How difficult is interstellar travel?

[Undesired Walrus]

You miss my point. If we could check out a bunch of stars across the galaxy, some of the more interesting nebula, swing by a few neutron stars to take some remote measurements, and check out some other planetary systems, then it might be worth it.

But is it worth several generations of people living on a spacecraft, an enormous amount of resources and so on just to get to one of the (very) local stars, such as alpha centauri, only to find a rather uninteresting star with no habitable planets or major resources? then what? Spend another century heading back to earth because the place you've arrived is not suitable for living there?

or keep going? Spend another several generations on your ship (presumably with near-unlimited resources) going to another (very) local star system?

Sometimes, DRBUZZO, being a skeptic, a realist, and a rationalist can make you immensly boring.

 

[DRBUZZ0]

It will be worth any investment when we can put an a self sustaining human population in other star systems. The earth and the sun are finite. Conservation efforts can only do so much. Eventually we have to consider this planet and star disposable. To say nothing of big rocks, or solar calamity.

While there may be no immediate urgency, ultimately we have to load up the truck and move to Beverly.

Well at the point where:

1. Earth has completely run out of resources and is just not going to do it, no matter how much is reused
2. Mars is not working either
3. We've mined or scavenged all the asteroids, planetary moons, interplanetary dust, comet fragments and other stuff in the solar system for materials/energy/water/oxygen
4. There is nothing left to live on. Nothing left to use. No raw materials that can be synthesized into something to use.

Well, okay... then we might need to start looking at other local stars. But we have a loooooooong time for that. An incomprehensibly long time. Millions, if not billions of years... That's beyond the survival time of any higher functioning species. That's... longer than can be fathomed.

So don't worry about it...

 

[Kenny 10 Bellys]

Dont kid yourselves, we're running out of resources at an alarming rate, and it's only going to get worse and at an accelerating rate. If I were in charge I'd have them working like crazy on a way of spreading humanity to space and the stars, opening up the next frontier and keeping us safe from pandemics, extinction level impacts, wars, etc and give people new opportunities to find living space and resources. Complacency will get us all bit in the ass.

 

[DRBUZZ0]

Dont kid yourselves, we're running out of resources at an alarming rate, and it's only going to get worse and at an accelerating rate. If I were in charge I'd have them working like crazy on a way of spreading humanity to space and the stars, opening up the next frontier and keeping us safe from pandemics, extinction level impacts, wars, etc and give people new opportunities to find living space and resources. Complacency will get us all bit in the ass.

What do you mean by "Running out of resources"? Could I see some evidence for this?

Where are these "resources" going? Unless they are being sent out into space, past earth orbit, they still should be here.

It may sound difficult to recapture the carbon in the atmosphere and resynthasize it back into usable materials, or to mine old landfills for metal and then seperate and re-smelt it.

It's a hell of a lot easier than going to the stars though. As things stand now, there is little chance we'll be running out of matter to synthasize stuff out of any time soon. (Again... difficult but much easier than going to a star)

But how does it help humanity to move to other planets? If we go to, say, mars, we'll need to bring massive amounts of technology from earth and keep ourselves alive artificially for hundreds, possibly thousands of years, before even the slightest hope that the planet could form a naturally sustainable enviornment fit for higher life forms. (and it very well may never)

And the stars? Again, spend hundreds and hundreds of years just to get to some of the extremely nearby stars? The couple dozen systems that we have even the slightest hope of getting to within less than a million years?

And then arive and find there are no suitable planets? Then what? Keep going for thousands more years?

The spacecraft required would possibly require more than all the world resources. And the idea that life could be sustained with artificial technology reliably for generation after generation after generation is not very realistic.

Yes, maybe getting to another star is possible, but not in my lifetime. Not in your lifetime, not in your childrens' childrens' childrens' lifetime. I realize that it's dangerous to limit the possibilities in the future, but it won't happen in any forseable future, unless there is some dramatic discovery which expands the laws of physics beyond what we currently think is possible.

There's no technology that could do this. There's no technology under development to do this. There's no extension of technology being considered for development for this. There's no technology which could possibly lead to a future technology which could be expanded to do this. It is many many many orders of magnitude beyond what we are even capable of considering.

The best we might be able to do is maybe, in a few cneturies, hope to send a small group of humans to alpha centauri and have them return to say "yeah. no planets. Not a very good star for habitation. We came back because we saw no other place to go"

 

[Schneibster]

Here's a question:

What makes causality so sacrosanct?

The fact that every time we think we have found an instance in which it is violated, we turn out to have missed something important. It's kind of like the conservation laws in that respect. In fact, the conservation laws are based on causality- without causality, none of the conservation laws make any sense.

The neutrino is pretty much the poster child for the conservation laws.

What happened was, physicists made observations and measurements of beta decay, a type of radioactive decay in which a neutron within a nucleus turns to a proton, and an electron is emitted from the nucleus. They did calculations of the residual energy, and figured out how much energy the electrons should have. And they measured the energy of the electrons. And what they found was, the energy they calculated was a maximum- and a value they almost never saw. They always saw something less than the maximum.

Wolfgang Pauli theorized that there had to be some other particle emerging from this interaction- a particle that didn't have an electric charge, didn't have much mass, and didn't interact with matter much (otherwise we'd detect it as easily as we did the electrons). Most physicists said, "well, that's nice, but show us one."

Pretty soon, physicists found that spin angular momentum was also conserved- and that this conservation law was also present in the macro world, as the conservation of angular momentum. And when they went and looked at beta decay, they had a problem: the spin of the proton and neutron were equal, so where did the spin of the electron come from? So now there were two conservation laws that the neutrino could save, assuming that it could have an equal and opposite spin to the electron.

So some theoretical physicists worked out what the properties of the neutrino had to be. And what they came up with was a particle that would be very hard to detect. For quite a long time, decades in fact, there was debate about the existence of the neutrino. But finally, someone came up with a way to detect them: they theorized that although there was a very small chance of seeing an interaction involving a neutrino, it was not zero, and if they could get enough mass together and watch for an interaction that without the neutrino would violate the conservation laws, then they could take a source of putative neutrinos and see whether they could establish that the occurrence of this interaction would be more common with a source of neutrinos than not. They did this experiment, showed that the interaction occurred far more often under circumstances where neutrinos would be expected, and won a Nobel Prize for the discovery of the neutrino.

All that from just the conservation laws.

So when we talk about causality, you have to keep in mind that the conservation laws are all based on causality; and the neutrino is hardly the only thing to have been discovered by looking into an apparent violation of these laws. It's to the point now where if someone sees what appears to be a violation of a conservation law, they don't even question the law; they go looking for the cause, because everyone who has explained such a thing has gotten famous.

So it's not that causality is sacrosanct; it's that we've never observed it to be violated. Just like conservation of mass/energy. Just like conservation of momentum or angular momentum. Just like conservation of parity.

The first order answer would have to be something to the effect of: without an assumption of the inviolability of causality, nothing would make sense!

As a matter of fact, that's very nearly it, from a non-technical point of view. Newton's Laws, for example, are dependent upon causality.

However, in terms of physical quantities, is entropy a stand-in for causality?

Not really. Entropy is more a consequence of causality, or more properly, without causality, entropy is not definable.

 

[Faithkills]

...Well, okay... then we might need to start looking at other local stars. But we have a loooooooong time for that. An incomprehensibly long time. Millions, if not billions of years... That's beyond the survival time of any higher functioning species. That's... longer than can be fathomed.

A rock could hit us next year and that's all she wrote.

Global conservation efforts may prove to be a political impossibility. Even with them if we do not plan ahead BEFORE we run out of resources it may not happen. We can afford to work toward it now. Once the situation becomes desperate it may be practically impossible. It will be a hard case to make to allocate extremely limited resources to space travel when most people are starving for example.

So don't worry about it...

I don't lose sleep over it, but on the other hand I don't see very many more worthwhile endeavors than humanity becoming interstellar either.

One egg, one basket.. not the wisest or safest perch to rest.

There's really no reason not to be planting seeds wherever we can as soon as we can.

What do you mean by "Running out of resources"? Could I see some evidence for this?

Well we are not running out of matter, however we are certainly using up our nicely organized resources and we are increasing entropy. Maybe it makes sense to be proactive when it's relatively easy to divert resources to this endeavor than when things are so tight that it may become politically impossible to do so?

As as I mentioned we are definitely running out of the most important resource, time, and it could be a lot shorter than we know. Why would we risk everything on the assumption we will not kill ourselves in a nuclear or biological armageddon? Or at least screw ourselves up beyond recovering. Or risk some thought control totalitarian regime becoming globally dominant. Certainly there are entities that want this position.

 

[Cuddles]

I think it is quite interesting that even in most sci-fi involving interstellar travel this is not usually started without a big kick in the pants. There is almost always some natural disaster or world war or something that gives people a good reason to leave Earth. It seems that no matter how much they are willing to bend the laws of physics, most sci-fi authors seem to agree that "because it is there" is unlikely to be the reason humans take up interstellar travel.

 

[jimbob]

So it's not that causality is sacrosanct; it's that we've never observed it to be violated. Just like conservation of mass/energy. Just like conservation of momentum or angular momentum. Just like conservation of parity.

[derail]
And Terry Pratchett's conservation of reality. It takes at least as much effort to do something using magic as not. [/derail]

 

[Correa Neto]

One thing we must consider is that when interstellar travel becomes technical feasible, maybe humans will be quite different from what we are now. If they will still be something that can be called human.

Genetical engineering, artificial implants and who-know-what-else may significantly change the perspectives. Maybe some of these future folks will live all their lives in huge space stations. Thus, a decades or centuries long travel may become accceptable.

 

[Kaarjuus]

It seems that no matter how much they are willing to bend the laws of physics, most sci-fi authors seem to agree that "because it is there" is unlikely to be the reason humans take up interstellar travel.

Err.. on the contrary, in most sci-fi, interstellar travel is taken up exactly for the cause of "because it's there".

Curiosity and want for adventure are importart drivers for us humans.

 

[mhaze]

Of course, it's possible that the robots will be the ones who decide to go. By the time we have the propulsion systems, we'll probably have the AI.
As for cost, I would gladly pay taxes comparable to what I pay for current NASA missions to Mars in order to support an interstellar mission. So, if it takes 100 years to build the ship, that's 100 years of taxpayers.
Of course, with today's technology and economy, there's not much point. We couldn't build the ship in 100 years, or 1000 years.

Would you rather pay for a robotic interstellar mission instead of a manned Mars mission, if both were the same price?

 

[mhaze]

Would you rather pay for a robotic interstellar mission instead of a manned Mars mission, if both were the same price?

Further considerations.

Assume you could send software updates to the robotic mission during part of its transit (obviously not while it was near light speed).

The equipment sent does not come back, all we get back is data streams.

 

[Meadmaker]

Would you rather pay for a robotic interstellar mission instead of a manned Mars mission, if both were the same price?

No doubt for me: robotic interstellar.

However, it seems unlikely they would be the same price. It seems to me almost certain that the interstellar mission would be much, much, more expensive than a manned Mars mission.

 

[whiteyonthemoon]

A thorough treatment by science fiction author Charlie Stross says forget about it.

 

[Dr. Mabuse]

frank462:
There was an old science fiction story...

I recall reading a similar story.

Dr. Mabuse:
Are you perhaps thinking of Robert A. Heinlein's "Time for the Stars"...

No, that's not the one I read. The one I recall had the astronaut in suspended animation, and when he is awakened close to his destination that's when he finds out the planet he was heading to had already been colonized by humans.

I can't recall who wrote the story... maybe A.E. van Vogt?

There have been many stories with similar situations.

The first ones that comes to mind is Star Trek (TOS) episode "Space Seed" where the pre-warp starship Botany Bay carrying astronauts from early 21st century Earth is intercepted by Enterprise.
Similar: Star Trek (TNG) episode "The Neutral Zone".

Also (sort of) Planet of the Apes.

 

[slyjoe]

No doubt for me: robotic interstellar.

However, it seems unlikely they would be the same price. It seems to me almost certain that the interstellar mission would be much, much, more expensive than a manned Mars mission.

Not sure I would agree with that. Putting people in the loop makes the price skyrocket (pun intended).

 

[Jimbo07]

Not sure I would agree with that. Putting people in the loop makes the price skyrocket (pun intended).

I agree, and people to Mars is a cool enough sci-fi-esque endeavour.

However...

We have sent probes to Mars, but not to other stars (in any meaningful sense). The scale of such an undertaking is so vast, that I can imagine a manned Mars mission as seeming (somewhat) more feasible than a functioning interstellar robotic probe.

 

[Meadmaker]

I agree, and people to Mars is a cool enough sci-fi-esque endeavour.

However...

We have sent probes to Mars, but not to other stars (in any meaningful sense). The scale of such an undertaking is so vast, that I can imagine a manned Mars mission as seeming (somewhat) more feasible than a functioning interstellar robotic probe.

In technological terms, getting a manned mission to Mars is easily doable, especially if money is no object.

In technological terms, we don't have a way of sending a probe to Alpha Centauri. (Proxima Centauri? I've seen both listed as our closest neighbor. These are two names for the same star, aren't they?) Using any propulsion system we know, it would be a vast undertaking, requiring huge resources, and it would be slow, slow, slow, as in decades, probably hundreds of years slow. We don't have electronic components that last that long, so the probe would die before it got there. We don't have anything that would send information back across that huge distance, so I guess we could record the images once the probe got there, and have it turn around and come back, which means twice the propellant. Oops. Actually, lots more than twice, because you have to accelerate all the propellant all the way to Centauri.

No, using today's technology, the stars are out of reach even for robots, and even if the whole darned planet caught the spacefaring bug and decided to cooperate and put resources into it together. We just can't get there from here.

I believe that will change, and someday, robots will go. People? Maybe, but far from certain. I think if the technology could be made to work, and a suitable habitat could be found, I think the will to go would exist, despite the huge cost. However, I don't know if that technology could ever exist.

If I were betting, I would say it would happen eventually, but I'll be dead long before I would pay or collect on that bet, along with any descendant of mine that would remember me in any family tree.

 

[RecoveringYuppy]

(Proxima Centauri? I've seen both listed as our closest neighbor. These are two names for the same star, aren't they?)

Alpha Centauri is a three star system consisting of two sun like stars orbiting each other and a third red dwarf at great distance. The names for the three stars are Rigil Kentaurus A, Rigil Kentaurus B and Proxima (the red dwarf). Proxima happens to be on our side of the system at the moment so it is our closest neighbor at the moment.

 

[Meadmaker]

Alpha Centauri is a three star system consisting of two sun like stars orbiting each other and a third red dwarf at great distance. The names for the three stars are Rigil Kentaurus A, Rigil Kentaurus B and Proxima (the red dwarf). Proxima happens to be on our side of the system at the moment so it is our closest neighbor at the moment.

Thanks.