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Extraterrestrials Probably Haven't Found Us - Yet
Posted by
Zonk
on Thu Jan 18, 2007 02:42 PM
from the hello-up-there dept.
from the hello-up-there dept.
kasparn writes "The Guardian today has a story about the Danish astrophysicist Rasmus Bjoerk, who recently conducted simulations on how long it will take to colonize the Milky Way. The basic idea is to send out probes in different directions (including various heights above the galactic plane). He estimates that it will take some 10 billion years to explore 4 % of the Milky Way. Since the age of the Universe is of the same order, his conclusion is that aliens can't have had time required to find us yet."
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I should hope so... (Score:5, Funny)
Actually the cylons will find us first (Score:4, Interesting)
Actually the "cylons" will find us first, it is far cheaper to send robotic explorers out. Then if anything interesting is found send the "manned" missions.
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Re:Actually the cylons will find us first (Score:4, Insightful)
I'll refer to my second sentence: "Then if anything interesting is found send the "manned" missions." Do you realize how much nothing is out there, where is the "fun" in finding another dead rock just like so many others? Forget the romantic fantasy of spaceflight, it will be uncomfortable, boring, and stressful. With robots doing the scouting there will be a greater number of interesting things for the manned missions to investigate, possible more than could be sent out. Now if manned missions did the initial exploration, the people would largely see nothing of particular interest. I think you are vastly overestimating the novelty of finding another dead rock in space, sure it would interest us, but a generation born after such discoveries become commonplace?
Actually it is a major point of debate, scientists favoring a large number of robotic missions, politicians favoring a handful of manned missions. Manned missions are multiple orders of magnitude more expensive.
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Eat at Earth (Score:5, Funny)
I am sure their galactic physicians will recommend they don't eat too many humans from the Northwestern Continent due to cholesterol or something, but that they can eat all the yellow humans from the east they want, even if they will be hungry again in a few parsecs.
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Based on poor assumptions (Score:4, Insightful)
Re:Based on poor assumptions (Score:5, Insightful)
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Re:Based on poor assumptions (Score:5, Funny)
(That said, I totally agree with you.)
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Fine assumptions, poor conclusion (Score:4, Interesting)
No one knows what aliens are going to look for in a planet. Our planet could be written off as an inhabitable nitrous sphere. They might be non-carbon based life forms. They could have progressed technologically much faster than we did as you suggested. By assuming aliens match our capabilities, he made an unstated assumption that was key to actually understanding the conclusion.
A more fitting conclusion from his work would be that it would take US 10 billion years to search a small portion of the Milky Way for life at our current technology levels.
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Re:Based on poor assumptions (Score:5, Informative)
- Obtain a good enough understanding of space-time to create wormholes to any destination you want.
- Make a list of all destinations you are aware of.
- Send a probe to all of them, evaluate each destination and scan for more destinations from there.
- Go to step 2.
Space ships are just such a small-planet-with-water way of thinking.Parent
SURVEY (Score:5, Funny)
How would you prefer to travel?
a. A blue Police Box that can traverse space and time, with a hot British former 'teen star' that is obviously in love with your weirdness.
b. A big ancient ring that can take you anywhere where there is a corresponding ancient ring, but you keep bumping into Egyption dog people who try to kill you.
c. A large dinner shaped spaceship that does warp factors, but you get to shoot at klingons and make sexy time with green chicks (remember its all about the Journey!) Just dont get assimilated by Bjork!
d. Travelling with the Robinson family and a stupid robot that shouts "Danger" long after it stopped being funny. Oh and a pedophile.
e. In a ship that can make the Kessel Run in less than twelve parsecs - With a great big hairy Wooky and a gay robot.
e. Spending time on the only ship to have survived an attack by robots with KITT in their face, where it is a daily battle to stay alive.
f. On a moon that was flung out of orbit by a massive thermonuclear explosion initiated by the build up of magnetic radiation, which there is much debate as to it being caused by global warming.
g. Traveling across universes with a guy that looks like Mike Moore, where each new universe you 'slide' into is exactly like being on LSD.
h. On a ship with a dorky hologram an evolved cat, a computer with an IQ of 6000 and a very stupid robot, but every day is hilarious!
I. The space shuttle. (yawn)
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Re:SURVEY (Score:4, Informative)
On a ship shaped like a sleek running shoe, perfectly white and
mindboggingly beautiful... (if you can stand the manic ship's computer and the terminally depressed robot).
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Re:SURVEY (Score:4, Funny)
I'm sorry, I didn't read past your first option. Where do I sign up?
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Re:SURVEY (Score:4, Informative)
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Re:Based on poor assumptions (Score:5, Informative)
1/10 c: 3.263e29 tons
Even then this seems absolutely ridiculous. If you used a matter/antimatter reaction so that your propellant was pure electromagnetic radiation (thus your exit velocity is c), you'd get these results
1/10 c: 1.105 tons
Of course, these are not adjusted for relativity, since I don't know any simple equations to do that. I would imagine (as a wild-ass guess) that the 1/10 c estimates are close, but the
Basically all I'm saying is that 1/10 c seems fairly reasonable. It's not feasible given our current technology, but its within reason. If you start looking at things like space-time warpage, then we have no idea on any usage or capabilities, so any kind of theory based on it gets even further and further from reality.
By the way, I am a rocket scientist, but only a student, and not a physicist at all, only an interested amateur.
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Re:Based on poor assumptions (Score:4, Insightful)
Why do you assume that any sane civilization would send out macro-sized probes?
Nanoscale or even microscale probes would completely change the economics of space exploration. And they would avoid the very serious problem of atomic abrasion that occurs at and above 0.1c.
That's why I laugh when people spot human-sized UFO craft. If there are UFOs here, they're microscopic.
Parent
I laugh at people who say things like that (Score:4, Insightful)
Assumptions are just that, assumptions. You can laugh all you want, but to me, it just shows one more scientific dogma. The attitude of "knowing it all" is sadly very prevalent here on Slashdot, and probably why so many spend time writing here, instead of discovering new stuff.
The problem is lack of creativity. In 0.5 seconds, I thought of nano-UFOs. Send one, or trillions of those, and let them dig into a moon or planet to rebuilt itself into a fully fledged macro-sized "UFO". Or, maybe if you want to "recreate yourself in your own image", why not send out organic "bombs"? Etc. etc. There are so many possibilities when you dont restrict your mind.
Just because you cant think of it, doesnt mean it isnt possible or thinkable. Please free your mind! There is so much more to know than we already know! And instead of giving focus to more effective ways to kill people, why not science of life?
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Re:Based on poor assumptions (Score:4, Funny)
That's why *I* laugh when people think we haven't solved the issue of atomic abrasion. Teflon was named after our home planet, after all. Ha ha ha...
Puny human!
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Re:Based on poor assumptions (Score:5, Insightful)
But the bad assumption remains: rocket technology. Like I said, who's to say they haven't gone further with physics, or pursued a different, or completely unthought-of (to us) means of travel?
No kidding. "If we put a thousand horses on a carriage, it still won't be fast enough to lift from the ground. But if we could discover the rumoured winged horse, we can do it."
Something tells me that we're a couple of paradigms away from comprehending galactic distances as attainable. Propellant propulsion systems are to interstellar travel what horses are to flight.
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Re:Based on poor assumptions (Score:4, Informative)
No, it is quite unreasonable. The Cassini probe is going 32km a second (71,000mph / 115,000kph). That is more than a thousand times faster than the record less than a hundred years earlier.
We pretty much already have the technological capability to get a small probe up to c/10. We have the knowlege and basic designs to do it... it is already "mere" enginering and $$$$ problem for us today. If we simply chose to allocate several gigabucks to do it, we could with absolute certainty get something up to c/10 within 10 to 20 years.
Assuming our civilization doesn't implode in one way or another in the next few hundred years, getting well over c/10 is a certainty. The only uncertainty is whether the speed of light really is an inviolate limit, or whether some unimagined phyisics will have us exploring the universe way beyond the speed of light.
But looking at his paper I see that the real problem with his figure isn't his c/10 speed limit, but his laughable assumptions and exploration strategy of tiny fixed number of probes zig-zaging between stars almost one at a time. Even with conservative assumptions.... assuming just 0.5c and an interstellar civilization manufacturing just one probe per year... and assuming a reasonable strategy... the entire Milky Way could be explored in just a few million years.
With more reasonable assumptions, the entire exploration rapidly becomes light-speed limited. After the initial local exploration, an advanced technology civilization could mass produce replication-capable miniprobes or microprobes and use a maximized galactic search strategy. Send those probes out on a straight line courses directly to the various sectors of the galaxy... with the worst case probe taking between 150,000 years and 225,000 years to reach the opposite side of the galaxy. Within a handful of years the probe locates an uninhabited rock and sets up an automated factory to send out a few million miniprobes or microprobes, which scout all of the stars in that sector within about 20,000 years. Elapsed time: less than a quarter million years to get a probe to every star.
And really you only need the tech and pay the $$$$ to make and launch *one* such replicator miniprobe. After that, the entire exploration proceeds automaticaly and "for free". We will probably have this technology within a hundred years. Some time within the next 10,000 years... hell lets call it some time in the next 100,000 years of civilization... someone can and will do somthing like this (if we are still around). Once anthing remotely like this gets started, it doesn't much matter how you tweak the assumptions. The most it does is add in a small multiplier factor to the timeline. It is almost inconceivable that we (assuming we are still around) will not have probed every star in the Milky Way within a million years from today.
10,000 years or 50,000 years of technology and manufacturing is an insignifigant blip in the analysis. That technology level and time span means that a civilization can and will trivially produce the resourses needed to explore at a stbstantial fraction of the speed of light. Actual strategy and behavior only accounts for a small constant multiplier. the defining factor is the speed of light, and it locks down the final answer somewhere between 160,000 years and just a few million years. His result of needing 10 BILLION years to explore just 4% of the Milky Way is comical.
The only real question is whether the speed of light really is inviolable. If that falls, then I say we only need between 100 and 1,000 years of technology and then we explore at close to the limit of whatever that new physics makes possible. If we can explore and *get answers* at far faster than the speed of light, then there is vastly more incentive to actually do so.
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Parent
Duh (Score:5, Insightful)
Sheesh, talk about "proof by lack of imagination." This is supposed to answer the Fermi Paradox?
You can't explore a galaxy with a handful of probes. 72 probes??? First of all, if you're going to do it that way, you'd create hundreds of thousands of probes, if not millions of probes (mass production would reduce the cost). Second, you still probably wouldn't do it that way. You'd wait until you had the technology to make self-replicating probes, and the galaxy could potentially be explored in thousands of years.
Not impressed by this guy's argument.
Re:Duh (Score:5, Informative)
Bingo. As usual, Wikipedia has a good article [wikipedia.org] on the topic.
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Re:Duh (Score:5, Funny)
Not impressed by this guy's argument.
He is probably just assuming that the aliens have a pretty much exact parallel to NASA.
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Re:Duh (Score:4, Insightful)
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Re:Duh (Score:4, Insightful)
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Re:Duh (Score:5, Funny)
So I guess you are both wrong.
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Self replicating probles will doom us ... (Score:4, Funny)
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Re:Duh (Score:5, Funny)
Negative. I find your argument untenable. I am in agreement with the Danish monkey-being. Probabilities of non-human life spreading through the Galaxy and discovering primitive monkey-beings in Sol System are minimal. Probability is on the same order of probability of a F'narthag slime-weasel evolving wings and taking flight. It is also highly improbable that extraterrestrial beings would colonize the pathetic planet Earth and blend into the primitive monkey-being society. They would be forced to hide in internet discussion groups and the tech sector so that they are mistaken for geeks when they display lack of monkey-being social skills.
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The Galactic Lottery (Score:5, Funny)
Plus he's not taking into account multiple alien races. So that's like double 4% which is almost 8%. Do that a few hundred times and you get 108%. This guy clearly doesn't understand math.
Re:The Galactic Lottery (Score:4, Funny)
Parent
Wrong, wrong, wrong (Score:5, Interesting)
This figure is based on some very reasonable assumptions. Colony ships travel at much below the speed of light. Each colony gets a thousand years of development time from first colonization before it starts sending out its own colony ships. As you can see, even though it seems quite "slow", thanks to the magic of exponential growth, the entire galaxy is colonized in short order.
We won't merely be discovered if aliens exist - we'll be colonized. That's the most likely scenario for running into aliens. If they never spread beyond their home planet, they'll just be one star out of trillions - but if they do start colonizing, we'd find them everywhere.
Well, DUH! (Score:4, Insightful)
That's why you have to make the probes self replicating.. utilizing in-situ resources to make more probes at each star they visit, the growth becomes exponential and it only takes a few thousand years to search the entire galaxy. And seeing as we're visiting all these stars anyway, how about looking for planets that don't have life on them, but have nice suitable conditions for starting life on them. Cover a virgin planet with a wide variety of Earth lifeforms and fly on.
Re:Well, DUH! (Score:5, Insightful)
So, yeah, you can't explore the galaxy in only a few thousand years.
Parent
I once worked out (Score:5, Funny)
More than one... (Score:4, Insightful)
Just reported... (Score:4, Funny)
It has been done already (Score:5, Insightful)
One of these Turing machines reached Earth about 4 billion years ago. It first had to start by building very simple amino acids, then it graduated to proteins, then to RNA and then to DNA, and then these DNA machines built bodies around them and started using natural selection to evolve into more and more capable organisms. The final aim of these DNA structures is to build powerful radio beacons and send the information back to the original aliens who created these molecules and scattered them to the (solar) wind.
Nothing to do with the Fermi paradox. (Score:4, Interesting)
1. It's incredibly stable. It's launching an exploration program using probes that are going to take billions of years to get a result back to the original civilization. It expects to be around to pick them up.
By the same logic:
2. Individual members are incredibly long-lived, or the society is static and conservative enough that individual goals are submerged. They expect that the people around in a few billion years still care about the stuff they're doing, AND they care about the people who'll be around then.
The technology he's postulating is also very advanced.
3. Large scale space-based industry is routine enough for them to build probes capable of refuelling themselves using the raw materials in an as-yet-unexplored solar system, with surplus fuel to launch and recover the sub-probes. If they can do that, they can do the same thing in their own solar system.
If the probes are cheap by their standards, there's no reason not to keep building them indefinitely. So let's say they're expensive. Let's say it takes this civilization a hundred years to build a probe. Why do they stop after 800 years? They're long-lived, stable, conservative, so assuming they have the will to do it in the first place why would they stop building probes? As the author notes, probes break down.
So what happens when you add another probe into the search every century, indefinitely? Well, after a million years you've got 10,000 probes out there. Now you're looking at a search time measured in millions rather than billions of years, and it only takes millions of years to do it.
But why are they doing this? Looking for planets to colonize, perhaps? If they're just looking for civilizations they'd do much better depending on "signal intelligence".
But if they've got the ability to send out colonies, even the most conservative long-lived space-based civilization is going to figure out eventually that they don't actually need habitable planets to support a permanent colony. It's riskier without habitable planets, but even if the planetless colony is 10 times less stable than the home system you're still better off with your civilization in two baskets. And before long (in the terms of this civilization) you've got a roughly spherical shell of colonized star systems, expanding as fast as they can reach new systems. At 0.1C colonizing (not just exploring) the galaxy is going to take mere millions of years.
On the other hand, what if the self-replicating probes are members of the designing species themselves?
So either this level of technology is impossible to achieve, or we're back to the question of why no species has done it yet. There's lots of plausible answers, of course, but this paper sheds no light on them.
Re:How close minded can one be? (Score:5, Funny)
when they show up, please ask them how they survived the big bang.
Parent
Re:How close minded can one be? (Score:4, Funny)
Holy shit, Tom Cruise posts on Slashdot!
Parent
Irrelevant to the Fermi Paradox (Score:5, Interesting)
The study in question does not even address the Fermi Paradox in any meaningful sense, much less "resolve" it. In fact, if this study is being offered as a resolution of the Fermi Paradox then it suggests the researcher does not understand why the Fermi Paradox is a paradox at all.
The fundamental difficulty with any explanation offered for the complete absence (so far) of any sign of other intelligent life in the universe is that the proposed explanation has to be universally valid.
The span of time for colonization, or dispersal of replicating probes, or of building vast telescopically detectable artifacts is so great that even one single exception from any proposed explanation would be capable of generating ubiquitous evidence in a tiny fraction of the life of the Universe.
Simply describing some model for exploration, and then arguing that this model won't do the job says nothing about other models. This study apparently does not consider the geometric growth that occurs with any exploration program that uses some form of replication of explorers, for example. If replication is thought to be impossible then the study would have the high hurdle of convincingly demonstrating this. (The material evidence of life on Earth seems to argue persuasively against it though.)
Arguments that "interstellar travel is impossible" would qualify for explaining why alien artifacts aren't being found locally (but do not address communication signals or telescopically detectable artifacts), but require convincing arguments that this is indeed true. On the contrary, physics does not seem to make this impossible at all, just very costly and slow. Too costly and slow for anyone to bother? Not even one single civilization?
The Fermi Paradox seems to be telling something important about the Universe. If only we knew what it is...
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Re:Such a limited view (Score:5, Interesting)
I for one would really like to explore the universe and make contact with alien species. Unfortunately, my just wishing this is the case doesn't make it so.
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Re:Heh (Score:5, Funny)
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Re:Heh (Score:4, Funny)
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Re:Heh (Score:4, Interesting)
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Re:Heh (Score:5, Informative)
He found that even if the alien ships could hurtle through space at a tenth of the speed of light, or 30,000km a second, - Nasa's current Cassini mission to Saturn is plodding along at 32km a second - it would take 10bn years, roughly half the age of the universe, to explore just 4% of the galaxy. His study is reported in New Scientist today.
No mention of colonization there.
Plus
Mr Bjork confined the probes to search only solar systems in what is called the "galactic habitable zone" of the Milky Way, where solar systems are close enough to the centre to have the right elements necessary to form rocky, life-sustaining planets, but are far enough out to avoid being struck by asteroids, seared by stars or frazzled by bursts of radiation.
So there's that too. Looks like you should have taken a look at the article first.
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Why about self-replication? (Score:4, Informative)
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What context?! (Score:5, Funny)
Average weight of humans up... sounds like and interstellar Hansel and Gretal
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Re:That's assuming... (Score:5, Interesting)
1. That they can't develop PROBES that travel faster than 1/10th the speed of light.
2. That probes of this form that would keep running long enough would be so massively expensive that even the most ambitious race would only be able to build 8 of them (He does address this complaint, and also considers 200 probes instead of 8, and von Neuman machines instead of static probes, neither of which drop the figures below 4x10^6 years to explore a mere 4% of the Galaxy).
3. He doesn't even consider non-material, photon-based probing methods, which would increase the rate of exploration by a factor of 10.
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Re:That's assuming... (Score:5, Funny)
You mean looking at stuff through a telescope?
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Re:That's assuming... (Score:5, Insightful)
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