In Which I Disagree With Steven Hawking   12 comments

The good doctor is in the news, with a quote apparently taken from his new Discovery show:

He suggests that aliens might simply raid Earth for its resources and then move on: “We only have to look at ourselves to see how intelligent life might develop into something we wouldn’t want to meet. I imagine they might exist in massive ships, having used up all the resources from their home planet. Such advanced aliens would perhaps become nomads, looking to conquer and colonise whatever planets they can reach.”

Of course, several bloggers the world round have weighed in with various positions.

Let’s look at this from a resource management view.  Any alien race which has the need to raid to sustain its resource consumption would probably be better off gathering supplies from celestial bodies other than our own little ball of dirt.

The first reason for this is that our ball of dirt actually isn’t so little.  Any resource that you want to gather from the Earth’s surface and schlep up into some sort of mothership in orbit requires you to break the gravity well of the Earth.  This is not cheap, at least, not using any sort of engine that requires reaction mass.

You need hydrocarbons?  Get them from Titan, which has much less of a gravity well than Earth’s and oceans of hydrocarbons.  The asteroid field has lots of nice loose chunks of industrial metals and would be far easier to mine than the Earth’s crust for anybody that has the capability of interstellar travel (it’s very nearly easier for us, and we don’t even have interstellar travel).  Earth trumps all the local system bodies for liquid water supplies, that’s certainly true, but Triton and Charon both have water ice on them, they’re farther away from the gravity well of the Sun.  This makes them easier to get to from outside the solar system (and away from, assuming your nomadic reavers are actually nomadic).

You have to get the supplies up onto the ship, and that takes some sort of energy, presumably.  Even the heavy elements like thorium and uranium are present elsewhere in the solar system.

On the other hand, if your technology is advanced enough for interstellar travel, you might not care about reaction mass… but if you don’t care about reaction mass, you probably don’t need to raid planetary bodies for supplies.  Whatever your technology looks like, you’re capable of violating a few of our understood laws of physics.

It’s likely that anybody that might want to drop by for a visit has to be some distance away… where “some distance” == “really, really far”.  There’s only so many candidates for likely life-supporting environments within 50 light years of our little ball of iron (and of course, it goes without saying that if your lifeform isn’t sufficiently like ours, you probably don’t regard liquid water as a necessary resource).

I dunno, Professor, I’m thinking that the likelihood of roving bands of aliens is pretty far-fetched, logistically speaking.

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Posted April 26, 2010 by padraic2112 in astronomy, science, Uncategorized

12 responses to “In Which I Disagree With Steven Hawking

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  1. I find Hawking’s hypothesis as plausible as any other at face value. One only has to look at 17th – 19th century colonialism for examples.

  2. 17-19th century colonialism didn’t have a very large resource constraint for the underlying activity, it’s a terrible comparison.

    You build a ship or five, plunk a couple hundred men on it, and send them on their merry way. Total cost to built the ship: negligible for the government in question. Total propulsion cost: zero, they used the wind. Travel time: well within the margins for available supplies for both a departing and returning trip. Payoff: extremely large in comparison to local resources.

    Building an interstellar vessel and sending it multiple light-years away is a huge resource cost. Given it might be worth it if your local space is mined out, but this still doesn’t give you a very big incentive to drop cargo vessels into the gravity well of the earth to mine our crust when you can pick up an asteroid with trillions of dollars worth of raw metals (much more easily accessible and extractable) without burning your way through an atmosphere, in two directions.

    Put another way: show me a resource that’s worth going after on Terra Firma, there’s another, more easily accessible source somewhere in our solar system without much effort. Even uranium and thorium are accessible elsewhere, with less of a logistical price tag.

  3. I could see, however, us going to war with an interstellar entity over access to the asteroid belt :)

  4. Actually, it’s not as different as you make out. Ships were quite expensive back then and travel times weren’t easily within the margins for both a departing and returning trip. We also do not know how much it would cost any alien race to build interstellar ships. I would guess that it would be hugely expensive, but cannot claim that to be anything other than a guess.

    As for resources – how about an oxygen-nitrogen atmosphere, liquid water, and a relatively low gravity? Colonization for one purpose or another is always a possibility after all.

    Of course I think the likelihood of this happening is astronomically slim (pun intended). I doubt many races’ civilizations survive and progress far enough to achieve interstellar travel. I would guess, based upon mankind’s existence, that most of their civilizations “cook off” sometime in the course of their technological equivalents of the 20th – 22nd centuries.

  5. For the purpose of this exercise, I’m assuming that any alien technology doesn’t violate the laws of physics as we currently know them. So no Warp drive, or Jump drive, Special Relativity holds, etc.

    This means that it’s going to take you a very long time to get from point A to point B. It’s also going to be extremely costly in fuel. That’s a constant, no matter how you build what you build, you have to be able to expend the resources to move it.

    Certainly, we don’t understand an alien’s construction methods, I’m again assuming that they don’t have physics-violating tools like direct matter conversion capability (largely because, if they’ve got it, they don’t need to go anywhere for anything). If they don’t, the bigger you build whatever you build, the more it costs you to get it built and the more you have to expend to move it.

    As I point out, liquid water isn’t necessary; you can get ice water from lots of different astronomical bodies with less effort. The gravity of the earth is a subjective thing; it’s a lot less than Jupiter, but it’s ginormous compared to, say, Europa. Which has ice and iron and etc. etc.

    Now, of course, if they’re *colonizing* the Earth (as opposed to simply raiding it, that is, they intend to stay here), then the atmosphere might be a plus, but the biosphere is a negative.

    It would be very unlikely that they could easily process native biosphere (the original War of the Worlds aside, it’s pretty unlikely that any living organism here would have any effect on an alien lifeform, positive or negative). They’d have to terraform the joint to make the atmospheric mix match their needs, they’d have to replace native biota with transplants, etc.

    If you’re going to that extent, why not choose a planetary body that isn’t already inhabited by someone who will fight you over it? Anybody that can live here can probably live on Mars.

    Again, if you can build a colony ship, you probably don’t need to terraform a planet, just build a bigger ship and go with that :)

    Now, there’s always the possibility of an interstellar crusade or jihad or non-us-cleansing sort of event, but the probability of that can’t even be measured.

  6. OK, no violating the laws of physics as we know them. That still leaves ramjet / fusion engines. There’d be ittle, if any, need for on-board fuel once they’re up to speed and even modern ion drives could do that for them.

    Large hulls could already technically be built by heat expanding / foaming asteroids with lasers, which would greatly reduce the costs of doing so and have the added advantage of placing ready-made weapons and/or commo gear at the ships’ build site. ;)

    That still does address the travel time-frame though, so any such “raiders” would have to be locust-like like the ones in ID4.

    But…We’re focusing on the negative possibility and why it’s unlikely. The same restrictions and cost-benefit analysis applies to friendly contact as well. Sad ain’t it?

  7. The jury is still out on Bussard ramjets, but to my thinking it doesn’t currently look good (http://en.wikipedia.org/wiki/Bussard_ramjet#Discussions_of_feasibility for starters).

    The “converting asteroids to a hull” idea via heat expansion is one of my favorite bits of extremely plausible speculative fiction (the other is von Neumann machines).

    The same restrictions and cost-benefit analysis definitely applies to friendly contact as well.

    I think the main reason why you don’t see aliens isn’t that they’re not looking either, it’s just that they’re damn far away that the only practical method of actually visiting elsewhere is via generational ships.

    So, unless you need to evacuate a planet, you’re very unlikely go to anywhere. Unfortunately, needing to evacuate a planet may be something that you don’t know you need to do until it’s logistically too difficult to accomplish the goal prior to the event that’s going to render the place uninhabitable.

    Me, I think we should get our butts off this rock, but that’s hard to quantify as necessary given the astronomical time scales between big extinction events. For entertaining reading, I recommend Phil Plait’s “Death from the Skies!”

  8. You all are missing out on the one resource that (to our knowledge) can’t be found in the rest of the solar system- intelligent life. Anyone looking for a client race (or perhaps even a convenient food source) will home right in on all the radio traffic we’ve been spewing out. Taken in that context, Hawking is exactly right- anyone who comes to Earth is probably looking for US, and unless they are really really nice (and what are the odds of that?) we could be in trouble. Frankly, it’s likely that any species capable of FTL travel probably has a cheap way out of the gravity well, too. So I think Hawking is exactly on the ball- anything that comes to us is likely to be something we don’t want to meet.

  9. > Anyone looking for a client race (or perhaps even a
    > convenient food source)

    [snip]

    > Taken in that context, Hawking is exactly right

    That’s two different contexts, and in one Hawking is exactly wrong, and in the other he’s off-base. :)

    If someone’s looking for customers, it’s probably a good thing to have them come here. They’d probably sell us something for less than what it’s worth on the interstellar market, but it’s probably still worth more to us than whatever we’d be giving to them. On the average, probably good for us.

    If you’re looking for a convenient food source… come on, Andy, get real. You’re going to travel dozens or hundreds of light years to metabolize some lifeform that has protein chains your lifeform isn’t even familiar with? We can’t eat most of the other life forms on our *own* planet, under what crazy convergent evolutionary model would someone, from someplace else, even look at human beings as a food source, let alone be capable of digesting us without a horrible case of the intergalactic runs or outright metabolic collapse?

    Yeah, I’m ranking that somewhere between “really small” and “close enough to zero to call it that” probability. Much closer to the latter.

    There are two real exception scenarios I can imagine.

    One, the other race, whatever it is, is freakishly paranoid and is looking for other forms of life in the Universe to exterminate before they become potential rivals for interstellar resources (which, as I pointed out above, would be a crazy thing to be paranoid about but hey, paranoia is by nature irrational). Now, this is minutely plausible because I could easily see humankind (our one actual intelligent race we can study) as winding up being this freakishly paranoid. In this case, it’s game over anyway… if they are scanning for us, they’re going to be using technology that is so far advanced from ours that they’re going to find us and send a large object our way at near light speeds before we know they’re out there. Our first knowledge that there might be other forms of life would be watching something with an eighth of the mass of the Earth come plowing towards us at a high enough rate of speed to powder the planet.

    Assuming of course that any race that paranoid possesses the capability of advancing technologically, since they’d also likely be unable to trust *each other* and thus cooperation would be nil. It would take them forever to get out of the stone age, if they possibly could.

    Two, the other form of life, whatever it is, has already sent some automated seeding terraforming entity out into the galaxy… and our planet, being some match for gravity and distance from the sun and all that jazz gets caught up in their probability window and they come here to inject alien biota in our atmosphere and prep the planet for eventual colonization.

    In *that* case, either they have the capacity to care about other intelligent species (in which case, their robo-genesis-machine avoids us *because* of our broadcasts) or they don’t (in which case, there are two other possibilities… either they passively scan and thus will come across us anyway because they don’t care about RF broadcasts, just planet position and atmosphere makeup and whatnot… or they actively scan in which case they might home in on our RF broadcasts, but that makes them functionally equivalent to the previous case of paranoid aliens).

  10. Ok,

    Can’t leave this one alone any longer. First it may just be terminology, you mean “efficient” when you say economical. Economical implies cost, currency, and even supply/demand curves. How economical is it for millions of households to purchase individual cars…. So you don’t gain any sense of rational behavior by applying our standards to intergalatic raiders. Maybe their irrational inefficiencies are driven by some internal mechanism that make even less sense than ours.

    I fear that the conquerers will arrive, and have no concept or care for efficiency. They may raid the methane from another planet, or bring and expend vast amounts of compounds we don’t yet have, because they are motivated solely by the number of beings that are under their control. They will force us to do meaningless tasks, possibly in windowless offices, and force some of us into controlling other humans and life forms. May not matter if it is just getting five dogs to fetch, sit, stay all day long. You see the most respected in their belief system have the most beings “reporting to them”. Scary isn’t it? Yes, colonization. Bringing us their religion and microbes I am sure.

    Now back to P’s dismissal of the paranoids… They could be paranoid, about every other species in the universe, possibly even have cleansed their own planet. Yet still function under some collective laws or not harbor ill will for those who look exactly like themselves. I don’t think I have to leave this rock for examples of this, do I?

    Anyway, that is the point I believe, if they can detect, and locate they CAN destroy as easily as befriend. I mean just consult the great philosophical writing of Mars Attacks!

  11. Hey, I didn’t say “economical” anywhere above (if that was directed at me) :)

    You’re right about the possibility of xenophobic-only paranoia . But again, if somebody out there is that freaked out about the possibility of competitors but still capable of self-species level cooperation (a la the Hudatha in Dietz’s Legion series)… they’re going to be finding other species by finding likely places for other species to exist and going there/purging them from a distance.

    They’re not going to wait for our RF signals (although of course it’s possible that our RF broadcasts bring us to their attention earlier than they might discover us otherwise).

  12. No, just resource cost from you on further review. But really, I assume irrational usage of resources just have no clue what they may value. Could be just interplanetary space tourists. “Have you been to Earth, dahling. You should, really should. And make sure to try the Cahalan on toast!”

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