It looks like you're using an Ad Blocker.
Please white-list or disable AboveTopSecret.com in your ad-blocking tool.
Thank you.
Some features of ATS will be disabled while you continue to use an ad-blocker.
jonnywhite
Why have they not shown up? Fermi's Paradox is what started the question in the popular consciousness but I'm sure many others contemplated the same thing long before. Essentially, if a species can colonize the entire galaxy in a matter of millions of years by employing the use of self-replicating machines or something similar then WHERE ARE THEY? Note that this does not require faster than light travel. It only requires vast numbers of self-replicating autonomous entities, mostly coordinating their activities to colonize as many star system as possible.