretty irrelevant exercise - except for personal enjoyment. The medical spin-offs from such activities are useful, no doubt. There is no parallel either with Migration or Interstellar exploration.

However, squabble amongst a big crew is also possible. Why do you think it's less likely?

Nothing is impossible but a basically urban sized group would have built in structures; government, infrastructure, a police force, even. For that, you need an appropriate population. The Starship Enterprise situation was well thought out, in that respect. (I would never normally quote Startrek Science on PF but they did get some things right.)
This thread has suffered from not discussing a particular project because we all have different models in mind. Personally, I think it's all too vague to be taken seriously.

 

[mfb]

If a colony ship fails, it is possible to send another colony ship. As long as humans are around and enough of them think it is worth the trip, a single failure does not matter much.

Compared to all the exploration of Earth, we have two advantages:
- we can study the destination in advance. We don't have to hope that there is some island - we know well in advance that there is a planet, its mass, its radiation conditions, its atmospheric composition, potentially its surface chemistry, volcanism and so on.
- we have communication. If a ship sank somewhere in the ocean 200 years ago, no one had any clue what happened - the mission just disappeared. If something happens with an interstellar spacecraft , chances are good they can send back some information about it.

Concerning a minimal viable population: A few hundred in terms of genetics (lower with frozen sperm and/or careful selection of colonists), more would certainly help with passing on knowledge. A lot more can be stored as digital information and learned from there.

 

[mheslep]

...
- we have communication. If a ship sank somewhere in the ocean 200 years ago, no one had any clue what happened - the mission just disappeared. If something happens with an interstellar spacecraft , chances are good they can send back some information about it.

I was thinking the opposite, that the chances of getiing some word from an interstellar colony are likely more difficult than in the age of sail. The age of sail at least had the odd shipwreck survivor, sister ships, and possibly people at the last remote port of call that might tell part the tale. In the interstellar case, first the message takes the time in light years to arrive. Second, the free space path loss (for, say, f=3GHz) for a light year is 365 dB, which requires transmitter power in the terrawatt range.

 

[nikkkom]

There is very little about this subject that's more than 'opinion' - apart from the Engineering aspects.
The tribal scale of life worked fine when there were many tribes about and if one failed, there would be others beyond the next hill, to continue the race. If the 'colony' is to have good chance of survival (after the investment that's been put into it) then it needs to be able to expand into the new world; hitting the ground running. You can't do that sort of thing on a tribal scale.

You are reiterating that it can't be done with less than about 1000 people, without actually giving justification. Repeating something you believe in does not make it true.

You don't need to have specialists in every imaginable profession. For many things, just having recorded knowledge how to do it, how to learn it, is sufficient. For example, you don't need architects or CPU designers on the ship. You don't need them even after it reached the destination. It's okay if only some of the future children grow up and decide to be architects.

 

[|Glitch|]

The only reason I can think of as to why we would send a manned-mission to another star is for the purpose of colonization. In order for that to happen we would first need to find an exoplanet that is a reasonably close match to Earth. With a similar atmospheric composition, an atmospheric pressure that is very close to Earth, and a temperature range that supports liquid water on the surface.

That is asking a great deal. While we do not yet know the atmospheric conditions of the exoplanets we have found thus far, the overwhelming majority of the exoplanets in the 0.75 to 1.50 Earth mass range do not fall within the habitable zone of their star. Finding one that has 78% nitrogen and 21% oxygen with 14.696 psi atmospheric pressure at "sea level" has to be exceedingly rare indeed. We shouldn't forget that Earth would be completely without oxygen if not for the life that developed on early Earth ~3.8 billion years ago. Therefore, for an exoplanet to also have oxygen in its atmosphere it would most likely indicate the existence of life. Since oxygen is highly reactive and will combine with just about anything, in order for molecular oxygen to exist in the atmosphere there would have to be some form of life continuously producing it. If life once existed on an exoplanet and then died out completely, any oxygen that life had produced would have combined with other elements (hydrogen, metals, etc.) and no longer be present in the atmosphere.

There are so many different variations of solar system formations, types of "rocky" exoplanets, atmospheric compositions and pressures, etc., that finding one that could come close to supporting any form of human life would be miraculous indeed. We could search for thousands of years, examining millions of exoplanets, and still never find one that is a reasonably close match to Earth. Yet until such a match is found, it does not seem probably that we would even attempt to send a manned-mission to another star. Assuming we had the technology.

 

[sophiecentaur]

You are reiterating that it can't be done with less than about 1000 people, without actually giving justification. Repeating something you believe in does not make it true.

You don't need to have specialists in every imaginable profession. For many things, just having recorded knowledge how to do it, how to learn it, is sufficient. For example, you don't need architects or CPU designers on the ship. You don't need them even after it reached the destination. It's okay if only some of the future children grow up and decide to be architects.

You forget that the expedition needs to be autonomous and ready to deal with the unexpected, at short notice. You can't claim that a massive information bank can solve all problems as they arrive. Remember, early colonists took experts with them. Too late to learn carpentry when you spring a leak.
Not possible to ring home (as in Apollo) for the solution to a problem.
10LY away and you wait 20y for advice from home. Everyone dies.
In any case, I can't see large scale as an objection.

 

[litup]

There are schemes involving the freezing of ova and sperm and such, basically a robot ship that may take a thousand years to get even to Alpha Centauri and then robots grow new humans after arrival or a few years before and teach those children the history of the human race and they go on to found a colony there.

In the meantime, science catches up and actually does make a faster than light drive and has already gotten a colony started 800 years before the robot ship arrives, hilarity ensues...

 

[Borg]

In the meantime, science catches up and actually does make a faster than light drive and has already gotten a colony started 800 years before the robot ship arrives, hilarity ensues...

Or not.

 

[Rubidium_71]

There is the foolish, self-destructive risk, like Russian Roulette, and then there is exploration inspired by an evidenced based theory that entails a considered risk.

Humans often admire "foolish, self destructive risk" even if it fails. The men who crewed the Hunley submarine in 1864 could certainly have been considered foolish. The vessel had already killed many people, but they accepted the mission anyway. They were successful in destroying the USS Housatonic, but died when the ship was lost during the mission. I've been to the Hunley museum in South Carolina - these men are regarded are heroes, not fools. Even though the Hunley ultimately failed the ship is revered and the technology was improved into the present day.
In my opinion this is one of humanity's strengths - we dare. For good or ill, I can see humans taking on the "crazy" risk of an interstellar journey. Personally, I wouldn't see an interstellar space mission as being comparable to Russian Roulette, with the space mission there's a greater mission and potential reward that might be possible.

 

[mfb]

In the interstellar case, first the message takes the time in light years to arrive. Second, the free space path loss (for, say, f=3GHz) for a light year is 365 dB, which requires transmitter power in the terrawatt range.

A highly directional transmitter doesn't need that much power, especially if you don't need a huge bandwidth.

the overwhelming majority of the exoplanets in the 0.75 to 1.50 Earth mass range do not fall within the habitable zone of their star.

Don't forget observation bias, Kepler is more likely to find planets closer to the stars. Something like 1% to 3% of all stars have "earth analogs" (source), the number gets significantly larger if you include colder planets where fission, fusion, or large-scale solar power can deliver the necessary power, and with exomoons orbiting larger planets. There are 50 stars within ~15 light years, so we expect to have several planets that can support human life (with some artificial heating), and on average one "Earth analog". That does not mean 21% oxygen and 101.3 kPa atmospheric pressure, but that is not necessary.

Since oxygen is highly reactive and will combine with just about anything, in order for molecular oxygen to exist in the atmosphere there would have to be some form of life continuously producing it.

Maybe. Maybe not. Be careful with "impossible" statements.

 

[mheslep]

Humans often admire "foolish, self destructive risk" even if it fails. The men who crewed the Hunley submarine in 1864 could certainly have been considered foolish.

Im not talking about what people ignorant of science and engineering available at the time might think. All the basic science was in place for a crude submarine: Archimedes, Newton, Boyle, the crude materials, pumps, metallergy. One could place on paper a logical, evidence based argument for how the Hunley could work, and from that model roughly predict it's capabilities. Success was one the possible outcomes.

Building a much larger Hunley with the same model and materials, and musing 'hey we sunk the Husatonic, now let's take this rig under the Arctic Ocean ice to the North Pole because we dare', that would be the work of fools, and there would be no museum commemorating the attempt. And I contend taking a hand propelled, hand pumped, blind steerage 19th century vessel to the North Pole had a better chance than an interstellar manned mission with current technology.

It occurs to me I'm spilling a lot of ink trying to illustrate the difference between the bold and the foolish, when the point was classically illustrated long ago.
https://en.m.wikipedia.org/wiki/Icarus#The_legend

 

[mheslep]

... several planets that can support human life (with some artificial heating), ...

How is 'support' defined in this context? Life can be supported on the Moon with sufficient artificial means.

 

[mfb]

'hey we sunk the Husatonic, now let's take this rig under the Arctic Ocean ice to the North Pole because we dare'

Human spaceflight missions so far had a success rate of 98-99%. Comparing that to a submarine that sank is not really fair.

Spoiler

315 launch attempts
- one crew got saved by the launch abort system seconds before the rocket exploded on the pad (Soyuz T-10-1)
- one crew died during launch (Challenger)
313 missions reached orbit and went back to attempt a landing
- one crew died from decompression shortly before entering the atmosphere (Soyuz 11)
- one crew died from disintegration of the vehicle in the atmosphere (Columbia)
- one crew (well, a single person) died on hard impact with the ground (Soyuz 1)
310 missions landed all passengers safely on Earth

4 missions with fatalities, one mission that did not fly, but without fatalities, and if you want to include Apollo 13 then we have one mission which did not reach its intended destination. 4-6 failures in 315 missions.

How is 'support' defined in this context? Life can be supported on the Moon with sufficient artificial means.

The planets mentioned are probably much better than the Moon. More like Mars.