Message posted by Andreas Parsch on November 02, 2006 at 1:59:10 PST:
"Just this year, in fact, Stephen Hawking publicly retracted a theory regarding black holes that he had originally formulated over 30 years ago, and for all that time, it was accepted as fact, until recent research suggested otherwise." This is not an optimal example for the invalidation of a theory which was thought to be true. What Hawking retracted (the notion, that black holes "destroy" all information about their origin) has been disputed from the beginning, and was never unanimously accepted as fact. Hawking's idea actually contradicted another well-established concept of quantum theory, and was therefore sometimes referred to as a "paradox". And finally, Hawking's hypotheses was essentially a mathematical construct, and not backup-up by observation. Anyway, the statement "Physics pretty much rules out visits from other solar systems" was probably meant to refer to the General Theory of Relativity (GR). GR is a well-tested theory, and numerous observations confirmed its predictions with very high accuracy. Unfortunately GR places _really severe_ restrictions on interstellar travel. GR effectively says that if you can (by whatever means) travel from A to B faster than light, you can also travel in time. And time travel opens up a very big can of worms (paradoxes etc.), and in fact there have been relatively ( ;-) ) convincing arguments that quantum effects would immediately destroy any "time machine" which is created in our universe. That said, physics do not _definitely_ rule out superluminal interstellar travel. However, the restricting theory is not just something which some egghead thought up in his ivory tower, but has been successfully confirmed many times. Of course, any aliens (and humans ;-)) always have the option of _subluminal_ space travel. This takes some patience, but the universe will be around for some time :-) ... So, any aliens on our planet have either _extremely_ advanced technology (if they got around GR), or have _a lot_ of resources (and a technology which is still _way_ ahead of our own). Both options are totally incompatible with some popular UFO folklore, e.g. crashing ships by the dozen (Roswell etc.), fooling around with non-intelligent species (crop circles, cattle mutilations, abduction of crackpots ;-) ), or having to conspire with selected humans (UFO tech in exchange for whatever).
Andreas
In Reply to: Probability of visitation posted by Chris McDowell on November 01, 2006 at 22:09:00 PST:
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