Aliens might have visited earth in the past, but humans may not have noticed them as they are too caught up with their assumptions to notice them, says Silvano P Colombano, a scientist at the NASA Ames Research Centre in Mountain View, California. “Aliens may look vastly different than the expectations that humans have of them such as being carbon-based organisms which would allow them to remain undetected,” Colombano writes in his research paper.
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"I want to point out the fact that the intelligence we might find and that might choose to find us (if it hasn’t already) might not be at all produced by carbon-based organisms like us,” Colombano writes.
"Our form of life and intelligence may just be a tiny first step in a continuing evolution that may well produce forms of intelligence that are far superior to ours and no longer based on carbon 'machinery'. I think the approach the scientific community could take, instead, is very similar to what SETI has done so far: find the signal in the noise," explains Colombano.
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"In the very large amount of "noise" in UFO reporting there may be "signals" however small, that indicate some phenomena that cannot be explained or denied," he says.
According to Colombano, scientists must “revisit our most cherished assumptions” and consider the idea of different characteristics — as well as the possibility that interstellar travel is already feasible for extra-terrestrials.
“Technological development began in a human civilization about ten thousand years ago while scientific methodologies began around five hundred years ago. Considering this fact, it can be predicted that humans might face the real issue in predicting technological development in the next 1000 years even. This is why there is a need for humans to reconsider their assumptions about the aliens,” he says.