Full Definition of PROOF
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a : the cogency of evidence that compels acceptance by the mind of a truth or a fact Source:
http://www.merriam-webster.com/dictionary/proof
Physical - also referred to as real evidence, consists of tangible articles such as hairs, fibers, latent fingerprints and biological material.
Source:
http://www.nfstc.org/pdi/Subject01/pdi_s01_m01_01.htm
PHYSICAL traces. Compressed and dehydrated vegetation, broken tree branches, and imprints in the ground have all been reported. Sometimes a soil sample taken from an area where a UFO had been close to the ground will be determined by laboratory analysis to have undergone heating or other changes not present in the control sample. CUFOS has a computer file of over 5600 such cases.
Dictionary Definition of UFO PROOF - Physical Trace Cases
