Slashdot Mirror
Fewer Than 10 ET Civilizations In Our Galaxy?
Al writes "The Fermi Paradox focuses on the existence of advanced civilizations elsewhere in the galaxy. If these civilizations are out there — and many analyses suggest the galaxy should be teeming with life — why haven't we seen them? Carlos Cotta and Álvaro Morales from the University of Malaga in Spain investigate another angle by considering the speed at which a sufficiently advanced civilization could colonize the galaxy. Various analyses suggest that using spacecraft that travel at a tenth of the speed of light, the colonization wavefront could take some 50 million years to sweep the galaxy. Others have calculated that it may be closer to 13 billion years, which may explain ET's absence. Cotta and Morales study how automated probes sent ahead of the colonization could explore the galaxy. If these probes left evidence of a visit that lasts for 100 million years, then there can be no more than about 10 civilizations out there."
All this is assuming that we would know immediately if there were a 50-100 million year old alien probe in our solar system's backyard.
Yes. There could be half a bajillion alien probes in the Kuiper belt, transmitting the latest antics of the Earthlings right to GalaxyTV, and we'd have no idea.
I disagree. I shall propose what will be known as The eldavojohn Paradox which states that: If extraterrestrial life were watching our TV, surely Fox and the WB would have been attacked by now ... or at least a very harshly worded intergalactic message would have been delivered to the Fox executives about their nonsensical canceling of shows like Firefly and Futurama while promoting unadulterated drivel.
... we'll just come back later when you're not busy, ok?"
You see, my assertion that extraterrestrials would enjoy the same television as I is just as utterly inept as assuming that their primary goal is establishing contact with other extraterrestrials. Who knows? Maybe they're too busy jumping between parallel universes to waste time talking to the Corky from Life Goes On of the Milky Way Galaxy? (that being us)
Maybe they showed up and watched World War I and II and said, "Wow, that is some heavy shit. We'll
Isn't the Maybe Game fun? It's like I'm a sci-fi writer with me as my own audience.
My work here is dung.
1 and 2 are both well known hypotheses. 3 is very unlikely, since we pick up radio emissions from natural sources all the time. 4 is very unlikely, but possible. 5 well known hypothesis 6 interesting! 7 very, very unlikely, given the natural sources we know about 8 what transmission medium does the telepathy use? Is it EM based? Is the range infinite so you don't have to use EM for long distance comm? 9 Yes, it's a bit silly. Radio isn't all that powerful. 10 Yeah, heard that one before once or twice, but not a well-known one. Good job! 11 well known hypothesis : all we can find at this point is beacons, and nobody is using them 12 well known hypothesis : optical works better, but of course is highly directional, and we're not on line of sight
No we don't.
We need robots, breeding tanks, freeze-dried embryos. Put a few thousand of 'em (along with DNA samples of a few thousand other humans) on a spaceship, and let the ship take care of the rest.
The goal isn't to offload Earth's population at some linear rate.
The goal is to spawn self-replicating colonies. If the ship travels at 10% of the speed of light (500 years to find a habitable planet within 50 light-years), but the ship can be made cheaply enough (suppose by the year 2200 we can do it for the GDP equivalent of an aircraft carrier and its support fleet), you just fire off a ship in a random direction every 10 years.
The ship finds a suitable world, sets up shop, and the colonists spend the next 1500 years bootstrapping themselves from a Serenity-like Wild West settlements into million-person planetary civilizations capable of building their own seedships. Lather, rinse, repeat.
Some colonies fail. Big deal. Sometimes you'll spread at 0.01c (500 years travel time, 4500 years of playing Sid Meier's Alpha Centauri). Sometimes you'll get lucky - (A ship that lasts for 4500 years and travels 450 light-years - and the lucky colonists reboot after only 1000 turns of gameplay :). Net effect is a wave of colonization spreading out at around 2-3% of c.
The colonies are largely independent of each other; it's unlikely that they're all going to annihilate each other, or simultaneously annihilate themselves. The galaxy's 100,000 light-years wide, or about 300,000 light-years in circumference. The whole thing should be colonized within 10 million years. At less than half a percent of c, we're still talking about a hundred million years.
That's an eyeblink, astronomically speaking. If it was going to have happened, it should already have happened. The universe has been around for 13.6 billion years. Life's been feasible for around 10 billion of those years, after the first wave of hydrogen/helium stars went supernova and gave the universe enough heavy elements to form planets and to do interesting chemistry. Our little rock has been around for around 4.5 billion years, and inhabited for 3.6 billion years of that time. It's hardly a stretch to think that something else started 0.1 billion years ahead of us. (or got started later, but skipped the billion-odd years of time that our biosphere spent dicking around with unicellular life in the precambrian era.)
We're talking about 0.1 billion years to colonize the galaxy. Trivial for an advanced technological civilization. Assuming we're not the first, it should have happened by now. The fact that it hasn't happened is an indication that we're the first. (And as a corollary, that however common life may be in the universe, intelligent life must be mind-bogglingly, astonishingly rare. We've only been sentient for a million years, and smelting metal for a few thousand. An eyeblink of an eyeblink of an eyeblink.)