It looks like you're using an Ad Blocker.
Please white-list or disable AboveTopSecret.com in your ad-blocking tool.
Some features of ATS will be disabled while you continue to use an ad-blocker.
In 4 decades of SETI projects there have been no results, in spite of the prevailing “contact optimism” of 1960s and 1970s, motivated largely by uncritical acceptance of the Drake equation. Conventional estimates of that period spoke about 10(6)–10(9) advanced societies in the Milky Way forming the “Galactic Club” (Bracewell, 1975). Today, even SETI optimists have abandoned such fanciful numbers, and settled on a view that advanced extraterrestrial societies are much rarer than previously thought. One of the important factors in this downsizing of SETI expectations has been demonstration by “contact pessimists,” especially Michael Hart and Frank Tipler, that the colonization—or at least visit—of all stellar systems in the Milky Way by means of self-reproducing von Neumann probes is feasible within a minuscule fraction of the galactic age.
Originally posted by bovarcher
Surely anyone who examines the evidence in a genuine spirit of open-minded skeptical inquiry will discover that we have been visited by civilizations from elsewhere for millenia.
Originally posted by dionysius9
reply to post by anhinga
SETI is looking for electromagnetic broadcasts.
Silly humans... That's not what they use.
But we don't understand THAT yet.
Other assumptions give values of N that are (much) less than 1, but some observers believe this is still compatible with observations due to the anthropic principle: no matter how low the probability that any given galaxy will have intelligent life in it, the universe must have at least one intelligent species by definition otherwise the question would not arise.
Some computations of the Drake equation, given different assumptions:
R* = 10/year, fp = 0.5, ne = 2, fl = 1, fi = fc = 0.01, and L = 50,000 years
N = 10 × 0.5 × 2 × 1 × 0.01 × 0.01 × 50,000 = 50
Alternatively, making some more optimistic assumptions, and assuming that 10% of civilizations become willing and able to communicate, and then spread through their local star systems for 100,000 years (a very short period in geologic time):
R* = 20/year, fp = 0.1, ne = 0.5, fl = 1, fi = 0.5, fc = 0.1, and L = 100,000 years
N = 20 × 0.1 × 0.5 × 1 × 0.5 × 0.1 × 100,000 = 5,000
Originally posted by Badge01
Unfortunately, every single sighting, every single encounter documented thus far, could be explained by prosaic, non-fantastic explanations...
When you try to scientifically examine the plausibility of not just any kind of life somewhere, but that a sentient spacefaring species has come -here-, it seems extremely implausible. It's just too difficult at almost every step.
The inevitable conclusion, imo, is that if there really were billions and billions of civilizations in our Galaxy, and countless trillions in our Universe, then almost by some law of averages (luck?) -if they were able to come here, they'd already be here-. AND, they'd be blatantly obvious. IOW, once one civilization succeeded to Type I or Type II, then lots of them would start making it as contact was made and advancements shared.
They're might be other reasons for radio silence also.