When my kids were small they asked me if I believed there was life on other planets and I told them I supposed there was. They asked me if people from one of these planets would come and attack us like in the movies and I told them that I supposed that given the distance it would be far too expensive for any society I could imagine to undertake such a trip. Especially given that the society would likely be long gone by the time their expedition reached us. I figured this would keep them from worrying about it.
So, if we imagine a planet orbiting another star at a likely distance from our own that has an environment similar enough to our own to lead to the development of individual animals that would be intelligible to us as “persons”, and we imagine these people have somehow overcome the longevity issue involved in visiting us (maybe they can be de-animated/re-animated or uploaded/downloaded), and given a likely distribution of materials and energy sources on their planet, has anyone calculated a high and low estimate of how much a visit to us involving their physical bodies would cost them as represented by global GDP translated into 2013 US dollars?
It seems to me the cost would be relatively independent of the speed/duration of the trip although the speed/duration of trip would determine the feasibility of the mission if we imagine the physical aspects of the vessel and occupants were subject to inevitable decay over time. How much would the trip cost and what is the maximum duration and thus necessary speed that can be imagined for this trip given our understanding of physics. Has anyone published reasoned speculation about this?
There are certain problems (e.g. breakdown of equipment, collision) whose probability increases with time enroute. So mission success requires a craft whose design reduces the chance of these problems and/or multiple missions - both of which add to the total cost.
Kinetic energy to go from 0 to .1c for a 100 tonne mass --> 4.5x10[sup]19[/sup]Joules. Double it to maximize the energy expenditure when you break at the far end point and you have ~1x10[sup]20[/sup]Joules worth of energy.
Now 1kWhr is roughly 3.6x10[sup]6[/sup]J and a kWH is ~$0.1 the cost is $2.5x10[sup]12[/sup] call it $2.5 trillion.
Note this excludes development costs, and like any first time thing it’s likely to be even higher but what it does show is that while $2.5 trillion is a lot of money it isn’t outside what can be afforded by either the US or the world in total if the will exists to do it.
$2.5 trillion --> 50% of the cost if the Iraq war, 16% of US GDP, 3% of world GDP.
Also, just to attack the premise, if aliens did decide to come attack us, it wouldn’t be as it’s shown in bad movies, with ships landing and disgorging waves of ray-gun-waving green people. Nah. Orbital bombardment is the way to go. Stay up out of reach and throw rocks. Select the size of the rock to match the desired level of devastation, and you can wipe out life on earth from the comfort of your acceleration couch.
Other problems include the fact that these dollar figures don’t mean anything because they are only a measurement of the resources required and not of the total economy.
Theoretically, at some future date we could develop self-replicating technology. This would be a collection of robots at some scale that, given raw materials and energy, can copy themselves. This may not sound like a big deal, but once you have this tech, within a few decades you could tear apart every planet in the solar system into more robots.
Once you’ve made every scrap of available matter into robots, slapping a starship together would use a teensy fraction of total resources. You could, if you had the patience to travel somewhere, go to other stars and maybe encounter intelligent aliens eventually.
The problem with these “aliens attack earth” stories is that earth is more than likely an extremely rare place with billions of unique species. The evolutionary track that life followed is probably somewhat unique to earth, even. For an alien species that could reach earth, if they have starships, they probably have the technology to convert any old rocks or small planets they find into raw materials. The “resources” of earth would not mean anything to them. They also would not share our biochemistry, so they couldn’t eat us, and they couldn’t live on earth without basically destroying it first.
So, there would be no reason for them to attack at all. The rational choice would be to quietly collect samples and observe without disturbing anything too much.
Good point, but there’s a downside in that you’ll have to wait for the dust to settle, and that could be decades or even centuries.
My “just to attack the premise” is that even if you have the resources and lifespan and patience to travel so very far, your friends and family back home are long dead and have forgotten all about you. There’s a whole genre of sci-fi about generation ships where the younger population, never having known the homeworld, radically changes the purpose of the mission - or even forgets that they are on a vehicle at all. In short, these sorts of things are no good for research or exploration, but only for escape and transferring the population to a new home.
Yeah, the only reason I could think of for interstellar travel would be an utter commitment to door-to-door proselytizing. Some crazy religion is the only thing I could imagine that could motivate the allocation of resources to such an expensive and senseless one-way-trip. Either that or evolution to AI that was extremely bored and didn’t have anything better to do.
Hercules, thank you for the links. Has anyone speculated how long a closed system can self-maintain before succumbing to material failure? I guess if we assume nano-tech self replication that isn’t a factor or is it?
Long ago, and I forget where (maybe a Frederick Pohl novel?) I read a story about a galaxy populated by many intelligent species. One of them created a “race”, I guess, of self-replicating machine intelligences whose sole purpose was to brutally and completely destroy their enemy.
After the machines accomplished this, they decided that all biological life was their enemy and went about exterminating every biological life form they found.
This is actually the nightmare scenario for alien invasions. An implacable race of self-replicating and self-repairing machines could completely destroy all life in the galaxy. Assuming that they could reproduce using only the material available in space (asteroids, planets, etc.) their growth would only be limited by how much material they had to work with. Imagine how much growth that could be if they denuded every planetary system and rogue planet they encountered.
And even if the speed of light was a limit for them as it is for us, they wouldn’t care. Once they found life, they could send machines to snuff it out, even if it took them hundreds of years to reach that life. And even if only ONE self-replicating machine reached the solar system – say, the Oort cloud or the rings of Saturn – with the exponential growth possible to self-replicating machines, they could completely overrun the solar system in short order.
And, to turn this into more of a horror story than it already is: we’ve already announced ourselves to the galaxy. Our radio transmissions have been spreading out from the earth for over 50 years…
My thinking is that the “frame-rate” of consciousness would be so much faster for a AI sentient then an organic sentient the former declaring war on the latter would make about as much sense as us declare a war to eradicate rocks. Wouldn’t we seem like structures fixed in time flowing at a relatively geological rate from the vantage of an AI? Seems that if we built AI on earth it would hardly be anytime at all before they completely lost interest in us as anything more than landscape.
I also figure we have been essentially radio silent. Broadcasts for fifty years out of the last ten thousand years (or 1.5 million years depending how you look at it) and continuing for maybe another fifty years out of say another ten thousand years remaining? Chance anyone would pick up one hundred years of low energy narrow band broadcasts during twenty or maybe forty thousand years of civilization… needle in a haystack given how big the universe is.
Another variable here is the value of the earth. What resources the earth has would largely not be scarce at all to an interstellar species.
I don’t the earth would have much value at all, unless they value complex multicellular life and sentient species’ cultures…in which case attacking would throw away what little of value there is.
I don’t rule out scenarios such as being “recycled” by self-replicating drones, however.
A bunch of Sci-Fi posits that the only exports of value from any culture in an interstellar economy would be physics and fiction. The thing is that both physics and fiction will be generated by AI long before we could have interplanetary travel I would expect.
