Extraterrestrials Probably Haven't Found Us - Yet 588
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."
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.
Re:Heh (Score:2, Interesting)
Some potentially invalid assumptions? (Score:3, Interesting)
2. The ET search is not targeted.
3. The ETs are not much closer to Earth and found us by luck, early in their search.
At any rate, while the math is interesting, it just shows that we're not likely, as in snowball's-chance-in-hell likely, to have been found already. From a logical point of view, though, one cannot say that we haven't been found yet.
As far as we know for certain, the Vogon construction fleet could be circling our system as we type these responses... though the chance of that being the truth is small enough that we could very well see an Improbability-driven ship come in for a landing at JFK or LAX.
Re:Heh (Score:4, Interesting)
Re:Heh (Score:1, Interesting)
Humans look at 9 planets in a solar system, and not very well mind you, and determine that life in the universe is unlikely? Who's to say that the Milky Way isnt 10% populated (1 habited planetary body per solar system)?
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.
Re:Duh (Score:2, Interesting)
Uh-huh. And how many self-replicating probes traveling at .1 c have you developed?
Hence my use of the phrase, "wait until you had the technology." No one is going to do this until they're so bored with their own solar system that it makes sense to tackle something of this magnitude.
The fact that we can imagine self-replicating interstellar probes doesn't mean they are practical or possible.
You're right, the whole idea of self-replication is clearly impossible.
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.
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.
Re:How close minded can one be? (Score:2, Interesting)
Magic words...
When it comes to Alien technology or understanding of the Universe. All we can do is assume. We judge and make predictions, our theories are based on our perception of things.
Re:How close minded can one be? (Score:2, Interesting)
Maybe the big bang wasn't a bang at all, but was instead the "bottom" of a black hole from a neighboring universe (A white hole)... their balck hole sucks up a "universe-load" of matter, condenses it, and funnels it down a spout... then all that matter comes out the other end into our universe. No longer under the influence of astronomical gravity the matter quickly expands and cools and, tada, here's a new universe.
Under that scenario the meta-verse could have been around for who knows how many years and could contain umpteen million universes spewing matter around amongst themselves and/or spawning off completely new "spaces". If a civilization could figure out a way to ride through one of these and into a fresh new universe they could potentially persist for billions or trillions of years.
The book Macrolife [amazon.com] includes many of these concepts and is an all-around great SF book.
Re:a few points to ponder though (Score:1, Interesting)
http://en.wikipedia.org/wiki/Flat_Earth [wikipedia.org]
"The modern misconception that people of the Middle Ages believed that the Earth was flat first entered the popular imagination in the nineteenth century, thanks largely to the publication of Washington Irving's fantasy The Life and Voyages of Christopher Columbus in 1828."
Who says they haven't been past already? (Score:2, Interesting)
Outside of human history - which is just a sliver of whole earthtime - there has been a lot of time on this planet where not much was going on, intelligence-wise. "We've found another planet of ferns, sir."
Or they could just not be particularly impressed with us. We seem to behave as though we are certain that we are best-looking girl in school so any available boy who doesn't ask us out must be gay or afraid. Take a look around - as a species we fight and squabble endlessly over dirt, water, bizarre ideas and myths. The top quarter of the race could give a crap that the bottom quarter endlessly suffers and dies when there's plenty of food and cures around for all. Maybe instead of sweeping in as benevolent parents to uplift us, they just see us as yet another batch of troublemakers who would not make good company. Above all, a people who definitely do not need a warp drive to take our ways on tour. To them, we could be just another example of a type that either grows out of this stage or eventually kills itself off. When we're worth talking to - and far less likely to shoot them or other folks - they may decloak/pull off their masks/come back.
Huntred
Re:It has been done already (Score:1, Interesting)
If we one day will colonize other planetery systems, we will first and foremost prove that its possible, and if it is possible, odds are that we were not the first to do it, but rather a subject to it.
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...
So Many Assumptions (Score:2, Interesting)
But it's interesting to note that the biggest single assumption in this type of logic is that the universe is not infinite in time and space. In a static electric universe, without a beginning to base your calculations upon, chances are high that neither stars nor galaxies have determinable ages. The entire system is essentially "transient" and papers like this are completely meaningless. As painful as it is to imagine it, aliens could have started seeding the universe an infinite amount of time ago. It's possible that not even they could tell you when they started. This is of course no more painful though than imagining what happened before the Big Bang.
I've also seen it mentioned amongst people who are aware of Electric Universe Theory that the more you understand plasma, the more the plasma of the universe appears to constitute a living organism. The fact that plasma can form double-layers to "protect" its charge suggests parts of a living entity. And if Chip Arp is correct, the notion that spiral galaxies can "spit" out quasars might be the process by which the organism spreads out of its original domain. The stars are the organism's cells and mobile charged particles act as the nutrients for the plasma, which would ironically be like the organism's blood. Within this context, the rocky planets are a rare, harmless non-plasma pocket where we humans, like tiny viruses, can multiply and possibly expand.
Taking the idea one step further, another strange curiosity of EU Theory is that all of the plasma phenomenon within the universe we've observed thus far are actually electrical loads and transmission lines. Once you've become acquainted with the theory, you begin to wonder what is in fact the *source* of the power. You'd have to conclude that we're likely not in range to view the source, but this is a very interesting question. It's the EU Theory version of asking how old the Big Bang Universe is.
Weird shit. Once the public starts to learn more about plasma, I think it's inevitable that it will become a popular topic for strange ideas like this.
Re:Why about self-replication? (Score:2, Interesting)
Older calculations where a multi-generation ship went to a star, colonized it, then gave a thousand years to grow the civilization until it could sent out more colonization ships gave a result on the order of millions to tens of millions of years to colonize the galaxy. But this relies on exponential growth, not speed of exploration or "turnaround".
This guy uses the same finite set of probes to do the searching. He might as well have simply calculated the average distance between the stars in his "Galactic Habitable Zone", then divided by the number of probes. As he points out, you can neglect the time to move a probe to "its own zone", or group of stars, to explore.
Re:It has been done already (Score:3, Interesting)
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:Irrelevant to the Fermi Paradox (Score:2, Interesting)
My hunch is that once a civilisation reaches a certain stage in their evolution when they can simulate reality completely, then they find very little need in continuing to exist in the present Universe, and migrate into this simulated reality.
What's the point in travesing a Universe that will take billions of years to get basically nowhere, when you can create your own Universe, with it's own rules, having total control of it.
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.
Re:SURVEY (Score:1, Interesting)