It's fun thinking about the Fermi paradox. In a nutshell, it goes like this: if there's even a slight chance that a planet could develop a civilization that spreads through the galaxy, why aren't they here yet?
For an introduction that fleshes this out, and lists some of the many answers, try the Wikipedia page below.
I should read Stephen Webb's book If the Universe Is Teeming with Aliens … WHERE IS EVERYBODY?: Fifty Solutions to the Fermi Paradox and the Problem of Extraterrestrial Life. But my friends Bruce Smith and James Dolan have suggested two interesting ideas about this puzzle: one pessimistic, one optimistic.
Bruce's goes like this. Assume that our corporations evolve toward ever faster exploitation of natural resources. The Earth is not enough! So, ultimately, they send out self-replicating von Neumann probes that eat up solar systems as they go, turning the planets into more probes. Different brands of probes compete among each other, evolving toward ever faster expansion. Eventually, the winners form a wave expanding outwards at nearly the speed of light - demolishing everything behind them, leaving only wreckage.
The scary part is that even if we don't let this happen, some other civilization might.
Indeed: even if something is unlikely, in a sufficiently large universe it will happen, as long as it's possible. And then it will perpetuate itself, as long as it's evolutionarily fit. Our universe seems pretty darn big. So, even if a given strategy is hard to find, if it's a winning strategy it will get played somewhere. So, even in this nightmare scenario of "spheres of von Neumann probes expanding at near lightspeed", we don't need to worry about a bleak future for the universe as a whole - any more than we need to worry that viruses will completely kill off all higher life forms. Some fraction of civilizations will probably develop defenses in time to repel the onslaught of these expanding spheres.
However, in this scenario, when we first meet an alien civilization, our solar system will quickly be disassembled and used to make more spacecraft.
James Dolan's proposed resolution of the Fermi paradox goes something like this. Suppose intelligent civilizations tend to create baby universes for their own use, instead of wasting time on space travel. Then the density of intelligent life in a given universe may never get very high! In this scenario, we're likely to be in a baby universe created for some unfathomable purpose by some civilization that we'll never meet, because they won't bother to travel around this one.
This is just far-out enough to be believable. Outguessing civilizations that have been around millions of years more than ours seems like a loser's bet: sort of like a chimpanzee trying to imagine space travel. But, if we're going to play this game, it probably pays to think big.
If you don't know about "von Neumann probes", try this:
http://en.wikipedia.org/wiki/Self-replicating_spacecraft
I don't know a good easy introduction to "baby universes" - which are, by the way, a quite speculative idea, sometimes studied by respectable physicists working on quantum gravity.
For an introduction that fleshes this out, and lists some of the many answers, try the Wikipedia page below.
I should read Stephen Webb's book If the Universe Is Teeming with Aliens … WHERE IS EVERYBODY?: Fifty Solutions to the Fermi Paradox and the Problem of Extraterrestrial Life. But my friends Bruce Smith and James Dolan have suggested two interesting ideas about this puzzle: one pessimistic, one optimistic.
Bruce's goes like this. Assume that our corporations evolve toward ever faster exploitation of natural resources. The Earth is not enough! So, ultimately, they send out self-replicating von Neumann probes that eat up solar systems as they go, turning the planets into more probes. Different brands of probes compete among each other, evolving toward ever faster expansion. Eventually, the winners form a wave expanding outwards at nearly the speed of light - demolishing everything behind them, leaving only wreckage.
The scary part is that even if we don't let this happen, some other civilization might.
Indeed: even if something is unlikely, in a sufficiently large universe it will happen, as long as it's possible. And then it will perpetuate itself, as long as it's evolutionarily fit. Our universe seems pretty darn big. So, even if a given strategy is hard to find, if it's a winning strategy it will get played somewhere. So, even in this nightmare scenario of "spheres of von Neumann probes expanding at near lightspeed", we don't need to worry about a bleak future for the universe as a whole - any more than we need to worry that viruses will completely kill off all higher life forms. Some fraction of civilizations will probably develop defenses in time to repel the onslaught of these expanding spheres.
However, in this scenario, when we first meet an alien civilization, our solar system will quickly be disassembled and used to make more spacecraft.
James Dolan's proposed resolution of the Fermi paradox goes something like this. Suppose intelligent civilizations tend to create baby universes for their own use, instead of wasting time on space travel. Then the density of intelligent life in a given universe may never get very high! In this scenario, we're likely to be in a baby universe created for some unfathomable purpose by some civilization that we'll never meet, because they won't bother to travel around this one.
This is just far-out enough to be believable. Outguessing civilizations that have been around millions of years more than ours seems like a loser's bet: sort of like a chimpanzee trying to imagine space travel. But, if we're going to play this game, it probably pays to think big.
If you don't know about "von Neumann probes", try this:
http://en.wikipedia.org/wiki/Self-replicating_spacecraft
I don't know a good easy introduction to "baby universes" - which are, by the way, a quite speculative idea, sometimes studied by respectable physicists working on quantum gravity.
