(or pseudo-sciencey, but it makes an interesting point.)
I want to talk about a problem I've thrown some thought-time at lately.
The universe is a very large place, and even our tiny galaxy within it is incredibly large compared to our system. Upper estimates put its largest diameter at 100,000 light years, while our furthest interstellar probe is about 90 AU (.0015 LY) from Earth. That probe was launched in 1977. Our fastest probes might be a bit quicker by now but I doubt they are by orders of magnitude, and nowhere near the speed of light. One of the most often asked questions about the galaxy is whether or not there is other life in it.
Some attempts have been made to quantify the preponderance of civilizations in our galaxy which are advanced enough to communicate, the most popular of which is the Drake equation. It's a many variable quantity, and its parameters are highly contested, but results can often give N=0-100, while some estimates can give extremely low values such as 1e-10, where N is the number of civilizations. A recent computer calculation which assumes that a sufficiently technologically advanced civilization could build a ship which moves at 10% the speed of light, populate the nearest star systems (using an average spacing of systems which is empirically determined), and then 500 years after landing send a new ship out to its nearest system finds that the entire galaxy could be colonize in 5 million years after the beginning of such a program. If N was on the order of 10 or so, the probability of at least one of these civilizations being born before us is high, and taking into account the age of most systems in the galaxy (~13 billion years) it is quite probable that at least one of these civilizations was born at least 5 million years before us. The question then, is why isn't the galaxy colonized yet? There are many anthropic assumptions made in the argument (i.e. they communicate by radio, build spaceships, want to leave their planet) but it still makes an interesting point to play the pessimistic side of this argument. Maybe a factor which isn't taken into account by all these estimates is that a civilization sufficiently advanced to create spaceships of the required type it is also sufficiently advanced to destroy itself, and the probability of this occuring within 500 years of the creation of such weapons might be higher than we think. It's something to think about.
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The question then, is why isn't the galaxy colonized yet? There are many anthropic assumptions made in the argument (i.e. they communicate by radio, build spaceships, want to leave their planet) but it still makes an interesting point to play the pessimistic side of this argument. Maybe a factor which isn't taken into account by all these estimates is that a civilization sufficiently advanced to create spaceships of the required type it is also sufficiently advanced to destroy itself, and the probability of this occuring within 500 years of the creation of such weapons might be higher than we think. It's something to think about.
"Anthropic assumptions" (anthropic predictions), must include all of the relevant features of the goldilocks enigma. This extends to predict that carbon based life will be found within a very fine region of the observed universe, and all of it arrises at the same time as we did in the history of the universe, so they won't be very much more or less technologically developed than we are. That's the real reason why we haven't heard anything from anybody... *yet*, (e.g. there is no Fermi Paradox), and you can even use the enigma to make testable predictions about when that might be, as well as where:
The Goldilocks Enigma
While I agree that using the full age of the universe as a possible time for a civilization to develop is probably malformed, when you say that all of it "arises at the same time" you must be talking about an interval of history and not a single moment. I've never done or seen any calculations of how wide an interval this would be (I'm not a string theorist, just a bread and butter particle physicist who is happy just to calculate diagrams successfully) but my first guess would be much wider than 5 million years? If you have any input I'd definitely like to hear!
That's a very interesting question that I've never really considered too hard, because I am more interested in the big picture to all of this from a non-string perspective. I'm intrigued by the temptation to wildly speculate about some large numbers relation between the age of the universe, 13.7 billion years, and the fine structure anomaly... 1/137, assuming that the approximation for the age of the universe is finally correct, but I won't go there.
I would, however, expect that this "range" or fine "layer of time" is extremely small, (like the cosmological constant), and the fact that we haven't heard yet from E.T. seems to support this notion, because I would naively expect that there is other life in our own galaxy.
It seems like we should be hearing something any day now, but again that's very naive, based on a hundred light years distance since our first radio broadcasts were made.
My understanding is that the anthropic constraint is very strong, because it's actually an energy conservation law that isn't understood only because Dirac's negative energy solutions have been misinterpreted. Time and the LHC will resolve this, for sure.
Do you know much about relativity, Trent?
http://www.lns.cornell.edu/spr/2006-02/msg0073320.html
Well, I tend to use relativistic kinematics in my work every day, so I'd say I know a bit. I'm a grad student in theoretical physics and I work in QCD mainly doing calculations about the quark-gluon plasma, etc...
I'm not too well studied on cosmology or general relativity though, beyond having seen the field equations and the simple schwarzschild solution.
Are you able to discern the point that I am making in that referred post to the moderated research group?... or these four extremly short comments will be more clear:
http://www.lns.cornell.edu/spr/2006-02/msg0073320.html
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