Dan Minet may be right in suggesting there is a ... good reason that advanced civilizations do not build Von Neumann machines to explore the galaxy.
What would keep humans from setting up a radio transmitter that could carry information a thousand light years or a radio receiver that is sensitive enough to pick up a transmission from a thousand light years away? Both a receiver and a transmitter cost. Both require at least 20th century technology. Suppose large funders had other things to do with their money? Suppose we converted to a technology that did not require as powerful radio transmissions or as great sensitivity? Then too few would know the requisite technology. Either would prevent our discovering technical, advanced extra-terrestial life that would otherwise want to communicate with us. And I can think of other reasons Earth civilizations might hold back. This list does not even concern itself with non-human hostiles: - military: will a warrior, say a warrior fighting a country such as the US assymetrically, develop and release non-biological Von Neumann machines, `grey goo', or biological ones, like small pox? - economic: will those who use fossil energy sources put off too long their conversion to non-fossil energy sources? - political: will the powers that be delay instituting mechanisms for handling global climate change? Interestingly, all have to do with the size of impacts. If they were smaller -- if the population were lower and we had a sufficiently backward technology -- we could presume Earth were infinite and flat. Bad impacts would fade away before they got big. But huge amounts of dirt are moved by humans every year, huge amounts of water consumed. We humans can transform much before the feedbacks become dangerous on a planetary scale. But when the impacts become really large, then we have to think about the planet as a whole. Millions of trees can be cut down. I don't think it would matter terribly much to the planet if the whole northeastern part of the United States were deforested again. Maybe it would have some effect, because that is a big region. I mean, that kind of deforestation is not trivial to the people or trees involved, but I think it is trivial in terms of the world. This is a practical matter. In our culture, people and markets do not perceive non-linear effects that depend on much larger territories than they imagine or much longer periods of time. Worse, if those a person does not don't know did not exist, the person would not be impacted. He or she could act as if the world were flat and not a ball. So there is increased reason to dislike unknown others ... In the past, you might be killed by a saber-toothed tiger, but you would not be hurt by the side effects of food growing on another continent! The solution is not to add complexity -- to put police over you to help food being grown on another continent -- that is too expensive. Besides, as a practical matter, except for a few, people prefer to kill unknown others (or have a sub-group kill for them) and return to what they think of as simplicity. The solution is to change culture, to add frequently used indicators of global impact. Current images include the picture of the whole Earth taken from the moon in the 1960s. That helps change culture, just as globes have for the past 500 years. Current indicators include that on world-wide dimming, an indicator of high altitude aerosols, and world-wide carbon dioxide and methane abundances, an indicator of climate change. Measures enable more action than simple changes of culture. -- Robert J. Chassell GnuPG Key ID: 004B4AC8 [EMAIL PROTECTED] [EMAIL PROTECTED] http://www.rattlesnake.com http://www.teak.cc _______________________________________________ http://www.mccmedia.com/mailman/listinfo/brin-l